University of Florida, IFAS - Range Cattle Research and Education Center, Ona, FL.
Department of Animal Science, Texas A&M University, College Station, TX.
J Anim Sci. 2018 Mar 6;96(2):618-631. doi: 10.1093/jas/sky016.
A 3 yr study evaluated the effects of three preweaning injections of bovine ST, administered 14 d apart, on growth and reproductive performance of Bos indicus-influenced beef heifers. On d 0 of each year, suckling Angus × Brangus heifers (n = 15 heifers/treatment/yr) were stratified by BW (147 ± 20 kg) and age (134 ± 11 d) and randomly assigned to receive an s.c. injection of saline (SAL; 5 mL; 0.9% NaCl) or 250 mg of sometribove zinc (BST; Posilac, Elanco, Greenfield, IN) on d 0, 14, and 28. Heifers and respective dams were managed as a single group on bahiagrass (Paspalum notatum) pastures from d 0 until weaning (d 127). From d 127 to 346, heifers were grouped by treatment, allocated to bahiagrass pastures (1 pasture/treatment/yr) and fed a molasses-based supplement (2.9 kg/heifer daily; DM basis) until d 346. Blood samples were collected on d 0, 14, 28, 42, and then every 9-10 d from d 179 to 346. In yr 3, liver biopsy samples were collected on d 0, 42, and 263. Heifers were exposed to mature Angus bulls from d 263 to 346. Growth performance and physiological parameters were analyzed using the MIXED procedure, whereas reproductive variables were analyzed using the GLIMMIX procedure of SAS. Effects of treatment × year and treatment × year × time were not detected for any variable measured in this study (P ≥ 0.14), except for calving percentage (P = 0.03). Heifers assigned to BST injections had greater overall plasma concentrations of IGF-1 and ADG from d 0 to 42 (P ≤ 0.05), less ADG from d 42 to 127 (P = 0.04), but had similar BW at weaning and postweaning ADG (P ≥ 0.25) compared to SAL heifers. Heifers assigned to BST tended to achieve puberty 26 d earlier (P = 0.10), had greater percentage of pubertal heifers on d 244, 263, 284, and 296 (P ≤ 0.04), tended to have greater overall pregnancy percentage (P = 0.10), and had greater (P ≤ 0.05) calving percentages in yr 1 and 2 (but not yr 3; P = 0.68) compared to SAL heifers. Liver mRNA expression of GHR-1B and IGF-1 on d 0 and 42 did not differ between treatments (P ≥ 0.15), but was greater for BST vs. SAL heifers on d 263 (P ≤ 0.02). Hence, administering three injections containing 250 mg of sometribove zinc at 14 d intervals before weaning (between 135 and 163 d of age) induced long-term impacts on liver gene expression and may be a feasible management practice to enhance puberty and pregnancy attainment in B. indicus-influenced replacement beef heifers.
一项为期 3 年的研究评估了在哺乳期内每隔 14 天注射 3 次牛 ST（牛生长激素）对印度牛影响的肉牛小母牛生长和繁殖性能的影响。在每年的第 0 天，将哺乳期的安格斯×婆罗门牛小母牛（n = 15 头/处理/年）按体重（147 ± 20 kg）和年龄（134 ± 11 d）分层，并随机分配接受皮下注射生理盐水（SAL；5 mL；0.9% NaCl）或 250 mg 索马鲁肽锌（BST；Elanco 的 Posilac，Greenfield，IN），分别在第 0、14 和 28 天。从第 0 天到断奶（第 127 天），小母牛及其各自的母牛作为一个群体在巴希甲草（Paspalum notatum）牧场上进行管理。从第 127 天到第 346 天，小母牛按处理分组，分配到巴希甲草牧场（1 个牧场/年/处理），并饲喂基于糖蜜的补充饲料（2.9 kg/头/日；干物质基础），直到第 346 天。在第 0、14、28、42 天采集血液样本，然后从第 179 天到第 346 天每隔 9-10 天采集一次。在第 3 年，在第 0、42 和 263 天采集肝活检样本。从第 263 天到第 346 天，小母牛接触成熟的安格斯公牛。使用 MIXED 过程分析生长性能和生理参数，使用 SAS 的 GLIMMIX 过程分析繁殖变量。除了产犊率（P = 0.03）外，本研究中测量的任何变量均未检测到处理×年份和处理×年份×时间的影响（P≥0.14）。接受 BST 注射的小母牛在第 0 天到第 42 天之间的总血浆 IGF-1 浓度和 ADG 更高（P≤0.05），从第 42 天到 127 天的 ADG 更低（P=0.04），但断奶和断奶后 ADG 的 BW 相似（P≥0.25）与 SAL 小母牛相比。接受 BST 注射的小母牛发情更早 26 天（P=0.10），在第 244、263、284 和 296 天的发情小母牛比例更高（P≤0.04），总体妊娠率更高（P=0.10），在第 1 年和第 2 年（但第 3 年没有；P=0.68）的产犊率更高，与 SAL 小母牛相比。在第 0 天和第 42 天，处理之间的 GHR-1B 和 IGF-1 的肝 mRNA 表达没有差异（P≥0.15），但在第 263 天，BST 处理的 GHR-1B 和 IGF-1 的肝 mRNA 表达高于 SAL 处理（P≤0.02）。因此，在哺乳期内每隔 14 天注射 3 次含有 250 mg 索马鲁肽锌，可在哺乳期（135-163 日龄）之前对肝脏基因表达产生长期影响，可能是提高印度牛影响的后备肉牛小母牛发情和妊娠率的可行管理措施。
