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Summary:Our objective was to validate a point-of-care handheld blood calcium analyzer to estimate circulating calcium concentrations in postpartum dairy cows. An accurate, rapid, and inexpensive tool to screen for hypocalcemia on-site would allow for implementation of selective treatment protocols but the meter assessed was not sufficiently accurate to quantify blood calcium concentration.

In-line milk progesterone (IMP4) monitoring (Herd Navigator, DeLaval) is a technology that uses a built-in lateral flow immunoassay module to measure real-time milk progesterone (P4) and determine postpartum onset of cyclicity, estrus, and pregnancy. Sampling starts at 20 DIM and occurs on average every 2 d until pregnancy, with sampling frequency adjusted according to the estimated stage of the estrous cycle. Estrus is detected based on a decline in P4 concentrations below a threshold, and pregnancy is assessed from 30 to 55 d after AI in cows without return to estrus. Here, we review the potential of IMP4 as a tool for reproductive management. In a series of observational studies with up to 158,961 IMP4 records from 4,353 AI events, we characterized predictors of P/AI and investigated IMP4 profiles in cows returning to estrus. Some of the predictors were short or prolonged luteal phases (LP) before first AI and suboptimal P4 profiles (such as prolonged LP or inadequate P4 concentrations) immediately before and after AI. Over a third of cows had at least one characteristic of P4 profile unfavorable to P/AI. However, these variables had low predictive abilities (ROC AUC <0.60). Among non-pregnant cows, 5% returned to estrus by 17 d after AI, 64% between 18 and 24 d, 16% between 25 and 30 d, and 15% between 31 and 55 d. This represents 85% of cows that are not pregnant 55 d after AI returning to estrus before 30 d, when first pregnancy diagnosis occurs in many dairies. Monitoring IMP4 might be used to identify subgroups of cows with different predicted P/AI to develop selective breeding strategies or targeted interventions. It can also aid in the identification non-pregnant cows early for timely re-insemination.

Our objectives were to evaluate the effects of complete replacement of supplementary inorganic salts of trace minerals (ITM; cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn) sulfates and sodium (Na) selenite) by organic trace minerals (OTM; Co, Cu, Mn, Zn proteinates, and selenized yeast) in both pre- and postpartum diets on trace minerals (TM) concentrations in body fluids and liver, antioxidant and inflammation biomarkers in blood, and postpartum health of dairy cows. Pregnant cows were blocked by parity and body condition score and randomly assigned to ITM (n= 136) or OTM (n= 137) 45 d before expected calving. Both groups received the same pre- and postpartum diets except for the source of supplementary TM. The day of calving was considered study d 0 and blood was collected on d –45, –21, –14, –10, –7, –3, 0, 3, 7, 10, 14, 23, 65, and 105 for analyses of TM and biomarkers. Concentrations of TM were also investigated in the liver (d 105), milk (d 7, 23, 65, 105), urine (d –21, 21, 65, 105), ruminal fluid and feces (d –21, 21, 65). Incidence of clinical and subclinical health conditions were evaluated. Complete replacement of ITM by OTM resulted in greater concentration of selenium (Se) in serum (0.084 vs. 0.086 µg/mL; P< 0.01), milk (0.24 vs. 0.31 µg/g; P< 0.01), and ruminal fluid (0.54 vs. 0.58 µg/g; P= 0.06), and reduced concentration of Se in urine (1.54 vs. 1.23 µg/g; P<0.01). For concentration of Co in serum, an interaction between treatment and time was detected (P< 0.01). Cows supplemented with OTM had greater concentrations of Co on d –7 and 0 (0.30 vs. 0.33 ng/mL; P< 0.01) but lower concentrations of Co on d 23, 65, and 105 (0.34 vs. 0.31 ng/mL; P< 0.05), in addition to reduced concentration of Co in feces (1.08 vs. 0.99 µg/g; P= 0.04) and, for multiparous only, in urine (0.019 vs. 0.014 µg/g; P< 0.01). Cows supplemented with OTM had lower postpartum concentrations of glutamate dehydrogenase (20.8 vs. 17.8 U/L; P< 0.05) and higher albumin on d –10 (36.0 vs. 36.7 g/L; P= 0.04) and 23 (36.9 vs. 37.6 g/L; P= 0.03) relative to calving. Primiparous cows fed OTM had lower concentration of ceruloplasmin in plasma (55 vs. 51 mg/L; P≤ 0.05). Cows supplemented with OTM had less incidence of lameness (14% vs. 7%; P= 0.05), elevated nonesterified fatty acids (NEFA) (61% vs. 44%; P< 0.01), and multiple metabolic problems (35% vs. 20%; P< 0.01). Despite the lack of differences in Cu, Mn, and Zn concentrations and antioxidant capacity, complete replacement of ITM by OTM altered concentrations of Se and Co, supported liver and hoof health, and reduced the risk of postpartum elevated NEFA.Complete replacement of inorganic salts of trace minerals (TM) by organic TM altered concentrations of Se and Co in circulation, supported liver and hoof health, and reduced the risk of postpartum elevated nonesterified fatty acids.Trace minerals (TM) are important for oxidative balance and immunity of cows. Different forms of TM are available for dietary supplementation of dairy cows. We tested whether replacing inorganic salts of TM by organic sources of TM in both pre- and postpartum diets improve TM concentration in body fluids and liver, antioxidant capacity in blood, and postpartum health of dairy cows. Despite the lack of difference in antioxidant capacity and in concentrations of Cu, Mn, and Zn, the complete replacement of inorganic salts by organic sources altered concentrations of Se and Co in circulation, and reduced the concentration of biomarkers associated with inflammation and liver damage, and the risk of lameness and postpartum metabolic problems.

