Mineral composition of serially slaughtered Holstein steers supplemented with zilpaterol hydrochloride

Calf-fed Holstein steers (n = 115; 449 ± 20 kg) were utilized in a serial harvest experiment. A baseline group of five steers was harvested after 226 d on feed (DOF), which was designated day 0. The remaining cattle were assigned randomly to 11 harvest groups, with slaughter every 28 d. Cattle were either not (CON) or were fed zilpaterol hydrochloride for 20 d followed by a 3 d withdrawal (ZH). There were five steers per treatment in each slaughter group ranging from days 28 to 308. Whole carcasses were divided into lean, bone, internal cavity, hide, and fat trim components. Apparent mineral retention (Ca, P, Mg, K, and S) within the body was calculated as the difference between mineral concentration at slaughter and day 0. Mineral concentration at day 0 was determined from body composition of steers harvested at day 0 multiplied by individual live body weight (BW) at day 0. All data were analyzed as a 2 × 11 factorial arrangement with individual animal as the experimental unit. Orthogonal contrasts were used to analyze linear and quadratic contrasts over time (11 slaughter dates). There were no differences in concentration of Ca, P, and Mg in bone tissue as feeding duration increased (P ≥ 0.89); concentration of K, Mg, and S in lean tissue did fluctuate across DOF (P < 0.01). Averaged across treatment and DOF, 99% of Ca, 92% of P, 78% of Mg, and 23% of S present in the body were in bone tissue; 67% of K and 49% of S were in lean tissue. Expressed as gram per day, apparent retention of all minerals decreased linearly across DOF (P < 0.01). Expressed relative to empty body weight (EBW) gain, apparent Ca, P, and K retention decreased linearly as BW increased (P < 0.01) whereas Mg and S increased linearly (P < 0.01). Apparent retention of Ca was greater for CON cattle (greater bone fraction) and apparent retention of K was greater for ZH cattle (greater muscle fraction) when expressed relative to EBW gain (P ≤ 0.02), demonstrating the increase in lean gain by ZH cattle. There were no differences in apparent retention of Ca, P, Mg, K, or S due to treatment (P ≥ 0.14) or time (P ≥ 0.11) when expressed relative to protein gain. Apparent retention averaged 14.4 g Ca, 7.5 g P, 0.45 g Mg, 1.3 g K, and 1.0 g S/100 g protein gain. Expressing apparent mineral retention on a protein gain basis minimized effects of rate and type of gain, allowing for better comparison across treatments and time. Feeding zilpaterol hydrochloride did not affect apparent mineral retention when expressed relative to protein gain.

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.

Estimation of carcass composition using rib dissection of calf-fed Holstein steers supplemented zilpaterol hydrochloride

A serial harvest was conducted every 28 d from 254 to 534 d on feed (DOF) to quantify changes in growth and composition of calf-fed Holstein steers (n = 115, initial body weight (BW) = 449.2 ± 19.9 kg). One-half were supplemented with the β-2 adrenergic agonist zilpaterol hydrochloride (ZH; 8.33 mg/kg 100% dry matter (DM) basis) during the final 20 d followed by a 3-d withdrawal prior to harvest; the remainder was fed a non-ZH control (CON) ration. Five steers were randomly selected and harvested after 226 DOF which served as a reference point for modeling purposes. Fabricated carcass soft tissue was ground, mixed, and subsampled for proximate analysis. Moreover, following the traditional method of rib dissection which includes the 9th, 10th, and 11th rib contained within the IMPS 103 primal, the relationship of carcass chemical composition to 9-10-11 rib composition was evaluated. Carcasses in this investigation had more (P < 0.01) separable lean, fat, ash, and moisture concomitant with less bone and ether extract than rib dissections. However, protein levels were similar (P = 0.27) between carcasses and rib dissections. Using regression procedures, models were constructed to describe the relationship of rib dissection (RD) composition including separable lean (RDSL), separable fat (RDSF), separable bone (RDSB), ether extract (RDEE), protein (RDP), moisture (RDM), and ash (RDA) with carcass composition. Carcass lean (CL), carcass fat (CF), and carcass bone (CB) were correlated (P < 0.01) with RDSL, RDSF, and RDSB with simple r values of 0.41, 0.71, and 0.50, respectively. Chemical composition of the rib and carcass, carcass ether extract (CEE), carcass protein (CP), carcass moisture (CM), and carcass ash (CA) were correlated (P ≤ 0.01) with simple r values of 0.75, 0.31, 0.66, and 0.37, respectively. Equations to predict carcass fatness from rib dissection variables and ZH supplementation status were only able to account for 50 and 56%, of the variability of CF and CEE, respectively. Overall, the relationships quantified and equations developed in this investigation do not support use of 9/10/11 rib dissection for estimation of carcass composition of calf-fed Holstein steers.

