Objective: This research study aimed to determine whether preweaning plane of milk-replacer nutrition influences health, standing and oral behaviors, and performance of high-risk calves. Materials and Methods: Thirty-six Holstein bull calves (1 d of age) from a commercial calf ranch were assigned to either a high plane of milk-replacer nutrition (HPN; n = 18; 20 and 28% DM lipid and protein, respectively, Cow's Match, Land O'Lakes Animal Milk Protein Co., Shoreview, MN) or a low plane of milk-replacer nutrition (LPN; n = 18; 20% DM lipid and protein, Herd Maker, Land O'Lakes Animal Milk Protein Co.) through weaning. Total serum protein concentrations confirmed that 72 and 76% of calves had failure of passive transfer (<5.2 g/dL) in HPN and LPN, respectively. All calves were bottle fed twice daily. The LPN were fed 455 g of DM/d of milk replacer (MR) until weaning, and the HPN calves were fed 830 g of DM/d of milk replacer during the first 10 d and 1,080 g from 11 d until weaning. Calf starter and water were offered ad libitum. Calves were step-down weaned beginning at 51 d and completely weaned after 58 d when consuming 1 kg of calf starter (as-fed basis). Data are reported as HPN versus LPN throughout, respectively. Results and Discussion: Risk for bloat and scouring were greater for calves fed the HPN, but there was no difference in antibiotic treatment or mortality. The HPN calves had greater performance over the preweaning period including final BW, ADG, and feed:gain (total kg of milk replacer + calf starter, kg of DM/kg of BW gain), but weaning was more stressful for HPN calves. Implications and Applications: In conclusion, the high-risk calves fed a HPN had increased preweaning ADG, but there was also an increased incidence of scours. There may be differences in the health status of calves that may affect the ability to consume and use high MR levels. When feeding high-risk calves there may be a need for alternate strategies when determining the quality and quantity of MR being fed when compared with low-risk calves. Differences in gut integrity may influence the ability of high-risk calves to handle high levels of MR early in life. Potential issues with high-risk calves being fed a HPN might be reduced with increased feeding times per day, a gradual step-up method, or other nutritional strategies that improve gastrointestinal development and function.

The objectives of this study were to determine whether plane of nutrition (PON) of milk replacer previously provided to calves, and dosage level of Mannheimia haemolytica (MH), influenced inflammatory responses to a combined viral-bacterial respiratory challenge. Holstein calves (1 d of age; n = 30) were assigned to treatments in a 2 × 3 factorial with pre-weaning PON and MH dose as main effects (n = 5 per treatment). Calves were fed either a low (LPN; n = 15) or a high PON (HPN; n = 15) from birth through weaning. Calves fed LPN were fed 436 g of dry matter (DM) per day of milk replacer until weaning, and HPN calves were fed 797 g of DM per day of milk replacer from d 1 to 10 and 1,080 g of DM per day from d 11 until weaning. Calf starter and water were offered ad libitum. Calves were step-down weaned beginning at d 54 and moved into an enclosed barn at d 70. Indwelling rectal temperature (RT) recording devices and jugular catheters were inserted at d 80. Calves were challenged with 1.5 × 108 plaque-forming units (pfu) per mL of bovine herpesvirus-1 (BHV-1) in each nostril at d 81 and with either 106, 107, or 108 cfu of MH at d 84. Blood samples were collected at varying intervals relative to BHV-1 and MH challenges. Four LPN calves either died or were euthanized soon after the 144-h observation period, whereas all HPN calves survived the entire observation period. As dosage of MH administered increased, acute and systemic inflammatory responses increased. Higher doses of MH resulted in increased leukocyte, neutrophil, and haptoglobin concentrations in infected calves. Data from the current study suggest that the highest dose, 108 cfu, triggered weaned calves' acute disease response, whereas the lower doses, 106 and 107 cfu, caused more moderate inflammation and disease. The effects of PON on inflammation responses to the disease challenge indicated that calves previously fed the LPN diet had more severe pathophysiological responses. Calves fed LPN showed higher peripheral neutrophil and leukocyte counts and serum haptoglobin concentrations following the BHV-1 challenge. Additionally, following the MH challenge, LPN calves had higher peripheral neutrophil counts, neutrophil-to-lymphocyte ratios, and serum tumor necrosis factor-α concentrations. These data demonstrate that higher doses of MH increase the acute inflammatory response and prolong inflammation, and that calves previously fed LPN responded more severely to the combined viral-bacterial respiratory challenge.

