Search

Because challenge models to infect peripheral lymph nodes (PLNs) with Salmonella have not been reported, we performed a series of experiments to develop and refine challenge models to evaluate an intervention applied at the animal level and to provide initial estimates of efficacy of an intervention (i.e., a vaccine) to aid in the design of future studies. In each of four experiments, steers (control or vaccinated) were inoculated with Salmonella strains Montevideo or Newport, and in experiment IV, Salmonella Senftenberg was also used. Calves were euthanized 14 to 42 days postinoculation, and PLNs were collected. In the first experiment, calves were challenged with ~1010 Salmonella cells, and few treatment differences were observed 14 days postchallenge. However, by day 21, Salmonella Newport was recovered from fewer vaccinated calves than control calves (P < 0.05). In experiment II, calves were challenged with ~107 Salmonella cells and, after two necropsies (14 and 28 days postchallenge), only one lymph node was Salmonella positive; therefore, the study was terminated. In experiment III, calves were again challenged with ~1010 Salmonella cells, and no significant effect of vaccine was observed in calves challenged with Montevideo or Newport strains. A transdermal route of challenge was explored in experiment IV, using a 10-lancet, allergy testing instrument. Sixteen steers were challenged with either Salmonella Newport or Salmonella Montevideo (Salmonella Newport right legs; Salmonella Montevideo left legs), and all steers were challenged on the lower abdomen with Salmonella Senftenberg. Transdermal inoculation resulted in predictably Salmonella-positive PLNs, and a modest vaccine effect was detected. Because it is well tolerated by the calves and results in predictable and regionally specific Salmonella recovery from PLNs, the transdermal route of challenge may be preferred by researchers wishing to evaluate the impact of interventions designed to reduce the carriage of Salmonella in PLNs. [ABSTRACT FROM AUTHOR]

Recent investigations have found that Salmonella can be routinely recovered from peripheral lymph nodes (PLNs) of cattle presented for harvest. When contained within the PLNs, this foodborne pathogen is protected from currently used postharvest, in-plant intervention strategies and, therefore, PLNs harboring Salmonella may be a potential contaminant of ground beef. The objective of this work was to develop a challenge model that effectively and repeatedly results in Salmonella-positive PLNs. A 10-lancet skin-allergy instrument was inoculated with Salmonella, and calves were inoculated intra- and/or transdermally by applying the device over various ventral regions of the skin. Salmonella was successfully and predictably recovered from region-specific PLNs up to 8 days postchallenge. Furthermore, serotypes inoculated within specific regions were only recovered from the PLNs draining those regions. This model provides a method to predictably infect PLNs with Salmonella. Further, this model makes it possible to determine the duration of infection and to evaluate candidate interventions that may shorten the duration of infection. [ABSTRACT FROM AUTHOR]

Strategies aimed at reducing fecal shedding of Salmonella and other foodborne pathogens may be effective for limiting transmission of pathogens from food animals to humans. The objective of this study was to determine the effectiveness of gallium maltolate (GaM) against Salmonella in vitro and to determine whether oral administration of GaM would reduce fecal shedding of Salmonella in cattle. Gallium is a semimetal exhibiting antimicrobial properties against some pathogenic bacteria, including Salmonella, by exploiting their need for iron to survive and replicate. In vitro growth studies were performed in pure cultures of Salmonella and in mixed cultures from ruminal fluid. Inclusion of GaM in culture medium or in mixed cultures of ruminal fluid resulted in a significant reduction in growth of Salmonella, suggesting that GaM may be effective for limiting growth and survival in vivo. Therefore, we subsequently administered two doses of GaM to Holstein steers, experimentally infected them with Salmonella, and quantitatively and qualitatively monitored fecal shedding at 12-h intervals. Sixty hours after beginning treatment, cattle were euthanized, and luminal contents and tissue were aseptically harvested from the rumen, jejunum, spiral colon, cecum, and rectum. The luminal contents were processed for quantitative and qualitative analysis of the challenge strains of Salmonella, and tissue samples were enriched and plated for qualitative analysis. We found no significant differences between control and treated animals in quantitative levels of Salmonella in the feces or the luminal contents. Likewise, we observed no pattern between control and treated animals in the frequency of positive or negative results from enriched feces, luminal contents, or tissue samples. These results suggest that GaM was not effective for reducing Salmonella in cattle. [ABSTRACT FROM AUTHOR]

Laying hens are typically induced to molt to begin a new egg-laying cycle by withdrawing feed for up to 12 to 14 d. Fasted hens are more susceptible to colonization and tissue invasion by Salmonella enterica serovar Enteritidis. Much of this increased incidence in fasted hens is thought to be due to changes in the native intestinal microflora. An alternative to feed withdrawal involves feeding alfalfa meal crumble to hens, which is indigestible by poultry but provides fermentable substrate to the intestinal microbial population and reduces Salmonella colonization of hens compared with feed withdrawal. The present study was designed to quantify differences in the cecal microbial population of hens (n = 12) fed a typical layer ration, undergoing feed withdrawal, or being fed alfalfa crumble by using a novel tag bacterial diversity amplification method. Bacteroides, Prevotella, and Clostridium were the most common genera isolated from all treatment groups. Only the ceca of hens undergoing feed withdrawal (n = 4) contained Salmonella. The number of genera present was greatest in the alfalfa crumble-fed group and least in the feed withdrawal group (78 vs. 54 genera, respectively). Overall, the microbial diversity was least and Lactobacillius populations were not found in the hens undergoing feed withdrawal, which could explain much of these hens' sensitivity to colonization by Salmonella. [ABSTRACT FROM AUTHOR]

Monensin and tylosin have activity against gram-positive bacteria, and it has been theorized that their effects on the intestinal environment may promote proliferation of gram-negative bacteria such as Escherichia coli. Effects of these antibiotics on the shedding of E. coli O157:H7 were studied in a feedlot environment, using 32 finishing steers. A diet containing 85% barley grain, 10% barley silage, and 5% supplement was amended with 33 ppm monensin, 11 ppm tylosin, both of these additives, or no additives (control). All steers were orally inoculated with 1010 CFU of a mixture of four strains of nalidixic acid-resistant E. coli O1 57:H7. Fecal (grab), oral (mouth swab) and water, water-water bowl interface, feed, and pen floor fecal pat samples were collected weekly for 12 weeks. Prevalence of E. coli O157:H7-positive fecal grab samples did not differ (P = 0.26) among treatments, nor did the rate (P = 0.81) or duration (P = 0.85) of shedding of the organism. Fecal grab samples were positive for E. coli O157:H7 more frequently (P < 0.001) than were oral swabs. More (P = 0.02) E. coli O157:H7-positive oral swabs were recovered from the tylosin group than from controls. E. coli O157:H7 was not detected in any of 47 water samples, but was present in 1 of 47 water bowl swabs, 7 of 48 feed samples, and 36 of 48 fecal pats. Pulsed-field gel electrophoresis suggested that differences existed among inoculated strains in their ability to persist in animals and in the environment. However, this study revealed no evidence that dietary inclusion of monensin or tylosin, alone or in combination, increased fecal shedding of E. coli O157:H7 or its persistence in the environment. [ABSTRACT FROM AUTHOR]

