Increased embryonic losses may be associated with inadequate progesterone (P4) concentrations in high-producing lactating dairy cattle. The objectives of the present studies were to determine if chronic administration of a gonadotropin-releasing hormone (GnRH) agonist, Deslorelin, would increase circulating P4 concentrations and subsequently increase pregnancy rates in dairy cattle. Administration of Deslorelin for 12 days increased (p < .05) luteal volume and circulating P4 concentrations in primiparous lactating dairy cows, but increased only luteal volumes in multiparous cows. Treatment with Deslorelin increased Day 45 pregnancy rates in cows as compared to untreated controls. Chronic treatment with Deslorelin in dairy cattle; (a) increased luteal volume of the primary CL, (b) induced accessory CL, (c) increased circulating P4 concentration in primiparous cows only, (d) did not lengthen the estrous cycle upon removal of treatment, and (e) increased pregnancy rates. Although luteal volume was increased in multiparous cows and circulating P4 concentrations were not with Deslorelin treatment, there was an apparent effect on pregnancy rates. This hormonal strategy may represent a suitable model to address local effects of P4 and GnRH/luteinizing hormone on uterine environment and subsequent embryonic survival.

中文翻译：

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长期施用促性腺激素释放激动剂对奶牛黄体功能和妊娠率的影响。

胚胎损失增加可能与高产泌乳奶牛中孕酮（P4）浓度不足有关。本研究的目的是确定长期施用促性腺激素释放激素（GnRH）激动剂Deslorelin是否会增加循环中的P4浓度并随后提高奶牛的妊娠率。给予Deslorelin 12天后，初产泌乳奶牛的黄体体积和循环中P4浓度增加（p <.05），而多胎牛的黄体体积仅增加。与未治疗的对照组相比，用Deslorelin进行治疗可提高母牛第45天的怀孕率。用Deslorelin对奶牛进行慢性治疗；（a）原发性CL的黄体体积增加，（b）诱发的副CL，（c）仅在初乳奶牛中增加循环中的P4浓度，（d）在取消治疗后并未延长发情周期，并且（e）妊娠率增加。尽管多胎母牛的黄体体积增加，而地洛瑞林治疗未使循环中的P4浓度升高，但对妊娠率有明显影响。这种激素策略可能代表一种合适的模型，以解决P4和GnRH /促黄体生成激素对子宫环境和随后的胚胎存活的局部作用。