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The primary objective of this study was to identify associations between the prepartum teat apex microbiome and the presence of Staphylococcus aureus intramammary infections (IMI) in primiparous cows during the first 5 weeks after calving. We performed a case-control study using shotgun metagenomics of the teat apex and culture-based milk data collected longitudinally from 710 primiparous cows on five organic dairy farms. Cases had higher odds of having S. aureus metagenomic DNA on the teat apex prior to parturition compared to controls (OR = 38.9, 95% CI: 14.84-102.21). Differential abundance analysis confirmed this association, with cases having a 23.8 higher log fold change (LFC) in the abundance of S. aureus in their samples compared to controls. Of the most prevalent microorganisms in controls, those associated with a lower risk of post-calving S. aureus IMI included Microbacterium phage Min 1 (OR = 0.37, 95% CI: 0.25-0.53), Corynebacterium efficiens (OR = 0.53, 95% CI: 0.30-0.94), Kocuria polaris (OR = 0.54, 95% CI: 0.35-0.82), Micrococcus terreus (OR = 0.64, 95% CI: 0.44-0.93), and Dietzia alimentaria (OR = 0.45, 95% CI: 0.26-0.75). Genes encoding for Microcin B17 AMPs were the most prevalent on the teat apex of cases and controls (99.7% in both groups). The predicted abundance of genes encoding for Microcin B17 was also higher in cases compared to controls (LFC 0.26). IMPORTANCE Intramammary infections (IMI) caused by Staphylococcus aureus remain an important problem for the dairy industry. The microbiome on the external skin of the teat apex may play a role in mitigating S. aureus IMI risk, in particular the production of antimicrobial peptides (AMPs) by commensal microbes. However, current studies of the teat apex microbiome utilize a 16S approach, which precludes the detection of genomic features such as genes that encode for AMPs. Therefore, further research using a shotgun metagenomic approach is needed to understand what role prepartum teat apex microbiome dynamics play in IMI risk. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine whether heifer calves born in individual maternity pens will have a lower risk for experiencing calfhood diseases versus heifer calves born in a multiple cow maternity housing area in a randomized clinical trial, conducted between January, 2005 and December, 2005. Four hundred and fifty two dairy heifer calves were recruited into the study from three Minnesota dairy farms. Pregnant cows were randomly allocated to calve in either the individual maternity pen (treatment group) or multiple cow maternity housing area. Fecal material and placental remains were removed from the individual maternity pens between each calving and calves were separated from their dams and removed from the maternity area, within 2 hours of birth. Calves born in multiple cow pens had varying times of separation from their dams. All calves were housed in individual hutches for 8 weeks and later transferred to group pens of 10 calves each. Calves born in individual calving pens were not commingled with those born in the multiple calving areas during the follow up period. Standard disease monitoring and diagnosis protocols were developed for the study. Disease events (enteritis and pneumonia) experienced by the calves, during the first 3 months of birth and treatments administered, were recorded by the calf managers. Incidence risk of disease and mortality, experienced by calves in either group were compared using Chisq-Test statistic (Table1). Days at risk for calves born in either calving location were compared using product limit estimates of survivor functions and there was no evidence to suggest differences in survival experience between groups (Log-Rank Test: Chisq=0.0744; df =1; p=0.79). Results suggest no difference in the incidence of calf morbidity and mortality between calves born in individual maternity areas when compared with those born in multiple cow maternity environments. [ABSTRACT FROM AUTHOR]

Good calving management should not only ease the transition of cows into lactation, but also contribute to providing healthy replacement animals for the herd. Difficulty during parturition has been found to be detrimental to the offspring. Because of the association of obstetrical intervention with undesirable outcomes, the general management recommendation for calving is to let cows give birth unassisted whenever possible. Unfortunately, very few studies have investigated the effects of planned early assistance during calving, regardless of whether or not another problem exists. To investigate the effects of early assistance during apparently normal calvings, a clinical trial was conducted on 257 Holstein cows. They were observed through the second stage of calving, and before calving they were divided randomly between 2 assigned interventions: not assisted or early assistance during the second stage of parturition. After calving, the animals were classified into 4 actual calving intervention groups: too quick to be assisted, not assisted, early assistance, and late assistance (for cows in the not assisted group that did not calve unassisted within the 1 h maximum time allowed). Early assistance was given 15 min after first sight of both front hooves of the calf and done using human force only. Heifer calves (n = 129) born from enrolled dams were followed until weaning to assess the effect of assigned and actual calving interventions on their growth, health, and survival. Heifer calves' weight at birth was positively associated with weight at 7 wk, but the effect varied by assigned and actual intervention. As a routine management practice, giving early assistance during calving to dairy cows did not influence average daily gain, health, or survival in dairy heifer calves up to weaning at 7 wk of age. [ABSTRACT FROM AUTHOR]

A critical time for dairy cattle is the perinatal period. Good calving management is critical to reduce periparturient losses and ensure the health of the offspring. Generally, it has been recommended that cows be allowed to calve unassisted when possible, but very few studies have been published that support or refute this general guideline. To investigate the effect of early assistance, a clinical trial enrolled 257 Holstein cows that were observed through the second stage of calving and assigned randomly to 1 of 2 calving interventions: not assisted (NA) or early assistance (EA) during the second stage of parturition. Early assistance was given 15 min after the first sight of both front hooves of the calf and done using only human force. After calving, the animals were classified into 4 actual calving intervention groups: too quick to be assisted (TQ), NA, EA, and late assistance (LA; for cows in the NA group that did not calve unassisted within the 1 h maximum time frame allowed). Giving early assistance to cows during calving as a routine management practice (assigned intervention) did not negatively influence calves' stillbirth risk, vigor at birth, or transfer of passive immunity. Calves in the LA intervention group had significantly greater odds of stillbirth than calves in the NA and EA groups, respectively. Calves in the LA group also had significantly worse vigor at birth than calves in the TQ, NA, or EA groups. Early assistance given at calving to cows that did not present signs of calving difficulties did not adversely affect calves' likelihood of being stillborn, vigor at birth, or transfer of passive immunity. [ABSTRACT FROM AUTHOR]

The article discusses research on the quality of maternal colostrum compared to commercial colostrum given to calves, by P. Pithua and colleagues, published in the 2010 issue of the "Journal of the American Veterinary Medical Association."

There has recently been increasing interest in feeding heat-treated colostrum to reduce transmission of infectious pathogens to calves. However early research pasteurizing colostrum using the same high temperatures as are typically used to pasteurize milk resulted in significant denaturation of colostral antibodies and often unacceptable feeding characteristics. Recent laboratory studies have suggested that heat-treating bovine colostrum at 60°C for 60 min would result in good pathogen kill while preserving antibodies. The objective of this study was to describe the effect of feeding heat-treated bovine colostrum on passive transfer in newborn calves. This study was conducted on a commercial transition cow management facility in Baldwin, WI. 8 to 16 L batches of fresh bovine colostrum were split into two equal aliquots. The first aliquot was maintained as raw, and refrigerated immediately in 4 L bottles. The second aliquot was heat-treated in a commercial batch pasteurizer at 60°C x 60 min, and then refrigerated in 4 L bottles. Fifty newborn singleton Holstein calves weighing > 70 lbs at birth were systematically (i.e. every other calf born) assigned to be fed 3.8 L of either raw (control) or heat-treated (treated) colostrum within 2 hrs of birth, using an esophageal feeder. Blood samples were collected at 0 and 24 hrs of age for determination of serum total protein (TP) and serum immunoglobulin G (IgG) concentrations. There was no effect of treatment on serum measures at 0 hrs of age. However mean (SD) calf serum TP and IgG concentrations were significantly greater at 24 hrs of age for calves fed heat-treated colostrum (TP = 6.3 ± 0.5 gm/dl; IgG = 22.3 ± 4.6 mg/ml) as compared to calves fed raw colostrum (TP = 5.9 ± 0.7 gm/dl; IgG = 17.5 ± 5.5 mg/ml) (P < 0.05). Though potential economic and health benefits still need to be described, these results suggest that farms can feed calves heat-treated colostrum to reduce pathogen exposure while maintaining, or even improving, passive transfer of colostral antibodies. [ABSTRACT FROM AUTHOR]

There is increasing adoption of on farm culture systems for selective treatment of clinical mastitis cases. They may also be useful for the diagnosis and selective treatment of subclinical intramammary infections in fresh cows. We present preliminary validation of an on-farm culture system (Minnesota Easy Culture System II). Farm personnel collected milk samples from clinical mastitis quarters, and from fresh cow quarters that tested positive using the Californian Mastitis Test (CMT) within three days after calving. The fresh samples were then plated on farm using a sterile cotton swab onto each half of a bi-plate. Plates were incubated overnight and then interpreted as 'no growth', when bacteria did not grow, or 'Gram-positive' or 'Gramnegative' depending if growth was on the Factor or the MacConkey media half of the bi-plate respectively. After plating, milk samples were frozen and later cultured in the laboratory using standard identification procedures. On farm culture results and corresponding in laboratory results are available from 80 quarter cases of clinical mastitis, and from 87 fresh cow CMT positive quarters. Using the on-farm culture method for clinical mastitis cases, producers were able to detect 83% of the Gram-positive cases (sensitivity), and classified correctly about 90% of the Gram-negative cases or cases where bacteria was not present (specificity). Consequently, 83% of the treated cases, 'Gram-positive' quarters underwent intramammary treatment, were truly Gram-positive (predictive value of a positive test; PV+), and 90% of the not treated cases, 'Gram-negative' or 'no growth', were truly uninfected or Gram-negative (predictive value of a negative test; PV-). For fresh cow CMT positive quarters, the sensitivity of the on-farm culture to detect gram-positive quarters was 88%, and the specificity was 70%. Accordingly, 80% of the treated cases were truly gram-positive (PV+), and 81% of the not treated cases were truly uninfected or Gram-negative (PV-). [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the lactation performance (measures of health, production, reproduction, and survival) of cows shedding Mycobacterium avium subsp paratuberculosis (Map) in feces prior to calving and of cows culled with clinical signs of Johne's disease (JD) during the subsequent lactation. 1,052 cows from two Minnesota dairies were enrolled in the study. Fecal samples were collected immediately prior to calving and tested using bacterial culture to detect Map. Observed signs of clinical disease (milk fever, retained placenta, metritis, ketosis, displaced abomasum, lameness, mastitis, pneumonia, and Johne's disease) and lactation performance data were recorded for each cow. Of the 1,052 study cows, 84 cows (8%) had Map positive fecal samples (46% light, 26% moderate, and 28% heavy shedders). Lactation length of fecal positive cows was on average 106 d less than negative fecal culture cows. Mean milk production for negative fecal culture cows was 9,700 kg and for light, moderate, and heavy shedders was 8,100 kg, 6,300 kg and 2,700 kg, respectively. Fecal culture positive cows were less likely to be bred and conceive than negative cows. Fifty-six cows were culled with clinical signs consistent with JD and remained in the herd an average of 202 days less than cows that completed the study and 49 days less than other cows culled from the herd. Cows culled with clinical signs of JD produced on average 3,280 kg less milk than cows that completed the study. Study results demonstrate the economic impact of fecal shedding and clinical JD on cow lactation performance, information important in motivating dairy producers to implement JD control programs. [ABSTRACT FROM AUTHOR]