This study was designed to investigate the effects of supplementing SmartCare (SC; Diamond V, Cedar Rapids, IA) in milk replacer and Original XPC (XPC; Diamond V) in calf starter on performance and health of preweaned calves following an oral challenge with Salmonella enterica. The study was performed in two 35-d periods with 30 Holstein bull calves (2 ± 1 d of age) per period. In each period, calves were blocked by location in the barn and randomly assigned to treatments that included control, base milk replacer and calf starter with no added Saccharomyces cerevisiae fermentation products; SC, milk replacer with 1 g of SC/calf per day and base calf starter; and SC+XPC, milk replacer with 1 g of SC/calf per day and calf starter with 0.5% XPC on a dry matter basis. Calves were fed 350 g of milk replacer solids at 14% dry matter twice daily at 0700 and 1700 h. Calf starter and water were offered ad libitum and intakes were recorded daily. Calves were challenged with 108 cfu of sulfamethazine-resistant Salmonella enterica serotype Typhimurium orally on d 14 of the study. Fecal Salmonella shedding was determined on d 14 to 21 (daily), 24, 28, and 35 using selective media. Blood samples were collected on d 0, 7, 14, 16, 18, 21, 24, 28, and 35 and analyzed for hematology; plasma were analyzed for haptoglobin concentrations. All data were reported as CON, SC, and SC+XPC, respectively. Calf starter intake was increased from d 22 to 35 among SC+XPC calves and from d 29 to 35 among SC calves. The SC+XPC calves had a lower neutrophil-to-lymphocyte ratio (0.81, 0.83, and 0.69 ± 0.051) throughout the study. The SC+XPC calves also had lower hematocrits (35.1, 35.3, and 33.4 ± 0.54%) and hemoglobin concentrations (10.8, 10.6, and 10.1 ± 0.16 mg/dL) throughout the study. We found a tendency for calves fed SC and SC+XPC to have more solid fecal scores during the week after the challenge. We observed no treatment or treatment × time differences on plasma haptoglobin concentrations (63, 48, and 60 ± 0.5 μg/mL). No treatment differences were observed in the fecal shedding of the Salmonella; however, we noted a tendency for a treatment difference in the percentage of calves positive for Salmonella present in the ileal tissue at d 21 after the challenge (25, 50, and 60%). Supplementing preweaned Holstein calves with both SC in milk replacer and XPC in calf starter improved starter intake and improved fecal consistency immediately after a mild Salmonella enterica challenge, but more data are needed to further understand how these yeast fermentation products influence the immune responses to Salmonella enterica.

