Development of an experimental model for liver abscess induction in Holstein steers using an acidotic diet challenge and bacterial inoculation.

Holstein steers (n = 40; initial BW = 84.9 ±â€…7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorum subsp. necrophorum (9.8 × 108 colony forming units [CFU]/mL), Trueperella pyogenes (3.91 × 109 CFU/mL), and Salmonella enterica serovar Lubbock (3.07 × 108 CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P ≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P ≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorum subsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorum subsp. necrophorum and Salmonella. The F. necrophorum subsp. necrophorum was clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophorum into the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA.

Liver abscesses (LA) in feedlots are costly to the beef industry. At harvest, LA cause an increase in liver condemnations, carcass trimming, and a decrease in quality grade. The objective of this research was to develop an experimental LA model in Holstein steers using an acidotic diet with and without intraruminal inoculation of bacteria involved in LA formation. These data suggest acidotic diet challenges in conjunction with bacterial inoculation were able to induce LA in Holstein steers. The acidotic diet alone caused reduced rumen content pH and caused rumen wall inflammation and damage, observed at harvest. Nonetheless, the addition of bacteria had a compounding effect on rumen damage. Both bacteria inoculated were isolated from 57% of LA suggesting they may work in synergy to form LA.

Removing maternal heat stress abatement during gestation modulated postnatal physiology and improved performance of Bos indicus-influenced beef offspring.

This study evaluated the growth and immune response of beef calves born from Bos indicus-influenced beef heifers provided pre- and postpartum heat abatement on pasture. On 83 ±â€…4 d prepartum (day 0), 64 Brangus crossbred beef heifers (~» B. indicus) were stratified by body weight (BW; 454 ±â€…37 kg) and body condition score (BCS; 6.3 ±â€…0.28; scale 1 to 9), and then allocated into 1 of 16 bahiagrass pastures (1 ha and 4 heifers per pasture). Treatments were randomly assigned to pastures (8 pastures per treatment) and consisted of heifers provided (SH) or not (NSH) access to artificial shade (4.5 m2 of shade area per heifer) from 83 d prepartum to 50 d postpartum (days 0 to 133). Heifers and calves were managed similarly from day 133 until the start of the breeding season (day 203). Calves were weaned on day 203 (at 119 ±â€…19 d of age), limit-fed the same drylot diet at 3.5% of BW (DM basis) days 209 to 268 (3 to 4 calves per pen; 8 pens per treatment) and vaccinated against respiratory disease pathogens on days 222 and 236. Heifer intravaginal temperatures from days 35 to 42 were lower (P ≤ 0.03) for NSH vs. SH heifers from 0000 to 0800 hours but greater (P ≤ 0.05) for NSH vs. SH heifers from 1100 to 1800 hours. Heifer intravaginal temperature from days 126 to 132 did not differ (P = 0.99) between NSH and SH heifers. Heifers assigned to NSH had greater respiration rates from days 20 to 96 (P ≤ 0.0007), greater plasma concentration of cortisol on days 35 (P = 0.07) and 55 (P = 0.02), less plasma concentration of insulin-like growth factor 1 (IGF-1) on days 35 (P = 0.10), 55, and 133 (P ≤ 0.05), and less BCS from days 55 to 203 (P ≤ 0.01) compared to SH heifers. Calves born from NSH heifers had less birth BW (P = 0.05), greater overall plasma haptoglobin concentrations (P = 0.05), greater seroconversion against bovine respiratory syncytial virus on day 222 (P = 0.02), tended to have greater ADG from days 209 to 268 (P = 0.07), and had greater BW on day 268 (P = 0.05) compared to SH offspring. Plasma concentrations of cortisol and serum titers against other respiratory disease pathogens did not differ (P ≥ 0.15) between NSH and SH offspring. Hence, removing maternal access to artificial shade: (1) increased prepartum intravaginal temperature and plasma concentrations of cortisol but reduced prepartum BCS and plasma concentrations of IGF-1 in grazing B. indicus-influenced beef heifers; and (2) increased post-weaning BW gain and had positive effects on humoral immune response of their offspring.

In dairy cattle, heat stress during late gestation negatively impacted offspring postnatal growth and immune function. The use of artificial shade is a management strategy that alleviates heat stress in environments with high temperatures and humidity. The effects of maternal access to artificial shade and its impacts on offspring performance have not been reported for Bos indicus influenced-beef cattle and were the main objective of the present study. From 83 d prepartum until 50 d postpartum, heifers had access or not to an artificial shade structure located centrally on their pastures. Overall, removing maternal access to artificial shade increased maternal internal body temperature and respiration rates, and reduced maternal body condition score from calving until the start of the breeding season and calf body weight at birth. However, calves born from heifers with no access to shade were remarkably heavier at the end of the drylot period and had lower plasma indicators of inflammatory response and positive effects to humoral immune response to vaccination.

Longitudinal Assessment of Prevalence and Incidence of Salmonella and Escherichia coli O157 Resistance to Antimicrobials in Feedlot Cattle Sourced and Finished in Two Different Regions of the United States.

