断奶后生长速度和青春期诱导方案对受影响的肉牛小母牛繁殖性能的影响。

Effects of post-weaning growth rate and puberty induction protocol on reproductive performance of -influenced beef heifers.

作者信息

Moriel P, Lancaster P, Lamb G C, Vendramini J M B, Arthington J D

出版信息

J Anim Sci. 2017 Aug;95(8):3523-3531. doi: 10.2527/jas.2017.1666.

DOI:10.2527/jas.2017.1666

Abstract

A 3-yr study evaluated the effectiveness of puberty induction using exogenous reproductive hormones in beef heifers undergoing different post-weaning growth rates. On d 0 of each year, grazing Angus × Brahman heifers (60 heifers/yr) were stratified by initial BW and age (BW = 253 ± 30 kg; age = 310 ± 18 d), and randomly assigned, in a 3 × 2 factorial design, to achieve a low (LOW; 0.45 kg/d), medium (MED; 0.73 kg/d), or high (HIGH; 1.00 kg/d) growth rate from d 0 to 168 (5 heifers/pasture; 4 pastures/growth rate/yr). Dietary supplements were offered 3 times weekly (Mondays, Wednesdays, and Fridays) at 0800 h to provide 1.8, 2.9, and 4.4 kg of supplement DM per heifer daily from d 0 to 168. On d 0 of each year, 2 pastures/growth rate treatment were randomly assigned to receive (SYNC) or not (NOSYNC) a puberty induction protocol, which consisted of intravaginal controlled internal drug release (CIDR) insertion on d 65, CIDR removal on d 72, followed by 100-µg i.m. injection of GnRH on d 74, and 25-mg i.m. injection of PGF on d 84. Immediately after the puberty induction protocol, all heifers were grouped by growth rate treatment (1 group/growth rate/yr) into a single pasture and exposed to yearling Angus × Brahman bulls from d 84 to 168 (1 bull/group/yr). Interactions among growth rate and puberty induction protocol were not detected for any variable ( ≥ 0.26). Overall heifer ADG achieved only 51 to 56% of targeted ADG, and percentage of mature BW on d 84 did not differ between MED and HIGH heifers ( = 0.30), but both were heavier than LOW heifers ( < 0.01). Percentage of pubertal heifers on d 84 was greater for MED and HIGH vs. LOW heifers ( ≤ 0.05), whereas puberty induction protocol increased puberty attainment on d 84 ( < 0.01). Overall pregnancy and calving percentages after first breeding season were not affected by growth rate or puberty induction protocol ( ≥ 0.25). However, heifers calved 11 d earlier when enrolled in the puberty induction protocol ( = 0.02). In summary, puberty induction and HIGH and MED growth rates resulted in earlier attainment of puberty and pregnancy in -influenced beef heifers. However, neither growth rate or puberty induction impacted overall heifer pregnancy and calving rates on their first breeding season.

摘要

一项为期3年的研究评估了在经历不同断奶后生长速度的肉用小母牛中使用外源生殖激素诱导青春期的效果。每年的第0天，将放牧的安格斯×婆罗门小母牛（每年60头）按初始体重和年龄分层（体重 = 253 ± 30千克；年龄 = 310 ± 18天），并采用3×2析因设计随机分配，使其在第0天至168天达到低（LOW；0.45千克/天）、中（MED；0.73千克/天）或高（HIGH；1.00千克/天）的生长速度（每个牧场5头小母牛；每年每个生长速度4个牧场）。从第0天至168天，每周一、周三和周五上午8点提供三次膳食补充剂，每头小母牛每天提供1.8、2.9和4.4千克补充剂干物质。每年的第0天，每个生长速度处理随机分配2个牧场接受（SYNC）或不接受（NOSYNC）青春期诱导方案，该方案包括在第65天插入阴道内控制释放装置（CIDR），第72天取出CIDR，随后在第74天肌肉注射100微克促性腺激素释放激素（GnRH），并在第84天肌肉注射25毫克前列腺素F2α（PGF）。青春期诱导方案结束后，立即将所有小母牛按生长速度处理分组（每年每个生长速度1组）放入一个牧场，并在第84天至168天让其接触一岁的安格斯×婆罗门公牛（每年每组1头公牛）。未检测到生长速度和青春期诱导方案之间对于任何变量的相互作用（P≥0.26）。总体而言，小母牛的平均日增重仅达到目标平均日增重的51%至56%，第84天成熟体重的百分比在MED和HIGH小母牛之间没有差异（P = 0.30），但两者均比LOW小母牛重（P<0.01）。第84天进入青春期的小母牛百分比，MED和HIGH组高于LOW组（P≤0.05），而青春期诱导方案提高了第84天的青春期达到率（P<0.01）。第一个繁殖季节后的总体怀孕率和产犊率不受生长速度或青春期诱导方案的影响（P≥0.25）。然而，参与青春期诱导方案的小母牛产犊时间提前了11天（P = 0.02）。总之，青春期诱导以及HIGH和MED生长速度导致受影响的肉用小母牛青春期和怀孕时间提前。然而，生长速度和青春期诱导均未影响小母牛在第一个繁殖季节的总体怀孕率和产犊率。