Our objective was to examine immunosuppression induced by dexamethasone (DEX) administration in cattle on immunological responses to a multivalent respiratory vaccine containing replicating and nonreplicating agents. Steers ( = 32; 209 ± 8 kg) seronegative to infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and parainfluenza-3 virus (PI3V) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) acute immunosuppression (ACU; 0.5 mg/kg BW DEX intravenously at 1000 h only on d 0), 2) chronic immunosuppression (CHR; 0.5 mg/kg BW DEX intravenously at 1000 h on d -3 to 0), or 3) a control (CON; no DEX). On d -4, steers were fitted with intravenous catheters in the jugular vein and placed into individual stanchions. At 1200 h on d 0, steers were administered a respiratory vaccine containing modified-live virus (MLV) isolates of IBRV, BVDV, BRSV, and PI3V and a (MH) toxoid. On d 4, cattle were transported (177 km) and housed in an isolated outdoor pen. Serum was harvested on d 0, 7, 14, 21, 28, 35, 42, and 56 to determine IBRV-, BVDV-, BRSV-, and PI3V-specific antibody titers and MH whole cell and leukotoxin antibody concentrations. Sera from d -2, 0, 1, 3, 7, and 14 were used to quantify haptoglobin (Hp) concentration and ceruloplasmin (Cp) activity. Nasal swab specimens were collected on d 0, 3, and 14 to determine the presence of IBRV, BVDV, BRSV, and PI3V via PCR analysis. There was a treatment × day interaction ( < 0.01) such that CHR steers had a greater ( ≤ 0.07) BVDV antibody titer on d 14, 21, and 28. Moreover, IBRV-specific antibodies increased beginning on d 14 for CHR and on d 28 for ACU and remained greater through d 56 compared with CON ( ≤ 0.03). Conversely, serum MH whole cell antibody concentration was least ( ≤ 0.06) for CHR from d 7 to 28 and greatest for CON ( ≤ 0.04) on d 56. Treatment altered Hp such that CON exhibited a greater ( < 0.01) Hp concentration than CHR but was not different from ACU ( = 0.16). On d 3, Cp was greatest for CON, intermediate for ACU, and least for CHR (treatment × day; ≤ 0.01). The prevalence of IBRV and BVDV in nasal swabs on d 14 was 67 and 56%, respectively, for CHR; 10 and 10%, respectively, for CON; and 9 and 0%, respectively, for ACU ( ≤ 0.006). Results suggest that CHR allowed increased replication of MLV vaccine agents. Conversely, DEX-induced immunosuppression blunted the acute phase protein and antibody response against the nonreplicating MH toxoid.

Two treatments were evaluated in commercial feedlot heifers to determine the effects of a yeast supplement on immune responses to a combined viral-bacterial respiratory challenge. Thirty-two beef heifers (325 ± 19.2 kg BW) were selected and randomly assigned to one of two treatments, and fed for 31 d: (1) Control (CON), receiving a standard feedlot ration without a yeast supplement, or (2) Yeast (YEAST), control ration plus a combination live yeast (2.5 g·hd–1·d–1) and yeast cell wall (2.5 g·hd–1·d–1) supplement (Phileo-Lesaffre Animal Care, Milwaukee, WI). All cattle were challenged intra-nasally with 1 × 108 PFU bovine herpesvirus-1 (BHV-1) on d –3 and then allowed to rest in outdoor pens for 3 d. On study d 0, each animal was challenged intratracheally with an average dose of 3 × 107 CFU Mannheimia haemolytica, was fitted with an indwelling jugular catheter and an indwelling vaginal temperature recording device, and was moved into individual stanchions in an environmentally-controlled barn. Whole blood samples were collected at the time of BHV-1 challenge at 1-h (serum) or 2-h (complete blood cell counts) intervals from 0 to 8 h, and at 12, 24, 36, 48, 60, and 72 h relative to M. haemolytica challenge. Data were analyzed using the mixed procedure of SAS specific for repeated measures with fixed effects of treatment, time, and their interaction. Water intake per hour tended (P = 0.06) to be greater in the YEAST group compared with CON. Nasal lesion scores tended (P = 0.07) to be decreased in the YEAST group compared with CON (2.50 ± 0.26 vs. 3.19 ± 0.26, respectively). There was no difference in cortisol concentrations or vaginal temperature between treatment groups (P ≥ 0.37). There was no treatment difference (P = 0.21) in total white blood cell counts following BHV-1 challenge. There was a trend (P = 0.13) for serum haptoglobin concentration to be reduced in the YEAST (11,757.3 ± 1631.7 μg/dL) group compared with CON (15,396.174 ± 1631.7 μg/dL). Cattle in the CON group tended (P = 0.07) to have greater neutrophils than YEAST (6.39 ± 0.39 vs. 5.37 ± 0.37 K/μL, respectively). In summary, feeding a combination live yeast and cell wall yeast supplement tended to reduce nasal lesion score, inflammatory response, and neutrophil count with no effect on febrile response in beef heifers. Further research is warranted to determine if other measures of the inflammatory response were influenced by yeast supplementation in this model of respiratory disease challenge.