The objective was to investigate the influence of cattle origin and region of finishing on the prevalence of Salmonella, Escherichia coli O157:H7, and select antimicrobial resistance in E. coli populations. Yearling heifers (n = 190) were utilized in a 2 × 2 factorial arrangement. After determining fecal Salmonella prevalence, heifers were sorted into one of four treatments: heifers originating from South Dakota (SD) and finished in SD (SD-SD); heifers originating from SD and finished in Texas (SD-TX); heifers originating from TX and finished in SD (TX-SD); and heifers originating from TX and finished in TX (TX-TX). Fecal, pen, and water scum line samples were collected longitudinally throughout the study; hide swab and subiliac lymph node (SLN) samples were collected at study end. A treatment × time interaction was observed (p ≤ 0.01) for fecal Salmonella prevalence, with prevalence being greatest for TX-TX and TX-SD heifers before transport. From day (d) 14 through study end, prevalence was greatest for TX-TX and SD-TX heifers compared with SD-SD and TX-SD heifers. Salmonella prevalence on hides were greater (p ≤ 0.01) for heifers finished in TX compared with SD. Salmonella prevalence in SLN tended (p = 0.06) to be greater in TX-TX and SD-TX heifers compared with TX-SD and SD-SD. Fecal E. coli O157:H7 prevalence had a treatment × time interaction (p = 0.04), with SD-TX prevalence being greater than TX-SD on d 56 and SD-SD and TX-TX being intermediate. A treatment × time interaction was observed for fecal trimethoprim-sulfamethoxazole-resistant and cefotaxime-resistant E. coli O157:H7 prevalence (p ≤ 0.01). Overall, these data suggest that the region of finishing influences pathogenic bacterial shedding patterns, with the initial 14 d after feedlot arrival being critical for pathogen carriage.

Short communication: evaluation of an endotoxin challenge and intraruminal bacterial inoculation model to induce liver abscesses in Holstein steers.

Holstein steers (n = 40; initial body weight [BW] = 96.0 ± 10.5 kg) were individually housed in a climate-controlled barn to evaluate potential models for the genesis of liver abscesses (LA). In this 2 × 2 factorial, steers were balanced by BW and randomly assigned to one of two treatments: 1) intravenous saline injection followed by intraruminal bacterial inoculation with Fusobacterium necrophorum subsp. necrophorum (1 × 109 colony forming unit [CFU]/mL) and Salmonella enterica serovar Lubbock (1 × 106 CFU/mL; CON; n = 20 steers); or 2) intravenous injection with 0.25 µg/kg BW of lipopolysaccharide (LPS; Escherichia coli O111:B4) followed by intraruminal bacterial inoculation of F. necrophorum subsp. necrophorum (1 × 109 CFU/mL) and S. enterica serovar Lubbock (1 × 106 CFU/mL; LBI; n = 20 steers) and 1 of 2 harvest dates (3 or 10 d post LPS infusion). Body weights were recorded on days -4, -1, 3, and 10, and blood was collected for hematology on days -4, 3, and 10, relative to LPS infusion on day 0. Intraruminal bacterial inoculation occurred on day 1. Steers from each treatment group were harvested at two different time points on day 3 or 10 to perform gross pathological examination of the lung, rumen, liver, LA (if present), and colon. Feed disappearance was less for LBI than CON (P < 0.01); however, BW did not differ (P = 0.33) between treatments. Neither treatment nor time differed for hematology (P ≥ 0.13), and no gross pathological differences were noted in the lung, liver, LA, or colon (P ≥ 0.25). A treatment × harvest date interaction was noted for ruminal pathology in which LBI had an increased percentage of abnormal rumen scores on day 3 (P < 0.01). These results suggest that an LPS challenge in combination with intraruminal bacterial inoculation of pathogens commonly isolated from LA was not sufficient to induce LA in steers within 3 or 10 d (P = 0.95) when compared to CON. Further evaluation is needed to produce a viable model to investigate the genesis and prevention of LA in cattle.

Liver abscesses in feedlot cattle can cause a decrease in feed intake, average daily gain, feed efficiency, and hot carcass weight. At harvest, liver abscesses result in liver condemnations, carcass trimming, and a potential decrease in quality grade, with an estimated economic cost to packers of $41.6 million annually. Our objective was to evaluate an intravenous endotoxin challenge followed by intraruminal inoculation of bacteria commonly isolated from liver abscesses over a 10-d period as a potential model to understand the genesis and etiology of liver abscesses in cattle and evaluate possible preventative interventions. Results suggest that an endotoxin challenge in combination with intraruminal bacterial inoculation is not a viable model to induce liver abscesses in steers, and bacterial inoculation alone was insufficient to induce liver abscesses. The length of time necessary to induce liver abscesses is also unknown. Based on our results, more research is needed to develop a noninvasive model to induce liver abscesses in cattle.

Antibimicrobial Susceptibility of Trimethoprim-Sulfamethoxazole and 3rd-Generation Cephalosporin-Resistant Escherichia coli Isolates Enumerated Longitudinally from Feedlot Arrival to Harvest in High-Risk Beef Cattle Administered Common Metaphylactic Antimicrobials.

Multidrug resistant (MDR) Escherichia coli threaten the preservation of antimicrobials to treat infections in humans and livestock. Thus, it is important to understand where antimicrobial-resistant E. coli persist and factors that contribute to its their development. Crossbred cattle (n = 249; body weight = 244 kg ±25 kg standard deviation) were blocked by arrival date and assigned metaphylactic antimicrobial treatments of sterile saline control, tulathromycin (TUL), ceftiofur, or florfenicol at random. Trimethoprim-sulfamethoxazole (COTR) and third-generation cephalosporin (CTXR)-resistant E. coli were isolated from fecal samples on days 0, 28, 56, 112, 182, and study END (day 252 for block 1 and day 242 for block 2). Then, susceptibility testing was conducted on all confirmed isolates. MDR was detected in both COTR and CTXR E. coli isolates. In COTR isolates, the number of antimicrobials each isolate was resistant to and the minimum inhibitory concentration (MIC) for amoxicillin-clavulanic acid, ceftriaxone, and gentamicin was greatest on day 28 compared with all other days (p ≤ 0.04). Similarly, chloramphenicol MIC was greater on day 28 than on day 0 (p < 0.01). Overall, sulfisoxazole MIC was less for TUL than all other treatments (p ≤ 0.02), and trimethoprim-sulfamethoxazole MIC was greater for TUL than all other treatments (p ≤ 0.03). Finally, there was no effect of treatment, day, or treatment × day for tetracycline or meropenem MIC (p ≥ 0.07). In CTXR isolates, there was an effect of day for all antimicrobials tested except ampicillin and meropenem (p ≤ 0.06). In conclusion, administering a metaphylactic antimicrobial at feedlot arrival did influence the susceptibility of COTR and CTXR E. coli. However, MDR E. coli are widely distributed, and the MIC for most antimicrobials was not different from the initial value upon completion of the feeding period.