Dystocia and stillbirth are important sources of economic loss for the dairy industry. The goal of this study was to assess parturient steroids and labor duration as potential risk factors for them. Close-up cows from a Transition Management Facility in Western Wisconsin (n = 78) and from a large dairy in Central Michigan (n = 50) were monitored hourly to identify animals in labor (e.g. mucoid vaginal discharge, calf limbs visible), which were moved into individual maternity pens for videotaping of parturition and recording of calf birth weight (BW) and status (alive, dead) and cow body condition score (BCS). In the Wisconsin cows, calving ease score (CES; 1 = easy to 5 = very difficult) was recorded and a venous blood sample collected within 1 h of delivery for enzyme immunoassay of serum cortisol and progesterone. In both herds, BCS and BW did not associate with calving difficulty. In the Wisconsin cows, progesterone was lower (P ≤ 0.05) in CES 5 cows (378.8 ± 167.2) than in cows with CES 1-4 (mean 1085.6 ± 18.0 pg/ml) with little difference in cortisol, driving the cortisol:progesterone ratio higher (P ≤ 0.05) in the CES 5 cows. All calves from CES 4-5 cows (n = 18) were born dead. In CES 1-3 cows, mean cortisol was higher (P = 0.03) in animals delivering live (22,315 ± 3,921 pg/ml; n = 31) versus dead calves (14,347 ± 2,488 pg/ml; n = 29). The same trend was observed for progesterone (P = 0.11). In the Michigan cows presenting with mucoid vaginal discharge, time to live assisted delivery was 212.2 ± 24.5 min and to dead assisted delivery was 293.1 ± 24.1 min (P ≤ 0.05) but times to live assisted and unassisted deliveries did not differ. Collectively, these preliminary results suggested that parturient concentrations of cortisol and progesterone and labor duration are potential risk factors for dystocia and stillbirth. Future studies will determine if variations in serum steroids are linked to cervical dilation and labor duration, which may underlie dystocia and (or) stillbirth. [ABSTRACT FROM AUTHOR]

Bovine respiratory disease (BRD) is one of the most common infectious causes of morbidity and mortality in young dairy cattle. The objective of this randomized clinical trial was to determine the effectiveness of 1 or 2 doses of a 5-way, modified-live viral vaccine, administered to heifer calves before weaning to aid in the prevention of BRD. The hypotheses were that vaccination would reduce the incidence of BRD and mortality and that 2 doses would be more effective than 1. A total of 2,874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1 to 7 d of age and were followed until 3 mo of age. Calves were randomly assigned to receive a commercial, intramuscular, modified-live vaccine against bovine vira diarrhea virus types 1 and 2, bovine respiratory syncytial virus, bovine herpesvirus type 1, and parainfluenza virus type 3 at 15 to 21 d of age (2 wk only), 35 to 42 d (5 wk only), both 2 and 5 wk, or sterile saline at both times (unvaccinated controls). The incidence of failure of passive transfer was 11 or 32%, using cut-points of serum total protein of 5.2 and 5.7 g/dL, respectively Overall, 22% of calves were treated at least once for BRD. The incidence risk of naturally occurring BRD was 7.7% before 2 wk of age, 8.0% between 2 and 5 wk and 9.5% between 5 wk and 3 mo of age, and was not different between vaccination groups. Overall mortality throughout the 3-mo study period was 3.5%. Mortality was 1.6% before 2 wk of age, 0.5% between 2 and 5 wk, and 1.2% between 5 wk and 3 mo of age. The risk of mortality was not affected by vaccination. Mean average daily gain of 1.07 kg/d from 5 wk to 3 mo of age was not different between vaccine groups. In this population of commercial, home-raised calves, with an overall low incidence of failure of passive transfer intramuscular vaccination with a multivalent, modified live viral vaccine at 2 or 5 wk of age or both was not associated with a decreased risk of BRD or mortality, or with growth until 3 mo of age. Reasons for these findings may include interference by maternal antibodies, unresponsiveness of the neonatal immune system, timing of immunity relative to pathogen exposure, disease caused by pathogens other than the viruses in the vaccine, or herd immunity. However, in populations with higher incidence of failure of passive transfer or risk of BRD, calves with low levels of specific antibodies may respond differently to vaccination. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the distribution of Mycobacterium paratuberculosis (Map) in the environment of infected and uninfected Minnesota dairy farms. Eighty herds known to be infected from Minnesota's Johne's Disease Control Program (JDCP) and 28 herds known to be uninfected from Minnesota Voluntary Johne's Disease Herd Status Program (VJDHSP) were sampled. Fecal samples from up to 100 cows in each herd were cultured in pools of 5 cows. Two environmental samples were obtained from each farm from various locations. All samples were tested using bacterial culture for Map. Eighty percent of the JDCP herds had at least one positive pool. Environmental samples were cultured positive in 78% of the JDCP herds. Two (7%) of the VJDHSP herds had one positive pool, and one herd had one positive environmental sample. Environmental samples were cultured positive in cow alleyways (77% of the herds), manure storage (68%), calving area (21%), sick cow pen (18%), water runoff (6%), and postweaned calves areas (3%). There was an association between maximum level of colonies per tube from cow alleyways and manure storage and fecal pool prevalence. Herds with both areas cultured negative were estimated to have 0.3 to 4% fecal pool prevalence. Herds with both areas having a heavy load of bacteria were estimated to have 53 to 73% fecal pool prevalence. The study results indicate that targeted sampling of cow alleyways and manure storage areas appears to be an alternative strategy for herd screening and Johne's infection status assessment and for estimating herd fecal prevalence. [ABSTRACT FROM AUTHOR]

Automated calf feeding systems are becoming more common on US dairy farms. The objective of this study was to evaluate calf health in these systems and to identify risk factors associated with adverse health outcomes on farms in the Upper Midwest United States. Over an 18-mo period on bimonthly farm visits to 38 farms, calves (n = 10,179) were scored for attitude, ear, eye, and nasal health, as well as evidence of diarrhea (hide dirtiness score of perianal region, underside of the tail, and tailhead). For all health score categories, a score of 0 represented an apparently healthy animal. Rectal temperatures were taken in calves scoring a ≥2 in any category, and those with a temperature >39.4°C were categorized as having a fever (n = 550). Associations were determined between farm-level variables and health scores to identify risk factors for higher (worse) scores. All health outcomes were associated with season of measurement, with fall and winter seasons increasing the odds of a high health score or detected fever. High bacterial counts measured in the milk or milk replacer were associated with increased odds for higher attitude and ear scores, and higher odds for calves having a detected fever. Higher peak milk allowance (L/d) was associated with lower hide dirtiness score, whereas a longer period of time (d) to reach peak milk allowance was associated with increased odds of higher scores for attitude, ear, eye, and hide dirtiness, as well as fever. Higher fat content in milk was associated with increased odds of high eye score. Less space per calf (m²/calf) was associated with higher ear and eye scores, whereas larger group sizes were associated with increased odds of higher nasal score and decreased odds of higher hide dirtiness score. Rectangular pen shape was associated with decreased odds of higher eye score. Absence of a positive pressure ventilation tube was associated with increased odds of having a calf detected with a fever. Based on these results, we hypothesize that these factors could be managed to improve health outcomes for dairy calves on automated feeding systems. [ABSTRACT FROM AUTHOR]

Little information is available about current practices around calving in dairy cattle. The aim of this study was to describe calving management practices in the Canadian dairy industry related to housing, calving protocols, monitoring of parturition, and calving assistance. Information was gathered by in-person interviews from 236 dairy farms from 3 Canadian provinces (Alberta, Ontario, and Québec) with freestalls and an automatic milking system (n = 24), freestalls with a parlor (n = 112), and tiestalls (n = 100). The most commonly used types of calving facilities were group calving pens (35%) followed by individual calving pens (30%). Tiestalls were used by 26% of all surveyed producers as their main type of calving area (49% of the tiestall, 7% of the freestall with parlor, and 13% of the automatic milking system farms). Written protocols related to calving were found on only 7% of the farms visited, and only 50% of those protocols were developed with a veterinarian. However, 90% of producers kept written records of calving difficulty. Monitoring of cows around calving occurred 5 times more often during the daytime (between morning and evening milking) compared with nighttime. Cameras were used to monitor cows around and during calvings on 18% of farms. Sixteen percent of producers vaginally palpated all animals during calving. Twenty-seven percent of producers interviewed assisted all calvings on their farms by pulling the calf, and 37% assisted all heifers at calving. According to the producers' reported perception, 93% of them had "a minor problem" or "no problem" with calving difficulties on their farms. This study provides basic data on current calving practices and identifies areas for improvement and potential targets for knowledge transfer efforts or research to clarify best management practices. [ABSTRACT FROM AUTHOR]