The objectives of these studies were to determine the effects of supplementing a blend of anaerobic bacteria on the growth and health of preweaned and immediately postweaned Holstein calves. Holstein calves within 1 d of birth were randomly assigned to 1 of 2 dietary treatments (N = 35). Treatments included a negative Control and MBiotix Calf (BTX) treatment, which was administered in the milk replacer and top-dressed on the starter during the preweaned and immediately postweaned periods, respectively. The BTX treatment dose was 2 × 109 CFU/d of a proprietary blend of Lactobacillus casei and Enterococcus faecium strains; however, during the first 3 d of the study, the BTX calves were given a 10× dose. The study was conducted in 3 periods (n = 20 Control and n = 15 BTX). Calves were individually housed and fed between 250 and 350 g depending on the period of a 22% CP and 20% fat milk replacer twice daily at 0730 and 1630. Calves had ad libitum access to a calf starter and water. Calves were individually housed until they were weaned at 56 d when they were grouped by treatment for an additional 28 d. Peripheral blood samples were collected on d 0, 7, 21, 56, 70, and 84, and analyzed for hematology. Data were analyzed as a repeated measures ANOVA with treatment, time, and treatment × time as the fixed effects and period as a random effect. Calf nested within treatment was the subject of the repeated statement. Data are reported as Control vs. BTX, respectively. There was a treatment × time interaction (P = 0.001) on calf starter intake during the preweaned period, whereas BTX calves began to consume more starter during the fourth week of life, and the difference in starter intake was different (P ≤ 0.05) during the sixth to eighth week of life. BTX calves were consuming more starter at weaning (1.065 vs. 1.305 ± 0.141 kg/d; P = 0.025). Further, the BTX calves had greater ADG during the 84 d observation period (0.701 vs. 0.883 ± 0.079 kg/d; P = 0.016). There were no treatment or treatment × time effects on hematocrit percentage (34.3 vs. 35.9 ± 1.98%; P ≥ 0.235). Further, there were no treatment or treatment × time effects (P ≥ 0.178) on any hematological variable. These data indicated that supplementing MBiotix Calf improved calf starter intake and average daily gain during the preweaned and immediate postweaned periods.

0099 In silico identification of natural product inhibitors of Brucella abortus threonyl-tRNA synthetase. M. Li, N. Zheng, F. Wen, Y. Zhang, S. Li, S. Zhao, and J. Wang, Ministry of Agriculture Laboratory of Quality & Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, Ministry of Agriculture–Milk and Dairy Product Inspection Center (Beijing), Beijing, China, State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China.

The objectives of the study were to determine if supplementing milk replacer with Safmannan (SM) and ActiSaf (AS) would affect calf growth and health throughout the preweaned and immediate postweaned periods. The study was performed over 67 d, with 39 Holstein bull calves. Calves were housed in individual pens in an environmentally controlled barn, and were provided ad libitum access to a texturized calf starter and water, as well as offered 350 g of milk replacer solids, 22% CP and 20% fat, at 0700 and 1600 from d 0 to 56. Calf starter and water refusals were recorded daily and intakes calculated. Calves were randomly assigned to treatments that included CON, milk replacer with no added supplements; SM, milk replacer with 5 g SM/calf/d; and SM + AS, milk replacer with 2 g SM/calf/d and 3 g AS/calf/d. Individual BW was measured on d 0, 21, 42, 56, and 67. Blood samples were collected and analyzed for hematology on d 10, 28, and 56; while plasma and whole blood were collected and analyzed for plasma haptoglobin concentrations, neutrophil surface expression of CD62L, and neutrophil phagocytosis and oxidative burst capacity to an environmental E. coli on d 0, 10, 28, and 56. All data were reported as CON, SM, and SM + AS, respectively. The LSMeans with various superscripts differ (P ≤ 0.05). Individual calf starter intake did not differ over the entire study, although from 0 d to 21 d, calves receiving the SM + AS supplement consumed more starter (0.025a, 0.034ab, 0.074b ± 0.018 kg/d; P < 0.05). Neither ADG (0.63, 0.68, 0.69 ± 0.054 kg/d; P = 0.699), nor feed:gain (1.74, 1.74, 1.73 ± 0.070 kg/kg; P = 0.990) differed among treatments. Total leukocyte counts were greater in the CON calves on d 10 than the other treatments (14.2a, 9.2b, 11.1b ± 1.2 106/mL; P < 0.05) and was lower in the SM calves on d 28 than the CON and SM + AS treatments (10.4a, 7.9b, 10.6a ± 0.87 106/mL; P < 0.037). Neutrophil surface expression of CD62L was greatest in SM calves when compared with CON calves (92,772a, 110,441b, 94,526ab ± 5334 mean fluorescence intensity; P = 0.052). Additionally, there were treatment × time interactions on neutrophil phagocytosis and oxidative burst P ≤ 0.024), whereas SM calves had greater percentages of neutrophils phagocytizing and producing an oxidative burst on d 28. These data suggest that both yeast supplementation strategies may influence the health of high-risk, preweaned Holstein calves.

