EVALUATION OF THE METABOLIC RESPONSE, BLOOD CHEMISTRY PROFILE, AND CARDIAC MORPHOLOGY OF BEEF HEIFERS SUPPLEMENTED WITH ZILPATEROL HYDROCHLORIDE FOLLOWED BY AN ENDOCRINE INDUCED STRESS CHALLENGE

The objective of this study was to determine the metabolic, stress, hematology, organ weights, histology and cardiac anatomical features of beef heifers supplemented with zilpaterol hydrochloride (ZH) when exposed to a corticotropin-releasing hormone (CRH) and arginine vasopressin (VP) challenge. Crossbred heifers (n = 20; 556 ± 7 kg BW) were randomized into two treatment groups: 1) Control (CON): no ZH, and 2) Zilpaterol (ZIL): supplemented with ZH at 8.33 mg / kg (DM basis). The ZIL group was supplemented ZH for 20 d, with a 3-d withdrawal period. On d 24, heifers received an intravenous bolus of CRH (0.3 µg / kg BW) and VP (1.0 µg / kg BW). Blood samples were collected at 30- and 60-min intervals for serum, and 60-min intervals for plasma and whole blood, from -2 to 8 h relative to the challenge. Heifers were harvested to collect organ weights and histology samples on d 25, 26, and 27. There was a treatment (P \u3c 0.001) effect for vaginal temperature (VT), with ZIL having a 0.1oC decrease in VT. A treatment x time effect (P = 0.002) was observed for non-esterified fatty acid such that concentrations were increased in CON heifers at 4, 6, 7, 7.5, and 8 hrs. There was a treatment effect for cortisol (P \u3c 0.01) and epinephrine (P = 0.003) with ZIL having decreased concentrations. Glucose concentrations within the longissimus muscle were greater (P = 0.03) in CON heifers. Lactate concentrations and glycolytic potential within the biceps femoris were greater in CON heifers (P = 0.05). A treatment effect (P ≤ 0.02) was observed for calcium and potassium, with ZIL heifers having decreased concentrations. Zilpaterol heifers had increased concentrations of creatinine (P = 0.02). A treatment x time interaction (P = 0.02) was observed for phosphorus. Raw liver weights tended (P = 0.08) to be less in ZIL heifers. These data suggest some variations between treatments in terms of response to ZH supplementation and challenge; however, in the environmental conditions of this study, the data suggests that the supplementation of ZH does not negatively alter the status of homeostasis in cattle. Advisor: Ty B. Schmid

EVALUATION OF THE METABOLIC RESPONSE, BLOOD CHEMISTRY PROFILE, AND CARDIAC MORPHOLOGY OF BEEF HEIFERS SUPPLEMENTED WITH ZILPATEROL HYDROCHLORIDE FOLLOWED BY AN ENDOCRINE INDUCED STRESS CHALLENGE

The objective of this study was to determine the metabolic, stress, hematology, organ weights, histology and cardiac anatomical features of beef heifers supplemented with zilpaterol hydrochloride (ZH) when exposed to a corticotropin-releasing hormone (CRH) and arginine vasopressin (VP) challenge. Crossbred heifers (n = 20; 556 ± 7 kg BW) were randomized into two treatment groups: 1) Control (CON): no ZH, and 2) Zilpaterol (ZIL): supplemented with ZH at 8.33 mg / kg (DM basis). The ZIL group was supplemented ZH for 20 d, with a 3-d withdrawal period. On d 24, heifers received an intravenous bolus of CRH (0.3 µg / kg BW) and VP (1.0 µg / kg BW). Blood samples were collected at 30- and 60-min intervals for serum, and 60-min intervals for plasma and whole blood, from -2 to 8 h relative to the challenge. Heifers were harvested to collect organ weights and histology samples on d 25, 26, and 27. There was a treatment (P \u3c 0.001) effect for vaginal temperature (VT), with ZIL having a 0.1oC decrease in VT. A treatment x time effect (P = 0.002) was observed for non-esterified fatty acid such that concentrations were increased in CON heifers at 4, 6, 7, 7.5, and 8 hrs. There was a treatment effect for cortisol (P \u3c 0.01) and epinephrine (P = 0.003) with ZIL having decreased concentrations. Glucose concentrations within the longissimus muscle were greater (P = 0.03) in CON heifers. Lactate concentrations and glycolytic potential within the biceps femoris were greater in CON heifers (P = 0.05). A treatment effect (P ≤ 0.02) was observed for calcium and potassium, with ZIL heifers having decreased concentrations. Zilpaterol heifers had increased concentrations of creatinine (P = 0.02). A treatment x time interaction (P = 0.02) was observed for phosphorus. Raw liver weights tended (P = 0.08) to be less in ZIL heifers. These data suggest some variations between treatments in terms of response to ZH supplementation and challenge; however, in the environmental conditions of this study, the data suggests that the supplementation of ZH does not negatively alter the status of homeostasis in cattle. Advisor: Ty B. Schmid

