de Lima R S, Martins T, Lemes K M, Binelli M, Madureira E H
Empresa Matogrossense de Pesquisa, Assistência e Extensão Rural (EMPAER), Pontes e Lacerda, Mato Grosso, Brazil.
Department of Animal Sciences, University of Florida, Gainesville, FL, USA.
Theriogenology. 2020 Sep 15;154:128-134. doi: 10.1016/j.theriogenology.2020.05.036. Epub 2020 May 29.
Induction protocols based on progesterone (P4) are used prior to a synchronization program for timed-AI (TAI) to increase number of pubertal heifers and pregnancy per AI (P/AI). Injectable, long-lasting P4 (iP4) is a novel, practical method to supplement P4 in cattle. Here, we aimed to test the effect of an induction protocol based on a single injection of iP4 on P/AI of heifers. Bos indicus (Nellore) heifers were classified as pubertal (PUB; n = 224) or prepubertal (PRE; n = 414) based on two ovarian ultrasonographyc exams conducted 10 d apart. Heifers with a corpus luteum (CL) in any of the exams were considered PUB. Within each puberty status, heifers were assigned to receive nothing (NoiP4) or an induction protocol (iP4). Induction consisted of a single injection of 150 mg of iP4 on D-31, followed by injections of 1 mg of estradiol benzoate (EB) and 150 μg of prostaglandin analogue (PGF) on D-21. On D-9, all heifers received 2 mg of EB + 75 μg of PGF associated to intravaginal P4-device insertion. On D-3, P4-releasing devices were removed and 150 μg of PGF injected. Heifers were inseminated based on estrus on D-1 or were TAI on D0. On D0, all heifers received a dose of GnRH analogue. On D-21, iP4 treatment stimulated a 50% increase in the uterine score (UTS) and a 19% increase in the diameter of the largest follicle of PRE heifers (P < 0.01). On D-9, PRE|iP4 group had a greater proportion (P < 0.01) of CL (63.3%) than PRE|NoiP4 group (11.6%). On D-3, exposure to 6 d P4-releasing device stimulated UTS of PRE|NoiP4 group in a similar fashion than the induction protocol, but it did not have any additional positive effect for PRE|iP4 heifers. P/AI of PRE|iP4 group was similar to that of the PUB groups (44.7 vs 46.9%), but was more than that of PRE|NoiP4 (34.2%). There was an overall 7.7% increment (P = 0.07) on P/AI of iP4 treated heifers (iP4: 46.0% vs. NoiP4: 38.3%). In conclusion, implementation of an induction protocol based on iP4 was efficacious to hasten puberty. Induction stimulated uterine development and follicular growth of prepubertal heifers, ultimately leading to pregnancy success similar to that of pubertal heifers.
在定时人工授精（TAI）同步程序之前，使用基于孕酮（P4）的诱导方案来增加青春期小母牛的数量和每次人工授精的怀孕率（P/AI）。注射用长效P4（iP4）是一种在牛中补充P4的新颖实用方法。在此，我们旨在测试基于单次注射iP4的诱导方案对小母牛P/AI的影响。根据相隔10天进行的两次卵巢超声检查，将印度瘤牛（内洛尔牛）小母牛分为青春期（PUB；n = 224）或青春期前（PRE；n = 414）。在任何一次检查中出现黄体（CL）的小母牛被视为青春期小母牛。在每个青春期状态内，小母牛被分配不接受任何处理（NoiP4）或接受诱导方案（iP4）。诱导包括在第-31天单次注射150 mg iP4，然后在第-21天注射1 mg苯甲酸雌二醇（EB）和150 μg前列腺素类似物（PGF）。在第-9天，所有小母牛接受2 mg EB + 75 μg PGF并插入阴道内P4装置。在第-3天，取出释放P4的装置并注射150 μg PGF。小母牛根据第-1天的发情情况进行人工授精或在第0天进行定时人工授精。在第0天，所有小母牛接受一剂促性腺激素释放激素类似物。在第-21天，iP4处理使青春期前小母牛的子宫评分（UTS）增加了50%，最大卵泡直径增加了19%（P < 0.01）。在第-9天，青春期前|iP4组的CL比例（63.3%）高于青春期前|NoiP4组（11.6%）（P < 0.01）。在第-3天，暴露于6天的释放P4装置以与诱导方案类似的方式刺激了青春期前|NoiP4组的UTS，但对青春期前|iP4小母牛没有任何额外的积极影响。青春期前|iP4组的P/AI与青春期小母牛组相似（44.7%对46.9%），但高于青春期前|NoiP4组（34.2%）。接受iP4处理的小母牛的P/AI总体增加了7.7%（P = 0.07）（iP4：46.0%对NoiP4：38.3%）。总之