The objective of this cohort study was to investigate animal welfare in 2 newer dairy housing options in the upper Midwest, cross-ventilated freestall barns (CV) and compost-bedded-pack barns (CB), compared with conventional, naturally ventilated freestall barns (NV). The study was conducted on 18 commercial dairy farms, 6 of each housing type, in Minnesota and eastern South Dakota. The primary breed in all farms was Holstein; 1 CV and 1 NV herd had approximately 30% Jersey-Holstein crossbreds. All freestall herds used sand for bedding. Farms were visited 4 times (once in each season) between January and November 2008, and approximately 93% of all animals in each pen were visually scored on each visit. Outcome-based measurements of welfare (locomotion, hock lesions, body condition score, hygiene, respiration rates, mortality, and mastitis prevalence) were collected on each farm. Lameness prevalence (proportion of cows with locomotion score ≥3 on a 1 to 5 scale, where 1 = normal and 5 = severely lame) in CB barns (4.4%) was lower than that in NV (15.9%) and CV (13.1%) barns. Lameness prevalence was similar between CV and NV barns. Hock lesion prevalence (proportion of cows with a lesion score ≥2 on a 1 to 3 scale, where 1 = normal, 2 = hair loss, and 3 = swelling) was lower in CB barns (3.8%) than in CV (31.2%) and NV barns (23.9%). Hygiene scores (1 to 5 scale, where 1 = clean and 5 = very dirty) were higher for CB (3.18) than CV (2.83) and NV (2.77) barns, with no differences between CV and NV barns. Body condition scores, respiration rates, mastitis prevalence, culling, and mortality rates did not differ among housing systems. The CV and NV barns were evaluated using the cow comfort index (proportion of cows lying down in a stall divided by all animals touching a stall) and the stall usage index (proportion of cows lying divided by all animals in the pen not eating). The CV barns tended to have greater cow comfort index (85.9%) than the NV barns (81.4%) and had greater stall usage index (76.8% and 71.5%, respectively). Dairy cattle housed in CB barns had reduced lameness and hock lesions compared with those housed in freestall barns and had no adverse associations with body condition, respiration rates, mastitis prevalence, culling, or mortality. When comparing the 2 freestall housing options, CV barns had improved cow comfort indices compared with NV barns. Although cows in CB barns had better feet and leg health, as indicated by the reduced lameness and hock lesion prevalence, acquiring bedding and managing the bedded pack could limit their use. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of an injection of 10% butaphosphan and cyanocobalamin (Catosal, Bayer, Shawnee Mission, KS) on the day of calving and 1 d later on the prevalence of subclinical ketosis in dairy cattle in the early postpartum period. Cows from 4 herds (n = 1,122) were randomized to receive either 25 mL of 10% butaphosphan and cyanocobalamin or 25 mL of sterile water subcutaneously on both days. Each milliliter of Catosal contained 0.05 mg of cyanocobalamin and 100 mg of butaphosphan, which provided 17.3 mg of P in the form of [1-(butylamino)-1- methylethyl]-phosphonic acid. Serum was sampled for β-hydroxybutyrate (BHBA) concentration at calving (pretreatment) and again between 3 and 10 d in milk. A subset of samples from mature cows was also evaluated for serum Ca and P concentrations. When cows from all age groups were included in the analysis, there was no difference between the median serum BHBA concentrations of cows in the 2 treatment groups, and no difference in the proportion of hyperketonemic cows (serum BHBA ⩾1,200 μmol/L) during the first week postpartum. When the analysis was restricted to mature cows (lactation ⩾3), both the median BHBA concentration and the proportion of hyperketonemic cows were significantly lower in the treatment group than in the placebo group. Serum Ca and P concentrations did not differ between treatment groups. Our results suggest that injection of butaphosphan and cyanocobalamin on the day of calving and 1 d later may decrease the prevalence of subclinical ketosis during the week after calving in mature dairy cows, but not in first- and second-lactation animals. [ABSTRACT FROM AUTHOR]

We trained machine learning models to identify intramammary infections (IMI) in late lactation cows at dry-off to guide antibiotic treatment, and compared their performance to a rule-based algorithm that is currently used on dairy farms in the US. We conducted an observational test-characteristics study using a data set of 3,645 cows approaching dry-off from 68 US dairy herds. The outcome variables of interest were cow-level IMI caused by all pathogens, major pathogens, and Streptococcus and Strep-like organisms (SSLO), which were determined using aerobic culture of aseptic quarter-milk samples and identification of isolates using MALDI-TOF. Individual cow records were extracted from the farm software to create 53 feature variables at the cow and 39 at the herd-level which were derived from cow-level descriptive data, records of clinical mastitis events, results from routine testing of milk for volume and concentrations of somatic cell count (SCC), fat, and protein. ML algorithms evaluated were logistic regression, decision tree, random forest, light gradient-boosting machine, naïve bayes, and neural networks. For comparison, cows were also classified according to a conventional rule-based algorithm that considered a cow as high risk for IMI if she had at one or more high SCC (>200,000 cells/ml) tests or ≥2 cases of clinical mastitis during the lactation of enrollment. Area under the curve (AUC) and Youden's index were used to compare models, in addition to binary classification metrics, including sensitivity, specificity, and predictive values. ML models had slightly higher AUC and Youden's index values than the rule-based algorithm for all IMI outcomes of interest. However, these improvements in prediction accuracy were substantially less than what we had considered necessary for the technology to be a worthwhile alternative to the rule-based algorithm. Therefore, evidence is lacking to support the wholesale use of ML-guided selective dry cow therapy at the moment. We recommend that producers wanting to implement algorithm-guided SDCT use a rule-based method., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Acidogenic boluses can mitigate potential negative effects of high milk yield at dry-off on udder health. This randomized controlled trial aimed to investigate the effect of administering acidogenic boluses at dry-off on dry period intramammary infection (IMI) dynamics and on milk production parameters, somatic cell count linear score (LSCC), clinical mastitis (CM), and herd removal in the next lactation. A total of 901 cows from 3 dairy farms were randomly allocated to a control (CON, n = 458; no administration of acidogenic boluses at dry-off) or treatment group (TRT, n = 443; administration of 2 acidogenic boluses at dry-off). Quarter milk samples were collected at dry-off and after calving and submitted for bacteriological milk culture. The effects of treatment on the presence of quarter-level postpartum IMI, cure of existing IMI, and acquisition of new IMI, and on the prevalence of cow-level high LSCC (LSCC ≥4) in the first 30 days in milk (DIM) were analyzed using mixed effects logistic regression. Mixed linear regression was used to analyze cow-level milk production parameters (i.e., milk yield, fat corrected milk, fat and protein yield, and LSCC) in the first 90 DIM and until 300 DIM. For CM and herd removal, Cox proportional hazard regression models were used. In addition to treatment group, lactation group at dry-off, presence of high LSCC in the last test-day, average milk yield in the week before dry-off, presence of CM in the lactation of enrollment, and biologically relevant interactions were offered in all models. There was no evidence of a difference in IMI dynamics or in milk, fat corrected milk, protein or fat yields in the subsequent lactation between groups. The TRT group had a lower LSCC in the first 2 mo postpartum compared with the CON group (2.58 ± 0.3 vs. 2.92 ± 0.3 and 2.42 ± 0.3 vs. 2.81 ± 0.3, for first and second month postpartum). The prevalence of high LSCC in the first 30 DIM was 9.1% lower in the TRT compared with the CON group (16.3% vs. 25.5%; risk difference: -9.2; 95% confidence interval [CI]: -15.8, -2.5). Cows in the TRT group exhibited reduced hazards of CM in the subsequent lactation compared with cows in the CON group (hazard ratio: 0.75; 95% CI: 0.63, 0.89) as well as a reduced hazard of herd removal (hazard ratio: 0.82, 95% CI: 0.77, 0.88). The administration of acidogenic boluses as a component of dry-off management is a promising approach to maintain good udder health and reduce the hazard of CM and herd removal during the subsequent lactation., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Blanket dry cow therapy (DCT) is a major contributor to overall antibiotic usage on dairy farms in the United States. With low prevalence of intramammary infections at dry-off in US herds today, alternative DCT approaches have been the focus of much research. We hypothesized that complete cessation of DCT [i.e., use of internal teat sealants (ITS) only at dry-off] could be a practical alternative to blanket DCT in well-managed herds. The objective of this negatively controlled clinical trial was to determine the effects of DCT on clinical mastitis (CM) and removal from the herd during the dry period and the first 200 d of the subsequent lactation in multiparous dairy cows treated with only ITS at dry-off. As a secondary objective, we conducted exploratory analysis to identify subpopulations in the herd (based on parity, previous CM history, and dry-period length) where DCT would not affect postcalving udder health, to generate hypotheses about potential alternative selective DCT programs. The study was conducted in a commercial dairy herd in South Dakota from June 2020 to January 2021. Dry-off sessions (n = 43) were scheduled such that all cows at a given session were dried off using ITS alone (ITS only, n = 20 sessions, n = 1,108 cows) or an intramammary DCT product containing 500 mg of cloxacillin (Dry-Clox, Boehringer Ingelheim) followed by ITS (ITS+ABX, n = 23 sessions, n = 1,331 cows). Culling and CM events were recorded by farm workers who were blinded to the treatment status of cows. Hazard ratios (HR) for the effects of the treatment group on CM and removal from the herd were estimated using multivariable Cox proportional hazards, adjusting for the clustered treatment allocation strategy. Risk of removal from the herd during the dry period was lower in ITS+ABX than ITS-only cows (1.1 vs. 2.7%; HR = 0.45; 95% CI: 0.25 to 0.81). Risk of removal from the herd during the first 200 d of lactation was similar in ITS+ABX and ITS-only cows (17.3 vs. 18.0%; HR = 0.98; 95% CI: 0.82 to 1.18). Risk of CM during the first 200 d of lactation was lower in ITS+ABX cows (6.9%; HR = 0.56; 95% CI: 0.41 to 0.76) compared with ITS-only cows (13.4%). The beneficial effects of DCT on CM and removal from the herd were consistently observed across strata of parity, previous CM history, and dry-period length, indicating that no subpopulations could be identified to withhold DCT. The findings from this study indicate that the omission of DCT from the dry-off procedure, when udder health is not taken into consideration, in multiparous cows can have a negative effect on cow health and welfare. Findings from previous research suggest that culture- or algorithm-guided selective dry cow therapy are likely to be safer approaches to improving antibiotic stewardship., (© 2023, The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Elevated milk production at dry-off can lead to increased udder pressure and, in turn, increased stress due to pain and discomfort, affecting natural behaviors. Administering acidogenic boluses at dry-off acts by inducing temporary and mild decreases in blood pH. This decreases dry matter intake, reduces milk yield, and increases cow comfort by lessening udder pressure. The objective of this study was to assess the effect of oral administration of acidogenic boluses at dry-off on total daily activity (TDA) and total daily rumination (TDR) behaviors in the first 2 wk of the dry period. This randomized clinical trial was conducted on a single farm and cows were randomly assigned to either treatment (TRT; n = 30) or control (CON; n = 34). The TRT group received 2 acidogenic boluses at dry-off and the CON group received no intervention. All cows received dry-cow therapy (intramammary antibiotic and internal teat sealant). The TDA and TDR data from 7 d before to 14 d after dry-off were measured using ear-mounted activity monitors. Analyses were performed using linear mixed-effects models with repeated measures. We observed a similar TDA in both groups throughout the study follow-up period. Overall, cows in the TRT group spent 17 min/d less time active than cows in the CON group in the first 2 wk after dry-off with the greatest difference observed on the second day of the dry period (TRT = 395 min/d; 95% CI: 370 to 420 vs. CON = 428 min/d; 95% CI: 404 to 451). The TRT group had lower TDR in the first 24 h after bolus administration (TRT = 437 min/d; 95% CI: 414 to 461 vs. CON = 488 min/d; 95% CI: 466 to 510) when compared with the CON group, but no differences were observed when comparing both groups in the 13 subsequent days. Our results indicate that administering acidogenic boluses at dry-off slightly decreased TDA during the first 2 wk of the dry period and decreased TDR on the first day after administration., (© 2023.)