The objective of this study was to determine the effects of OmniGen-AF (OG) and Provia 6086 (PV) on the performance and health of preweaned and immediately postweaned Holstein calves. Holstein calves within 1 d of birth were randomly assigned to one of four dietary treatments (N = 80). The study was conducted in two consecutive periods with 40 calves/period (n = 10 calves/treatment/period). Dietary treatments were given in both the milk replacer and calf starter. Treatments were arranged and analyzed as a 2 × 2 factorial with OG and PV as the main fixed effects. Diets were formulated to supply approximately 10 g/d of OG and 2 billion CFU/d of PV if calves were consuming milk only or 1.36 kg of calf starter only. Calves were housed in an enclosed barn and fed 275 g of a 22% CP and 20% fat milk replacer daily at 0730 and 1630. Calves had ad libitum access to calf starter and water. The quantity of water and starter offered as well as refused was recorded and adjusted daily for approximately 10% orts. Calves were individually housed until they were weaned at 56 d when they were grouped within treatment with four calves/pen for an additional 28 d. There were no treatment or treatment × time differences on starter intake during either the preweaned (P ≥ 0.111) or postweaned (P ≥ 0.297) periods. Additionally, there were no treatment or treatment × time differences (P ≥ 0.500) in ADG during either the preweaned (0.593 ± 0.096 kg/d) or postweaned (0.845 ± 0.096 kg/d) periods. The surface expression of CD14 on peripheral blood monocytes decreased (P ≤ 0.001) with increased calf age; however, there were no treatment or treatment × time differences (P ≥ 0.339). Similarly, there were no treatment or treatment × time differences (P ≥ 0.316) on the surface expression of CD62L on peripheral blood neutrophils. There was an OG × PV × time interaction (P = 0.018) in peripheral blood neutrophil counts, whereas there was a tendency (P = 0.089) for the Control and OG + PV to have reduced neutrophils when compared with OG and PV calves at 21 d. Lastly, there were no treatment × time differences (P ≥ 0.430) on hematocrit percentages; however, there was a significant time effect (P = 0.001), whereas hematocrits were elevated at 14 and 21 d. These data indicate that OmniGen-AF and Provia 6086 supplementation during the preweaned and immediate postweaned periods did not influence growth performance, leukocyte, or hematological measures in these Holstein calves.

