We aimed to evaluate the effects of rumen‐protected lysine (RPL) supplementation during the close‐up period on uterine involution and the resumption of ovarian function in dairy cows. Fifty‐two multiparous Holstein cows were categorized based on parity and expected calving date and randomly assigned to the RPL or control (CON) groups. The RPL group received 80 g of RPL daily from day 21 before the expected calving date until parturition. Blood samples were obtained twice weekly from pre‐supplementation to 6 weeks postpartum. The onset of luteal activity postpartum was determined via ultrasonography twice weekly for up to 6 weeks postpartum. Uterine involution was tracked at 3 and 5 weeks postpartum through the vaginal discharge score, percentage of polymorphonuclear cells (PMN) in endometrial cytology samples, presence of intrauterine fluid, and gravid horn diameter via ultrasonography. Before supplementation, the RPL group showed amino acid imbalance, which was improved by RPL supplementation. There were no significant differences in the onset of luteal activity, percentage of PMN, intrauterine fluid, or the diameter of the uterine horn between the two groups. The vaginal discharge score in the RPL group decreased from 3 to 5 weeks postpartum, whereas that in the CON groups did not decrease. The number of cows with clinical endometritis was lower in the RPL group. Overall, RPL supplementation during the close‐up period enhanced vaginal discharge clearance, potentially averting clinical endometritis, but did not affect the first ovulation in dairy cows.

中文翻译：

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在关闭期间补充瘤胃保护赖氨酸可改善荷斯坦奶牛的阴道分泌物清除率

我们的目的是评估在关闭期间补充过瘤胃保护赖氨酸（RPL）对奶牛子宫复旧和卵巢功能恢复的影响。根据胎次和预期产犊日期对 52 头经产荷斯坦奶牛进行分类，并随机分配到 RPL 组或对照组 (CON)。 RPL组从预产期前21天直至分娩每天接受80克RPL。从补充前到产后 6 周，每周采集两次血样。通过超声检查每周两次确定产后黄体活动的开始情况，持续时间长达 6 周。产后 3 周和 5 周，通过阴道分泌物评分、子宫内膜细胞学样本中多形核细胞 (PMN) 的百分比、宫内液体的存在以及超声检查妊娠角直径来跟踪子宫复旧情况。补充前，RPL组表现出氨基酸不平衡，补充RPL后改善了这一情况。两组之间的黄体活动开始时间、中性粒细胞百分比、宫腔积液或子宫角直径没有显着差异。 RPL组的阴道分泌物评分从产后3至5周下降，而CON组则没有下降。 RPL 组中患有临床子宫内膜炎的奶牛数量较低。总体而言，在特写期间补充 RPL 增强了阴道分泌物清除率，有可能避免临床子宫内膜炎，但不影响奶牛的第一次排卵。