Teat sealants (TSs) consist of sterile formulations with no antibacterial activity. Alone or in combination with antimicrobial (AM) or non-AM treatments, TSs have been commonly used in dairy cows at dry-off to prevent intra-mammary infections (IMIs) during the dry period. This study aimed to identify and synthesise the available evidence on the efficacy of combining TSs with AM treatments on the incidence and prevalence of IMIs. A comprehensive search of three electronic databases, two relevant conference proceedings, and reference lists of reviews and eligible articles was conducted to retrieve and identify studies that could answer the following question: in dairy cows, how does the efficacy of an AM-TS combination administered at dry-off compare with an AM alone for preventing new IMI? In addition to the general IMIs, bacterial species-specific data were extracted and combined into nine distinct pathogen groups: coagulase-positive and negative staphylococci; S. dysgalactiae; non-dysgalactiae Streptococci; E. coli; non-E. coli Enterobacteriaceae; Corynebacterium spp.; yeast and other frequent mastitis pathogens. The structural relationship between each study's prevalence and incidence, as the new (incidence) and persistent (uncured) infections make up the prevalence, was utilised to approximate a variance-covariance matrix for the within-study correlation between their study-specific log odds ratios (ORs). A bivariate random-effects meta-analysis was employed, utilising the within- and between-study correlations to synthesise both outcomes simultaneously. The risk of bias was assessed using the Cochrane ROBINS-I tool, and the quality of the body of evidence was rated using the GRADE approach. A total of 17 trials (16 studies), providing either IMIs incidence (n = 4), prevalence (n = 3) or both (n = 10), were identified. Overall, quarters infused with AM-TS combinations showed lower odds of new IMIs post-calving (OR=0.70; 95% CI=0.57-0.86; Wald test P < 0.001) than those which received only AMs. Across the pathogen groups, varying levels of reduction of new IMIs were found, where administration of TSs was most effective against S. dysgalactiae (OR=0.47; 95% CI=0.23-0.98), non-dysgalactiae streptococci (OR=0.60; 95% CI=0.49-0.74), E. coli (OR=0.62; 95% CI=0.50-0.77), Corynebacterium spp. (OR=0.68; 95% CI=0.52-0.90) and coagulase-negative staphylococci (OR=0.85; 95% CI=0.76-0.94). However, additional TS infusion did not significantly reduce new IMIs in the remaining pathogen groups. The current meta-analytic evidence supports the efficacy of using TS add-on infusions in dairy cows at dry-off for reducing the incidence and prevalence of IMIs post-calving; however, pathogen group differences should be considered., Competing Interests: Declarations of interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Antibiotic stewardship on dairy farms can be heightened through the implementation of selective dry-cow therapy (SDCT). However, some producers are concerned that this practice may be related to poor udder health outcomes in cows with high milk production at the time of dry-off. The objective of this study was to evaluate if the effect of culture-guided SDCT (Cult-SDCT) and algorithm-guided SDCT (Alg-SDCT) on dry-period intramammary infection (IMI) dynamics and postcalving udder health and performance [when compared with blanket dry-cow therapy (BDCT)] varied according to milk production level before dry-off. Data were compiled from clinical trials conducted in the United States and Canada that compared Cult-SDCT and Alg-SDCT to a positive control, i.e., BDCT. In those trials, cows were enrolled 1-2 d before dry-off, randomized to their dry-cow therapy strategy and followed until 120 d in milk of the subsequent lactation. The number of cows and quarters in the final data set were 1,485 and 5,097, respectively. Measured outcomes included quarter-level antibiotic use at dry-off, quarter-level IMI prevalence after calving, quarter-level dry-period IMI cure risk, quarter-level dry-period new IMI risk, cow-level clinical mastitis and removal from the herd during 1-120 d in milk, and somatic cell count and milk yield during 1-120 DIM. The primary objective of analysis was to investigate if the effect of Cult-SDCT and Alg-SDCT on these outcomes, when compared with BDCT, varied according to milk production level before dry-off. To do this, each cow was classified as having low, mid or high production, based on her milk yield tertile group at the most recent herd test before enrollment (low: <23.7 kg/d, mid: 23.7 to 30.4 kg/d, and high >30.4 kg/d). Multivariable generalized estimating equations were used to estimate risk differences and differences in means, and Cox regression was used to estimate hazard ratios. For Cult-SDCT, the proportion of quarters treated with dry-cow antibiotics within each milk production level were 40.7% (low), 41.7% (mid) and 47.2% (high). For Alg-SDCT, the proportions were 60.6% (low), 38.7% (mid), and 35.1% (high). Measures of udder health were not markedly different when comparing Cult-SDCT to BDCT and Alg-SDCT to BDCT. This was consistently observed in low, mid and high producing cows. In conclusion, the findings from this study indicate that Cult-SDCT and Alg-SDCT can be successfully implemented in cows of all milk production levels., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry provides accurate species-level identification of many, microorganisms retrieved from bovine milk samples. However, not all those microorganisms are pathogenic. Our study aimed to: (1) determine the species-specific prevalence of microorganisms identified in bovine milk of apparently healthy lactating quarters vs. quarters with clinical mastitis (CM); and (2) map current information and knowledge gaps on udder health relevance of microorganisms retrieved from bovine milk samples. A mixed study design (meta-analysis and mapping review) was chosen. We gathered several large Canadian, US and Brazilian data sets of MALDI-TOF results for organisms cultured from quarter milk samples. For meta-analysis, two datasets (apparently healthy quarters vs. CM samples) were organized. A series of meta-analyses was conducted to determine microorganisms' prevalence. Then, each species reported was searched through PubMed to investigate whether inflammation (increased somatic cell count (SCC) or signs of CM) was associated with microorganism's recovery from milk. A total of 294 different species of microorganisms recovered from milk samples were identified. Among 50,429 quarter-milk samples from apparently healthy quarters, the 5 most frequent species were Staphylococcus chromogenes (6.7%, 95% CI 4.5-9.2%), Aerococcus viridans (1.6%, 95% CI 0.4-3.5%), Staphylococcus aureus (1.5%, 95% CI 0.5-2.8%), Staphylococcus haemolyticus (0.9%, 95% CI 0.4-1.5%), and Staphylococcus epidermidis (0.7%, 95% CI 0.2-1.6%). Among the 43,924 quarter-milk CM samples, the 5 most frequent species were Escherichia coli (11%, 95% CI 8.1-14.3%), Streptococcus uberis (8.5%, 95% CI 5.3-12.2%), Streptococcus dysgalactiae (7.8%, 95% CI 4.9-11.5%), Staphylococcus aureus (7.8%, 95% CI 4.4-11.9%), and Klebsiella pneumoniae (5.6%, 95% CI 3.4-8.2%). When conducting the PubMed literature search, there were 206 species identified by MALDI-TOF for which we were not able to find any information regarding their association with CM or SCC. Some of them, however, were frequently isolated in our multi-country dataset from the milk of quarters with CM (e.g., Citrobacter koseri , Enterococcus saccharolyticus , Streptococcus gallolyticus ). Our study provides guidance to veterinarians for interpretation of milk bacteriology results obtained using MALDI-TOF and identifies knowledge gaps for future research.

Administering intramammary antimicrobials to all mammary quarters of dairy cows at drying-off [i.e., blanket dry cow therapy (BDCT)] has been a mainstay of mastitis prevention and control. However, as udder health has considerably improved over recent decades with reductions in intramammary infection prevalence at drying-off and the introduction of teat sealants, BDCT may no longer be necessary on all dairy farms, thereby supporting antimicrobial stewardship efforts. This narrative review summarizes available literature regarding current dry cow therapy practices and associated impacts of selective dry cow therapy (SDCT) on udder health, milk production, economics, antimicrobial use, and antimicrobial resistance. Various methods to identify infections at drying-off that could benefit from antimicrobial treatment are described for selecting cows or mammary quarters for treatment, including utilizing somatic cell count thresholds, pathogen identification, previous clinical mastitis history, or a combination of criteria. Selection methods may be enacted at the herd, cow, or quarter levels. Producers' and veterinarians' motivations for antimicrobial use are discussed. Based on review findings, SDCT can be adopted without negative consequences for udder health and milk production, and concurrent teat sealant use is recommended, especially in udder quarters receiving no intramammary antimicrobials. Furthermore, herd selection should be considered for SDCT implementation in addition to cow or quarter selection, as BDCT may still be temporarily necessary in some herds for optimal mastitis control. Costs and benefits of SDCT vary among herds, whereas impacts on antimicrobial resistance remain unclear. In summary, SDCT is a viable management option for maintaining udder health and milk production while improving antimicrobial stewardship in the dairy industry., (© 2022, The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