An updated profile of the bovine acute phase response following an intravenous lipopolysaccharide challenge.

The objective was to provide an updated profile of the bovine acute-phase response to include recent advancements in technologies and expanded hematological, cytokine, and serum chemistry variables. Beef steers (n = 32; body weight [BW] = 251 ±â€…19.5 kg) were fitted with indwelling jugular catheters 1 d before lipopolysaccharide (LPS; 0.25 µg LPS/kg BW from Escherichia coli O111:B4) administration to facilitate serial blood collection. Rectal temperature was measured using indwelling probes, and ocular temperature was measured using infrared thermal imaging. Blood samples were collected for subsequent analysis of serum chemistry, hematology, and cytokine concentrations. Pearson correlation of rectal temperature and ocular infrared temperature was 0.61 (P < 0.01) and the Spearman correlation coefficient was 0.56 (P < 0.01). Interactions of hour × method were observed for ocular and rectal measurements of body temperature in response to endotoxin exposure. Maximum observed temperature was 39.6 °C at 2.5 h for both rectal and ocular measurements. Body temperature differed by method at hours 0.5, 2.5, 4.5, 7.5, 12.5, 36.5, and 47.5 (P < 0.01), but were not different otherwise. All variables of serum chemistry and complete blood count were influenced by LPS administration, except creatinine, serum glucose, and percent basophils (P ≤ 0.02). Alanine aminotransferase and alkaline phosphatase peaked at hour 2 relative to LPS administration, returned to baseline at hour 12 and continued to decrease below the baseline value at hour 48 (P < 0.01). Total protein concentration decreased 3% in response to LPS (P = 0.01). Total white blood cell count decreased 75% after LPS administration at hour 1 (P < 0.01). Lymphocyte count recovered to baseline at hour 6; sooner than neutrophil count at hour 36. Serum cortisol concentration increased 294% relative to baseline at hour 1 followed by a sustained decrease and return to normal concentration at hour 4 (P < 0.01). Additionally, circulating cytokine concentrations changed with time in response to the LPS challenge, excluding aFGF, bFGF, IGF-1, IL-2, IL-4, MCP-1, and ANG-1 (P ≤ 0.08). Maximum observed concentration of TNF-α at hour 1 was 117% greater than the pre-challenge value (P < 0.01). Data presented herein add to existing works to understand the endocrine and immune responses of beef steers administered exogenous LPS, and incorporate recent technologies, additional biomarkers, and an expanded cytokine profile that can be used as referential data in future research.

The acute phase response is a component of innate immunity initiated by infection, inflammation, or tissue damage. Characteristics of these host responses can be emulated by administration of exogenous endotoxin and closely studied in controlled settings to understand the response to inflammatory diseases that are commonplace in livestock production. Beef steers were administered exogenous lipopolysaccharide, and responses of body temperature, serum chemistry, complete blood count, cortisol, and cytokines were quantified. A moderate correlation of body temperature measured via rectal probe or ocular infrared temperature was observed, but both methods had a similar temporal response and were sensitive to changes in body temperature. Response of serum chemistry variables highlighted the links between metabolism and the inflammatory response. The initial inflammatory response was initiated by cortisol and pro-inflammatory cytokines at hour 1 and tempered by anti-inflammatory cytokines at hours 3 and 4. Therefore, these data offer an expanded view to our understanding of the bovine acute phase response.

Sexual Dimorphic Innate Immune Response to a Viral-Bacterial Respiratory Disease Challenge in Beef Calves.

The potential for sexually dimorphic innate immune responses to respiratory disease was evaluated, where eight steers and seven heifers (280 ± 4 kg) were subjected to a viral−bacterial respiratory disease challenge utilizing bovine herpesvirus-1 (BoHV-1; intranasal; 1 × 108 PFU/nostril) and Mannheimia haemolytica (MH; intratracheal; 1.3 × 107 CFU/head) administered 72 h later. Body temperature was lesser in heifers than steers (p < 0.01). There was a sex × time interaction (p = 0.05) for white blood cells where heifers had reduced concentrations compared with steers at −72 and 0 h but greater concentrations from 36 to 60 h post-MH. Concentrations of neutrophils were lesser in heifers compared to steers from 0 to 4 h, and from 8 to 12 h (p = 0.03). Lymphocytes were greater in heifers compared to steers at 12 h and from 36 to 60 h post-MH (p < 0.01). The neutrophil−lymphocyte ratio was lesser in heifers compared to steers from 2 to 24 h and at 48 h post-MH (p < 0.01). Monocytes were greater in heifers compared to steers from 24 to 60 h post-MH (p < 0.01), while eosinophils were greater in heifers compared to steers at 48 and 60 h (p < 0.01). Serum IL-4 was lesser in heifers compared to steers at 0 h and from 2 to 72 h post-MH challenge (p = 0.02). Non-esterified fatty acid concentrations were lesser (p < 0.01) in heifers compared to steers from 2 to 4 h post-MH challenge. Urea nitrogen concentrations were greater (p < 0.01) in heifers than steers at 36 h post-MH challenge. Data from this study reveal distinct differences in the acute phase response following a respiratory disease challenge where steers produced an early response, while the response in heifers appeared to be delayed.

The effects of administering different metaphylactic antimicrobials on growth performance and health outcomes of high-risk, newly received feedlot steers.

