Department of Nutrition and Animal Production, College of Veterinary and Animal Science, University of São Paulo, Duque de Caxias North Avenue, n 225, Pirassununga, São Paulo 13635-000, Brazil.
Department of Animal Science, Federal University of Amazonas, Macurany Avenue, Jacareacanga, Parintins, Amazonas 69152-240, Brazil.
Domest Anim Endocrinol. 2021 Jan;74:106526. doi: 10.1016/j.domaniend.2020.106526. Epub 2020 Jul 20.
This study investigated the effects of growth rates and compensatory growth on puberty attainment in Nellore heifers. Nellore heifers (n = 120), weaned at 8 ± 0.75 mo of age, were blocked by sire and BW (180 ± 8.6 kg) and assigned randomly to receive 1 of 4 treatments over a 10-mo period. Treatments included ad libitum feeding (high gain, HG), feed intake to gain 0.6 kg/d (medium gain, MG), restricted feeding (0.2 kg/d) for 4 mo followed by ad libitum feeding for 6 mo (compensatory gain, CG), and alternating periods of ad libitum and restricted feeding for 2 mo each throughout the trial (alternated CG, ACG). Puberty was assessed weekly by transrectal ultrasonography. Blood samples were collected at 8, 11, and 18 mo of age and at puberty to determine circulating concentrations of leptin. At 18 mo of age, nonpubertal heifers were treated with a puberty induction protocol using an intravaginal progestin device. There was no treatment effect (P = 0.17) on the percentage of heifers pubertal by 18 mo of age (HG: 66, MG: 40, CG: 58, and ACG: 52%), BW at puberty, and age at puberty. However, HG heifers had higher ADG (P < 0.01), dry matter intake (P < 0.01), and leptin concentrations (P = 0.03) than heifers from other groups. The response to the puberty induction protocol was similar (P = 0.90) among treatments. Regarding sire effects (genetic effects), there was an effect (P = 0.03) on the percentage of heifers pubertal by 18 mo of age and a tendency (P = 0.07) of sire effect in response to the puberty induction protocol. Compensatory growth appears to be an effective managerial approach to decrease feeding costs and stimulate puberty in Nellore heifers.
本研究旨在探讨生长速度和补偿生长对尼里-拉菲牛小母牛青春期发育的影响。120 头断奶时 8 ± 0.75 月龄、按父本和体重（180 ± 8.6 千克）分组的尼里-拉菲小母牛，随机分配接受为期 10 个月的 4 种处理之一。处理包括自由采食（高增重，HG）、每天摄入 0.6 千克饲料以获得 0.6 千克增重（中增重，MG）、前 4 个月限量饲喂（0.2 千克/天），然后自由采食 6 个月（补偿增重，CG）、以及整个试验期间每隔 2 个月交替进行自由采食和限量采食（交替 CG，ACG）。每周通过直肠超声评估青春期。8、11 和 18 月龄以及青春期时采集血液样本，以测定循环瘦素浓度。18 月龄时，使用阴道内孕激素装置对未发情小母牛进行发情诱导方案处理。处理对 18 月龄时发情小母牛的比例（HG：66%、MG：40%、CG：58%和 ACG：52%）、发情时体重和发情年龄没有影响（P = 0.17）。然而，HG 小母牛的 ADG（P < 0.01）、干物质采食量（P < 0.01）和瘦素浓度（P = 0.03）高于其他组的小母牛。发情诱导方案的反应在处理之间相似（P = 0.90）。关于父本效应（遗传效应），18 月龄时发情小母牛的比例有影响（P = 0.03），发情诱导方案的反应有父本效应的趋势（P = 0.07）。补偿生长似乎是一种有效的管理方法，可以降低饲养成本并刺激尼里-拉菲牛小母牛的青春期发育。