The objective of this observational study was to compare 4 cow-level algorithms to predict cow-level intramammary infection (IMI) status (culture and MALDI-TOF) in late-lactation US dairy cows using standard measures of test performance. Secondary objectives were to estimate the likely effect of each algorithm, if used to guide selective dry cow therapy (SDCT), on dry cow antibiotic use in US dairy herds, and to investigate the importance of including clinical mastitis criteria in algorithm-guided SDCT. Cows (n = 1,594) from 56 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each farm visit, aseptic quarter-milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status, which was considered the reference test in this study. Clinical mastitis records and Dairy Herd Improvement Association test-day somatic cell count data were extracted from herd records and used to perform cow-level risk assessments (low vs. high risk) using 4 algorithms that have been proposed for SDCT in New Zealand, the Netherlands, United Kingdom, and the United States. Agreement between aerobic culture (reference test; IMI vs. no-IMI) and algorithm status (high vs. low risk) was described using Cohen's kappa, test sensitivity, specificity, negative predictive value, and positive predictive value. The proportion of cows classified as high risk among the 4 algorithms ranged from 0.31 to 0.63, indicating that these approaches to SDCT could reduce antibiotic use at dry-off by 37 to 69% in the average US herd. All algorithms had poor agreement with IMI status, with kappa values ranging from 0.05 to 0.13. Sensitivity varied by pathogen, with higher values observed when detecting IMI caused by Streptococcus uberis, Streptococcus dysgalactiae, Staphylococcus aureus, and Lactococcus lactis. Negative predictive values were high for major pathogens among all algorithms (≥0.87), which may explain why algorithm-guided SDCT programs have been successfully implemented in field trials, despite poor agreement with overall IMI status. Removal of clinical mastitis criteria for each algorithm had little effect on the algorithm classification of cows, indicating that algorithms based on SCC alone may have similar performance to those based on SCC and clinical mastitis criteria. We recommend that producers implementing algorithm-guided SDCT use algorithm criteria that matches their relative aspirations for reducing antibiotic use (high specificity, positive predictive value) or minimizing untreated IMI at dry-off (high sensitivity, negative predictive value)., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objectives of this study were to (1) use partial budget analysis to estimate the cash impact for herds that switch from blanket dry cow therapy (BDCT) to culture- or algorithm-guided selective dry cow therapy (SDCT) and (2) conduct a sensitivity analysis to investigate effects in situations where SDCT increased clinical and subclinical mastitis risk during the subsequent lactation. A partial budget model was created using Monte Carlo simulation with @Risk software. Expenditures associated with dry-off procedures and health outcomes (clinical and subclinical mastitis) during the first 30 d in milk were used to model herd-level effects, expressed in units of US dollars per cow dry-off. Values for each economic component were derived from findings from a recent multisite clinical trial, peer-reviewed journal articles, USDA databases, and our experiences in facilitating the implementation of SDCT on farms. Fixed values were used for variables expected to have minimal variation within the US dairy herd population (e.g., cost of rapid culture plates) and sampling distributions were used for variables that were hypothesized to vary enough to effect the herd net cash impact of one or more DCT approach(es). For Objective 1, herd-level udder health was assumed to be unaffected by the implementation of SDCT. For culture-guided SDCT, producers could expect to save an average of +$2.14 (-$2.31 to $7.23 for 5th and 95th percentiles) per cow dry-off as compared with BDCT, with 75.5% of iterations being ≥$0.00. For algorithm-guided SDCT, the mean net cash impact was +$7.85 ($3.39-12.90) per cow dry-off, with 100% of iterations being ≥$0.00. The major contributors to variance in cash impact for both SDCT approaches were percent of quarters treated at dry-off and the cost of dry cow antibiotics. For Objective 2, we repeated the partial budget model with the 30-d clinical and subclinical mastitis incidence increasing by 1, 2, and 5% (i.e., risk difference = 0.01, 0.02, and 0.05) in both SDCT groups compared with BDCT. For algorithm-guided SDCT, average net cash impacts were ≥$0.00 per cow dry-off (i.e., cost effective) when mastitis incidence increased slightly. However, as clinical mastitis incidence increased, economic returns for SDCT diminished. These findings indicate that when SDCT is implemented appropriately (i.e., no to little negative effect on health), it might be a cost-effective practice for US herds under a range of economic conditions., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this prospective cohort study was to explore associations between intramammary infection (IMI) in late-lactation cows and postcalving udder health and productivity. Cows (n = 2,763) from 74 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each visit, aseptic quarter milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status at enrollment. Cows were followed from enrollment until 120 d in milk (DIM) in the subsequent lactation. Herd records were used to establish whether subjects experienced clinical mastitis or removal from the herd, and DHIA test-day data were used to record subclinical mastitis events (somatic cell count >200,000 cells/mL) and milk yield (kg/d) during the follow-up period. Cox regression and generalized estimating equations were used to evaluate the associations between IMI and the outcome of interest. The presence of late-lactation IMI caused by major pathogens was positively associated with postcalving clinical mastitis [hazard ratio = 1.5, 95% confidence interval (CI): 1.2, 2.0] and subclinical mastitis (risk ratio = 1.5, 95% CI: 1.3, 1.9). Species within the non-aureus Staphylococcus (NAS) group varied in their associations with postcalving udder health, with some species being associated with increases in clinical and subclinical mastitis in the subsequent lactation. Late-lactation IMI caused by Streptococcus and Streptococcus (Strep)-like organisms, other than Aerococcus spp. (i.e., Enterococcus, Lactococcus, and Streptococcus spp.) were associated with increases in postcalving clinical and subclinical mastitis. Test-day milk yield from 1 to 120 DIM was lower (-0.9 kg, 95% CI: -1.6, -0.3) in late-lactation cows with any IMI compared with cows without IMI. No associations were detected between IMI in late lactation and risk for postcalving removal from the herd within the first 120 DIM. Effect estimates reported in this study may be less than the underlying quarter-level effect size for IMI at dry-off and postcalving clinical and subclinical mastitis, because of the use of late-lactation IMI as a proxy for IMI at dry-off and the use of cow-level exposure and outcome measurements. Furthermore, the large number of models run in this study (n = 94) increases the chance of identifying chance associations. Therefore, confirmatory studies should be conducted. We conclude that IMI in late lactation may increase risk of clinical and subclinical mastitis in the subsequent lactation. The relationship between IMI and postcalving health and productivity is likely to vary among pathogens, with Staphylococcus aureus, Streptococcus spp., Enterococcus spp., and Lactococcus spp. being the most important pathogens identified in the current study., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing. However, there is little evidence to suggest that pair-housed calves maintain their social and growth advantages past the weaning phase. The objective of this study was to investigate the effect of pair housing on measures of calf performance, health, and behavior up to 16 wk of age. Healthy Holstein and crossbred heifer calves were enrolled in the study after colostrum feeding, with the first calf randomly assigned to 1 of 2 housing treatments: pair (PR; 2 hutches with common outdoor space) or individual (INDV; 1 hutch plus outdoor space). All calves were bucket fed 4 L of milk replacer twice daily and weaned at 50 d of age. Weaned calves (6/group) remained with their treatment group until exit from the study at 16 wk. A venous blood sample was collected from each calf between 24 h and 7 d of age to test for serum total protein (g/dL). Body weights (kg) were obtained at birth, weaning, and 16 wk. Each enrolled calf was scored for health each week and calf health treatments were also collected. A hair sample was collected from the left shoulder at birth and 16 wk to assess hair cortisol (pg/mL). At enrollment, each calf was fitted with a triaxial accelerometer on the left hind leg for continuous recording of standing and lying time (min/24 h) for 16 wk. Latency to find feed, water, and lie down (min) at entrance to the weaned pen were recorded by continuous video observation. Open field testing with a novel object was performed at 5, 10, and 16 wk. Behaviors analyzed by video observation included latency to approach the object (s), vocalizations (n), and time spent immobile, walking, or running (s/10 min). Linear mixed models were used to determine the effect of treatment (INDV or PR) on calf growth, activity, and behavioral outcomes, which accounted for time, breed, the interaction of time and treatment, the random pen, and variability in testing day and repeated measurements within calf when appropriate. Twenty-four Holstein and crossbred calves (PR: n = 12, 6 pairs; INDV: n = 12) were enrolled from November 2 to December 23, 2018. The PR calves were 7.1 kg heavier at weaning and gained 0.15 kg/d more during the preweaning period as compared with INDV calves. In the 24 h after movement to the postweaning pen, PR calves lay down for longer periods of time (14.3 vs. 11.0 ± 0.4 h/d), and PR calves urinated more during novel object testing at 5 wk of age. Our study demonstrated benefits, such as better growth and increased lying time, of pair housing calves during the preweaning period., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Selective dry-cow therapy (SDCT) could be used to reduce antibiotic use on commercial dairy farms in the United States but is not yet widely adopted, possibly due to concerns about the potential for negative effects on cow health. The objective of this study was to compare culture- and algorithm-guided SDCT programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure, non-inferiority trial for the following quarter-level outcomes: antibiotic use at dry-off, dry period intramammary infection (IMI) cure risk, dry period new IMI risk, and IMI risk at 1 to 13 d in milk (DIM). Two days before planned dry-off, cows in each of 7 herds were randomly allocated to BDCT, culture-guided SDCT (cult-SDCT), or algorithm-guided SDCT (alg-SDCT). At dry-off, BDCT cows received an intramammary antibiotic (500 mg of ceftiofur hydrochloride) in all 4 quarters. Antibiotic treatments were selectively allocated to quarters of cult-SDCT cows by treating only quarters from which aseptically collected milk samples tested positive on the Minnesota Easy 4Cast plate (University of Minnesota, St. Paul, MN) after 30 to 40 h of incubation. For alg-SDCT cows, antibiotic treatments were selectively allocated at the cow level, with all quarters receiving antibiotic treatment if the cow had either a Dairy Herd Improvement Association test somatic cell count >200,000 cells/mL during the current lactation or 2 or more clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods. The effect of treatment group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic), with marginal standardization to derive risk difference (RD) estimates. Quarter-level antibiotic use at dry-off for each group was BDCT (100%), cult-SDCT (45%), and alg-SDCT (45%). The crude dry period IMI cure risk for all quarters was 87.5% (818/935), the crude dry period new IMI risk was 20.1% (764/3,794), and the prevalence of IMI at 1 to 13 DIM was 23% (961/4,173). Non-inferiority analysis indicated that culture- and algorithm-guided SDCT approaches performed at least as well as BDCT for dry period IMI cure risk. In addition, the final models indicated that the risks for each of the 3 IMI measures were similar between all 3 treatment groups (i.e., RD estimates and 95% confidence intervals all close to 0). These findings indicate that under the conditions of this trial, culture- and algorithm-guided SDCT can substantially reduce antibiotic use at dry-off without negatively affecting IMI dynamics., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to compare culture- and algorithm-guided selective dry-cow therapy (SDCT) programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure clinical trial for the following cow-level outcomes: clinical mastitis, removal from the herd, and Dairy Herd Improvement Association (DHIA) test-day milk yield and SCC measures during the first 120 d in milk (DIM). Two days before planned dry-off, cows in each of 7 herds were randomly allocated to BDCT, culture-guided SDCT (cult-SDCT), or algorithm-guided SDCT (alg-SDCT). At dry-off, BDCT cows received an intramammary antibiotic (500 mg of ceftiofur hydrochloride) in all 4 quarters. Antibiotic treatments were selectively allocated to quarters of cult-SDCT cows by only treating quarters from which aseptically collected milk samples tested positive on a rapid culture system after 30 to 40 h of incubation. For alg-SDCT cows, antibiotic treatments were selectively allocated at the cow level, with all quarters receiving antibiotic treatment if the cow met at least one of the following criteria: (1) any DHIA test with a somatic cell count >200,000 cells/mL during the current lactation, and (2) ≥2 clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Clinical mastitis and removal from the herd events (i.e., culling or death) and DHIA test-day data from dry-off to 120 DIM were extracted from herd records. Hazard ratios (HR) for the effect of treatment group on clinical mastitis and removal from the herd during 1 to 120 DIM were determined using Cox proportional hazards regression. The effects of treatment group on test-day log e -transformed SCC and milk yield were determined using linear mixed models. Final models indicated that either SDCT program was unlikely to increase clinical mastitis risk (HR cult-SDCT/BDCT = 0.82, 95% CI: 0.58, 1.15; HR alg-SDCT/BDCT = 0.83, 95% CI: 0.63, 1.09) or test-day log e SCC (cult-SDCT minus BDCT = 0.05, 95% CI: -0.09, 0.18; alg-SDCT minus BDCT = 0.07, 95% CI: -0.07, 0.21). Risk of removal from the herd and test-day milk yield were similar between treatment groups. Findings from this study indicate that culture- or algorithm-guided SDCT can be used at dry-off without negatively affecting cow health and performance in early lactation., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The need for consortial programs to provide advanced education in food animal veterinary production medicine has been recognized and lauded for nearly three decades. This article describes one effort to create a dairy production medicine curriculum funded by a United States Department of Agriculture (USDA) Higher Education Challenge Grant. This National Center of Excellence in Dairy Production Medicine Education for Veterinarians is housed at the Dairy Education Center of the University of Minnesota and the project was a collaboration of the University of Minnesota, the University of Illinois, the University of Georgia, and Kansas State University. The article reviews the need for innovative ways to educate students who will optimally serve the dairy industry, provides a broad overview of the process of developing and delivering the eight-week dairy production medicine curriculum, and describes the challenges faced and lessons learned as a result of offering such a program.