Bovine respiratory disease (BRD) is the primary animal health concern facing feedlot producers. Many antimicrobial mitigation strategies are available, but few studies have compared feedlot performance during both the receiving and finishing periods following application of different antimicrobials used as metaphylaxis at arrival. The objective of this study was to compare antimicrobial metaphylaxis methods on clinical health and growth performance across both the receiving and finishing periods. A total of 238 multiple-sourced steers in two source blocks were used in a generalized complete block design. The four treatments included: 1) a negative control, 5 mL of sterile saline injected subcutaneously (CON); 2) subcutaneous administration of florfenicol at 40 mg/kg of BW (NUF); 3) subcutaneous administration of ceftiofur in the posterior aspect of the ear at 6.6 mg/kg of BW (EXC); and 4) subcutaneous administration of tulathromycin at 2.5 mg/kg of BW (DRA). The morbidity rate for the first treatment of BRD was decreased for the DRA and EXC treatments compared to CON and NUF (P < 0.01). Additionally, average daily gain (ADG), dry matter intake (DMI), and gain-to-feed (G:F) were greater (P ≤ 0.02) in the DRA treatment during the receiving period compared to all other treatments. The ADG was also greater (P < 0.05) for EXC than the CON treatment throughout the finishing period. Nonetheless, other growth performance variables did not differ among metaphylactic treatments during the finishing period (P ≥ 0.14). Likewise, no differences in carcass characteristics or liver abscess score were observed (P ≥ 0.18). All complete blood count (CBC) variables were affected by day (P ≤ 0.01) except mean corpuscular hemoglobin concentration (P = 0.29). Treatment × time interactions were observed for platelet count, white blood cell (WBC) count, monocyte count and percentage, and lymphocyte percentage (P ≤ 0.03). However, there were no observed hematological variables that differed among treatment (P ≥ 0.10). The results indicate that some commercially available antimicrobials labeled for metaphylactic use are more efficacious than others in decreasing morbidity rate.

Stair-step strategy and immunomodulatory feed ingredient supplementation for grazing heat-stressed Bos indicus-influenced beef heifers.

On day 0 of years 1 and 2, 64 Brangus crossbred heifers per year were stratified by initial body weight (BW) and age (mean = 257 ± 20 kg and 271 ± 22 d) and allocated into 16 bahiagrass (Paspalum notatum) pastures (4 heifers per pasture per yr). Treatments were randomly allotted to pastures in a 2 × 2 factorial arrangement of treatments (4 pastures per treatment per yr). Treatments consisted of concentrate dry matter (DM) supplementation at 1.50% of BW from days 0 to 100 (CON) or concentrate DM supplementation at 1.05% of BW from days 0 to 49 and 1.95% of BW from days 50 to 100 (SST). Then, each respective supplementation strategy was added or not with immunomodulatory feed ingredients from days 0 to 100 (OMN; 4 g/45 kg of BW). Heifers were assigned to an estrus synchronization protocol from days 100 to 114. Heifers detected in estrus from days 111 to 114 were inseminated (AI) 12 h after estrus detection. Heifers not detected in estrus were timed AI on day 114. All heifers were exposed to Angus bulls from days 120 to 210 (1 bull per pasture). Effects of supplementation strategy × OMN inclusion × hour were detected (P < 0.0001) only for intravaginal temperature from days 26 to 30, which were the least (P ≤ 0.03) for SST heifers offered OMN supplementation and did not differ (P ≥ 0.17) among all remaining treatments from 0830 to 1600 hours. Effects of supplementation strategy × OMN inclusion and OMN inclusion were not detected (P ≥ 0.12) for any variable, except for the percentage of heifers detected in estrus, which was greater (P = 0.01) for heifers supplemented with vs. without OMN. Total concentrate DM offered from days 0 to 100 and heifer BW on days 0 and 56 did not differ (P ≥ 0.49) between CON and SST heifers, but SST heifers were heavier (P ≤ 0.01) on days 100 and 210 compared with CON heifers. Body surface temperature on day 25 and plasma IGF-1 concentrations on day 75 were greater (P ≤ 0.04) for SST vs. CON heifers. Percentage of pubertal heifers, heifers detected in estrus, and pregnancy to AI did not differ (P = 0.36) between SST and CON heifers but the final pregnancy percentage was greater (P = 0.04) for SST vs. CON heifers. Thus, OMN supplementation decreased the intravaginal temperature of SST heifers but failed to improve their growth and reproduction, whereas the SST strategy improved body thermoregulation, growth, and final pregnancy percentage of heat-stressed Bos indicus-influenced beef heifers compared with a constant concentrate supplementation strategy.

In Bos taurus beef heifers, altering the timing of body weight (BW) growth pattern either reduced feed costs without decreasing reproduction or enhanced reproduction without increasing feed costs. Moreover, supplementation of OmniGen-AF (OMN, a patented immunomodulatory feed ingredient) decreased internal body temperature in dairy and beef B. taurus cattle, with variable impacts on growth and reproduction. Combining both nutritional strategies for Bos indicus-beef heifers developed under heat stress conditions of tropical and subtropical environments has not been reported in the literature yet and was the main objective of the present study. For 100 d before the breeding season, heifers received either a constant supplementation amount or stair-step (SST) supplementation strategy (50 d of low followed by 50 d of high supplement amount), with or without OMN inclusion. Overall, OMN supplementation alleviated the internal body temperature of heifers but did not improve their growth and reproduction, whereas the SST strategy increased BW gain and final pregnancy percentage of B. indicus-influenced beef heifers under heat stress conditions.

Prenatal immune stimulation alters the postnatal acute phase and metabolic responses to an endotoxin challenge in weaned beef heifers.