We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH), and nitroethane (NE) on growth and survivability of Listeria monocyrogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For example, specific growth rates of L. monocytogenes strain 18 declined (P < 0.05) 76, 60, and 29% from controls during aerobic culture at 37°C in brain heart infusion broth containing 10 mM 2NPOH, 2NEOH, or NE, respectively. Mean specific growth rate for the controls incubated likewise without added nitrocompound was 0.62 ± 0.02 h-1. Specific growth rates of L. monocytogenes Scott A decreased (P < 0.05) 67, 45, and 11%, respectively, from controls (0.67 ± 0.02 h-1) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30°C were reduced (P < 0.05) 76, 60, and 30%, respectively, and were reduced (P < 0.05) 78, 23, and 23% during anaerobic culture at 30°C in brain heart infusion broth containing 15 mM 2NPOH, 2NEOH, or NE (control rates ranged from 0.37 ± 0.07 to 0.74 ± 0.05 h-1). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 months at 4°C) in brain heart infusion broth containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH, and NE against L. monocyrogenes in vitro. [ABSTRACT FROM AUTHOR]

Salmonella is one of the most serious foodborne pathogenic bacteria in the United States, causing an estimated 1.3 million human illnesses each year. Dairy cows can be reservoirs of foodborne pathogenic bacteria, including Salmonella spp.; it is estimated that from 27 to 31% of dairy herds across the United States are colonized by Salmonella. The present study was designed to examine the occurrence of Salmonella spp. on dairies and to examine the serotypic diversity of Salmonella isolates on sampled dairies from across the United States. Fecal samples (n = 60 per dairy) were collected from 4 dairies in each of 4 states for a total of 960 fecal samples representing a total population of 13,200 dairy cattle. In the present study, 93 of 960 samples (9.96%) collected were culture-positive for Salmonella enterica. At least one Salmonella fecal-shedding cow was found in 9 of the 16 herds (56%) and the within-herd prevalence varied in our study from 0% in 7 herds to a maximum of 37% in 2 herds, with a mean prevalence among Salmonella-positive herds of 17%. Seventeen different serotypes were isolated, representing 7 different Salmonella serogroups. There were 2 or more different serogroups and serotypes present on 7 of the 9 Salmonella-positive farms. Serotypes Montevideo and Muenster were the most frequent and widespread. From our data, it appears that subclinical colonization with Salmonella enterica is relatively common on dairy farms and is represented by diverse serotypes on US dairy farms. [ABSTRACT FROM AUTHOR]

Escherichia coli O157:H7 is a virulent foodborne pathogen that causes severe human illness and inhabits the intestinal tract of food animals. Colicins are antimicrobial proteins produced by E. coli strains that inhibit or kill other E. coli. In the present study, the efficacy of three pore-forming colicins (E1, N, and A) were quantified in vitro against E. coli O157:H7 strains 86–24 and 933. Colicins E1 and N reduced the growth of E. coli O157:H7 strains, but the efficacy of each colicin varied among strains. Colicin E1 was more effective against both strains of E. coli Ot57:H7 than colicins A and N and reduced (P < 0.05) populations of E. coli O157:H7 at concentrations <0.1 μg/ml. These potent antimicrobial proteins may potentially provide an effective and environmentally sound preharvest strategy to reduce E. coli O157:H7 in food animals. [ABSTRACT FROM AUTHOR]

Examines the effects of dietary manipulations on Escherichia coli populations in cattle. Information on gastric shock survival; Effects of management strategies on Escherichia coli populations; Importance of the cleanliness of animals.

The objective of the current research was to determine if feeding the citrus by-products D-limonene (DL) and citrus molasses would reduce the concentration and prevalence of Salmonella in weanling pigs experimentally infected with Salmonella Typhimurium. Twenty crossbred weanling pigs (average body weight [BW], 19.9 kg) were randomly assigned to one of four treatments: control, low-dose DL (1.5 ml/kg of BW per day), high-dose DL (3.0 ml/kg of BW per day), and citrus molasses (0.05 kg/kg of BW per day). Treatments were administered in the feed (twice daily) for 7 days, with one-half of the dose administered at each feeding. Fecal samples were collected twice daily (prior to administration of treatment) and cultured for quantitative and qualitative determination of the challenge strain of Salmonella. Upon termination of the study, pigs were euthanized and tissues from the stomach, ileum, cecum, spiral colon, and rectum, as well as luminal contents, were collected. In addition, the popliteal and ileocecal lymph nodes and liver, spleen, and tonsil tissue were collected for qualitative Salmonella culture. No significant treatment differences (P > 0.05) were observed among treatments for fecal concentration or prevalence of Salmonella throughout the 7-day collection period. Likewise, no treatment differences (P > 0.05) were observed for any of the tissue or luminal content samples collected. Salmonella was not cultured from the muscle-bound popliteal lymph node but was cultured from the mesenteric ileocecal lymph nodes. While there were no effects in the current experiment, future research may examine the effect of a lower challenge dose and/or different administration (dose or duration) of the citrus by-products. [ABSTRACT FROM AUTHOR]

Escherichia colt O157:H7 is a foodborne pathogenic bacterium that can reside undetected in the gastrointestinal tract of cattle because colonization by this bacterium is asymptomatic. Recent research has indicated that swine can carry and transmit this pathogen as well. The development of more advanced and sensitive detection techniques has improved the limit of detection and increased sensitivity for this important pathogen. This study was undertaken to determine the prevalence of E coli O157 in cattle and swine in Mexico with the more sensitive detection technique of immunomagnetic bead separation. Samples (n = 60 per farm) were taken from four cattle and four swine farms (n = 240 cattle samples, n = 240 swine samples) located throughout central Mexico in October 2001. The prevalence of E. colt O157 was found to be only 1.25% on cattle farms and 2.1 % on swine farms. The prevalence in cattle in this study is lower than that reported in the United States and could be related to the lower reported prevalence of E. coli O157 in humans in Mexico. However, further research is needed to verify prevalence throughout other regions of Mexico, as well as prevalence during other seasons of the year. [ABSTRACT FROM AUTHOR]

