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J Anim Sci ; 95(12): 5327-5338, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-29293749


The objectives of this study were 1) to determine if supplementation of zilpaterol hydrochloride (ZH) altered select organ weights, histology, and cardiac anatomical features at harvest and 2) to determine if administration of a corticotropin-releasing hormone (CRH) and vasopressin (VP) challenge following 20 d of ZH supplementation altered the blood chemistry profile in cattle. Crossbred heifers ( = 20; 556 ± 7 kg BW) were randomized into 2 treatment groups: 1) control (CON), without ZH, and 2) zilpaterol (ZIL; ZH at 8.33 mg/kg [DM basis] for 20 d). On d 20 of supplementation, heifers were fitted with indwelling jugular catheters. On d 24, starting at 0800 h and continuing until 1600 h, blood samples were collected at 60-min intervals. At 1000 h, heifers received an i.v. bolus of CRH (0.3 µg/kg BW) and VP (1.0 µg/kg BW) to activate the stress axis. Serum was separated and stored at -80°C until analyzed for a large-animal chemistry panel. Following the CRH/VP challenge, heifers were harvested on d 25, 26, and 27 (5, 6, and 7 d after ZH supplementation); BW, HCW, select organ weights, and histology were measured, and a total heart necropsy was performed. A treatment effect ( ≤ 0.02) was observed for Ca, K, creatinine, alkaline phosphatase, and sorbitol dehydrogenase. Zilpaterol-fed heifers had decreased ( ≤ 0.02) concentrations of Ca and K and increased concentrations ( 0.01) of creatinine ( = 0.02) during the CRH/VP challenge when compared to control heifers. Control heifers had greater ( ≤ 0.05) alkaline phosphatase and sorbitol dehydrogenase concentrations when compared with ZIL heifers. A treatment × time interaction ( = 0.02) was observed for P; concentrations were similar between treatments from -2 to 6 h postchallenge, and 7 h postchallenge CON heifers had decreased P. Liver ( = 0.06) and kidney ( = 0.08) weights as a percentage of BW tended ( ≤ 0.08) to be reduced in ZIL heifers. Gross liver weights tended ( = 0.08) to be lower in ZIL heifers. Other organ (heart, lung, adrenals) to BW ratios remained similar ( ≥ 0.41). These data suggest that there are some variations observed between treatments in terms of response to ZH supplementation and the CRH/VP challenge; however, in the environmental conditions of this study, limited variation in blood metabolic responses and organ weights suggests that the supplementation of ZH did not detrimentally alter the physiology of cattle.

Bovinos/fisiología , Hormona Liberadora de Corticotropina/farmacología , Suplementos Dietéticos , Compuestos de Trimetilsililo/metabolismo , Vasopresinas/farmacología , Animales , Análisis Químico de la Sangre/veterinaria , Composición Corporal/efectos de los fármacos , Bovinos/sangre , Dieta/veterinaria , Femenino , Tamaño de los Órganos/efectos de los fármacos , Distribución Aleatoria
J Anim Sci ; 94(7): 2798-810, 2016 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-27482667


The objective of this study was to determine the metabolic, stress, and hematology response of beef heifers supplemented with zilpaterol hydrochloride (ZH) when exposed to an endocrine stress challenge. Heifers ( = 20; 556 ± 7 kg BW) were randomized into 2 treatment groups: 1) control (CON), no ZH supplementation, 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 corticotropin-releasing hormone (CRH; 0.3 µg/kg BW) and arginine vasopressin (VP; 1.0 µg/kg BW) to activate the stress axis. Blood samples were collected at 30-min intervals for serum and 60-min intervals for plasma and whole blood, from -2 to 8 h relative to the challenge at 0 h (1000 h). Samples were analyzed for glucose, insulin, NEFA, blood urea nitrogen (BUN), cortisol, epinephrine, norepinephrine, and complete blood cell counts. Following the challenge, cattle were harvested over a 3-d period. Liver, LM, and biceps femoris (BF) samples were collected and analyzed for glucose, lactate, and glycolytic potential (GP). There was a treatment ( ≤ 0.001) effect for vaginal temperature (VT), with ZIL having a 0.1°C decrease in VT when compared with CON. A treatment × time effect ( = 0.002) was observed for NEFA. A treatment effect was observed for BUN; ZIL had decreased BUN concentrations compared with CON ( < 0.001) prior to the challenge; however, no treatment × time effect was observed. There was also a treatment effect for cortisol ( ≤ 0.01) and epinephrine ( = 0.003); ZIL had decreased cortisol and epinephrine during the CRH/VP challenge when compared with CON. There was a time effect for total white blood cells, lymphocytes, and monocytes; each variable increased ( ≤ 0.01) 2 h postchallenge. Additionally, neutrophil counts decreased ( ≤ 0.01) in response to CRH/VP challenge in both treatment groups. Glucose concentrations within the LM were greater ( = 0.03) in CON when compared with ZIL. Lactate concentrations and GP within the BF were greater in CON ( = 0.05) when compared with ZIL. These data suggest there are some variations observed between treatments in terms of response to the CRH/VP challenge; however, in the environmental conditions of this trial, none of the variations observed suggest that the supplementation of ZH detrimentally alters the ability of cattle to effectively respond to stressful stimuli.

Agonistas Adrenérgicos beta/farmacología , Bovinos/fisiología , Suplementos Dietéticos , Hormonas/administración & dosificación , Compuestos de Trimetilsililo/farmacología , Animales , Recuento de Células Sanguíneas/veterinaria , Glucemia/análisis , Nitrógeno de la Urea Sanguínea , Hormona Liberadora de Corticotropina/administración & dosificación , Dieta/veterinaria , Femenino , Músculos Isquiosurales/efectos de los fármacos , Músculos Isquiosurales/metabolismo , Hematología , Insulina/sangre , Estrés Fisiológico/efectos de los fármacos , Vasopresinas/administración & dosificación
Annu Rev Anim Biosci ; 4: 335-55, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-26667362


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 DFM supplementation. 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.

Dieta/veterinaria , Ganado/fisiología , Aves de Corral/fisiología , Probióticos/administración & dosificación , Bienestar del Animal , Animales , Suplementos Dietéticos/microbiología , Ganado/microbiología , Aves de Corral/microbiología