This study evaluated whether administration of lipopolysaccharide (LPS) at each trimester of gestation would alter the acute phase (APR) and metabolic responses to a postnatal LPS challenge in weaned heifers. Pregnant crossbred multiparous cows (n = 50) were randomized into prenatal immune stimulation (PIS; n = 24; administered 0.1 µg/kg BW LPS subcutaneously at 71 ± 2, 170 ± 2 and 234 ± 2 d of gestation) and saline (CON; n = 26) groups. From these treatment groups, heifer calves (n = 12 PIS and 11 CON) were identified at weaning (244 ± 3 d of age) to receive an LPS challenge. On d 0, heifers were fitted with vaginal temperature (VT) devices, jugular catheters, and moved into individual stalls. On d 1, heifers were challenged i.v. with LPS (0.5 µg/kg BW) at 0 h. Blood samples were collected and sickness behavior scores (SBS) recorded at 0.5 h intervals from -2 to 8 h and at 24 h relative to LPS challenge. Serum was analyzed for cortisol, cytokines, glucose, non-esterified fatty acids (NEFA), and serum urea nitrogen (SUN) concentrations. Baseline VT was lesser in PIS heifers from -11 to -5 h pre-LPS (treatment × time: P < 0.01) compared to the CON; however, the post-LPS VT response did not differ between treatments (P = 0.89). There was a treatment × time interaction (P < 0.01) for SBS with PIS heifers having lesser SBS from 0.5 to 2 h post-LPS compared to CON. There was a treatment × time interaction (P = 0.03) for cortisol with PIS heifers having greater cortisol at 0.5, 3, 3.5, 5.5 and 6.5 h post-LPS compared to CON. There were treatment × time interactions for the post-LPS cytokine responses (P ≤ 0.05). Specifically, PIS heifers had greater TNF-α from 1.5 to 2 h, yet less TNF-α at 3 h than CON (P < 0.01), and PIS heifers had greater IFN-γ from 3.5 to 5.5 h post-LPS than CON (P < 0.01). In contrast, IL-6 was less in PIS than CON heifers from 1.5 to 8 h post-LPS (P < 0.001). Glucose concentrations were greater in PIS heifers at -1 h, but less at 2, 3 and 5.5 h compared to CON (treatment × time: P < 0.01). Serum NEFA concentrations were greater (P = 0.04) in PIS than CON heifers. There was a treatment × time interaction (P < 0.01) for SUN with PIS heifers having greater SUN concentrations at -2, -1.5, 2, 3, 6.5 and 24 h than CON. These data demonstrate that in utero exposure to multiple low doses of endotoxin has lasting physiological and immunological effects when the offspring encounter a similar postnatal immunological insult.

Evaluation of Bacillus subtilis PB6 on feedlot phase growth performance, efficiency of dietary net energy utilization, and fecal and subiliac lymph node Salmonella prevalence in spring placement yearling beef steers fed in southeastern South Dakota,.

Yearling crossbred beef steers [N = 238; initial shrunk body weight (BW) = 402 ± 31.2 kg] were used to investigate the influence of a Bacillus subtilis probiotic on animal growth performance, efficiency of dietary net energy (NE) utilization, carcass characteristics, and fecal and subiliac lymph node Salmonella prevalence during a 140-d finishing period at the Southeast Research Farm in Beresford, SD. Steers were allotted to 1 of 24 pens (N = 9-10 steers/pen) and assigned to 1 of 2 dietary treatments (12 pens/treatment): no probiotic (CON) or 0.5 g/steer/d of a B. subtilis PB6 probiotic (CLOSTAT500, Kemin Industries, Des Moines, IA; CLO). Bunks were managed according to a slick bunk management approach. Fecal samples were collected on study days 1, 28, 56, 112, and 140 from a subsample of steers from each pen (N = 5 steers/pen) via rectal palpation and composited by pen for the determination of Salmonella prevalence using selective enrichment and culture media. Upon harvest, subiliac lymph nodes were obtained from an equal number of steers from each treatment (collected from every other steer) following evisceration and hide removal. Data were analyzed as a randomized complete block design and pen served as the experimental unit; an α of 0.05 determined significance. Live-basis final BW and average daily gain tended (P ≤ 0.06) to be reduced for CLO. No differences were detected (P ≥ 0.11) between treatments for dry matter intake or gain efficiency. Treatment neither altered the efficiency of dietary NE utilization nor calculated dietary NE content based upon observed performance (P ≥ 0.46). No differences were detected between treatments for any carcass traits (P ≥ 0.15). No Salmonella was recovered in any fecal samples collected on study days 1, 28, or 56. On day 112, steers from CLO had a numerically lower (P = 0.17; 25.0 vs. 8.3%) incidence of fecal Salmonella compared to CON. On study day 140, fecal Salmonella incidence did not differ between treatments (P = 0.34; 0.0 vs. 8.3%) for CON and CLO, respectively. Upon harvest, no Salmonella was recovered in any subiliac lymph nodes. These data indicate that B. subtilis PB6 did not influence feedlot phase growth performance or fecal Salmonella prevalence. Additionally, Salmonella was not observed in the subiliac lymph nodes of any steers upon harvest.

Influence of Yeast Products on Modulating Metabolism and Immunity in Cattle and Swine.

Nutritional supplementation has been used by livestock producers for many years in order to increase animal performance, improve animal health, and reduce negative effects associated with enteric and/or respiratory pathogens. Supplements such as yeast and yeast-based products have broad applications across many livestock production systems, including poultry, aquaculture, cattle, and swine and have been shown to benefit animal production at various stages. These benefits include improvement in milk production, weight gain and feed conversion, as well as immune function. Initial research into the mode of action for these effects has focused on stimulation of the immune system by the ß-glucan fractions of yeast. However, emerging studies have revealed that some of the beneficial effects of yeast products may stem from altering metabolism, including the availability of glucose and fatty acids. These changes in metabolism, and potentially energy availability, may partially explain differences in immune function observed in yeast-supplemented livestock, as the energy demands of an activated immune system are extremely high. Thus, this paper explores the influence of yeast products on metabolism in cattle and swine, and how changes in metabolism and energy availability may contribute to improvements in immune function in supplemented animals.