Live yeast (LY) supplementation to ruminants has been shown to increase nutrient digestibility and improve the rumen environment by increasing its pH in dairy cows. Few studies have determined the impact of LY in the rumen of growing cattle receiving high-concentrate diets. This study was designed to evaluate the effects of LY-(Saccharomyces cerevisiae) Actisaf (Phileo Lesaffre Animal Care) on rumen pH and dry matter digestibility during three feeding phases [grower (GRW), transition (TRANS), and finisher (FIN)]. Eight ruminally cannulated cattle (n=4 steers and n=4 heifers) were blocked by sex into two pens containing Calan gate feeders and received a standard diet (13.7% CP, 42.4% NDF, 88% DM) without LY for 10 d (d -10 to d -1). On d 0, each animal was randomly assigned to one treatment [control (CON), LY1 (2.5 g/d per head), LY2 (5 g/d per head), or LY3 (10 g/d per head)], and fed every morning (0800) for 55 d. Each of the three diets (GRW, TRANS, and FIN) were fed sequentially as follows: GRW for 27 d, TRANS for 14 d, and FIN for 14 d. There were nine collection days (d -1 and every 7 after) in which ruminal pH was determined and nylon bags containing 5 g of diet substrates (GRW, TRANS, and FIN) were incubated in the rumen at 1200 for 48 h to determine the DM digestibility (DMD) of the three diets. Data was analyzed as a RCBD with day as a repeated measure. For the GRW diet, TRT was not different (P=0.12) for pH, but for the TRANS diet, TRT was different (P=0.02) and had a quadratic pattern (P=0.01) in which LY1 and LY3 had the greatest pH (P<0.05). For the FIN diet, TRT was also different (P=0.03), but had a linear pattern (P<0.01) in which LY2 and LY3 had greater pH than CON (P<0.05). For DMD, TRT was different (P<0.001) and had quadratic and cubic patterns (P<0.001) for the grower diet in which L2 had the lowest DMD (P> 0.05). For the TRANS diet, TRT was also different (P<0.001) and had a cubic pattern (P=0.054) in which L2 had the lowest DMD (P>0.05). For the FIN diet, TRT affected the DMD (P<0.001) and had a quadratic pattern (P<0.001) in which L2 had the lowest DMD (P>0.05). Our results indicated that the daily supplementation of 10 g of LY yielded greater DMD and ruminal pH than CON in growing cattle. [ABSTRACT FROM AUTHOR]

Direct Fed Microbials (DFM) are probiotic-type compounds that are utilized in calf feeding operations as novel, non-antibiotic technologies to improve health and performance. The modes of action of most probiotics remain unknown, but their impacts on the microbial ecology of the GI tract may be responsible for positive changes in animal health and performance. Therefore, the objective of this study was to evaluate changes in the microbiome of the ileum of Holstein steer calves supplemented with a DFM comprised of a patented strain of Bacillus subtilus (CLOSTAT®; 13 g/hd/d for 35d: Kemin Industries Des Moines, IA) following an experimental, oral Salmonella challenge. Holstein steer calves (n=40) were assigned to treatments in a 2 x 2 factorial design and either fed CLOSTAT (CLO) or not (CON) and inoculated with Salmonella Typhimurium (SAL; 1.1x 106 CFU) or not (NOSAL) in the calves' milk replacer. Our lab previously reported CLO supplementation reduced Salmonella in the GI tract and reduced the febrile response in CLO calves following SAL challenge. Upon harvest in the present study, ileum tissue samples were collected and the microflora of each calf was analyzed using Ilumina MiSeq. Diversity was examined for overall richness (OTU), quantified using the Chao 1 richness estimator, and data were examined for richness and evenness distribution amongst distinct taxa using the Shannon Diversity Index. Group differences were analyzed using permutational multivariate analysis of variance. There was no difference in the number of distinct species or genera present within the microbiome between CLO and CON or the interaction of CLO supplementation and SAL inoculation (P>0.20). Inoculation of calves with Salmonella increased species/genera richness (P=0.02) in the ileum. Overall, there was no difference in the Shannon Diversity Index due to CLO (P>0.05), but the diversity was increased with SAL inoculation (P<0.01). However, there was no interaction of CLO and SAL (P>0.05) on any measure of microbial diversity. Similarly, the number of OTU's were not affected by CLO (P>0.05); however, SAL increased the number of OTU's (P=0.02) in ileal contents. While positive effects on animal health were observed in SAL calves fed CLO, there was no overall difference in the composition of the microbiome of the ileum. However, SAL administration, as expected, significantly influenced the ileal microbiome of Holstein steer calves. More research is needed to fully elucidate the effects of CLO supplementation on the microbiome of calves in the various compartments of the GI tract. [ABSTRACT FROM AUTHOR]

An active dry yeast (ADY) supplement (Vistacell, AB Vista, UK) was proposed to favorably influence ruminal parameters of heat loaded cattle. Eight British-cross steers (365 ± 27 kg) were fed a 90% concentrate diet (1.8% of BW intake, DM basis) and supplemented with either ADY (3.0 g/d; providing 6 × 1010 CFU/d) or no yeast (0.0 g/d; CON) for 14 d. Rumen boli were inserted through the esophagus on d 0 for continuous monitoring of pH and rumen temperature. On d 13 and 14, steers were housed in an open circuit calorimetry chamber for 48 h in either thermoneutral (TN) (18 ± 0.55°C; 35% RH) or heat loaded (HL) (35 ± 0.55°C; 35% RH) temperature. After 48 h, rumen fluid (500 mL) was extracted via esophageal pump and immediately processed for further analysis and in vitro fermentation using a 2×2 factorial arrangement with the in vitro gas production technique (IVGP). The IVGP revealed an effect of ADY on DMD versus CON (61.7% vs 32.8%, P = 0.031) but there was no effect of temperature. No effects were observed on the fermentation dynamics of the DM. There was a significant interaction of supplement and temperature on estimated ME in which ADY+TN, CON+HS, and ADY+HL were greater (P = 0.0307) than CON+TN (2.97, 2.84, 2.72 vs 1.95 Mcal/kg, respectively). The IVGP of methane (CH4) g/L or CH4 g/L/g of DM digested was not affected. Mean rumen pH of steers tended to be affected by temperature and supplement: HL steers had lower pH than TN (P = 0.064), and CON steers had lower pH than ADY (P = 0.077). Time spent below pH of 6 was affected by supplement: ADY was much less than CON (390.0 vs 882.5 min/d, P = 0.05). Time spent below pH of 5.0 was affected by temperature: TN was much less than HL (1.75 vs 590.75 min/d, P = 0.034, respectively). Mean rumen temperature and time spent above 40°C was affected by temperature but not by supplement. As expected HL steers had greater rumen temperature and spent more time above 40°C than TN steers (40.51 vs 39.21 °C, P = 0.0165; 1,216.25 vs 27.5 min/d, P = 0.002). Our results indicated that supplementation of 3.0 g/d of an ADY in the diets of steers consuming 90% concentrate diets under severe heat loads may increase DMD, increase available ME, and relieve subacute ruminal acidosis. [ABSTRACT FROM AUTHOR]