The objective of this study was to determine the effects of supplementing a Saccharomyces cerevisiae fermentation product prototype (Prototype) on the pathophysiological response during a combined viral-bacterial respiratory challenge. Holstein steer calves (126.5 ± 6.11kg; N = 16) were completely randomized to treatments including 0 (CON) or 20 g/head/d of Prototype (n = 8). Calves were housed in open, dry lot corrals with four calves per pen (2 pens/treatment). Calves were offered ad libitum access to a 50:50 total mixed ration of a commercially available 16% CP pelleted calf grower and 18% CP chopped alfalfa hay. Treatments were top dressed for 30 d. Orts were measured daily and the quantity of feed was adjusted for approximately 10% orts. Calves were moved to individual stanchions (2.13 × 0.76 cm) in an enclosed barn, fitted with rectal temperature monitoring devices, and allowed 24 h adaptation before initiating the respiratory challenge. All calves were challenged with 1.5 × 108 PFU·mL–1·nostril–1 of bovine herpesvirus-1 cooper strain at –72 h using a mucosal atomizer and with 106 CFU of M. haemolytica (MH) intratracheal at 0 h. Blood samples were collected via jugular venipuncture at –96, –72, –48, –24, 0, 6, 24, 48, 72, 120, 168, and 240 h relative to the MH challenge. Total leukocytes counts tended (P = 0.063) to be greater at 24 h among CON steers. Neutrophil:lymphocyte also tended to be greater (P ≤ 0.095) at 24 and 72 h among CON steers. Monocyte phagocytosis of an environmental Escherichia coli tended (P = 0.056) to be greater in steers fed the Prototype at 24 h. Neutrophil oxidative burst to an environmental Escherichia coli tended (P = 0.071) to be greater at 6 h and was greater (P = 0.011) at 168 h among steers fed the Prototype. However, monocyte oxidative burst tended (P = 0.052) to be greater among CON at 72h. Neutrophil L-selectin did not differ between treatments (P = 0.515). Neither serum haptoglobin concentrations (P = 0.773) nor rectal temperature (P = 0.985) differed between treatments. These data demonstrate that the Saccharomyces cerevisiae fermentation product prototype may influence some acute leukocyte responses during a viral-bacterial respiratory challenge, but did not have strong influences on measures of inflammation or disease.

The objective of this study was to determine the dose response effects of supplementing Saccharomyces cerevisiae fermentation product prototype on leukocyte functionality and ex vivo cytokine production during a dexamethasone (DEX) challenge. Holstein steers (125.1 ± 8.16 kg; N = 32) were assigned to treatments including 0, 20, 40, or 60 g/head/d of prototype (n = 8). Calves were housed for 21 d in dry lot corrals with four calves per pen (2 pens/treatment). Calves were offered ad libitum access to a 50/50 TMR of a commercially available 16% crude protein pelleted grower and 18% CP chopped alfalfa hay. Treatments were top dressed. The quantity of feed offered and orts were measured daily. After the 21 d adjustment to diets, calves were jugularly catheterized and moved into individual stations (2.13 × 0.76 cm) in an environmentally controlled barn and allowed 48 h to adapt before the first DEX injection. Blood samples were collected at –24, –6, 0, 6, 12, 18, 24, 48, and 72 h relative to the first DEX injection. DEX was administered via jugular catheter at 0.1 mg/kg BW at 0, 6, and 12 h. Peripheral blood neutrophil (PMN) concentrations increased (P < 0.001) at 6 h and remained elevated through 72 h in all steers. Neutrophil L-selectin and PMN and monocyte (MONO) oxidative burst (OB) and phagocytosis (PHAG) of an environmental Escherichia coli decreased (P < 0.059) at 6 h in all steers. L-selectin returned to baseline at 72 h while OB and PHAG failed to return to baseline by 72 h. Total leukocyte counts (P < 0.001) and PMN concentrations (P = 0.001) increased linearly with prototype dose. PMN L-selectin concentrations did not differ (P = 0.684) among treatments. Oxidative burst intensity in PMN (P = 0.025) and MONO (P = 0.003) increased linearly with prototype dose at 72 h, as well as in MONO PHAG intensity (P = 0.004) at 6 h. The percentage of PMN (P = 0.012) and MONO (P = 0.013) that were both PHAG and OB positive increased linearly with prototype at 72 h. Ex vivo whole blood lipopolysaccharide stimulated TNF-α concentrations was greater (P = 0.026) in prototype steers than control steers at –24 h. Overall, these data demonstrate that the dexamethasone challenge induced severe leukocyte dysfunction, and prototype supplementation influenced plasma neutrophil concentrations and may have increased recovery of neutrophil and monocyte function.