The effect of zilpaterol hydrochloride on beef producer and processor revenue of calf-fed Holstein steers

A serial harvest was conducted every 28 d from 254 to 534 days on feed (DOF) to quantify changes in growth and composition of calf-fed Holstein steers (n = 110, initial BW = 449.2 ± 19.9 kg). One-half were supplemented the β-2 adrenergic agonist zilpaterol hydrochloride (ZH; 8.33 mg/kg 100% DM basis), and the remainder fed a control (CON) ration during the final 20 d followed by a 3 d withdrawal prior to harvest. Cattle were randomly allocated to dietary treatment and harvest endpoint (254, 282, 310, 338, 366, 394, 422, 450, 478, 506, and 534 DOF) using a 2 × 11 factorial treatment structure and a completely randomized experimental design structure. The objective of this ad-hoc investigation was to quantify changes in value across multiple harvest endpoints and marketing strategies for cattle supplemented with ZH. Cattle-fed ZH had increased (P < 0.01) value when sold on a dressed basis (+$82.64) or on a value-based formula (+$75.59) compared with CON cattle. No differences (P ≥ 0.14) were detected between ZH and CON carcasses for premiums and discounts related to HCW, yield grade, or quality grade. Moreover, no differences (P = 0.98) were detected for overall adjusted carcass value between ZH and CON carcasses. Fabrication values revealed that ZH carcasses had greater (P < 0.01) revenue than CON carcasses for primal round (+$36.23), loin (+$38.16), flank (+$8.95), rib (+$16.33), and chuck (+$27.49) regardless of DOF. Increased primal values ultimately led to greater (P < 0.01) processor revenue (+$138.94) and carcass value per 45.4 kg (+$6.45) for cattle-fed ZH compared with CON cattle. Overall, increased carcass weight and improved fabrication yield led to greater revenue at all harvest endpoints for cattle-fed ZH. Linear increases in live and dressed values indicated the daily change in live value was $3.48, which is less than an increase of $3.77 daily for dressed carcass value. Greater beef processor margin and profitability are expected when this growth technology is used.

Effects of dexamethasone treatment and respiratory vaccination on rectal temperature, complete blood count, and functional capacities of neutrophils in beef steers

The objective of this research was to examine the effects of dexamethasone (DEX) treatment on various aspects of immunity following administration of a multivalent respiratory vaccine, using a model intended to mimic acute versus chronic stress. Angus × Hereford steers ( = 32; 209 ± 8 kg) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) acute stress (ACU), in which 0.5 mg/kg BW DEX was intravenously administered at 1000 h only on d 0; 2) chronic stress (CHR), in which 0.5 mg/kg BW DEX was intravenously administered at 1000 h on d -3 to 0; or 3) control (CON), in which no DEX was administered. Steers were fitted with indwelling jugular catheters and rectal temperature (RT) recording devices on d -4 relative to vaccination and placed in individual stanchions in an environmentally controlled facility. Blood samples were collected and serum was isolated 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 multivalent respiratory vaccination at 1200 h on d 0. Additional blood samples were used to analyze complete blood cell count (CBC) and functional capacities of neutrophils. There was a treatment × time interaction ( < 0.01) for RT such that DEX treatment in CHR and ACU steers decreased RT on d -3 and 0, respectively. A treatment × time interaction ( < 0.01) was observed for total white blood cells (WBC), neutrophils, lymphocytes, and monocytes. Specifically, DEX increased WBC and neutrophils in CHR and ACU steers ( < 0.001) yet decreased lymphocytes in CHR steers ( = 0.02) compared with CON steers. Neutrophil concentration increased rapidly, within 2 h of the DEX infusion, in ACU steers. Monocytes transiently increased ( < 0.001) in response to DEX treatment in CHR and ACU steers. In contrast, eosinophils were greater ( < 0.01) in CON steers than in ACU and CHR steers. A treatment × time interaction ( = 0.004) was observed for interferon-γ, with CON cattle exhibiting greater concentrations than the ACU and CHR cattle at 5 h after vaccination, through d 3. Treatment also influenced ( ≤ 0.001) the expression of L-selectin on the surface of neutrophils. The percentage of neutrophils engaging in phagocytosis and the oxidative burst were suppressed ( ≤ 0.001) among only the CHR steers, whereas the intensity of the oxidative burst was suppressed ( ≤ 0.001) for both ACU and CHR steers. These data suggest that our model induced acute and chronic immunosuppression and defined the acute response to a multivalent vaccine in CON steers.