To evaluate the effects of a patented Bacillus subtillus probiotic (CLOSTAT®), weaned Holstein steers, (n = 200; ~90kg) were supplemented (CLO) or not (CON) with CLOSTAT® (13 g/hd/d; Kemin Industries, Des Moines, IA) in a starter ration at a calf ranch for 35 d (n = 50 head per pen; 2 pens/trt.). A subset of 40 calves was selected for an oral Salmonella challenge based on body weight, treatment records, and lack of Salmonella shedding. The calves were transported to Lubbock, TX (105 km) and assigned to 1 of 4 treatments in a 2x2 factorial design with CLO and CON calves that were orally administered Salmonella (STM) or not (CLOSTM, CLONoSTM, CONSTM, CONNoSTM). Calves assigned to receive Salmonella were challenged with 1.6 x 106 Salmonella Typhimurium (resistant to 50µg/ml nalidixic acid) in 1 L of milk replacer on d 0. Blood samples for serum and hematology were collected via jugular catheters every 8 h for 96 h, and body temperature was collected every 5 min via indwelling rectal temperature recording devices. Five calves from each treatment were harvested 48 h post-challenge, and the remaining calves were harvested 96 h post-challenge. During necropsy, tissues were collected for the isolation and quantification of the inoculated STM from various tissues. The CLO group had reduced STM concentrations in the jejunum, ileum, and transverse colon 48 h after the challenge (P ≤ 0.03) and numerically reduced STM concentrations in all gastrointestinal tissues 96 h post-challenge. There was a difference in rectal temperature (P < 0.001) in which CLOSTM calves displayed decreased rectal temperatures after the challenge when compared to CONSTM calves. White blood cells and lymphocytes were increased (P ≤ 0.05) in CLOSTM calves after the challenge in comparison to other treatments. Calves in the CLO treatment maintained greater numerical BW throughout the study; however, there was no difference (P = 0.89) in BW change during the study. In calves given STM, the CLO group had greater feed disappearance before and after the challenge (P = 0.006) in comparison to the CON group. Increased serum IL-6 and IFNγ was observed in the CONSTM group compared to other treatments. There was no difference (P = 0.42) in circulating cortisol between the treatments. Overall, CLO reduced Salmonella presence and concentrations in gastrointestinal tissues while simultaneously reducing the severity of the salmonellosis as indicated by blood parameters and the reduced febrile response. [ABSTRACT FROM AUTHOR]

Active dry Yeast (ADY) has been suggested to moderate ruminal acid load in growing beef cattle diets potentially enhancing feeding performance and carcass characteristics. The objective of this study was to determine the effects of adding ADY (1.5 g/d; 6 × 1010 CFU/d) to the diets of feedlot steers on ruminal pH, feeding performance, and carcass characteristics. Sixty British-cross steers were blocked by weight (Heavy; HVY (n=2) or Light; LT (n=2)) across four pens in a two treatment by two period parallel design where steer was the experimental unit. Treatments were control basal diet (CON) or basal diet plus ADY. Period 1 (P1) consisted of 70 d of a grower diet (NEg of 0.95 Mcal/kg) and period 2 (P2) consisted of a 14 d step up to a finishing diet (NEg of 1.22 Mcal/kg) fed for 56 d. A stratified subset of 30 steers were equipped with rumen pH measuring boli spanning the diet transition (50 d). Mean ruminal pH did not differ between CON and ADY (6.28 vs. 6.21, respectively; P = 0.21) but tended to be different between P1 and P2 (6.26 vs. 6.24, respectively; P = 0.12). There was no significant effect of TRT or period on area under the curve (AUC) of pH 5.4, average time below pH 5.4, or frequency of crossing pH 5.4 threshold. However, cumulative variation of AUC revealed a TRT x Period interaction (P < 0.001) increasing significantly for CON steers from P1 to P2 but not for ADY steers (3.89 to 109.35 h vs. 1.04 to 17.76 h, respectively). There was no significant effect of TRT on final BW, DMI, ADG, F:G ratio, RFI, or carcass characteristics (HCW, 12th rib fat thickness, REA, Yield Grade, or Quality Grade). Liver abscess occurrence was 26.3% and tended to be affected by TRT in which frequency was greater for CON than for ADY (34.48 vs. 17.9 %, respectively; P = 0.15). Severity of abscess was not affected by TRT (P = 0.46) but CON steers had a greater frequency of A+ liver scores than ADY steers (14.92 vs. 7.14 %, respectively). At the current ADY feeding rate, feedlot steers had similar growth performance and carcass characteristics across treatments. However, we observed a significant decrease in the variability of AUC in the sub-acute acidosis domain and a tendency for fewer liver abscesses in ADY fed steers compared to CON fed steers. [ABSTRACT FROM AUTHOR]

