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Comparison of long-term progestin-based protocols to synchronize estrus prior to natural service or fixed-time artificial insemination in Bos indicus-influenced beef heifers.
Animal Reproduction Science ( IF 2.2 ) Pub Date : 2020-04-30 , DOI: 10.1016/j.anireprosci.2020.106475
J W C Locke 1 , J M Thomas 2 , E R Knickmeyer 1 , M R Ellersieck 3 , J V Yelich 4 , S E Poock 5 , M F Smith 2 , D J Patterson 2
Affiliation  

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.



中文翻译:

Bos indicus影响的牛肉小母牛在自然服务或固定时间人工授精之前基于长期孕激素的方案同步发情的比较。

本实验旨在评估在田间管理条件下,在受到Bos印度感染的牛肉小母牛(n = 1456)中涉及自然服务或定时人工授精(FTAI)的育种策略。在分配给以下五种治疗方法之一之前,已为小母牛获得了体重和生殖道分数(RTS; 1-5级):1)非同步控制的自然服务暴露(NS),n = 299;2)乙酸美仑孕酮+天然溶剂(MGA + NS; 0.5 mg /小母牛/天),n = 295; 3)14 d受控内部药物释放插入物+自然服药(CIDR + NS),n = 289;4)14-d MGA-前列腺素(PG)+ FTAI,Ñ= 295; 或5)14天CIDR-PG + FTAI,n =278。将可育公牛与三个NS治疗组的小母牛一起放牧在牧场中,持续65天,从孕激素治疗(MGA或CIDR)结束后的10天开始。FTAI治疗组的小母牛分别在CIDR去除后16天或MGA撤除后19天分别给予PG(25 mg,IM),并在PG后66(CIDR-PG)或72 h(MGA-PG)进行FTAI。FTAI给予促性腺激素释放激素(GnRH; 100μg,im)。在65天的繁殖期结束时确定怀孕状态。关于天21和繁殖期的65怀孕率差异基于预处理青春期状态(治疗组之间P ≤0.02)和体重(P≤0.05),但各组之间没有差异。这些数据表明需要继续进行研究,以改善受Bos感染的雌性的生殖管理。

更新日期:2020-04-30
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