Some aspects of the acute phase immune response to a lipopolysaccharide (LPS) challenge are mitigated by supplementation with a Saccharomyces cerevisiae fermentation product in weaned beef calves.

This study was conducted to determine if feeding a Saccharomyces cerevisiae fermentation product (SCFP) to calves would alter the acute phase response to a lipopolysaccharide (LPS) challenge. Crossbred steer calves [n = 32; 274 ± 1.9 kg body weight (BW)] were randomly allotted to two treatment diets for 21 d: 1) control, fed RAMP (Cargill, Dalhart, TX) and 2) SCFP, fed the control ration supplemented with NaturSafe at 12 g/hd/d mixed into the TMR (NaturSafe, Diamond V, Cedar Rapids, IA). On day 22, steers were fitted with indwelling jugular catheters and rectal temperature monitoring devices and placed in individual bleeding stalls. On day 23, steers were challenged i.v. with 0.25 µg/kg BW LPS. Blood samples were collected at 0.5-h (serum) or 2-h (complete blood counts) intervals from -2 to 8 h and again at 24 h relative to the LPS challenge at 0 h. Sickness behavior scores (SBS) were recorded after the collection of each blood sample. Rectal temperatures were greater in SCFP steers from 6 to 11 h, at 13 h, from 15 to 20 h, and from 22 to 24 h following the LPS challenge compared to Control steers (treatment × time: P = 0.01). Additionally, SCFP-supplemented steers had reduced (P < 0.01) SBS compared to Control steers. Platelet concentrations remained greater in SCFP-supplemented steers compared to Control steers throughout the study (P = 0.05), while there was a tendency (P = 0.09) for SCFP steers to have greater white blood cells and eosinophils concentrations than Control steers. There was a treatment × time interaction for serum cortisol and glucose (P < 0.01). Specifically, cortisol was greater at 0.5 and 2 h postchallenge but was reduced at 3 h for SCFP steers compared to Control steers. Glucose was greater in SCFP steers at -0.5, 2, and 7.5 h compared to Control steers. Serum amyloid A was reduced in SCFP steers at 0.5 h, yet greater at 1 and 7.5 h postchallenge compared to Control steers (treatment × time: P < 0.01). Fibrinogen concentrations were greater (P < 0.01) in SCFP compared to Control steers. There was a treatment × time interaction (P < 0.01) for tumor necrosis factor-α (TNF-α) such that concentrations were reduced in SCFP steers from 1 to 2 h postchallenge compared to Control steers. Overall, these data suggest that supplementing calves with SCFP may have primed the innate immune response prior to the challenge, particularly platelets, which resulted in an attenuated sickness behavior and TNF-α response to LPS.

Correlation of Ambient Temperature With Feedlot Cattle Morbidity and Mortality in the Texas Panhandle.

Anecdotal data would suggest that weather patterns influence beef cattle health in feedyards, and cattle producers often associate the seasonality of some illnesses with changes in environmental temperatures. However, to our knowledge, there is little information from large-scale feeding operations and precision weather stations that establishes a link or lack thereof between weather patterns and cattle health. Additionally, we are unaware of any studies correlating other weather parameters with animal health data. Therefore, the objective of this study was to test for associations between monthly temperature variation and animal morbidity/mortality in feedlots in the Texas Panhandle. Weather data was collected from a Texas Tech University Mesonet weather station in close proximity to 19 beef cattle feedyards in the Texas Panhandle. Additionally, near real-time morbidity and mortality data was collected from those yards from 2015 to 2018. These data document a seasonal pattern relative to cattle morbidity and mortality with most health events occurring from November to January. This pattern is differentiated when comparing morbidity and mortality by listed causation (e.g., respiratory, digestive, other), and the majority of deaths over the entire time course were attributed to respiratory disease. Most cattle morbidity was documented in the winter months, most of which were classified as respiratory disorders. Additionally, an increase in health events was observed as the population of the feedyard increased. However, the overall effects of ambient temperature on cattle health were minimal and the two may not be causally linked. The initial overview of the relationships documented in this manuscript may warrant further stratification and exploration.

Modulation of the metabolic response using dexamethasone in beef steers vaccinated with a multivalent respiratory vaccine.

Available energy plays a critical role in the initiation and maintenance of an immune response to a pathogen, a process that is further altered by activation of the stress system. This study was designed to determine the effect of an acute vs chronic stress model on the metabolic response to vaccination in naïve beef steers. Steers (n = 32; 209 ± 8 kg) were blocked by body weight (BW) and randomly assigned to one of three treatments: 1) Chronic stress (CHR), 0.5 mg/kg BW dexamethasone (DEX) administered i.v. at 1000 h on day 3 to day 0; 2) Acute stress (ACU), 0.5 mg/kg BW DEX administered i.v. at 1000 h on day 0 only; or 3) Control (CON), no DEX. On day -4, steers were fitted with jugular vein catheters and moved into individual bleeding stalls in an environmentally-controlled facility. Blood samples were collected at -74, -50, and -26 h, at 0.5-h intervals from -4 to 6 h, and at 12, 24, 36, 48, and 72 h relative to vaccination with a combination vaccine (Pyramid 5 + Presponse SQ, Boehringer Ingelheim Animal Health USA, Duluth, GA) at 1200 h on day 0. Data were analyzed by the MIXED procedure of SAS specific for repeated measures. There was a treatment × time interaction (P < 0.001) for serum glucose concentrations. Specifically, glucose concentrations increased at -50 h in CHR steers and at 1200 h in ACU steers and remained elevated through 72 h postvaccination period in these two treatments compared to CON steers. The change in nonesterified fatty acid (NEFA) concentrations relative to baseline values was affected by treatment and time (P < 0.001) such that the change in NEFA was greater in CHR (0.06 ± 0.01 mmol/L), followed by CON (-0.01 ± 0.01 mmol/L) and ACU steers (-0.04 ± 0.01 mmol/L). There was a tendency (P = 0.08) for a treatment × time interaction for change in serum NEFA concentrations. Serum urea nitrogen (SUN) was affected by treatment and time (P < 0.001) such that SUN concentrations were greatest in CHR (12.0 ± 0.1 mg/dL) followed by ACU (10.4 ± 0.1 mg/dL) and CON steers (9.6 ± 0.1 mg/dL); however, the treatment × time interaction was not significant (P = 0.12). These data demonstrate that activation of the stress and immune axes using an acute or chronic stress model can increase energy mobilization prior to and following vaccination in naïve steers, potentially affecting available energy needed to mount an adequate antibody response to vaccination.