Fatty Acid Composition of Beef Fed OmniGen- AF at Receiving or Finishing

Beef fatty acid profiles and superoxide dismutase activity were determined for cattle receiving OmniGen- AF supplementation (a patented nutritional supplement) at receiving (first 28 d at the feedlot) or throughout finishing (all 210 d of finishing) vs. a control group (non- supplemented). Th e most meaningful change in fatty acid composition from inclusion of OmniGen- AF was total poly- unsaturated fatty acid (PUFA) content where beef from the finishing group had more PUFA content in relation to the receiving group and was not different from the control group. Despite this increase in PUFA, cattle supplemented through finishing tended to have less lipid oxidation than the other two treatments yet this difference could not be explained by the superoxide dismutase activity

Effect of Feeding Different Types of Byproducts and Concentrations Throughout a Beef Growing System on Ground Beef Color and Lipid Oxidation

The objective of this trial was to evaluate the effect of feeding different concentrations of wet distillers grains during winter backgrounding and either modified wet distillers grains or Sweet Bran® during the finishing phase on ground beef color and lipid oxidation. After a 14 day aging period, ground beef patties were made and placed in a simulated retail display for seven days. There were no overall differences in lipid oxidation between treatments but was a treatment by day interaction for discoloration. Ground beef from heifers finished with modified wet distillers grains discolored at a greater extent when compared to ground beef from heifers finished with Sweet Bran

Evaluation of the Immune Response of Angus Heifers with Different Genetic Markers for Marbling when Challenged with Lipopolysaccharide

Nineteen heifers (274 ± 24 kg) were blocked into two treatment groups based upon DNAm; heifers with no DNAm (noQG), and heifers with one or more DNAm (1+QG). Prior to challenge (24 h), heifers were fitted with indwelling jugular catheters and indwelling vaginal temperature (VT) monitoring devices. Blood samples were collected at 30-min intervals while RT were collected at 1-min intervals from -2 to 8 h relative to a lipopolysaccride (LPS) challenge (0.5 ìg/kg BW) at 0 h. Serum was analyzed for concentrations of cortisol and pro-inflammatory cytokines. All physical, endocrine, and immune measurements increased relative to LPS challenge. No differences observed for IL-6 or TNF-á; however, 1+QG heifers had a greater circulating INF-ã (P \u3c 0.001). Furthermore, 1+QG heifers had an elevated VT (P = 0.04). This would suggest a different immune system approach to an LPS challenge

Evaluation of the metabolic response, blood chemistry profile, and cardiac morphology of beef heifers supplemented with zilpaterol hydrochloride followed by an endocrine induced stress challenge

The objective of this study was to determine the metabolic, stress, hematology, organ weights, histology and cardiac anatomical features of beef heifers supplemented with zilpaterol hydrochloride (ZH) when exposed to a corticotropin-releasing hormone (CRH) and arginine vasopressin (VP) challenge. Crossbred heifers (n = 20; 556 ± 7 kg BW) were randomized into two treatment groups: 1) Control (CON): no ZH, and 2) Zilpaterol (ZIL): supplemented with ZH at 8.33 mg / kg (DM basis). The ZIL group was supplemented ZH for 20 d, with a 3-d withdrawal period. On d 24, heifers received an intravenous bolus of CRH (0.3 µg / kg BW) and VP (1.0 µg / kg BW). Blood samples were collected at 30- and 60-min intervals for serum, and 60-min intervals for plasma and whole blood, from -2 to 8 h relative to the challenge. Heifers were harvested to collect organ weights and histology samples on d 25, 26, and 27. There was a treatment (P \u3c 0.001) effect for vaginal temperature (VT), with ZIL having a 0.1°C decrease in VT. A treatment x time effect (P = 0.002) was observed for non-esterified fatty acid such that concentrations were increased in CON heifers at 4, 6, 7, 7.5, and 8 hrs. There was a treatment effect for cortisol (P \u3c 0.01) and epinephrine (P = 0.003) with ZIL having decreased concentrations. Glucose concentrations within the longissimus muscle were greater (P = 0.03) in CON heifers. Lactate concentrations and glycolytic potential within the biceps femoris were greater in CON heifers (P = 0.05). A treatment effect (P ≤ 0.02) was observed for calcium and potassium, with ZIL heifers having decreased concentrations. Zilpaterol heifers had increased concentrations of creatinine (P = 0.02). A treatment x time interaction (P = 0.02) was observed for phosphorus. Raw liver weights tended (P = 0.08) to be less in ZIL heifers. These data suggest some variations between treatments in terms of response to ZH supplementation and challenge; however, in the environmental conditions of this study, the data suggests that the supplementation of ZH does not negatively alter the status of homeostasis in cattle

