We determined the length of time within which frozen-thawed semen delivered a high conception rate in present-day lactating dairy cows. The cows utilized were a total 100 milking Holstein-Friesian cows kept in tie-stall style farms. We carried out artificial insemination (AI) during the periovulatory period at a predicted time based on ovulation, and checked ovulation at 6-h intervals after AI. The period from AI to ovulation ranged from 48 h (i.e., 48 h before ovulation) to -12 h (i.e., 12 h after ovulation). High conception rates averaging 63.0% were obtained by carrying out AI > 6–30 h before ovulation, significantly higher than the conception rates of 30.0% (P < 0.05) and 26.9% (P < 0.01) from AI carried out earlier than 30 h before ovulation and later than 6 h before ovulation, respectively. It was concluded that frozen-thawed semen delivers a conception rate of ≥ 60% for > 24–30 h after AI, and that a conception rate of ≥ 60% can be achieved by carrying out AI 6–30 h before ovulation using frozen-thawed semen.

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冻融精液在泌乳奶牛中产生高受孕率的时间段的调查

我们确定了冻融精液在当今泌乳奶牛中产生高受孕率的时间长度。使用的奶牛是饲养在平栏式农场的总共 100 头正在挤奶的荷斯坦-弗里斯兰奶牛。我们在排卵期根据排卵预测的时间进行人工授精 (AI)，并在 AI 后每隔 6 小时检查一次排卵。从AI到排卵的时间范围从48小时（即排卵前48小时）到-12小时（即排卵后12小时）。排卵前> 6-30小时进行人工授精可获得平均63.0%的高受孕率，显着高于30小时之前进行人工授精的30.0% (P < 0.05)和26.9% (P < 0.01)的受孕率分别在排卵前和排卵前 6 小时后。