Effects of a single supplemental dose of gonadotropin-releasing hormone in 2 different fixed-time artificial insemination synchronization protocols among beef cows and heifers

IF 1.4 Q3 AGRICULTURE, DAIRY & ANIMAL SCIENCE Applied Animal Science Pub Date : 2023-12-01 DOI:10.15232/aas.2023-02429
Jerica J.J. Rich , Emmalee J. Northrop-Albrecht , Kaitlin M. Epperson , Saulo Menegatti Zoca , Stephanie D. Perkins-Oines , Julie A. Walker , Rick N. Funston , PAS, Vitor R.G. Mercadante , George A. Perry , PAS
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Abstract

Objective

Studies evaluating single and multiple gonadotropin-releasing hormone (GnRH) treatments at time of prostaglandin (PG) administration using the 7-d CO- Synch + controlled internal drug-release device (CIDR) protocol reported decreased interval to estrus and increased estrus expression, or increased conception rates, respectively. Therefore, the objectives of these studies were to determine effects of supplementing GnRH at PG on estrus expression and conception rates in beef females synchronized with different protocols.

Materials and Methods

In Exp 1 and 2, heifers (n= 1,626) and cows (n = 1,409), respectively, were synchronized using the 7-d CO-Synch + CIDR fixed-time AI (FTAI) protocol. In Exp 3, heifers (n = 3,270) were synchronized using the melengestrol acetate-PG FTAI heifer protocol; all animals were randomly assigned to receive a single dose of GnRH (5 μg) at PG or no GnRH (control). Estrus and pregnancy rates were analyzed using the GLIMMIX procedure of SAS.

Results and Discussion

In all experiments, there was no effect of treatment on estrus (P ≥ 0.21), but there was an effect of estrus (P < 0.0001) on FTAI pregnancy rates. Estrual females had greater FTAI pregnancy rates compared with nonestrual females. In Exp 1 there was a treatment × estrus interaction (P = 0.01) on FTAI pregnancy rates. Heifers in the control group that exhibited estrus had greater (P ≤ 0.04) FTAI pregnancy rates (72.8 ± 3.2%) compared with estrual heifers that received 5 μg of GnRH (67.2 ± 3.4%) and compared with heifers that did not exhibit estrus in the control (54.4 ± 4.7%) or 5 μg of GnRH (60.8 ± 4.6%) groups. There was no effect (P ≥ 0.17) of treatment on breeding-season pregnancy rates in any of the experiments.

Implications and Applications

Utilization of a supplementary dose of 5 μg of GnRH may be a useful tool to address differences in fertility of FTAI in short-term progestin synchronization protocols among animals that do not exhibit estrus.

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单次补充促性腺激素释放激素对肉牛和小母牛两种不同定时人工授精同步方案的影响
目的在前列腺素(PG)给药时,采用CO- Synch +可控内释药装置(CIDR)方案评估单次和多次促性腺激素释放激素(GnRH)治疗的研究分别报告了缩短发情间隔和增加发情表达或增加受孕率的结果。因此,这些研究的目的是确定在PG时补充GnRH对不同方案同步的牛肉雌性发情表达和受孕率的影响。材料与方法实验1和实验2采用7 d co - sync + CIDR固定时间人工智能(FTAI)协议,分别选取小母牛(n= 1,626)和奶牛(n= 1,409)进行同步。在实验3中,母牛(n = 3,270)使用醋酸甲孕酮- pg FTAI母牛方案进行同步;所有动物被随机分配接受单剂量GnRH (5 μg) PG或不接受GnRH(对照组)。采用SAS的GLIMMIX程序分析发情率和受孕率。结果与讨论在所有实验中,治疗对发情无影响(P≥0.21),但对发情有影响(P <0.0001)对妊娠率的影响。发情期雌性比非发情期雌性有更高的FTAI妊娠率。在Exp 1中,治疗与发情交互作用对FTAI妊娠率有显著影响(P = 0.01)。发情对照组犊牛FTAI妊娠率(72.8±3.2%)高于5 μg GnRH组(67.2±3.4%),高于5 μg GnRH组(54.4±4.7%)和5 μg GnRH组(60.8±4.6%)。在所有试验中,处理对繁殖季节妊娠率没有影响(P≥0.17)。意义和应用补充剂量5 μg的GnRH可能是解决短期黄体酮同步方案中未表现出发情的动物FTAI生育差异的有用工具。
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来源期刊
Applied Animal Science
Applied Animal Science AGRICULTURE, DAIRY & ANIMAL SCIENCE-
CiteScore
3.00
自引率
6.70%
发文量
68
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