Fatty Acid Composition of Beef Fed OmniGen- AF at Receiving or Finishing

Beef fatty acid profiles and superoxide dismutase activity were determined for cattle receiving OmniGen- AF supplementation (a patented nutritional supplement) at receiving (first 28 d at the feedlot) or throughout finishing (all 210 d of finishing) vs. a control group (non- supplemented). Th e most meaningful change in fatty acid composition from inclusion of OmniGen- AF was total poly- unsaturated fatty acid (PUFA) content where beef from the finishing group had more PUFA content in relation to the receiving group and was not different from the control group. Despite this increase in PUFA, cattle supplemented through finishing tended to have less lipid oxidation than the other two treatments yet this difference could not be explained by the superoxide dismutase activity

The Role of Direct-Fed Microbials in Conventional Livestock Production

Supplementation of direct-fed microbials (DFM) as a means to improve the health and performance of livestock has generated significant interest over the past 15+ years. A driving force for this increased interest in DFM is to reduce or eliminate the use of low-dose antibiotics in livestock production. This increased attention toward DFM supplementation has generated an extensive body of research. This effort has resulted in conflicting reports. Although there has been considerable variation in the design of these studies, one of the main causes for this lack of consistency may be attributed to the variation in the experimental immune challenge incorporated to evaluate DFMsupplementation. Taking into account the experimental immune challenge, there is strong evidence to suggest that DFM supplementation may have an impact on the immune response, overall health, and performance of livestock

Exogenous administration of lipids to steers alters aspects of the innate immune response to endotoxin challenge

This study examined the effects of increasing energy availability from both dextrose and lipid treatments on the proinflammatory response to LPS in Holstein steers. Steers were randomly assigned to one of three groups: saline at 0.5 ml/ kg body weight (Control) or 50% dextrose [0.5 ml/kg body weight (Dextrose) to mimic calm cattle’s response to LPS] administered immediately prior to LPS (0.5 mg/kg body weight at 0 h) or continuous lipid emulsion infusion from –1 to 6 h [Intralipid 20% (Baxter, Deerfield, IL USA); 0.5 ml/kg/hr (Lipid) to mimic temperamental cattle]. Concentrations of non-esterified fatty acids (NEFA) were greater in Lipid compared with Control and Dextrose steers. A greater decrease in the change in rectal temperature, relative to baseline, was observed in response to LPS in Dextrose in comparison to control and Lipid steers. Cortisol was greater in Lipid than Dextrose and Control steers from –0.5 to 0 h, yet decreased from 0.5 to 5.5 h relative to LPS challenge. Concentrations of IL-6 were decreased in Lipid steers compared with Dextrose and Control steers, and were decreased in Dextrose compared with Control steers post-LPS challenge. These data suggest that increasing circulating NEFA using an exogenous Lipid emulsion may modulate the pro-inflammatory response in steers

The Role of Direct-Fed Microbials in Conventional Livestock Production

Supplementation of direct-fed microbials (DFM) as a means to improve the health and performance of livestock has generated significant interest over the past 15+ years. A driving force for this increased interest in DFM is to reduce or eliminate the use of low-dose antibiotics in livestock production. This increased attention toward DFM supplementation has generated an extensive body of research. This effort has resulted in conflicting reports. Although there has been considerable variation in the design of these studies, one of the main causes for this lack of consistency may be attributed to the variation in the experimental immune challenge incorporated to evaluate DFMsupplementation. Taking into account the experimental immune challenge, there is strong evidence to suggest that DFM supplementation may have an impact on the immune response, overall health, and performance of livestock