Translocation of Orally Inoculated Salmonella Following Mild Immunosuppression in Holstein Calves and the Presence of the Salmonella in Ground Beef Samples.

The objective of this study was to determine if immunosuppression through daily dexamethasone (DEX) infusion altered Salmonella translocation from the gastrointestinal tract. Weaned Holstein steers (n = 20; body weight [BW] = 102 ± 2.7 kg) received DEX (n = 10; 0.5 mg/kg BW) or saline (control [CON]; n = 10;) for 4 days (from day -1 to 2) before oral inoculation of naldixic acid-resistant Salmonella enterica Typhimurium (SAL; 3.4 × 106 colony-forming units [CFU]/animal) on day 0. Fecal swabs were obtained daily, and blood was collected daily for hematology. At harvest (day 5), ileum, cecal fluid, lymph nodes (ileocecal, mandibular, popliteal, and subscapular), and synovial (stifle, coxofemoral, and shoulder) samples were collected for isolation of the inoculated strain of SAL. White blood cell (WBC) and neutrophil concentrations were elevated (p < 0.01) in DEX calves following each administration event. Following inoculation, 100% of DEX calves shed the experimental strain of SAL for all 5 days, 90% of CON calves shed from day 1 to 3, and 100% of CON calves shed from day 4 to 5. Greater (p < 0.01) concentrations of SAL were quantified from the cecum of DEX calves (3.86 ± 0.37 log CFU/g) compared with CON calves (1.37 ± 0.37 log CFU/g). There was no difference in SAL concentrations between DEX and CON calves in ileal tissue (p = 0.07) or ileocecal (p = 0.57), mandibular (p = 0.12), popliteal (p = 0.99), or subscapular (p = 0.83) lymph nodes. Of the stifle samples collected, 3.3% were positive for SAL, highlighting a contamination opportunity during hindquarter breakdown. While more research is needed to elucidate the interactions of immunosuppression and pathogen migration patterns, these data confirm that orally inoculated SAL can translocate from the gastrointestinal tract and be harbored in atypical locations representing a food safety risk.

Bacillus subtilis PB6 Supplementation in Weaned Holstein Steers During an Experimental Salmonella Challenge.

To evaluate the effects of a patented Bacillus subtilis probiotic, weaned Holstein steers, not shedding Salmonella (n = 40; ∼90 kg), were supplemented (CLO) or not (CON) with CLOSTAT® (13 g/hd per day; Kemin Industries, Des Moines, IA) in a starter ration for 35 d. The calves were assigned to one of four treatments in a 2 × 2 factorial design with CLO and CON calves that were orally administered Salmonella (STM) or not (NoSTM). Calves were challenged with 1.6 × 106 colony-forming unit (CFU) Salmonella Typhimurium (resistant to 50 µg/mL nalidixic acid) in 1 L of milk replacer on day 0. Blood samples were collected through jugular catheters every 6 h for 96 h, and body temperature was measured every 5 min through indwelling rectal temperature recording devices. Five calves from each treatment were harvested 48 h postchallenge, and the remaining calves were harvested 96 h postchallenge. During necropsy, tissues were collected for the isolation and quantification of the inoculated STM from various tissues. The CLOSTM group had reduced STM concentrations in the jejunum, ileum, and transverse colon 48 h after the challenge (p ≤ 0.03), but were not different 96 h postchallenge (p > 0.05). Decreased (p < 0.01) pyrexia was observed after the challenge in CLOSTM calves when compared with CONSTM calves. White blood cells and lymphocyte counts were increased (p ≤ 0.05) in CLOSTM calves after the challenge in comparison with other treatments. In calves given STM, the CLO group had greater feed intake before and after the challenge (p < 0.01) compared with the CON group. Increased serum IL-6 and IFN-γ concentrations were observed in the CONSTM group compared with other treatments. Overall, CLO reduced Salmonella presence and concentrations in gastrointestinal tissues while simultaneously reducing the severity of the challenge as indicated by blood parameters and the reduced febrile response.

Acute immunologic and metabolic responses of beef heifers following topical administration of flunixin meglumine at various times relative to bovine herpesvirus 1 and Mannheimia haemolytica challenges.