Objective biometric measurements of calf-fed Holstein steers fed in confinement

Understanding the maximum slaughter size for calf-fed Holstein steers based on hip-height has become a contemporary issue in the beef processing industry. Increased carcass size, in terms of both weight and length, has outpaced the ability of some abattoirs to handle the larger animals. Moreover, some abattoirs have begun rejecting animals that exceed 147.3 cm (58 inches) at the hip, creating a challenge for Holstein cattle feeders. The objective of this study was to quantify the skeletal growth rate of calf-fed Holstein steers fed in confinement. Hip-height of calf-fed Holstein steers ( ≤ 135) was measured every 28 d from 226 to 422 d on feed. Hip-height was a dependent variable modeled via linear regression procedures utilizing days of age and BW as independent variables. Additionally, logistic regression was used to estimate the probability of a steer exceeding a hip-height of 147.3 cm (58 inches) from independent variables of days of age and BW. The linear relationship of BW to hip-height had an adjusted value of 0.7112 (Hip-height, cm = [0.0593 × BW, kg] + 109.00) and on average the calf-fed Holstein steers grew 1.0 cm for each 16.9 kg of BW gain during the finishing phase. The 10%, 50%, and 90% probability of a steer exceeding 147.3 cm (58 inches) of hip-height was achieved at 563, 653, and 743 kg of BW, respectively. The linear relationship of days of age to hip-height had an adjusted value of 0.6687 (Hip-height, cm = [0.0937 × days of age] + 104.4) and the calf-fed Holstein steers grew 1.0 cm for each 10.7 d of age during the finishing phase. The 10%, 50%, and 90% probability of a steer exceeding 147.3 cm (58 inches) of hip-height was estimated to occur at 408, 459, and 510 d of age, respectively. Knowledge of Holstein steer growth rate in relation to BW and age may allow for more accurate sorting to prevent oversized cattle arriving at the abattoir and subsequent discounts or being rejected for slaughter.

Fabrication yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride

Holstein steers ( = 110) were fed zilpaterol hydrochloride (ZH) for 0 or 20 d before slaughter during a 280-d serial harvest study. Cattle were harvested every 28 d beginning at 254 d on feed (DOF) and concluding at 534 DOF. After slaughter, carcasses were chilled for 48 h and then fabricated into boneless closely trimmed or denuded subprimals, lean trim, trimmable fat, and bone. Inclusion of ZH increased cold side weight (CSW) by 10.3 kg ( < 0.01; 212.7 vs. 202.4 kg [SEM 1.96]) and saleable yield by 10.4 kg ( < 0.01; 131.9 vs. 121.5 kg [SEM 1.16]) in calf-fed Holstein steer carcasses. Additionally, saleable yield as a percentage of CSW increased ( ≤ 0.01) by 2.19% (62.64 vs. 60.45% [SEM 0.22]) for cattle supplemented with ZH. Subprimal weights were heavier ( ≤ 0.05) from cattle that received ZH except for the bottom sirloin ball tip, back ribs, and outside skirt regardless of slaughter endpoint. Yield of top round, bottom round, and knuckle was increased ( ≤ 0.01) following ZH supplementation by 0.37, 0.24, and 0.18%, respectively. Yield of the top sirloin butt, strip loin, and tenderloin was increased ( ≤ 0.01) concurrent with ZH supplementation by 0.18, 0.11, and 0.09%, respectively. Regarding the rib primal, the rib eye roll tended ( = 0.08) to had increased yield (2.80 vs. 2.72% [SEM 0.03]) with ZH supplementation; both back ribs and blade meat exhibited increased ( ≤ 0.04) yields of 0.04%. Relative to the chuck primal, increased ( ≤ 0.03) yields of shoulder clod, pectoral meat, and mock tender were observed (0.13, 0.07, and 0.04%, respectively). Yield changes for subprimal brisket, plate, and flank were limited to increased ( < 0.01) proportion of flank steak and elephant ear (cutaneous trunci), 0.07 and 0.04%, respectively. Feeding duration notably altered ( ≤ 0.01) weights and percentages of all subprimals except the brisket. Saleable yield increased ( ≤ 0.01) by 0.192 kg/d with additional DOF. Moreover, trimmable fat and bone increased ( ≤ 0.01) by 0.146 and 0.050 kg/d, respectively. These data illustrate improved saleable meat yields for calf-fed Holstein steers supplemented with ZH and provide the beef industry knowledge of fabrication yield changes throughout a wide range of harvest endpoints.