Probiotics are gaining increased interest in calf feeding operations as some producers seek novel, non-antibiotic technologies to improve health and performance. Therefore, the objective of this study was to evaluate changes in serum metabolomic compounds of Holstein steer calves supplemented with CLOSTAT® (13g/hd/d for 35d; Kemin Industries, Des Moines, IA) following an experimental oral Salmonella challenge. Holstein steer calves (n = 40) were assigned to treatments in a 2 x 2 factorial design and either fed CLOSTAT (CLO) or not (CON) and inoculated with Salmonella Typhimurium (SAL; 1.1 x 106) or not (NOSAL) via milk replacer. Data has previously reported CLO supplementation greatly reduced Salmonella concentrations in the gastrointestinal tract of calves after experimental infection and mitigated some of the negative effects of the disease challenge. Additionally, rectal temperature was greatly reduced in calves subjected to the challenge. For this study, serum was analyzed from blood samples collected 48 h after experimental infection representing peak rectal temperature. Serum metabolites were identified and quantified using GC-MS (West Coast Metabalomics Center, UC Davis). Data were log transformed prior to analysis to achieve normality. Data were analyzed using univariate ANOVA, principal component analysis, and partial least squares-discriminate analysis using the fixed effects of metabolite, treatment, Salmonella, and their interactions using Metaboanalyst 3.0. Mean separation was determined at α = 0.05. A total of 334 compounds were quantified, and 118 were of known identity. Overall, serum metabolome was shifted more due to CLO supplementation (9.6%) as opposed to SAL inoculation (7.1%). Clostat increased the concentrations of leucine and 32 other metabolites (P < 0.05). Salmonella was responsible for increasing myristic acid, heptadecanoic acid, and other fatty acids (P < 0.05) which have known antimicrobial properties. Uric acid was increased (P < 0.05) in CLO supplemented calves and may have enhanced macrophage killing capabilities which may correlate to reduced migration, colonization, and translocation observed in the gastrointestinal tract of supplemented calves. This may partially explain the previously reported reduced rectal temperature in CLO supplemented calves. Salmonella additionally altered 25 other metabolites (P < 0.05). Only 9 interactions existed between supplementation and Salmonella infection across 334 compounds. These data suggest that supplementation of calves with CLO may alter serum metabolites and shift metabolic and immune pathways regardless of their Salmonella status which may have played a role in reducing the negative effects of a Salmonella challenge. [ABSTRACT FROM AUTHOR]

The objective of the current study was to examine the effect of pasteurization of waste milk, used to feed dairy calves, on the bacterial diversity of their lower gut. Using 16S rDNA bacterial tag-encoded FLX amplicon pyrosequencing, fecal samples from dairy calves, ages 1 wk to 6 mo old and fed either pasteurized or nonpasteurized waste milk, were analyzed for bacterial diversity. Calves were maintained on 2 separate farms and, aside from how the waste milk was treated, were housed and cared for similarly. Fifteen calves were sampled from each age group (1, 2, and 4 wk, and 2, 4, and 6 mo of age; n = 90 samples per milk treatment, 180 total samples) on each farm via rectal palpation and the samples shipped and frozen before analysis. In general, bacterial diversity, as represented by the total number of different species, was greater for the calves fed pas- teurized waste milk at all ages (except 1 wk of age) and increased with increasing age in both treatments. Proteobacteria, Bacteroidetes, and Firmicutes were the predominant phyla. Differences in phyla and class were observed among treatments and age of calf but with no consistent trends. Salmonella were detected in 9 out of 14 (64%) of the 1-wk-old calves fed nonpasteurized milk. Treponema, an important beneficial bacterium in cattle rumen, was more prevalent in the pasteurized waste milk-fed animals and became higher in the older animals from this group. Escherichia-Shigella were detected among treatments at all ages, and highest at 1 wk of age, averaging approximately 21 and 20% of all bacteria for calves fed pasteurized and nonpasteurized waste milk, respectively, and decreasing as calves aged (2.6 and 1.3%). The consistent detection of Salmonella in the younger animals fed nonpasteurized milk and its absence in all other groups is an important finding related to this feeding practice. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effect of experimental chlorate product (ECP) feed supplementation on Salmonella Typhimurium (ST) in the crop and ceca of market-age broilers. In trial 1, 160 market-age broilers were randomly assigned to 8 treatment groups and replicated twice, with 20 broilers per pen for 1 wk. Trial 2 used the same design, but used 80 market-age broilers with 10 broilers per pen. Treatments were as follows: 1) control feed + double-distilled drinking water (dd H2O); 2) control + 18.5% experimental zeolite carrier with dd H2O; 3 to 7) control feed supplemented with 0.5, 1.0, 5.0, 10.0, or 18.5% of a feed grade ECP + dd H2O; 8) control feed + 1× ECP (0.16% w/v; containing 15 mM chlorate ion equivalent) added to dd H2O. Seven-week-old broilers were provided experimental treatments for 7 d, killed, and then ceca and crops were removed and evaluated for ST. Broilers fed 5 to 18.5% ECP or water ECP had a significantly lower (P < 0.05) incidence of ST in the crop (36 to 38% and 14%, respectively) when compared with the control (60%). Broilers fed 10% ECP or water ECP had significantly lower ST crop concentrations (1.03 log10 and 0.38 log10 ST/g, respectively) when compared with broilers fed a control diet (1.54 log10 ST/g). Crop and ceca ST incidence (32 to 48%) and concentration (1.00 to 1.82 log10 ST/g) were significantly lower in broilers fed 5 to 18.5% ECP as compared with the control (78%; 2.84 log10 ST/g). Broilers fed 5% or greater ECP had significantly higher water consumption (380 to 580 mL water/d) and litter moisture (31 to 56%) when compared with the control (370 mL water/d; 23% moisture). Only broilers fed 18.5% ECP had significantly lower 7-wk BW (2.77 kg of BW) when compared with the controls (3.09 kg of BW). Average daily gains were significantly depressed in broilers fed 10 or 18.5% ECP compared with the controls. These results indicate broilers supplemented with feed ⩽ 5% ECP or water ECP 7 d before slaughter reduced ST without affecting growth parameters. [ABSTRACT FROM AUTHOR]

