摘要
It was recently reported that cows inseminated at approximately 10 or 20 h before an expected ovulation deliver predominately a bull or heifer calf, respectively. The objective of this study was to further investigate the effect of timing of insemination on the gender of offspring in cattle. Angus heifers (n = 41) and cows (n = 98) were used in the study. Heifers were synchronized with a 16-d treatment of melengestrol acetate followed 17 d later with an injection of PGF2alpha. Cows were synchronized with GnRH followed 7 d later with PGF2alpha. A HeatWatch electronic estrus detection system was used to determine the onset of estrus. Based on previous studies, it was assumed that ovulation occurs approximately 32 h after the onset of estrus. Therefore, animals were artificially inseminated at either 8 to 10 h (early; ≥ 20 h before expected ovulation) or 20 to 25 h (late; ≤ 10 h before expected ovulation) after the onset of estrus. Sixty to 80 d after insemination, ultrasonography was used to confirm pregnancy status and to determine the gender of fetuses. Gender of calves was subsequently confirmed at calving. Data were analyzed for effects of time of insemination and sire or semen batch on gender ratio, as well as any effect of length and/or intensity of estrus on conception rate and gender ratio. Twenty-nine of 41 heifers and 69 of 98 cows were detected in estrus after synchronization and were inseminated; 20 of 29 heifers and 48 of 69 cows were subsequently confirmed pregnant. Neither the length of estrus nor its intensity (number of mounts) had an effect on pregnancy rate or gender ratio (P ≥ 0.418). Timing of insemination (early versus late) had no effect on gender ratio (P = 0.887). Semen from 13 sires representing 17 lots was used to inseminate the cows and heifers. No differences (P = 0.494) were detected in the gender ratios resulting from different sires or semen batches. In contrast to previous findings, our results indicate that inseminating beef cattle at approximately 20 or 10 h before an expected ovulation does not alter the gender ratio of the resultant calves.
摘要译文
最近报道，在预期的排卵大约在公牛或小母牛小牛的大约10或20小时前分娩的母牛。本研究的目的是进一步研究授精时间对牛后代性别的影响。安格斯小母牛（n \x3d 41）和母牛（n \x3d 98）用于本研究。小母牛与醋酸美仑孕酮的16-d处理同步，17天后注射PGF2α。母牛与GnRH同步，7天后与PGF2α同步。HeatWatch电子发情检测系统被用来确定发情的发作。基于以前的研究，假设排卵发生在发情后约32小时。因此，动物在发情后8至10小时（早期;≥预期排卵前≥20小时）或20至25小时（晚期;预期排卵前≤10小时）人工受精。人工授精后60〜80 d采用超声检查确认妊娠状态，确定胎儿性别。随后在产犊时确认了犊牛的性别。数据分析了受精时间和父母或精液批次对性别比例的影响，以及任何长度和/或发情强度对受孕率和性别比率的影响。同步后发现41头母牛中的29头母牛和98头母牛中的69头被发情，并被授精; 29头母牛中的20头和69头母牛中的48头随后证实怀孕。发情时间长短和强度（坐数）对妊娠率或性别比例均无影响（P≥0.418）。授精时间（早期和晚期）对性别比率没有影响（P \x3d 0.887）。来自13个17代的种子的精液被用来给母牛和小母牛授精。无差异（P \x3d 0。494）是由不同的公羊或精液批次产生的性别比例检测到的。与以前的发现相反，我们的结果表明，在预期的排卵前约20或10小时，授精的肉牛不会改变产生的小牛的性别比例。
RWRorie[1];TDLester[1];BRLindsey[2];RWMcNew[3];. Effect of timing of artificial insemination on gender ratio in beef cattle[J]. Theriogenology, 1999,52(6): 1035-1041