The effect of days on feed and zilpaterol hydrochloride supplementation on feeding behavior and live growth performance of Holstein steers

This experiment was designed to study the effect of days on feed (d 225-533) and zilpaterol hydrochloride (ZH) supplementation on Holstein steer ( = 110) performance and feeding behavior as part of a serial slaughter trial. Steers were randomly assigned to 1 of 11 harvest groups with 10 steers ( = 5 control and = 5 ZH; ZH at 8.33 mg/kg diet) harvested each 28 d. Steers were weighed every 28 d (d 225, 253, 281, 309, 337, 365, 393, 421, 449, 477, 505, and 533); individual daily meal consumption data for each steer were recorded using GrowSafe technology. In the pretreatment period, dry matter intake expressed a negative quadratic relationship with days on feed (DOF) {DMI = -5.7120 + (0.08370 x DOF)- (0.00011 x DOF); Adj. = 0.2574; RMSE = 0.25 75; 0.01}. A linear increase in BW ( < 0.01) occurred during the pretreatment 308 d period from 466 to 844 kg, {BWend = 137.61 + (1.4740 x DOF); Adj. = 0.8819; RMSE = 37.06; < 0.01}, whereas ADG and G:F decreased linearly. Dry matter intake per meal exhibited a quadratic relationship over days on feed and peaked ( < 0.01) during d 365 to 392 at 1.065 kg coinciding with the highest numerical daily DMI (11.19 kg). Daily consumption visit duration differed ( < 0.01) during the 308 d period, with a low of 52.29 min (d 337-364) and a high of 55.59 min (d 365-392). Consumption rate peaked at 714 g/min (d 337-364) and exhibited a quadratic relationship to DOF. The difference ( < 0.04) in DMI between control and ZH treated cattle across all 11 harvest groups averaged 0.575 kg. Moreover, ZH treatment resulted in decreased ( 0.01) DMI per meal event of 0.093 kg. Gain to feed tended to improve ( = 0.06) with ZH treatment by 0.017 kg gain per kg feed relative to the control cattle. Daily bunk, consumption, and meal visit durations were influenced by ZH during the 20 d treatment period ( = 0.01); the average difference between control and ZH supplemented cattle over the 308 d trial was 9.09, 8.71, and 11.39 min per d, respectively. The data collected in this trial indicate live growth performance and feeding behavior were impacted by both DOF and ZH supplementation.