Two studies were conducted to evaluate the effects of melatonin on Salmonella Enteritidis infection in experimentally challenged laying hens subjected to a forced molt. Leghorn hens (>50 wk of age) were randomly assigned to rooms, acclimated to a 16L:8D regimen, and provided ad libitum access to a nonmedicated mash layer diet and water. Birds in one room were molted (8L:16D; complete feed withdrawal), whereas birds in the second room served as nonmolted controls (CONT). Within each room, birds were randomly assigned to melatonin treatment (MEL; 12 birds/treatment), dosed orally commencing the same day as feed withdrawal for 10 d: (experiment I: 0 or 5 mg of melatonin; experiment II: 0, 10, or 20 mg of melatonin). Three days following feed withdrawal, all birds were experimentally infected with Salmonella Enteritidis, and after 10 d of feed withdrawal, all birds were killed and necropsied. In experiment I, concentrations of Salmonella Enteritidis in the cecal contents and the number of Salmonella Enteritidis-positive tissues from the crop, ceca, liver, spleen, and ovary were higher (P < 0.0001) in the MOLT compared with the CONT treatments. No differences (P > 0.10) were observed in any of the parameters examined due to MEL treatment. For experiment II, cecal concentrations of Salmonella Enteritidis were generally higher in the MOLT compared with the CONT treatment and within molted birds, cecal concentrations were higher in the MEL treatment (P < 0.05). Melatonin treatment in molted birds increased (P < 0.05) the percentage of positive crops in the MOLT+20 MEL treatment (P < 0.05). Salmonella-positive cecal tissue was increased (P < 0.001) in MOLT compared with CONT birds and was also higher in MOLT+10 MEL and MOLT+20 MEL birds compared with the MOLT-only treatment. Results from the current research suggest that dosage with high levels of melatonin may exacerbate Salmonella Enteritidis infection in layers subjected to forced molt. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine microbial population shifts and short-chain fatty acid (SCFA) responses in the gastrointestinal tract of Salmonella Enteritidis-challenged molted and nonmolted hens fed different dietary regimens. Fifteen Salmonella-free Single Comb Leghorn hens (>50 wk old) were assigned to 3 treatment groups of 5 birds each based on diet in 2 trials: 100% alfalfa crumbles (ALC), full-fed (FF, nonmolted) 100% commercial layer ration, and feed withdrawal (FW). A forced molt was induced by either a 12-d alfalfa diet or FW. In all treatment groups, each hen was challenged by crop gavage orally 4 d after molt induction with a 1-mL inoculum containing 106 cfu of Salmonella Enteritidis. Fecal and cecal samples (d 4, 6, 8, 11, and necropsy on d 12) were collected postchallenge. Microbial population shifts were evaluated by PCR-based 16S ribosomal RNA gene amplification and denaturing gradient gel electrophoresis, and SCFA concentrations were measured. Total SCFA in fecal and cecal contents for FW molted hens were generally lower (P ≤ 0.05) in the later stages of the molt period when compared to ALC and FF treatment groups. The overall trend of SCFA in cecal and fecal samples exhibited similar patterns. In trials 1 and 2, hens molted with ALC diet generally yielded more similar amplicon band patterns with the FF hens in both fecal and cecal samples by the end of the molting period than with FW hens. The results of these studies suggest that ALC molted hens supported microflora and fermentation activities, which were more comparable to FF hens than FW hens by the end of the molting period. [ABSTRACT FROM AUTHOR]

High fiber and nonstarch polysaccharide-based poultry diets have received more interest recently for retaining or promoting beneficial gastrointestinal microbial populations. The objective of this study was to investigate and compare the in vitro potential fermentability of high-fiber feed substrates (HFFS) by laying hen cecal microflora. Feed sources examined included soybean meal, soybean hull, beet pulp, wheat middlings, ground sorghum, cottonseed meal, 100% alfalfa meal, 90% alfalfa + 10% commercial layer ration, 80% alfalfa + 20% commercial layer ration, and 70% alfalfa + 30% commercial layer ration. Cecal contents and HFFS were incubated anaerobically in serum tubes at 39°C for 24 h. Samples from 2 trials were analyzed at 0 and 24 h for short-chain fatty acids (SCFA). Short-chain fatty acids in samples at 0 h were subtracted from 24-h samples to determine the net production of SCFA. In both trials involving HFFS incubations with cecal inocula, acetate production was highest followed by propionate and butyrate whereas isobutyrate and isovalerate production were in trace amounts. In trial 2, detectable valerate production appeared to consistently occur with alfalfa-based HFFS. It was clear that SCFA production was largely dependent upon HFFS, because cecal inoculum alone yielded little or no detectable SCFA production. For HFFS incubations without cecal inocula, acetate production was highest; propionate and butyrate were similar, and isobutyrate, valerate, and isovalerate production were in trace amounts. Polymerase chain reaction-based denaturing gradient gel electrophoresis results from both trials indicated 69 and 71% similarity for comparison of all feed mixtures in trials 1 and 2, respectively. All alfalfa-based HFFS yielded a higher similarity coefficient in trial 2 than in trial 1 with a band pattern of 90% similarity; diets containing 90% alfalfa + 10% commercial layer ration and 80% alfalfa + 20% commercial layer ration in trial 2 formed a subgroup with a 94% microbial similarity coefficient. These data suggest that high fiber sources may contribute to the fermentation and microbial diversity that occurs in the ceca of laying hens. [ABSTRACT FROM AUTHOR]

Previously, an experimental chlorate product (ECP) has been observed to reduce Escherichia coli and Salmonella infections in swine, cattle, and broilers. The following studies were performed to investigate the effects of different concentrations and durations of administering ECP on crop and ceca Salmonella typhimurium (ST) colonization of turkeys. In 2 separate trials, each conducted with 2 replicates, 15-wk-old turkey toms were challenged with 107 to 109 cfu of ST. In Experiment 1, toms were administered 0, 0.5, 1.0, 2.0, or 4.0× of ECP (a 1.0× concentration is equivalent to a 15 mM chlorate ion concentration) in the drinking water for 38 h. In Experiment 2, toms were administered a 2× concentration of ECP in the drinking water for 0, 14, 26, or 38 h prior to water withdrawal. All treatments were followed by a 10-h water withdrawal and an 8-h feed withdrawal prior to organ sampling. In Experiment 1, turkeys provided ECP had significantly (P < 0.05) lower populations and incidences of crop (>1.4 log reduction) and ceca (>0.6 log reduction) ST as compared with control birds (2.1 and 0.94 log ST average for all trials, respectively), with little or no additional benefit from administration of higher ECP concentrations. In Experiment 2, toms provided ECP had lower populations of crop (>2.2 log reduction) and ceca (>1.5 log reduction) ST when compared with controls (3.1 and 1.8 log ST. respectively). Again, there appeared to be little benefit in longer administration intervals on quantitative reduction of ST. These experiments suggest that the ECP significantly reduces Salmonella colonization in commercial turkeys when administered prior to feed and water withdrawal. [ABSTRACT FROM AUTHOR]

Foodborne diseases caused by enterohemorrhagic Escherichia coli, Salmonella, and Cam pylobacter species are of public health and economic significance. Shedding of these pathogens during production and slaughter are risks for contamination of products for human consumption. Consequently, strategies are sought to prevent or reduce the carriage of these pathogens in food animals before slaughter. Experimental products containing chlorate salts have been proven efficacious in reducing concentrations of E. coli and Salmonella Typhimurium in the gut of cattle, sheep, swine, and poultry when administered as feed or water additives. Mechanistically, chlorate selectively targets bacteria expressing respiratory nitrate reductase activity, such as most members of the family Enterobacteriaceae, as this enzyme catalyzes the reduction of chlorate to lethal chlorite. Most beneficial gut bacteria lack respiratory nitrate reductase activity, and thus the technology appears compatible with many bacteria exhibiting competitive exclusion capabilities. More recently, select nitrocompounds have been investigated as potential feed additives, and although these nitrocompounds significantly reduce pathogens on their own, evidence indicates that they may most effectively be used to complement the bactericidal activity of chlorate. A particularly attractive aspect of the nitrocompound technology is that, as potent inhibitors of ruminal methanogenesis, they may allow producers the opportunity to recoup costs associated with their use. At present, neither chlorate nor the nitrocompounds have been approved as feed additives by the US Food and Drug Administration, and consequently they are not yet available for commercial use. [ABSTRACT FROM AUTHOR]