Our objective was to compare four tests to standard milk culture followed by MALDI-ToF in quarters of cows at dry-off. Cows (n = 432) were randomly selected from seven U.S. dairy herds already participating in a multi-site clinical trial in summer 2018. Aseptic foremilk samples were collected from quarters (n = 1728) two days prior to dry-off, and subjected to index and reference tests. The four index tests included rapid culture, a predictive algorithm, an esterase strip test measuring somatic cell count (SCC) and a cow-side lactate dehydrogenase (LDH) test. Rapid culture was performed by inoculating quarter milk samples onto a commercial rapid culture plate. Plates were evaluated by technicians after 30-40 h of incubation at 37 ± 2 °C. Quarters were classified as infected if any bacterial growth was observed. For the algorithm test method, all quarters were classified as infected if the cow met any of the following criteria: 1) any Dairy Herd Improvement Association (DHIA) test with a SCC > 200,000 cells / ml during the current lactation or 2) two or more clinical mastitis cases during the current lactation. Esterase-SCC and cow-side LDH tests involved adding milk to the test strip and reading for color changes. For esterase-SCC and cow-side LDH tests, low (≥250 cells / ml and ≥100 U / L) and high (≥500 cells / ml and ≥200 U / L) thresholds were used to classify quarters as infected or not. Composite samples (4 × 2 mL quarter-milk samples commingled) were also tested for rapid culture, esterase-SCC and cow-side LDH tests, such that if a composite sample was positive, then all quarters contributing to that sample were classified as infected. The reference test was traditional aerobic culture conducted in an accredited laboratory using MALDI-ToF for identification of isolates. Traditional culture was only conducted on quarter-milk samples, and consequently, IMI was always considered at the quarter-level. Unconditional logistic regression was used to estimate sensitivity (SE), specificity (SP), apparent prevalence, positive predictive values (PPV) and negative predictive values (NPV) for each index test. Cohen's Kappa (κ) was used to measure agreement between tests. Algorithm, esterase-SCC and cow-side LDH tests had poor agreement with the reference test (κ ranging from 0.01 to 0.12), while rapid culture had fair agreement (κ = 0.28). No test had concurrently high SE and SP. Negative predictive values were moderate to high for all tests., Competing Interests: Declaration of Competing Interest The Minnesota Easy® 4Cast® plate is manufactured by the University of Minnesota (St. Paul, MN). However, the study investigators have no financial interest in the sale of this plate., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The use of an internal teat sealant (ITS) at dry-off has been repeatedly shown to improve udder health in the subsequent lactation. However, almost all ITS research conducted in North America has evaluated one product (Orbeseal, Zoetis, Parsippany, NJ). The objective of this study was to evaluate a new ITS product (Lockout, Boehringer-Ingelheim Animal Health, Duluth, GA), by comparing it directly to Orbeseal in a multi-site, randomized, positively controlled equivalence trial for health indicators during the dry period [quarter-level new intramammary infection (IMI) risk, IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM] and during the first 100 DIM [clinical mastitis and culling or death risk and test-day milk somatic cell count (SCC) and milk yield]. At dry-off, cows were randomly allocated to be treated with Orbeseal or Lockout after blanket administration of a cloxacillin dry cow therapy product. Cows were then followed from dry-off until 100 DIM. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods, allowing for the measurement of IMI dynamics during the dry period (i.e., IMI cures and new IMI). The effect of ITS group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic). Marginal standardization was used to derive risk difference estimates. An equivalence hypothesis test was conducted to compare ITS groups for dry period new IMI risk (margin of equivalence was ±5% units). The effect of ITS group on clinical mastitis and culling or death was determined using Cox proportional hazards regression. The effect of ITS group on test-day SCC and milk yield was determined using linear mixed models. Final models indicated that measures of quarter-level IMI dynamics were similar between ITS groups (i.e., risk difference estimates and 95% confidence intervals all close to zero). Furthermore, Lockout was found to be equivalent to Orbeseal for dry period new IMI risk using an equivalence hypothesis test. Hazard ratio estimates for clinical mastitis and culling or death were close to 1 and differences in SCC and milk yield between ITS groups were close to 0, indicating negligible effects of ITS group on test-day SCC and milk yield. In most cases, these effect estimates were relatively precise (i.e., narrow 95% confidence intervals). We conclude that producers using blanket dry cow therapy could consider including Orbeseal or Lockout treatment in their programs., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Objectives of this study were to (1) describe the intramammary infection (IMI) prevalence and pathogen profiles in quarters of cows approaching dry-off in US dairy herds, (2) compare IMI prevalence in quarters of cows exposed to different bedding material types, and (3) identify associations between bedding bacteria count and IMI in cows approaching dry-off. Eighty herds using 1 of 4 common bedding materials (manure solids, organic non-manure, new sand, and recycled sand) were recruited in a multi-site cross-sectional study. Each herd was visited twice for sampling. At each visit, aseptic quarter-milk samples were collected from 20 cows approaching dry-off (>180 d pregnant). Samples of unused and used bedding were also collected. Aerobic culture was used to determine the IMI status of 10,448 quarters and to enumerate counts (log 10 cfu/mL) of all bacteria, Staphylococcus spp., Streptococcus spp. and Streptococcus-like organisms (SSLO), coliforms, Klebsiella spp., noncoliform gram-negatives, Bacillus spp., and Prototheca spp. in unused (n = 148) and used (n = 150) bedding. The association between bedding bacteria count and IMI was determined using multivariable logistic regression with mixed effects. Quarter-level prevalence of IMI was 21.1%, which was primarily caused by non-aureus Staphylococcus spp. (11.4%) and SSLO (5.6%). Only modest differences in IMI prevalence were observed between the 4 common bedding material types. Counts of all bacteria in unused bedding was positively associated with odds of IMI caused by any pathogen [ALL-IMI; odds ratio (OR) = 1.08]. A positive association was also observed for counts of SSLO in unused bedding and SSLO-IMI (OR = 1.09). These patterns of association were generally consistent across the 4 common bedding materials. In contrast, the association between counts of all bacteria in used bedding and ALL-IMI varied by bedding type, with positive associations observed in quarters exposed to manure solids (OR = 2.29) and organic non-manure (OR = 1.51) and a negative association in quarters exposed to new sand (OR = 0.47). Findings from this study suggest that quarter-level IMI prevalence in late-lactation cows is low in US dairy herds. Furthermore, bedding material type may not be an important risk factor for IMI in late lactation. Higher levels of bacteria in bedding may increase IMI prevalence at dry-off in general, but this relationship is likely to vary according to bedding material type., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Because cloth udder towels (CUT) may function as a fomite for mastitis-causing pathogens, most udder health laboratories offer towel culture services as a tool to monitor towel hygiene. However, no studies have investigated if an association exists between bacteria levels in CUT and udder health outcomes. The objectives of this cross-sectional study were to (1) describe associations between herd-level measures of towel bacteria count (ToBC) and quarter-level intramammary infection (IMI) status in late-lactation cows, (2) establish pathogen-specific target levels of bacteria in CUT to aid the interpretation of towel culture reports, and (3) identify laundering-related risk factors for high ToBC. The study was conducted in 67 herds from 10 dairy states in the United States that used CUT. These 67 herds were originally recruited as part of a larger (80 herd) cross-sectional study of bedding management. Each herd was visited once during December 2017 to April 2018 and quarter-milk samples (n = 4,656) were collected from late-gestation (>180 d pregnant) cows (n = 1,313). Two recently laundered CUT were collected and a questionnaire was used to collect information about pre-milking teat preparation and CUT management practices. Quarter-level IMI status was determined using standard bacteriologic methods. In addition, colony-forming units of all bacteria (total bacteria), Staphylococcus spp., Streptococcus spp. or Streptococcus-like organisms (SSLO), coliforms, noncoliform gram-negatives, and Bacillus spp. were determined for each pair of CUT (log 10 cfu/cm 2 ). The association between ToBC and IMI was determined using multivariable logistic regression with mixed effects. After dichotomizing ToBC into high and low categories, associations between towel management practices and ToBC category were determined using unconditional logistic regression. The quarter-level prevalence of IMI was 19.6%, which was predominantly caused by non-aureus Staphylococcus spp. (NAS; 10.2%) and SSLO (5.1%). The predominant bacteria in CUT were Bacillus spp. (median = 3.13 log 10 cfu/cm 2 ). Total bacteria count was not associated with odds of IMI (odds ratio = 1.06), likely due to the predominance of Bacillus spp. in CUT and low number of IMI caused by Bacillus spp. In contrast, counts of Staphylococcus spp. and SSLO were positively associated with odds of IMI caused by NAS (odds ratio = 1.33) and SSLO (odds ratio = 1.45), respectively. Of 12 CUT management practices evaluated, only the failure to use a dryer was identified as a clear predictor of risk for a high ToBC (risk ratio of high coliform count = 8.17). Our study findings suggest that CUT may act as a fomite for NAS and SSLO. We recommend that herds aim to keep counts of Staphylococcus spp. and SSLO in CUT below 32 cfu/cm 2 (or 5 cfu/in 2 ), and that laundered towels be completely dried in a hot air dryer., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Bedding is an important source of teat end exposure to environmental mastitis pathogens. To better control environmental mastitis, we need an improved understanding of the relationships among bedding selection and management, bedding bacteria counts (BBC), and udder health (UH). The objectives of this cross-sectional observational study were (1) to describe BBC, bedding characteristics, udder hygiene scores, bulk tank milk (BTM) quality, and UH in US dairy herds using 1 of 4 bedding materials; (2) describe the relationship between BBC and herd measures of UH; and (3) identify benchmarks for monitoring bedding hygiene. Local dairy veterinarians and university researchers enrolled and sampled 168 herds from 17 states. Herds were on a Dairy Herd Improvement Association (DHIA) testing program and used 1 of 4 bedding types for lactating cows: new sand, reclaimed sand, manure solids (MNS), or organic non-manure materials. Each herd was sampled twice (winter and summer) in 2016. Samples and data collected included unused and used bedding, BTM samples, udder hygiene scores, DHIA test data, and descriptions of facilities and herd management practices. Bedding was cultured to determine the total bacteria count and counts of Bacillus spp., coliforms, Klebsiella spp., non-coliform gram-negative organisms, streptococci or streptococci-like organisms (SSLO), and Staphylococcus spp. Bedding dry matter, organic matter, and pH were also measured. Bulk tank milk samples were cultured to determine counts of coliforms, NAS, SSLO, Staphylococcus aureus, and Mycoplasma spp. Udder health measures included DHIA test-day average linear score (LS); the proportion of cows with an intramammary infection (IMI), where infection was defined as LS ≥4.0; the proportion of cows with a new IMI, where new IMI was defined as LS changing from <4.0 to ≥4.0 in the last 2 tests; the proportion of cows with a chronic infection, where chronic was defined as LS ≥4.0 on the last 2 tests; and the cumulative incidence of clinical mastitis in the 30-d period preceding sample collection. Although much variation existed within and among bedding types, mixed linear regression showed the use of MNS bedding to be generally associated with higher BBC, dirtier udders, increased coliform and SSLO counts in BTM, and poorer UH measures compared with organic non-manure materials, reclaimed sand, or new sand bedding materials. While controlling for important farm traits and management practices, mixed linear regression showed that increased counts of coliforms, Klebsiella spp., SSLO, and Staphylococcus spp. in both unused and used bedding were associated with poorer values for 1 or more herd-level measures of UH. Achievable benchmarks identified for counts of coliforms (unused: ≤500 cfu/cm 3 ; used: ≤10,000 cfu/cm 3 ), Klebsiella spp. (0 cfu/cm 3 for unused and used), Staphylococcus spp. (0 cfu/cm 3 for unused and used), and SSLO (unused: 0 cfu/cm 3 ; used: ≤500,000 cfu/cm 3 ) can be used to monitor bedding hygiene in most bedding materials, with minor variations suggested for SSLO in unused MNS (≤1,000 cfu/cm 3 )., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Mesophilic and thermophilic spore-forming bacteria represent a challenge to the dairy industry, as these bacteria are capable of surviving adverse conditions associated with processing and sanitation and eventually spoil dairy products. The dairy farm environment, including soil, manure, silage, and bedding, has been implicated as a source for spores in raw milk. High levels of spores have previously been isolated from bedding, and different bedding materials have been associated with spore levels in bulk tank (BT) raw milk; however, the effect of different bedding types, bedding management practices, and bedding spore levels on the variance of spore levels in BT raw milk has not been investigated. To this end, farm and bedding management surveys were administered and unused bedding, used bedding, and BT raw milk samples were collected from dairy farms (1 or 2 times per farm) across the United States over 1 yr; the final data set included 182 dairy farms in 18 states. Bedding suspensions and BT raw milk were spore pasteurized (80°C for 12 min), and mesophilic and thermophilic spores were enumerated. Piecewise structural equation modeling analysis was used to determine direct and indirect pathways of association among farm and bedding practices, levels of spores in unused and used bedding, and levels of spores in BT raw milk. Separate models were constructed for mesophilic and thermophilic spore levels. The analyses showed that bedding material had a direct influence on levels of spores in unused and used bedding as well as an indirect association with spore levels in BT raw milk through used bedding spore levels. Specific bedding and farm management practices as well as cow hygiene in the housing area were associated with mesophilic and thermophilic spore levels in unused bedding, used bedding, and BT raw milk. Notably, levels of spores in used bedding were positively related to those in unused bedding, and used bedding spore levels were positively related to those in BT raw milk. The results of this study increase the understanding of the levels and ecology of mesophilic and thermophilic spores in raw milk, emphasize the possible role of bedding as a source of spores on-farm, and present opportunities for dairy producers to reduce spore levels in BT raw milk., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Background: Coagulase negative Staphylococcus (CNS) species are currently the most prevalent intra-mammary pathogens causing subclinical mastitis and occasional clinical mastitis or persistent infection in lactating dairy cattle. More than 10 CNS species have been identified, but they are generally managed as one group on most dairies in the United States. However, improved management decisions and treatment outcomes may be achieved with better understanding of the prevalent species, pathogenicity and strain diversity within and across dairies., Methodology: A total of 604 CNS isolates were cultured from milk samples collected during a dry-cow treatment clinical trial conducted on 6 dairy herds in 4 states in the US. All the study cows were randomized to receive 1 of the 3 different intra-mammary antimicrobial infusions (Quatermaster, Spectramast DC or ToMorrow Dry Cow) at dry-off. Milk samples were collected at dry-off, calving (0-6 days in milk, DIM), post-calving (7-13 DIM) and at mastitis events within the first 100 DIM. The CNS isolates were identified to species level by partial sequencing of the rpoβ gene, and genetic relatedness within species was investigated by phylogenetic analysis of the pulse-field gel electrophoresis profiles of the isolates., Results: The major CNS species identified were S. chromogenes (48.3%), S. haemolyticus (17.9%), S. simulans and S. epidermidis (each at 6.5%). Other CNS species identified at lower frequencies included S. hominis , S. auricularis , S. sciuri , S. spp KS-SP, S. capitis , S. cohnii , S. warneri , S. pasteuri, S. xylosus, S. hyicus, S. equorum, S. microti, S. rostri, S. gallinarum, S. saprophyticus and S. succinus . Phylogenetic analyses of the major species types demonstrated an association between genetic relatedness and epidemiological distributions of S. chromogenes, S. simulans, S. haemolyticus and S. auricularis. Additionally, identical strains of S. chromogenes and S. simulans were isolated from the same udder quarter of several cows at consecutive sample stages. The rest of the minor species had no deducible genetic-epidemiological link., Discussion: The observed association between genetic and epidemiological distributions indicated animal-adapted nature of four CNS species, suggesting possible host-adapted and environmental transmission of these species. Multi-stage isolation of the same udder quarter strain was evidence for chronic intra-mammary infection., Conclusion: The different CNS species and strains circulating on US dairy herds were genetically diverse. Four species identified were likely udder-adapted pathogens, 2 of which caused persistent infection. Our findings are important in guiding the design of effective mastitis control strategies., Competing Interests: The authors declare there are no competing interests.