OBJECTIVE: To quantify acute immunologic and metabolic responses of beef heifers following topical administration of transdermal flunixin meglumine (TDFM) at various times relative to bovine herpesvirus 1 (BHV1) and Mannheimia haemolytica challenges. ANIMALS: 32 beef heifers (mean body weight, 170 kg). PROCEDURES: Heifers were assigned to 1 of 4 groups. Heifers in the control group did not receive TDFM, whereas 1 dose of TDFM (3.3 mg/kg) was topically applied to heifers of groups A, V, and B at -144, -72, and 0 hours. All heifers were inoculated with 1 × 108 plaque-forming units of BHV1 in each nostril at -72 hours and with 1.18 × 106 CFUs of M haemolytica intratracheally at 0 hours. Vaginal temperature was recorded and blood samples were collected for quantification of select immunologic and metabolic biomarkers at predetermined times from -144 to 360 hours. RESULTS: Mean vaginal temperature was similar between group A and the control group. Mean vaginal temperatures for groups V and B were generally lower than that for the control group following BHV1 and M haemolytica challenges, respectively. Mean neutrophil oxidative burst capacity and L-selectin expression at 0 hours were significantly decreased for group V relative to the other groups. Other biomarkers did not differ among the groups at any time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that topical administration of TDFM to beef cattle effectively alleviated pyrexia without adverse effects on acute immunologic or metabolic responses when TDFM was administered at the same time as, but not before, respiratory pathogen challenge.

Effect of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation to lactating sows on growth and indicators of stress in the postweaned pig1,2.

Dietary omega-3 polyunsaturated fatty acids (n-3 PUFA) are precursors for lipid metabolites that reduce inflammation. Two experiments were conducted to test the hypothesis that enriching the sow diet in n-3 PUFA during late gestation and throughout lactation reduces stress and inflammation and promotes growth in weaned pigs. A protected fish oil product (PFO; Gromega) was used to enrich the diet in n-3 PUFA. In the initial experiment, time-bred gilts were fed a gestation and lactation diet supplemented with 0% (control; n = 5), 0.25% (n = 4), 0.5% (n = 4), or 1% (n = 5) PFO from 101 ± 2 d of gestation to day 16 of lactation. Adding 1% PFO to the diet increased the n-3:n-6 PUFA ratio in colostrum and milk compared with controls (P = 0.05). A subsequent experiment was performed to determine whether supplementing the sow diet with 1% PFO improved growth and reduced circulating markers of acute inflammation and stress in the offspring. Plasma was harvested from piglets (16 per treatment group) on day 0 (d of weaning) and days 1 and 3 postweaning. Pigs from the 1% PFO treatment group weighed more (P = 0.03) on day 3 postweaning and had a greater (P ˂ 0.05) n-3:n-6 PUFA ratio in plasma on each day sampled compared with 0% PFO controls. There was an overall treatment effect on plasma total cortisol (P = 0.03) and haptoglobin (P = 0.04), with lesser concentrations in pigs on the 1% PFO diet. Plasma corticosteroid-binding globulin (CBG) concentrations were not different between treatment groups but were less (P ˂ 0.001) on days 1 and 3 when compared with day 0. The resultant free cortisol index [FCI (cortisol/CBG)] was less (P = 0.02) on days 1 and 3 for pigs from the 1% treatment group compared with the controls. An ex vivo lipopolysaccharide (LPS) challenge of whole blood collected on days 0 and 1 was used to determine whether 1% PFO attenuated release of inflammatory cytokines (IL-1ß, IL-6, and TNF-α). Blood from pigs within the 1% PFO treatment group tended (P = 0.098) to have a lesser mean concentration of TNF-α in response to LPS compared with blood from controls. These results suggest that providing a PFO supplement as 1% of the diet to sows beginning in late gestation and during lactation can increase the n-3:n-6 PUFA ratio in their offspring, which may improve growth and reduce the acute physiological stress response in the pigs postweaning.

Changes in the Hematological Variables in Pigs Supplemented With Yeast Cell Wall in Response to a Salmonella Challenge in Weaned Pigs.

Stressors experienced by pigs at weaning may negatively impact health and productivity. Thus, supplements that enhance pig immunity during the early post-weaned period are of great interest to the swine industry. The objective of this experiment was to evaluate the performance and hematological responses of weaned pigs supplemented with yeast cell wall (YCW) when challenged orally with Salmonella Typhimurium. Weaned pigs were assigned to one of three treatments for 22d (n = 13/treatment): Control diet, which was a non-medicated starter diet (Control); Control diet supplemented with YCW at 250 mg/kg BW (YCW250; Phileo Lesaffre Animal Care, Milwaukee, Wisconsin, USA); and Control diet supplemented with YCW at 500 mg/kg BW (YCW500). On d19 blood samples were collected from -6 to 72 h relative to oral Salmonella Typhimurium (1 × 106 cfu/pig) challenge. Gain:feed was greater (P = 0.01) in YCW250 treatment compared to both Control and YCW500 pigs. Baseline intraperitoneal temperature was greater (P < 0.001) in YCW250 pigs than Control or YCW500 pigs. There was a treatment x time interaction for the change in intraperitoneal temperature (P < 0.01), post-challenge cortisol, white blood cell counts (WBC), neutrophils, and neutrophil:lymphocyte ratio (P ≤ 0.03). Control pigs had greater (P < 0.05) cortisol concentrations than both YCW-supplemented groups at 0 h, but Control pigs had reduced (P < 0.05) cortisol compared to YCW500 pigs at 24 and 30 h post-challenge. Control pigs had greater (P < 0.05) WBC counts than both YCW-supplemented groups 6 and 12 h post-challenge, and YCW250 pigs had reduced (P < 0.01) WBC counts than Control and YCW500 pigs 18 h post-challenge. Neutrophil counts were greater (P < 0.05) in Control pigs than both YCW-supplemented groups at 6 and 12 h post-challenge and were greater (P = 0.02) than YCW250 pigs at 18 h post-challenge. Lymphocytes were greater (P < 0.001) in Control and YCW500 pigs pre- and post-challenge compared to YCW250 pigs. Control pigs had the greatest (P < 0.001) monocyte counts compared to YCW treatments. There was no effect of yeast supplementation on fecal shedding or Salmonella counts in the rectum, colon or cecum (P ≥ 0.05). While some differences were observed in intraperitoneal temperature and some hematological variables, data suggests there were minimal effects of yeast supplementation on the acute immune response to Salmonella challenge.