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In the dairy industry, mate allocation is mainly based on the parents’ breeding values and inbreeding coefficients aiming to achieve the producer’s breeding goal. With artificial insemination, the portfolio of sires to choose from is large and the quality of the semen doses is standardized. However, not all sire-dam matings are equally likely to produce a successful pregnancy. Among other reproduction issues, the success of a mating could vary due to the incompatibility of gametes coming from the sire and the dam and could influence the fertilization’s success, additionally to the reproductive capacity of the parents. Considering the gametic incompatibility of the potential parents could be a novel option to improve mating plans. Under the hypothesis that gametic incompatibility has a significant effect on reproduction and reduces the odds of fertilization and pregnancy, this study aimed to determine the genetic background of gametic incompatibility. Transmission ratio distortion (TRD), which detects deviations from Mendelian inheritance expectations, is commonly used to identify deleterious mutations. We adapted the TRD model by including an interaction effect between the gametes leading to the offspring genotype to detect regions with TRD effects and gametic incompatibility. Our dataset contained 436,651 genotyped (50K SNP) Canadian Holstein cattle from 283,817 parents-offspring trios. A total of 482 regions with TRD containing 671 positional genes were found. The functional analysis detected biological pathways associated with uterus development, embryonic skeletal system development, and nervous system development. Additionally, gene ontology terms from the topology-based pathway enrichment analysis were mostly related to the steroid hormones signalling pathway. Although difficult, genes specific to gametic incompatibility could be differentiated from genes underlying other reproduction processes by refining the genetic regions with TRD. With further investigation, we will provide new information to improve mate allocation for the dairy cattle industry.

Summary:Automated milk feeders are computerized systems that provide producers with the opportunity to increase the milk allowance offered to preweaning calves. These computerized systems are thought to potentially aid in disease detection of preweaning dairy calves using individual feeding metrics. This retrospective case-control study analyzed data from 56 preweaning dairy calves (28 cases and 28 controls) and found milk consumption and drinking speed to be valuable disease predictors as early as 5 and 4 days before disease diagnosis, respectively. Unrewarded visits were found to be a useful predictor 3 days before disease diagnosis. Rewarded visits were not found to be a useful disease predictor.

The objective of this study was to investigate parenteral vitamin E for the prevention of peripartum disease in dairy cows. A randomized clinical trial was conducted in 21 commercial dairy herds. Cows (n=1142) were randomly assigned to receive either a single subcutaneous injection of 3000 IU of vitamin E, or placebo, 1 wk before expected calving. Serum α-tocopherol was significantly increased in treated cows at 7 and 14 d, but not at 21 d after injection. Overall, there were no significant differences between treatment groups in the incidence of retained placenta, clinical mastitis, metritis, endometritis, ketosis, displaced abomasum, or lameness. However, there was a conditional benefit of treatment for reduction of the incidence of retained placenta. Cows with marginal pretreatment vitamin E status (serum α-tocopherol to cholesterol mass ratio<2.5×10−3) that received an injection of vitamin E tended to have reduced risk of retained placenta. However, in cows with adequate serum vitamin E, there was no reduction in the incidence of any disease. For clinical application, primiparous animals were most likely to benefit from prepartum injection of vitamin E.

The objective of this study was to assess the use of GnRH in a controlled breeding program (7 d prior to the second of two injections of PGF2α, 14 d apart) as a means to improve the expression and detection of estrus, first service conception rate, and overall pregnancy rate of lactating dairy cows. On 17 farms, 348 cows were assigned randomly to either of two breeding programs prior to first insemination. Cows in both programs received PGF2αapproximately 2 wk prior to the end of a herd-specific voluntary waiting period for breeding. One group received GnRH 1 wk later, 7 d prior to the second of two injections of PGF2α. Control cows received saline and a second injection of PGF2αat corresponding times. Cows were observed for 7 d and were bred by artificial insemination following detection of estrus. There were no differences between programs in estrus detection rate, observed signs of estrus, conception rate, days to first service, or interval from calving to conception. The means and standard deviations of the interval from PGF2αto estrus were not different between programs. Administration of GnRH 1 wk prior to PGF2αdid not alter the expression of estrus or fertility in lactating dairy cows. In this study population, no advantage was found for the addition of GnRH to a controlled breeding program that was based on two administrations of PGF2αat a 14-d interval.

Summary:Antimicrobials are commonly used to treat dairy calves, which increases the risk of development of antimicrobial resistance and, as a result, shedding resistant bacteria. However, it is unclear how dairy producers decide to use antimicrobials for treating their calves. Questionnaires were administered to 144 dairy producers across 5 provinces in Canada. Nearly all producers used antimicrobials to treat calf respiratory disease and almost three-fourths of producers used antimicrobials to treat calf diarrhea. Less than 40% of dairy producers had written treatment protocols for calf diseases. Improvements can be made for more prudent antimicrobial use in Canadian dairy calves.