British and British × Continental crossbred beef steers, n = 2,100; 313 ± 38 kg of initial body weight (BW) were used to evaluate the effects of Bacillus subtilis PB6 supplementation to yearling steers in a commercial feedyard on health, prevalence of Salmonella spp., growth performance, and carcass characteristics. Steers were blocked by arrival date and assigned randomly to pen within block; pens were randomly assigned to 1 of 2 dietary treatments within block. Treatments, replicated in 15 pens/treatment with 70 steers/pen, included: 1) control (CON), diets containing no supplemental direct-fed microbials; 2) CLOSTAT (CLO), diets supplemented with 0.5 g/steer/d Bacillus subtilis PB6 (CLOSTAT 500, Kemin Industries, Des Moines, IA) to provide 6.6 × 109 CFU/g of active ingredient. Supplementing CLO decreased the overall incidence of morbidity (P = 0.03), 10.38% (CLO) vs. 13.43% (CON), decreased the percentage of steers treated once for bovine respiratory disease (BRD; P < 0.01), 9.14% (CLO) vs. 12.76% (CON), and decreased the incidence of BRD retreatment (P = 0.03) compared with CON. Mortality did not differ among treatments (P = 0.23); however, overall deads and removals tended to be less for CLO than CON (53 head vs. 73 head respectively, P = 0.06). Prevalence of fecal Salmonella did not differ among treatments, (P ≥ 0.35); overall fecal Salmonella counts tended to be less for CLO (1.59 log (10) CFU/g) than CON (2.04 log (10) CFU/g; P = 0.07). Salmonella concentration in subiliac lymph nodes (n =150/treatment) was not different (P = 0.62) between CON (0.22 log (10) CFU/g) or CLO (0.19 log (10) CFU/g); however, there was a 46% reduction in the overall mean prevalence of lymph node Salmonella (P = 0.46; 15.48% vs. 28.66%) for CLO and CON, respectively. With deads and removals included, final BW was heavier for CLO steers than CON, (654 kg vs. 641 kg, respectively, P = 0.05), and average daily gain (ADG; P = 0.08) and gain efficiency (G:F; P = 0.06) tended to be greater for CLO than CON. With deads and removals excluded, final BW, ADG, and G:F did not differ among treatments (P ≥ 0.30). Carcass traits were not different between treatments (P ≥ 0.15). Supplementing CLO throughout the feeding period in a commercial feedyard improved the health outcomes of yearling steers by decreasing BRD and overall treatment rates, reducing the overall abundance of Salmonella, and resulted in fewer steers removed from the study compared with CON.

Anecdotal evidence suggests that weaning/stocker weights, ADG, and carcass weights have increased for Southeast cattle over the last 30 years. Simultaneously, morbidity and mortality have not improved, and according to some reports, have significantly increased. Albeit, over the last 30 years, there have been several new vaccines and antibiotics introduced into the beef cattle market. Ceteris paribus, there appears to be a discrepancy related to prevailing theories that placing heavier cattle into stocker and feedlot operations reduces the incidence of morbidity and mortality. But, has there truly been an increase in weaning weights or placement weights of stocker/feedlot calves over the last 30 years? Perhaps, even with greater genetic selection by cow/calf producers for improved weaning weights and pre-weaning ADG, the genetic potential of these animals is not being realized until the stocker/feedlot sector. Indeed, Engler et al. (2014) reported that hot carcass weight (HCW) increased 4.9 lbs per year from 2001 to 2013 while others have reported no actual increase in weaning weights during this period. Undoubtedly HCW have increased, but the contributing factors are multifaceted including genetic selection for increased lean deposition, better nutritional programs, and the expanded variety of growth promoting implants, ionophores, and beta agonists. Likewise, morbidity and mortality are multifaceted manifestations affected by a variety of inputs including genetics, nutrition, environmental stressors, immunocompetence, and the prevalence and genetic diversity of pathogens. Therefore, while genetic selection for increased pre-weaning performance may be more prevalent, cow/calf producers may not be reaping the full potential of their calves due to management practices that do not capitalize on the genetic potential of the pre-weaned calf. Placing more emphasis on genetic selection for pre-weaning growth may have inadvertently resulted in calves that are less resistant to the stresses and strains associated with post-weaning production systems.

