1Department of Animal Science,Texas A&M University,College Station,TX 77845,USA.
2Range Cattle Research and Education Center,University of Florida,Ona,FL 33865,USA.
Animal. 2019 Jun;13(6):1208-1213. doi: 10.1017/S1751731118002628. Epub 2018 Oct 25.
Excitable temperament disrupts physiological events required for reproductive development in cattle, but no research has investigated the impacts of temperament on growth and puberty attainment in Bos indicus females. Hence, this experiment evaluated the effects of temperament on growth, plasma cortisol concentrations and puberty attainment in B. indicus heifers. A total of 170 Nelore heifers, weaned 4 months before the beginning of this experiment (days 0 to 91), were managed in two groups of 82 and 88 heifers each (mean ± SE; initial BW=238±2 kg, initial age=369±1 days across groups). Heifer temperament was evaluated via exit velocity on day 0. Individual exit score was calculated within each group by dividing exit velocity into quintiles and assigning heifers with a score from 1 to 5 (1=slowest; 5=fastest heifer). Heifers were classified according to exit score as adequate (ADQ, n=96; exit score⩽3) or excitable temperament (EXC, n=74; exit score>3). Heifer BW, body condition score (BCS) and blood samples were obtained on days 0, 31, 60 and 91. Heifer exit velocity and score were recorded again on days 31, 60 and 91. Ovarian transrectal ultrasonography was performed on days 0 and 10, 31 and 41, 60 and 70, 81 and 91 for puberty evaluation. Heifer was declared pubertal at the first 10-day interval in which a corpus luteum was detected. Exit velocity and exit score obtained on day 0 were correlated (r⩾0.64, P<0.01) with evaluations on days 31, 60 and 91. During the experiment, ADQ had greater (P<0.01) mean BCS and BW gain, and less (P<0.01) mean plasma cortisol concentration compared with EXC heifers. Temperament × time interactions were detected (P<0.01) for exit velocity and exit score, which were always greater (P<0.01) in EXC v. ADQ heifers. A temperament × time interaction was also detected (P=0.03) for puberty attainment, which was delayed in EXC v. ADQ heifers. At the end of the experiment, a greater (P<0.01) proportion of ADQ were pubertal compared with EXC heifers. In summary, B. indicus heifers classified as EXC had reduced growth, increased plasma cortisol concentrations and hindered puberty attainment compared to ADQ heifers. Moreover, exit velocity may serve as temperament selection criteria to optimize development of B. indicus replacement heifers.
易激动的气质会扰乱牛的生殖发育所需的生理事件，但尚无研究调查气质对印度瘤牛雌性生长和青春期获得的影响。因此，本实验评估了气质对印度瘤牛小母牛生长、血浆皮质醇浓度和青春期获得的影响。总共 170 头尼洛里小母牛，在实验开始前 4 个月断奶（第 0 天至 91 天），分为两组，每组 82 头和 88 头（平均±SE；初始 BW=238±2kg，初始年龄=369±1 天，两组间）。通过第 0 天的出口速度评估小母牛的气质。通过将出口速度分为五等份并为小母牛分配 1 到 5 的分数（1=最慢；5=最快的小母牛），在每组内计算小母牛的个体出口分数。根据出口分数，小母牛分为正常（ADQ，n=96；出口分数⩽3）或易激动（EXC，n=74；出口分数>3）气质。在第 0、31、60 和 91 天测量小母牛的 BW、体况评分（BCS）和血液样本。在第 31、60 和 91 天再次记录小母牛的出口速度和出口分数。在青春期评估时，在第 0 和 10、31 和 41、60 和 70、81 和 91 天进行卵巢经直肠超声检查。当检测到黄体时，小母牛被宣布进入青春期。第 0 天获得的出口速度和出口分数与第 31、60 和 91 天的评估结果相关（r ⩾0.64，P<0.01）。在实验过程中，ADQ 的平均 BCS 和 BW 增加更高（P<0.01），平均血浆皮质醇浓度更低（P<0.01），与 EXC 小母牛相比。出口速度和出口分数存在气质×时间交互作用（P<0.01），EXC 小母牛的出口速度和出口分数总是高于 ADQ 小母牛（P<0.01）。气质×时间的交互作用也检测到（P=0.03）青春期的获得，EXC 小母牛的青春期获得延迟。在实验结束时，与 EXC 小母牛相比，更多的 ADQ 小母牛达到了青春期（P<0.01）。总之，与 ADQ 小母牛相比，被归类为 EXC 的印度瘤牛小母牛生长速度较慢，血浆皮质醇浓度增加，青春期获得延迟。此外，出口速度可以作为气质选择标准，以优化印度瘤牛后备小母牛的发育。