Byproduct yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride

A 2 × 11 factorial treatment structure was applied in a completely randomized experimental design to investigate differences in noncarcass tissue among serially harvested Holstein steers. Steers ( = 110) were randomly assigned to 1 of 2 dietary treatments: a ration supplemented with zilpaterol hydrochloride (ZH) fed at a rate of 8.3 mg/kg DM for 20 d followed by a 3-d withdrawal or a control ration with no ZH included in the diet. Within treatment, steers were assigned to harvest groups of 254, 282, 310, 338, 366, 394, 422, 450, 478, 506, or 534 d on feed (DOF) prior to initiation of the trial. Cattle fed ZH realized an empty BW (EBW) increase ( ≤ 0.03) of 2.8% (644.2 vs. 626.4 kg [SEM 5.4]) and a HCW increase of 5.0% (429.1 vs. 408.4 kg [SEM 4.0]) with a concomitant 12% reduction (45.1 vs. 51.2 kg [SEM 3.1]) in gastrointestinal contents and 2.1 percentage unit increase in dressed carcass yield (62.1 vs. 60.0% [SEM 0.01]). Additionally, ZH supplementation decreased (P ≤ 0.03) the absolute weight of the liver and kidneys by 0.3 and 0.1 kg, respectively. When noncarcass components were expressed on an empty body basis (g/kg EBW), reductions ( ≤ 0.01) in the limbs (18.8 vs. 19.5 g/kg EBW [SEM 0.1]), hide (81.1 vs. 78.1 g/kg EBW [SEM 0.7]), liver (14.2 vs. 13.2 g/kg EBW [SEM 0.2]), kidneys (2.6 vs. 2.3 g/kg EBW [SEM 0.04]), small and large intestines (74.9 vs. 69.6 g/kg EBW [SEM 1.2]), and gastrointestinal tract (119.8 vs. 113.4 g/kg EBW [SEM 1.3]) were observed with ZH supplementation. Additionally, there was a tendency ( = 0.07) for the proportion of total offal to be reduced (253.2 vs. 247.4 g/kg EBW [SEM 2.5]) with ZH supplementation. Empty BW and HCW linearly increased ( < 0.01) by 1.16 and 0.758 kg/d ( < 0.01), respectively, with additional DOF. The weight of the liver and intestines linearly increased ( < 0.01) by 0.007 and 0.133 kg/d ( < 0.01), respectively, with additional DOF. These data indicate the magnitude of change in noncarcass tissues that can be expected when calf-fed Holstein steers are supplemented with ZH.

Carcass grading characteristics of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride

Serial harvests were conducted using Holstein steers ( = 110) fed zilpaterol hydrochloride (ZH) for 0 or 20 d prior to harvest. Steers were harvested in 28-d increments beginning at 254 d on feed (DOF) and ending at 534 DOF. After harvest and a 36-h chill period, carcasses were evaluated using grading methods standard for the United States (USDA), Canada (Canadian Beef Grading Association [CBGA]), and Japan (Japanese Meat Grading Agency [JMGA]). No ZH treatment differences ( = 0.81) were detected for 12th-rib fat thickness; however, additional DOF resulted in a daily linear increase ( < 0.01) of 12th-rib fat thickness by 0.004 cm/d. Longissimus muscle area was increased ( < 0.01) by 8.7 cm with ZH supplementation and linearly increased ( < 0.01) 0.08 cm2/d with additional DOF. Calculated USDA yield grade (YG) decreased ( < 0.01) 0.33 units due to ZH treatment and linearly increased ( < 0.01) 0.009 units/d. Steers supplemented with ZH exhibited increased ( < 0.01) CGBA LM width; however, no difference ( = 0.37) was detected in CGBA LM length. No ZH treatment differences ( = 0.64) were observed for CBGA fat class; however, CGBA fat class linearly increased ( < 0.01) by 0.01 units/d. No ZH differences ( ≥ 0.17) were detected for the CBGA estimated lean percentage or YG equations. Evaluation for JMGA occurs at the sixth and seventh rib interface; LM area was 4.6 cm2 greater ( = 0.02) for cattle supplemented with ZH and linearly increased ( < 0.01) by 0.07 cm2/d with additional DOF. Subcutaneous fat thickness was not different among ZH treatments ( = 0.10) but linearly ( < 0.04) increased ( < 0.01) by 0.005 cm/d with additional DOF using the JMGA grading method. No difference ( ≥ 0.21) was calculated between ZH treatments or DOF for JMGA estimated yield. No ZH treatment differences ( = 0.85) were detected in USDA marbling score; however, marbling linearly increased ( < 0.01) 0.07 units/d. These data illustrate the impact of ZH and increasing DOF on economically important carcass grading outcomes used in the USDA, CBGA, and JMGA grading programs.

Dexamethasone treatment differentially alters viral shedding and the antibody and acute phase protein response after multivalent respiratory vaccination in beef steers

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.

Experimental studies of the collateral circulation in the head and neck of sheep (Ovis aries)

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Arterial anastomoses in the head and neck of the sheep

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