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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]

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]

Cattle can carry foodborne pathogenic bacteria, especially E. coli O157:H7, in their gastrointestinal tracts. These pathogens are spread to consumers through contaminated meat products, water, fruits or vegetables. The microbial population of the ruminant is inefficient and also produces methane which can waste up to 12% of the GE of the diet of the animal. Methods to improve food safety do not currently carry an economic advantage to implementation; but if a method to reduce pathogens simultaneously reduces the inefficiencies of fermentation then the economics of food safety can be improved. Isoamyl acetate (IA; banana oil) is a naturally occurring aliphatic carboxylic ester widely used as a flavoring agent in foods that has been reported to have bacteriacidal activity. In the present study we added IA at various concentrations (from 0 to 50 mM) to pure cultures of E. coli O157:H7 (initial concentration of 106 cfu/mL) and found that approximately 30 mM IA demonstrated significant (P < 0.05) antibacterial activity. Mixed rumen contents from grass-fed Holstein cows were used for the in vitro mixed culture studies. Rumen fluid (containing 1 g/L glucose and xylose) was inoculated with 104 cfu/mL E. coli O157:H7 and added to separate anaerobic tubes (n=16). IA was added to achieve final concentrations from 0 to 50 mM in each tube. Tubes were incubated at 39°C for 24 h. Samples were serially diluted (10-fold increments) and plated to determine populations of inoculated E. coli O157:H7. E. coli O157:H7 populations were reduced (P < 0.05) in tubes containing >30 mM IA. Parallel tubes (n=16) were incubated to determine the effects of IA on the ruminal fermentation. Total gas volume, CH4, and total VFA concentrations were reduced (P < 0.05) in tubes containing >30 mM IA. Results suggest that IA could be used as a surface or hide disinfectant with more efficacy than as a feed additive because the impact on the overall fermentation efficiency appears to be probably detrimental. [ABSTRACT FROM AUTHOR]

Fecal prevalence of E. coli O157 in ruminants is highest in the summer months and decreases to low or undetectable levels in the winter. We hypothesize that the seasonal variation of this pathogen is a result of physiological responses within the host animal to changing day-length. The thyroid is one gland known to respond to changing day-length. Two experiments were conducted to determine if a hyperthyroid status would initiate fecal shedding of E. coli O157 in cattle during the winter when shedding is virtually non-existent (Winter experiment) or influence cattle actively shedding E. coli O157 (Summer experiment). Yearling cattle were group-penned under dry-lot conditions, adjusted to a high concentrate ration, and randomly assigned to treatment: Control (1 mL corn oil injected s.c. daily) or T3 (1.5 mg T3 suspended in corn oil injected s.c daily). Cattle were individually processed daily for collection of fecal and blood samples. Treatment with exogenous T3 produced a significant change in serum thyroid hormone concentrations indicative of a hyperthyroid status in both experiments. No differences (P > 0.10) were observed in fecal shedding of E. coli O157 in the winter experiment. In the summer experiment, fecal shedding of E. coli O157 was decreased (P = 0.05) by administration of T3 during the treatment period (d 1 to 10), tended to be lower (P = 0.08) during the following 7-d period of no treatment and was lower (P = 0.01) when examined across the entire experimental period. Results of this research indicate that the thyroid or its hormones may be involved in the seasonal shedding patterns of E. coli O157 in cattle. [ABSTRACT FROM AUTHOR]

Objectives of this study were to examine the effects of a methaneinhibitor (nitroethane; NE) on methane (CH4) emissions, and ruminal CH4-producing activity in Holstein steers (403 ± 26 kg BW). Steers were fed a 50% concentrate diet and orally administered NE twice daily at 0 (0X), 80 (1X) or 160 (2X) mg NE/kg BW d-1 for 14 d. Methane emissions were measured for 22 h/d on d 0, 6 and 13 of the study, using the sulfur hexafluoride tracer gas technique. Ruminal and fecal contents were collected on d-1, 1, 2, 7 and 14 of treatment for measurement of VFA and CH4 -producing activity. Compared to control steers (14.6; 1.24 kg/d), DMI and ADG were higher (P<0.01) in 1X-treated steers (15.0; 1.49 kg/d), but lower (P<0.01) in 2X treated steers (13.1; 0.86 kg/d). Methane emissions (L/d) decreased (P<0.07) as NE dose increased (283, 270 and 246 ± 11 for 0X, 1X and 2X steers, respectively). Methane emissions per unit gross energy intake (% GEI) were also lower (P<0.03) in 1X-(3.76 ± 0.14%) compared to control steers (4.22 ± 0.14 %). However, lower DMI of 2X-treated steers resulted in similar CH4 emissions between 2X- (4.15 ± 0.14%) and control steers. Methane emissions were not affected by day of study or day x treatment. Ruminal CH4 producing activity (8.5, 7.9 and 4.7 ± 0.5 umol/g h-1) and calculated ruminal CH4 based on fermentation balance (23.1, 23.1 and 19.1 ± 1.3 mol CH4 /100 mol VFA) were lower (P<0.01) in 2X- compared to 0X- and 1X-treated steers. Fecal CH4 producing activity was lower in 1X- and 2X-treated steers compared to 0X-steers (3.9, 1.4 and 1.4 ± 0.4 umol/g h-1). Day of study affected ruminal CH4 activity, but day x treatment was not significant. Results from both in vivo and in vitro measurements of CH4 production suggest that NE inhibits methanogenesis in steers for up to 14 d. [ABSTRACT FROM AUTHOR]

Many human foodborne illnesses can be caused by consumption of foodstuffs (including meat products) contaminated with pathogenic bacteria from animal intestinal contents or hides. Steps that have been taken in the slaughter plant to decrease the spread of foodborne pathogenic bacteria (e.g., hazard analysis and critical control point methods) have been very effective; however, meat products are still the source of foodborne bacterial human illnesses. Increasing numbers of human Escherichia coli O157:H7 illnesses have also been related to contact with animals or to water supplies contaminated by run-off from cattle farms. Thus, strategies that specifically target foodborne pathogenic bacteria in the animal at the farm or feedlot level have great potential to improve food safety and decrease human illnesses. In this review, we describe a broad range of live-animal intervention strategies, both probiotic and antipathogen. Additionally, we examine some of the effects of diet and management strategies on foodborne pathogenic bacterial populations. The use of antibiotics in food animals to decrease foodborne pathogens also will be briefly examined. Overall, the concurrent use of several of these preslaughter intervention strategies could synergistically decrease human illnesses by providing for additional barriers in a multiple-hurdle approach to improving food safety.