The gastrointestinal microbial consortium in dairy cattle is critical to determining the energetic status of the dairy cow from birth through her final lactation. The ruminant's microbial community can degrade a wide variety of feedstuffs, which can affect growth, as well as production rate and efficiency on the farm, but can also affect food safety, animal health, and environmental impacts of dairy production. Gut microbial diversity and density are powerful tools that can be harnessed to benefit both producers and consumers. The incentives in the United States to develop Alternatives to Antibiotics for use in food-animal production have been largely driven by the Veterinary Feed Directive and have led to an increased use of probiotic approaches to alter the gastrointestinal microbial community composition, resulting in improved heifer growth, milk production and efficiency, and animal health. However, the efficacy of direct-fed microbials or probiotics in dairy cattle has been highly variable due to specific microbial ecological factors within the host gut and its native microflora. Interactions (both synergistic and antagonistic) between the microbial ecosystem and the host animal physiology (including epithelial cells, immune system, hormones, enzyme activities, and epigenetics) are critical to understanding why some probiotics work but others do not. Increasing availability of next-generation sequencing approaches provides novel insights into how probiotic approaches change the microbial community composition in the gut that can potentially affect animal health (e.g., diarrhea or scours, gut integrity, foodborne pathogens), as well as animal performance (e.g., growth, reproduction, productivity) and fermentation parameters (e.g., pH, short-chain fatty acids, methane production, and microbial profiles) of cattle. However, it remains clear that all direct-fed microbials are not created equal and their efficacy remains highly variable and dependent on stage of production and farm environment. Collectively, data have demonstrated that probiotic effects are not limited to the simple mechanisms that have been traditionally hypothesized, but instead are part of a complex cascade of microbial ecological and host animal physiological effects that ultimately impact dairy production and profitability., (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/).)

Calf diarrhea, a common disease mainly induced by Escherichia coli infection, is one of the main reasons for nonpredator losses. Hence, an effective nonantibacterial approach to prevent calf diarrhea has become an emerging requirement. This study evaluated the microalgae Schizochytrium sp. (SZ) and lactoferrin (LF) as a nutrient intervention approach against E. coli O101:K99-induced preweaning calve diarrhea. Fifty 1-d-old male Holstein calves were randomly divided into 5 groups (n = 10): (1) control, (2) blank (no supplement or challenge), (3) 1 g/d LF, (4) 20 g/d SZ, or (5) 1 g/d LF plus 20 g/d SZ (LFSZ). The experimental period lasted 14 d. On the morning of d 7, calves were challenged with 1 × 10 11 cfu of E. coli O101:K99, and rectum feces were collected on 3, 12, 24, and 168 h postchallenge for the control, LF, SZ, and LFSZ groups. The rectal feces of the blank group were collected on d 14. Data were analyzed using the mixed procedure of SAS (version 9.4; SAS Institute Inc.). The E. coli K99 challenge decreased the average daily gain (ADG) and increased feed-to-gain ratio (F:G) and diarrhea frequency (control vs. blank). Compared with the control group, the LFSZ group had a higher ADG and lower F:G, and the LFSZ and SZ groups had lower diarrhea frequency compared with the control group. In addition, the LFSZ and SZ groups have no differences in diarrhea frequency compared with the blank group. Compared with the control group, the blank group had lower serum nitric oxide (NO), endothelin-1, d-lactic acid (D-LA), and lipopolysaccharide (LPS) concentrations, as well as serum IgG, IL-1β, IL-6, IL-10, and TNF-α levels on d 7 and 14. On d 7, compared with the control group, all treatment groups had lower serum NO level, the SZ group had a lower serum D-LA concentration, and the LF and LFSZ groups had lower serum LPS concentration. On d 14, compared with the control group, the fecal microbiota of the blank group had lower Shannon, Simpson, Chao1, and ACE indexes, the LFSZ group had lower Shannon and Simpson indexes, the SZ and LFSZ groups had a higher Chao1 index, and all treatment groups had a higher ACE index. In fecal microbiota, Bifidobacterium and Actinobacteria were negatively associated with IL-10 and d-lactate, while Akkermansia was negatively associated with endothelin-1 and positively correlated with LPS, fecal scores, and d-lactate levels. Our results indicated that LF and SZ supplements could alleviate E. coli O101:K99-induced calf diarrhea individually or in combination. Supplementing 1 g/d LF and 20 g/d SZ could be a potential nutrient intervention approach to prevent bacterial diarrhea in calves., (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/).)

Cashew nut shell extract (CNSE) is a byproduct of the cashew nut industry, containing bioactive compounds that alter rumen fermentation patterns. Therefore, study objectives were to evaluate the effects of CNSE (59% anacardic acid and 18% cardol) on production, rumen fermentation variables, metabolism, and inflammation in transition dairy cows. A total of 51 multiparous Holstein cows were used in a randomized design and assigned to treatment based on their previous 305-d mature equivalent milk and parity. Cows were assigned to 1 of 2 treatments 21 d before expected calving: (1) CON (control diet; n = 17) or (2) CNSE-5.0 (control diet and 5.0 g/d CNSE granule [containing 50% CNSE]; n = 34). Following parturition, 17 cows (preselected at initial treatment assignment) from the CNSE-5.0 treatment were reallocated into a third treatment group: CNSE-2.5 (control diet and 2.5 g/d CNSE granule; n = 17), resulting in 3 total treatments postpartum: (1) CON, (2) CNSE-2.5, and (3) CNSE-5.0. Prepartum rumen pH was unaltered by treatment; however, postpartum rumen pH was increased (0.31 units) in CNSE cows relative to CON. Prepartum rumen ammonia N concentration tended to be decreased (34%) in CNSE-5.0 cows compared with CON, and there tended to be a quadratic effect on postpartum ammonia N, as it was decreased in CNSE-2.5 compared with CON and CNSE-5.0. Prepartum dry matter intake (DMI) was unaffected by treatment; however, postpartum DMI was increased (8%) in CNSE cows relative to CON. No treatment differences were observed in pre- or postpartum digestibility measurements. Milk and protein yields from cows fed CNSE tended to be increased (6% and 7%, respectively) relative to CON. No treatment differences were detected for energy-corrected milk, feed efficiency, body weight, body condition score, energy balance, milk composition, milk urea nitrogen, or somatic cell count. Prepartum fecal pH decreased (0.12 units) in CNSE-5.0 cows relative to CON cows but was similar between treatments postpartum. Supplementing CNSE did not affect prepartum glucose, nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), or insulin. However, prepartum circulating blood urea nitrogen tended to be decreased and glucagon was decreased in CNSE-5.0 cows compared with CON (9 and 20%, respectively). Additionally, CNSE supplementation decreased glucose and insulin concentrations postpartum relative to CON cows (6% and 20%, respectively). Quadratic effects were detected for postpartum circulating NEFA and BHB such that their levels were increased in CNSE-2.5 cows relative to CON and CNSE-5.0. Pre- and postpartum circulating serum amyloid A, lipopolysaccharide-binding protein, and haptoglobin were unaffected by treatment. Overall, CNSE influenced some key rumen fermentation variables, altered postabsorptive metabolism, and increased production parameters in transition dairy cows., (© 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/).)

