Effects of combining immunocastration and β-adrenergic agonists on the blood metabolites and their correlations with performance and carcass traits of finished Nellore cattle

ABSTRACT The objective of this study was to evaluate the effects of combining immunocastration and β-adrenergic agonists (β-AA) on blood metabolites and their correlations with performance and carcass traits of Nellore cattle. Ninety-six Nellore males were distributed in a randomized block design with a 2×3 factorial arrangement. The factors were two sexual conditions (immunocastrated and non-castrated), and three diets (control, with no inclusion of β-AA; RH, with 300 mg of ractopamine hydrochloride/d; and ZH, with 80 mg of zilpaterol hydrochloride/animal/d). The trial was conducted during 100 d, during which animals were fed ZH and RH for the last 30 and 33 d, respectively. Blood metabolites related to lipid and protein metabolism were assessed at the baseline (0 d of β-AA supplementation) and after 13 and 30 d of β-AA supplementation. No effect of sexual condition × β-AA supplementation × time on feed interaction was observed. Combining immunocastration with β-AA supplementation modified cholesterol and non-esterified fatty acids concentrations without affecting protein metabolism. Immunocastration enhances lipogenesis and reduces skeletal muscle accretion by increasing high-density lipoprotein and triglycerides concentrations and decreasing creatinine and creatine kinase concentrations, respectively. Zilpaterol hydrochloride enhances skeletal muscle accretion by decreasing urea and total protein concentrations and increases creatinine and creatine kinase concentrations without modifying lipid metabolism.

摘要 本研究旨在评估免疫去势与β-肾上腺素能激动剂（β-adrenergic agonists, β-AA）联合使用对内洛尔牛（Nellore cattle）血液代谢物的影响，及其与生产性能和胴体性状的相关性。选取96头内洛尔公牛，采用随机区组设计，设置2×3因子排列方案。试验因子分为两类：一是两种性别处理（免疫去势与非去势），二是三种日粮（无β-AA添加的对照组；RH组：每日添加300mg盐酸莱克多巴胺；ZH组：每头每日添加80mg盐酸齐帕特罗）。试验周期为100天，其中ZH组与RH组分别于试验最后30天与33天饲喂对应试验日粮。分别在β-AA补充基准点（即β-AA补充第0天）、补充β-AA后第13天及第30天，检测与脂质及蛋白质代谢相关的血液代谢物水平。未观察到性别处理×β-AA补充×饲喂时长的三因素交互效应。免疫去势与β-AA补充联合使用可改变胆固醇与非酯化脂肪酸浓度，但不影响蛋白质代谢。免疫去势可分别通过升高高密度脂蛋白与甘油三酯浓度、降低肌酐与肌酸激酶浓度，促进脂肪生成并减少骨骼肌沉积。盐酸齐帕特罗可通过降低尿素与总蛋白浓度促进骨骼肌沉积，并升高肌酐与肌酸激酶浓度，但不改变脂质代谢水平。