Locke J W C, Thomas J M, Knickmeyer E R, Ellersieck M R, Yelich J V, Poock S E, Smith M F, Patterson D J
Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States; College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, United States.
Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States.
Anim Reprod Sci. 2020 Jul;218:106475. doi: 10.1016/j.anireprosci.2020.106475. Epub 2020 Apr 30.
This experiment was designed to evaluate breeding strategies involving natural service or fixed-time artificial insemination (FTAI) in Bos indicus-influenced beef heifers (n = 1456) when there were field-type management conditions. Body weights and reproductive tract scores (RTS; Scale 1-5) were obtained for heifers before assignment to one of five treatments: 1) Non-synchronized control exposed for natural service (NS), n = 299; 2) melengestrol acetate + natural service (MGA + NS; 0.5 mg/heifer/d), n = 295; 3) 14-d controlled internal drug release insert + natural service (CIDR + NS), n = 289; 4) 14-d MGA-prostaglandin F (PG) + FTAI, n = 295; or 5) 14-d CIDR-PG + FTAI, n = 278. Fertile bulls were placed in pastures with heifers of the three NS treatment groups for a 65-day period which began 10 days after progestin treatments (MGA or CIDR) ended. Heifers in FTAI treatment groups were administered PG (25 mg, IM) 16 days after CIDR removal or 19 days following MGA withdrawal, respectively, and FTAI was performed at 66 (CIDR-PG) or 72 h (MGA-PG) after PG. Gonadotropin-releasing hormone (GnRH; 100 μg, i.m.) was administered at FTAI. Pregnancy status was determined at the end of a 65-day breeding period. Pregnancy rates on Days 21 and 65 of the breeding period differed among treatment groups based on pre-treatment pubertal status (P ≤ 0.02) and body weight (P ≤ 0.05) but did not differ by group. These data highlight the need for continued research efforts to improve reproductive management of Bos indicus-influenced females.
本实验旨在评估在野外型管理条件下，涉及自然交配或定时人工授精（FTAI）的育种策略对印度瘤牛影响的肉用小母牛（n = 1456头）的效果。在将小母牛分配到以下五种处理之一之前，记录其体重和生殖道评分（RTS；1 - 5级）：1）非同步对照，自然交配（NS），n = 299头；2）醋酸甲地孕酮 + 自然交配（MGA + NS；0.5 mg/小母牛/天），n = 295头；3）14天控释内植剂 + 自然交配（CIDR + NS），n = 289头；4）14天MGA - 前列腺素F（PG） + FTAI，n = 295头；或5）14天CIDR - PG + FTAI，n = 278头。将可育公牛与三个NS处理组的小母牛一起放入牧场65天，该时间段在孕激素处理（MGA或CIDR）结束后10天开始。FTAI处理组的小母牛分别在取出CIDR后16天或停用MGA后19天注射PG（25 mg，肌肉注射），并在注射PG后66小时（CIDR - PG）或72小时（MGA - PG）进行FTAI。FTAI时注射促性腺激素释放激素（GnRH；100 μg，肌肉注射）。在65天的繁殖期结束时确定妊娠状态。基于处理前的青春期状态（P≤0.02）和体重（P≤0.05），繁殖期第21天和第65天的妊娠率在各处理组间存在差异，但组间无差异。这些数据凸显了持续开展研究工作以改善受印度瘤牛影响的雌性动物繁殖管理的必要性。