Subacute rumen acidosis may cause postruminal intestinal barrier dysfunction, but this does not appear to be due to increased hindgut fermentation. Alternatively, intestinal hyperpermeability may be explained by the plethora of potentially harmful substances (e.g., ethanol, endotoxin, and amines) produced in the rumen during subacute rumen acidosis, which are difficult to isolate in traditional in vivo experiments. Therefore, objectives were to evaluate whether abomasal infusion of acidotic rumen fluid collected from donor (Donor) cows elicits systemic inflammation or alters metabolism or production in healthy recipients. Ten rumen-cannulated lactating dairy cows [249 ± 63 d in milk; 753 ± 32 kg of body weight (BW)] were randomly assigned to 1 of 2 abomasal infusion treatments: (1) healthy rumen fluid (HF; 5 L/h; n = 5) or (2) acidotic rumen fluid (AF; 5 L/h; n = 5) infused. Eight rumen-cannulated cows [4 dry, 4 lactating (lactating = 391 ± 220 d in milk); 760 ± 70 kg of BW] were used as Donor cows. All 18 cows were acclimated to a high-fiber diet (46% neutral detergent fiber; 14% starch) during an 11-d prefeeding period during which rumen fluid was collected for the eventual infusion into HF cows. During period (P) 1 (5 d), baseline data were obtained and on d 5 Donor were corn-challenged (2.75% BW ground corn after 16 h of 75% feed restriction). Cows were fasted until 36 h relative to rumen acidosis induction (RAI), and data were collected through 96 h RAI. At 12 h RAI, an additional 0.50% BW of ground corn was added, and acidotic fluid collections began (7 L/Donor every 2 h; 6 M HCl was added to collected fluid until pH was between 5.0 and 5.2). On d 1 of P2 (4 d), HF/AF cows were abomasally infused with their respective treatments for 16 h, and data were collected for 96 h relative to the first infusion. Data were analyzed in SAS (SAS Institute Inc.) using PROC MIXED. Following the corn challenge in the Donor cows, rumen pH only mildly decreased at nadir (pH = 5.64 at 8 h RAI) and remained above the desired threshold for both acute (5.2) and subacute (5.6) acidosis. In contrast, fecal and blood pH markedly decreased to acidotic levels (nadir = 4.65 and 7.28 at 36 and 30 h RAI, respectively), and fecal pH remained below 5 from 22 to 36 h RAI. In Donor cows, dry matter intake remained decreased through d 4 (36% relative to baseline) and serum amyloid A and lipopolysaccharide-binding protein markedly increased by 48 h RAI in Donor cows (30- and 3-fold, respectively). In cows that received the abomasal infusions, fecal pH decreased in AF from 6 to 12 h relative to the first infusion (7.07 vs. 6.33) compared with HF; however, milk yield, dry matter intake, energy-corrected milk, rectal temperature, serum amyloid A, and lipopolysaccharide-binding protein were unaffected. Overall, the corn challenge did not cause subacute rumen acidosis but markedly decreased fecal and blood pH and stimulated a delayed inflammatory response in the Donor cows. Abomasal infusion of rumen fluid from corn-challenged Donor cows decreased fecal pH but did not cause inflammation, nor did it create an immune-activated phenotype in recipient cows., (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 study was to investigate the effects of dietary energy levels and rumen-protected lysine supplementation on serum free fatty acid levels, β-hydroxybutyrate levels, dry matter (DM) intake, and milk production and composition. Treatments were arranged in a 2 × 2 factorial design with 2 dietary energy levels [high net energy for lactation (NE L ) = 1.53 Mcal/kg of DM vs. low NE L = 1.37 Mcal/kg of DM; HE vs. LE) fed either with rumen-protected lysine (bypass lysine; 40 g/cow per day) or without rumen-protected lysine (control). Sixty-eight third-lactation Holstein dairy cows entering their fourth lactation were randomly allocated to 4 treatments groups: HE with bypass lysine, HE without bypass lysine, LE with bypass lysine, and LE without bypass lysine. Groups were balanced based upon their expected calving date, previous milk yields, and body condition score. All cows were fed the same diet (NE L = 1.34 Mcal/kg of DM) during the dry period prior to the trial. Rumen-protected lysine was top-dressed on a total mixed ration to deliver 9.68 g/d of metabolizable lysine to pre- and postpartum cows. After calving, all cows received the same TMR (1.69 Mcal/kg of DM). Blood samples were collected at -21, -14, -7, 0, 3, 7, 14, and 21 d relative to calving, and free fatty acids and β-hydroxybutyrate concentrations were measured. Amount of feed offered and orts were collected and measured for individual cows 4 d/wk. Milk samples were collected once per week following calving, and milk composition was analyzed. Feeding high NE L to close-up cows decreased the concentrations of free fatty acid and β-hydroxybutyrate in prepartum cows but not in postpartum cows. Addition of rumen-protected lysine increased postpartum DM intake, and decreased serum free fatty acid and β-hydroxybutyrate concentrations. Neither energy nor rumen-protected lysine supplementation nor their interaction affected milk yield or fat or lactose yields. However, cows in the group receiving HE with bypass lysine tended to produce more milk compared with other groups and had a lower blood β-hydroxybutyrate concentration postpartum. These results indicate that feeding a high-energy diet together with rumen-protected lysine improved DM intake and lowered serum free fatty acid and β-hydroxybutyrate concentrations in transition cows., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)