The majority of dairy heifer calves in the United States are destined to be dairy replacements. However, many dairy heifer and bull calves die before 6 mo of age. Of these calves, about 6% (more than 500,000 calves) die at birth or shortly after (i.e., currently termed "stillbirth"). An additional 6% of dairy heifers die during the preweaning period. Death loss in dairy calves is primarily due to stillbirths, failure to adapt to extrauterine life, and infectious disease processes. The reasons for preweaning heifer calf deaths caused by infectious diseases are generally categorized based on easily recognizable clinical signs such as digestive disease/scours or respiratory disease. Most causes of calf death can be mitigated by appropriate preventive care or well-tailored treatments, meaning that the typical death loss percentage could be decreased with better management. Producers could gather information on the circumstances near birth and at death if they had appropriate guidance on what details to record and monitor. This paper provides recommendations on data to collect at the time of birth (i.e., calf birth certificate data). The recording of these critical pieces of information is valuable in evaluating trends over time in morbidity and mortality events in dairy calves. Ideally, necropsy examination would substantially improve the identification of cause of death, but even without necropsy, attribution of cause of death can be improved by more carefully defining death loss categories in on-farm record systems. We propose a death loss categorization scheme that more clearly delineates causes of death. Recommendations are provided for additional data to be collected at the time of death. Recording and analyzing birth certificate and death loss data will allow producers and veterinarians to better evaluate associations between calf risk factors and death, with the goal of reducing dairy calf mortality., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this prospective cohort study was to describe the relationship between exposure to antimicrobials, through both the milk diet and systemic therapy, and to describe antimicrobial resistance of fecal Escherichia coli in dairy calves pre- and postweaning. A convenience sample of 15 Minnesota dairy farms was chosen, representing 3 equal cohorts of milk diet fed to preweaned calves: medicated milk replacer (MMR), nonmedicated milk replacer (NMR), or pasteurized nonsaleable milk (PNM). Five newborn calves were enrolled on each farm, with fecal samples collected from each calf at 1, 3, 5, and 16 wk of age. After isolation, 3 colonies of E. coli were randomly selected from each sample to determine antimicrobial susceptibility by minimum inhibitory concentration (Sensititer, Thermo Scientific, Waltham, MA) to 8 antimicrobials in 8 classes. The isolate was given an antimicrobial resistance score (ARS) according to the number of antimicrobial classes to which it was resistant. Any isolate resistant to 3 or more antimicrobials was defined as being multidrug resistant (MDR). Relationships between ARS and MDR (dependent variables) and possible explanatory variables were analyzed using mixed multivariable linear and logistic regression models, respectively, with critical P-values adjusted for multiple contrasts. Seventy percent of isolates were resistant to sulfadimethoxine. For wk 1 and 3, the mean ARS values were greatest for fecal E. coli from calves fed MMR or PNM compared with NMR, with no difference in ARS values between the MMR and PNM groups at either time point. At wk 5, the mean ARS value was greatest for fecal E. coli from calves fed MMR (3.56 ± 0.45; mean ± SE), intermediate for calves fed PNM (2.64 ± 0.45), and lowest for calves fed NMR (1.54 ± 0.45). However, by wk 16, the mean ARS values were ≤1.0 and did not differ among milk diets. Evaluation of the proportion of isolates with MDR mirrored the results of the ARS analysis (MDR more prevalent in MMR and PNM groups preweaning; no difference among milk diets at 16 wk). There was a tendency for an increase in ARS at wk 5 (1.28 ± 0.70), and the odds for MDR in fecal E. coli were estimated to be 5.2 (95% confidence interval = 0.67, 35.7) and 101.1 (95% confidence interval = 1.15, >999.9) higher at wk 3 and 5 if the calf was treated with a systemic antimicrobial within the 14-d period before sampling. These findings suggest that exposure to antimicrobials through the milk diet or systemic therapy may result in a transient increase in resistance in fecal E. coli, but once the antimicrobial pressure is removed, susceptible E. coli are able to flourish again, resulting in an overall decrease in resistance., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to describe the effect of offering a fixed or increasing milk allowance in the first 1 to 2 wk of life. We hypothesized that calves offered a fixed amount of milk early in life would not experience more scours, but rather would experience improved health and growth compared with calves that had their daily milk allowance slowly increased over a period of 1 to 2 wk. This randomized controlled clinical trial was conducted on 5 dairy farms in Minnesota with both a summer (June-August 2016) and winter (December-February 2017) period of enrollment. Heifer calves were enrolled at birth, weighed, and systematically assigned by birth order to either the slowly increasing (INC) control group or fixed allowance (FIX) treatment group by farm personnel. Calves assigned to the INC group were slowly increased from 4 to 5 L/d to gradually reach the full peak milk allowance of 6 to 8 L/d over a 7- to 14-d period, whereas calves assigned to the FIX group were offered a full peak milk allowance of 6 to 8 L/d beginning on d 1 after birth. The average FIX calf consumed an extra 14 L of milk as compared with INC calves over the first 2 wk of life, corresponding to an average INC intake of 5 L/d during first 1 to 2 wk of life as compared with an average intake of 6.8 L/d in FIX calves. Study technicians visited all farms weekly to collect health and performance data. Multivariable mixed models were used to describe the effect of treatment (INC/FIX) on 3-wk average daily gain (kg/d), 3-wk weight (kg), and hip height at wk 1, 3, and 7, controlling for the effect of season, birth weight, and the random effect of calf within farm. Multivariable logistic regression models were used to describe the effect of treatment on odds of technician and producer reported health events. A total of 1,264 heifer calves were enrolled (FIX n = 641; INC n = 623) with no difference in enrollment weight or hip height between groups. By 3 wk of age, FIX calves weighed 1.4 (0.59) kg more than INC calves, though the magnitude of this difference varied depending on the period of time INC calves were slowly increased in milk allowance (7 vs. 10 vs. 14 d). Calves in the FIX group grew 0.1 kg/d faster and were taller at wk 3 (0.3 ± 0.15 cm) of life. Forty-two percent (536/1,264) of all enrolled calves had a first treatment event, with no effect of treatment on technician-reported health scores and no overall effect on producer-reported treatment or mortality events. Under the conditions of this study, offering a fixed milk allowance from d 1 of life improved calf growth during the first 3 wk as compared with a gradual increase in milk allowance, with no detrimental effect on calf health., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Group housing and computerized feeding of preweaned dairy calves are gaining in popularity among dairy producers, yet disease detection remains a challenge for this management system. The aim of this study was to investigate the application of statistical process control charting techniques to daily average feeding behavior to predict and detect illness and to describe the diagnostic test characteristics of using this technique to find a sick calf compared with detection by calf personnel. This prospective cross-sectional study was conducted on 10 farms in Minnesota (n = 4) and Virginia (n = 6) utilizing group housing and computerized feeding from February until October 2014. Calves were enrolled upon entrance to the group pen. Calf personnel recorded morbidity and mortality events. Farms were visited either every week (MN) or every other week (VA) to collect calf enrollment data, computer-derived feeding behavior data, and calf personnel-recorded calf morbidity and mortality. Standardized self-starting cumulative sum (CUSUM) charts were generated for each calf for each daily average feeding behavior, including drinking speed (mL/min), milk consumption (L/d), and visits to the feeder without a milk meal (no.). A testing subset of 352 calves (176 treated, 176 healthy) was first used to find CUSUM chart parameters that provided the highest diagnostic test sensitivity and best signal timing, which were then applied to all calves (n = 1,052). Generalized estimating equations were used to estimate the diagnostic test characteristics of a single negative mean CUSUM chart signal to detect a sick calf for a single feeding behavior. Combinations of feeding behavior signals were also explored. Single signals and combinations of signals that included drinking speed provided the most sensitive and timely signal, finding a sick calf up to an average (±SE) of 3.1 ± 8.8 d before calf personnel. However, there was no clear advantage to using CUSUM charting over calf observation for any one feeding behavior or combination of feeding behaviors when predictive values were considered. The results of this study suggest that, for the feeding behaviors monitored, the use of CUSUM control charts does not provide sufficient sensitivity or predictive values to detect a sick calf in a timely manner compared with calf personnel. This approach to examining daily average feeding behaviors cannot take the place of careful daily observation., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