Heat stress (HS) in feedlot cattle can be detrimental to performance, health and profitability; however, utilization of feed additives has the potential to mitigate some of these negative effects. Therefore, this study was designed to determine if supplementation of a combination live yeast and yeast cell wall product in feed could mitigate the negative impacts associated with HS. Crossbred, phenotypically similar beef heifers (n=32; BW=385±43 kg) were divided into 2 pens in which one pen was fed a standard finishing ration (CON), and the other was fed the same ration plus supplemented via top dress with a combination of a live yeast (1.5 g/hd/d) and yeast cell wall product (2.5 g/hd/d; YEAST; Phileo Lesaffre Animal Care, Milwaukee, WI). After 50 d of supplementation, cattle were transported to an environmentally controlled facility and placed in individual stanchions where indwelling jugular catheters and vaginal temperature (VT) loggers were inserted. Heifers were kept in thermoneutral (TN) conditions for 48 h (temperature-humidity index ∼67; THI) then were subjected to HS for 4 d (THI∼80). From d 2 to 6, hourly blood samples were collected for serum isolation from 1400-1800 h and again from 2200-0200 h which represented the targeted peak and nadir of THIs over the 5-d period. A whole blood sample was collected twice daily at 1400 and 2200 h for complete blood counts (CBC). Data collected included BW, water intake, respiration rate (RR; measured at 1600 and 2400 h daily) and serum cortisol, glucose and NEFAs. There was no change in BW (P=0.14) or ADG (P=0.53) between the treatments during the heat stress. Yeast supplemented heifers exhibited decreased VT during HS (P<0.01). There was no difference in water intake during the TN phase (P=0.25); however, YEAST heifers consumed more water/h (P<0.01) and had increased drinking bouts (P<0.01) during HS. Respiration rates were similar (P=0.21) during TN, but YEAST heifers tended (P=0.09) to have decreased RR during HS. There were no differences between treatments when evaluating hematology. There was a tendency (P=0.08) for increased cortisol in the CON heifers during HS; however, glucose (P=0.38) or NEFA (P=0.70) concentrations did not differ. In summary, supplementation of live yeast and yeast cell wall products to feedlot heifers may mitigate some of the negative effects associated with HS in feedlot cattle.

The objective of this study was to evaluate the effects of timing associated with the administration of a modified-live respiratory viral vaccine (bovine herpes virus-1, bovine viral diarrhea virus, bovine parainfluenza-3, bovine respiratory syncytial virus) on d 0 or on d 14 of a receiving period on performance, feed intake, antibody titer response, and the febrile response in beef heifers. Our hypothesis was that vaccine timing will alter the febrile response and feed intake of feeder cattle. Thirty-six heifers (Angus and Angus crosses; initial BW = 265 ± 20 kg) were ranked by BW and assigned to treatment pens (9 pens total) in a completely randomized design. Treatments (3 pens/treatment with 4 heifers/pen) included no vaccine (CON), vaccination on d 0 (DO), and a delayed vaccination on d 14 (D14) of the receiving period. Heifers were fed in 6 × 12m pens equipped with GrowSafe feeding systems. Daily feed intakes were recorded and BW measured on d −1, 0, 14, 27, and 28. Temperature data loggers were attached to blank controlled intrauterine drug-release devices (CIDR; contained no active compound) that recorded vaginal temperatures every 5min for the experiment; vaginal temperatures were then averaged for every hour before data analysis. All data were analyzed using pen as the experimental unit. No differences (P > 0.10) among treatments were observed for initial BW, final BW, ADG for d 0 to end, or overall G:F. A treatment × day interaction (P < 0.05) was observed for feed intake. Daily intake was decreased for D14 versus D0 on d 14 (P < 0.01) and 15 (P < 0.10) and decreased (P < 0.05) on d 15 for the average of vaccinated calves versus CON. Eating rate (grams consumed/eating duration) was decreased (P < 0.05) on d 14 for D14 versus D0. No differences (P > 0.10) among treatments were noted in the number of eating events per day. A treatment × day interaction (P < 0.01) was observed for vaginal temperature. Vaginal temperature was increased (P < 0.10) on d 1 for D0 versus D14 heifers and increased for D14 versus D0 on d 14 (P < 0.01), 15 (P < 0.05), and 16 (P < 0.05). Our results suggest that time of administration of a modified-live respiratory viral vaccine can alter feed intake and vaginal temperature in feeder heifers.