The objective of this study was to quantify the effect of shipping to feedyards in western Kansas from the Southeast on the immune response of beef steers using complete blood counts. Angus- and Hereford-sired steers (n = 24, BW = 266.3±24.9 kg) from E.V. Smith Research Center in Shorter, AL, were weaned on June 14, 2018. The following day, blood was collected for analysis. These calves were a subset from a larger project involving grazing. As such, calves were then maintained in drylots for 14 d until grazing was available. Once grazing was initiated, these calves were placed in drylot pens with a diet consisting of dry hay with supplemented with 1% of BW of dried distiller’s grains with solubles. After 80 d, half of the calves were shipped (n = 12, SC) to Hy-Plains Feedyard, LLC. in Montezuma, KS. Immediately prior to shipment, immediately post-shipment, and after 24-hr rest, blood was collected. Blood was also collected from the unshipped calves (UC) at similar time points. Whole blood collected at each time point was analyzed for complete blood counts. The data was analyzed using the Mixed Procedure in SAS. No significant differences (P > 0.05) were detected post-weaning or pre-shipping. Immediately post-shipment, white blood cell, and neutrophil counts were greater in SC while lymphocytes counts were less (P < 0.05) than UC; however, these were not different after 24-hr rest (P > 0.05). Hematocrit and monocyte count were elevated in SC both immediately post-shipping and after 24 hr of rest (P <0.05), while reticulocyte count was lower in SC at those same time points (P < 0.05). Basophil counts were lower in SC at the 24-hr rest time point (P = 0.03). Results of this study indicate that SC did not completely rehydrate after 24 hr of rest and complete blood counts show differences in immune response due to shipping

The objective of this study was to evaluate if diet during the background phase has an effect on complete blood counts as an indicator of the stress response and immune function of calves shipped to feedyards in western Kansas from the Southeast. One hundred twenty (n = 120) Angus- and Hereford-sired steers (n = 60, 237.9±21.6 kg BW) and heifers (n = 60, 227.6±17.9 kg BW) from the E.V. Smith Research Center in Shorter, AL, were weaned on June 14, 2018. The following day, calves were weighed and blood was collected for analysis. Calves were then held in drylots for 14 d until forages reached an adequate height to begin grazing. Calves were then stratified by weight and randomly assigned to four dietary treatments, with three pens per treatment: Grazing (G), Grazing with supplement (GS), dry hay with supplement (HS), or baleage with supplement (BS). Dried distiller’s grains with solubles fed at 1% of BW was used in each diet including supplementation. After 80 d on treatment diets, calves were shipped to Hy-Plains Feedyard, LLC. in Montezuma, KS. Immediately prior to shipment, immediately post-shipment, and after 24 hr rest, blood was collected for analysis. Whole blood collected at each of the four times points was analyzed for complete blood counts using a ProCyte Dx Hematology Analyzer. The data were analyzed using the Mixed Procedure in SAS. While no significant differences (P > 0.05) were detected post-weaning and prior to initiation of dietary treatments, differences across diets were seen in red blood cell count, hemoglobin, hematocrit, reticulocyte count, platelet count, white blood cell count, neutrophil count, lymphocyte count, neutrophil to lymphocyte ratio, and basophil counts (P < 0.05). Results of this study show that post-weaning backgrounding diets can have an effect on immune response to shipping stress

The objective of this study was to determine the effects of daily dexamethasone (DEX) infusions on hematology and body temperature in response to experimental, oral inoculation with Salmonella typhimurium. Weaned Holstein steer calves (n = 20; BW=102±2.7 kg) received DEX (n = 10; 0.5mg/kg BW) or saline (CON; n = 10; 0.5mg/kg BW) for 4 d (from d -1 to d 2) while simultaneously receiving an oral inoculation of a naldixic acid resistant Salmonella typhimurium (3.4x106 CFU/animal) via milk replacer on d 0. Fecal swabs for SAL shedding were obtained daily and samples were confirmed positive starting 24 h post inoculation (d 1) to harvest (d 5). Dexamethasone (DEX) administration was achieved via indwelling jugular catheters which were fitted simultaneously with rectal temperature (RT) recording devices on d −2 relative to inoculation and placed in individual pens in an environmentally controlled facility. Whole blood was collected at -24, -12, and 0 h; and at 8-h intervals from 8 to 120 h for hematology. There was a time x treatment (There should be) for RT such that the DEX treatment resulted in a decreased RT on d -1 to 2. A treatment × time interaction (P < 0.05) was observed for total white blood cells (WBC), neutrophils, lymphocytes, eosinophils, and monocytes. Specifically, DEX increased WBC and neutrophils in DEX steers (P < 0.0001) yet lymphocytes increased following DEX administration (P < 0.05 at 24 and 48 h, respectively). Monocytes initially increased (P < 0.001) in response to the -24 h DEX treatment but slowly decreased beyond CON group levels following the 48 h DEX treatment. These data may be interpreted as either mimicking multiple acute stressors with respect to daily DEX injections, mild immunosuppression due to multiple DEX exposures, or a combination of both scenarios when juxtaposing DEX and Salmonella inoculation.