In dairy herds, application of antimicrobials at drying-off is a common mastitis control measure. This article describes a protocol for systematic review and meta-analysis to address three crucial points regarding antimicrobial usage at drying-off: (1) comparative efficacy of antimicrobials used for preventing new and eliminating existing intramammary infections (IMI); (2) comparison of selective and blanket dry cow therapy approaches in preventing new and eliminating existing IMI; and (3) assessment of the extra prevention against new IMI that can be gained from using antimicrobial-teat sealant combinations versus antimicrobials alone. Five PICO (Population, Intervention, Comparator, Outcome) questions were formulated to cover the three objectives of the review. Medline, CAB Abstracts, Web of Science, and conference proceedings will be searched along with iterative screening of references. Articles will be eligible if: (1) published after 1966; (2) written in English or French; and (3) reporting field clinical trials and observational studies, conducted on dairy cows at drying-off, with at least one antimicrobial-treated group and one IMI-related outcome. Authors will independently assess the relevance of titles and abstracts, extract data, and assess bias and the overall quality of evidence. Results will be synthesized and analyzed using pairwise and network meta-analysis. The proposed study will significantly update previously conducted reviews.

A critical time for dairy cattle is the perinatal period. Good calving management is critical to reduce periparturient losses and ensure the health of the offspring. Generally, it has been recommended that cows be allowed to calve unassisted when possible, but very few studies have been published that support or refute this general guideline. To investigate the effect of early assistance, a clinical trial enrolled 257 Holstein cows that were observed through the second stage of calving and assigned randomly to 1 of 2 calving interventions: not assisted (NA) or early assistance (EA) during the second stage of parturition. Early assistance was given 15min after the first sight of both front hooves of the calf and done using only human force. After calving, the animals were classified into 4 actual calving intervention groups: too quick to be assisted (TQ), NA, EA, and late assistance (LA; for cows in the NA group that did not calve unassisted within the 1h maximum time frame allowed). Giving early assistance to cows during calving as a routine management practice (assigned intervention) did not negatively influence calves' stillbirth risk, vigor at birth, or transfer of passive immunity. Calves in the LA intervention group had significantly greater odds of stillbirth than calves in the NA and EA groups, respectively. Calves in the LA group also had significantly worse vigor at birth than calves in the TQ, NA, or EA groups. Early assistance given at calving to cows that did not present signs of calving difficulties did not adversely affect calves' likelihood of being stillborn, vigor at birth, or transfer of passive immunity., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Good calving management should not only ease the transition of cows into lactation, but also contribute to providing healthy replacement animals for the herd. Difficulty during parturition has been found to be detrimental to the offspring. Because of the association of obstetrical intervention with undesirable outcomes, the general management recommendation for calving is to let cows give birth unassisted whenever possible. Unfortunately, very few studies have investigated the effects of planned early assistance during calving, regardless of whether or not another problem exists. To investigate the effects of early assistance during apparently normal calvings, a clinical trial was conducted on 257 Holstein cows. They were observed through the second stage of calving, and before calving they were divided randomly between 2 assigned interventions: not assisted or early assistance during the second stage of parturition. After calving, the animals were classified into 4 actual calving intervention groups: too quick to be assisted, not assisted, early assistance, and late assistance (for cows in the not assisted group that did not calve unassisted within the 1 h maximum time allowed). Early assistance was given 15 min after first sight of both front hooves of the calf and done using human force only. Heifer calves (n=129) born from enrolled dams were followed until weaning to assess the effect of assigned and actual calving interventions on their growth, health, and survival. Heifer calves' weight at birth was positively associated with weight at 7 wk, but the effect varied by assigned and actual intervention. As a routine management practice, giving early assistance during calving to dairy cows did not influence average daily gain, health, or survival in dairy heifer calves up to weaning at 7 wk of age., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

A series of trials were conducted to evaluate Brix refractometry (Brix %) for the assessment of failure of passive transfer (FPT) in dairy calves compared to: (1) serum IgG (reference standard) when measured by radial immunodiffusion (RID) or a turbidometric immunoassay (TIA), and (2) serum total protein refractometry (STP). For the serum samples tested with TIA, STP, and Brix % (n = 310; Holstein calves), the median concentrations were 21.3 g/L IgG, 58 g/L STP, and 9.2%, respectively. For the serum samples tested with RID, STP and Brix % (n = 112; Jersey calves), the mean concentrations were 38 g/L IgG, 68 g/L STP, and 10.2%, respectively. For samples tested with only Brix % and STP (n = 265; Holstein calves), median STP and Brix % were 50 g/L STP and 8.5%, respectively. Correlations between Brix % and RID, and between Brix % and TIA were equal (r = 0.79, respectively). Brix % and STP were positively correlated (r = 0.99). Brix % estimated serum IgG concentrations determined by TIA and RID (r(2) = 0.63, 0.62, respectively). When FPT was defined as serum IgG < 10 g/L, Brix % ≤ 8.5% showed optimal sensitivity (100%) and specificity (89.2%) to predict FPT. At the same IgG cut-point, an STP value of ≤ 52 g/L showed a similar sensitivity (100%) and specificity (80.4%) to predict FPT. Brix refractometry predicted successful transfer of passive immunity in dairy calves, but further evaluation as a diagnostic tool for the diagnosis of FPT is warranted., (Copyright © 2016. Published by Elsevier Ltd.)

In summer 2007, a randomized controlled field trial was initiated on 6 large Midwest commercial dairy farms to investigate the effect of feeding heat-treated (HT) colostrum on transmission of Mycobacterium avium ssp. paratuberculosis (MAP) and on future milk production and longevity within the herd. On each farm, colostrum was collected daily from fresh cows, pooled, divided into 2 aliquots, and then 1 aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60min. A sample from each batch of colostrum was collected for PCR testing (MAP-positive vs. MAP-negative). Newborn heifer calves were removed from the dam within 30 to 60min of birth and systematically assigned to be fed 3.8 L of either fresh (FR; n=434) or heat-treated (HT; n=490) colostrum within 2h of birth. After reaching adulthood (>2 yr old), study animals were tested once annually for 3 yr (2010, 2011, 2012) for infection with MAP using serum ELISA and fecal culture. Lactation records describing milk production data and death or culling events were collected during the 3-yr testing period. Multivariable model logistic and linear regression was used to investigate the effect of feeding HT colostrum on risk for testing positive to MAP during the 3-yr testing period (positive/negative; logistic regression) and on first and second lactation milk yield (kg/cow; linear regression), respectively. Cox proportional hazards regression was used to investigate the effect of feeding HT colostrum on risk and time to removal from the herd. Fifteen percent of all study animals were fed PCR-positive colostrum. By the end of the 3-yr testing period, no difference was noted in the proportion of animals testing positive for MAP, with either serum ELISA or fecal culture, when comparing the HT group (10.5%) versus the FR group (8.1%). There was no effect of treatment on first- (HT=11.797kg; FR=11,671kg) or second-lactation (HT=11,013kg; FR=11,235kg) milk production. The proportion of cows leaving the herd by study conclusion was not different for animals originally fed HT (68.0%) versus FR (71.7%) colostrum. Although a previous study showed that feeding HT colostrum (60°C for 60min) produces short-term benefits, including improved passive transfer of IgG and reduced morbidity in the preweaning period, the current study found no benefit of feeding HT colostrum on long-term outcomes including risk for transmission of Mycobacterium avium ssp. paratuberculosis, milk production in the first and second lactation, and longevity within the herd., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)