Relationship between the timing of the first postpartum ovulation and antral follicle counts in Holstein cows
Relationship between the timing of the first postpartum ovulation and antral follicle counts in Holstein cows
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DOI：
10.1186/s13048-020-0610-5
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发表时间：
2020-01-11
影响因子：
4
通讯作者：
Nagano, Masashi
中科院分区：
文献类型：
--
作者：
Furukawa, Eri;Masaki, Tomoyuki;Nagano, Masashi
背景产后第一次排卵的时间是影响奶牛发情恢复时间的重要因素。产奶量大且能量严重负平衡的奶牛，产后第一次排卵延迟。已知窦卵泡计数（AFC）和血清抗苗勒管激素浓度是卵巢储备的指标，卵巢储备是一对卵巢中剩余卵泡的数量和质量，并被称为女性生育能力的指标。具有较高AFC的奶牛已被证明具有较高的妊娠率和较短的产犊至受孕间隔;然而，产后首次排卵的时间与卵巢储备之间的关系尚不清楚。因此，本研究探讨产后卵泡动态，卵巢周期，营养状况和卵巢储备之间的关系。方法对26头奶牛从产犊至70-120日龄（DIM）进行经直肠超声检查，监测AFC、卵泡动态和卵巢周期。体重（BW）和产奶量被用作营养状况的指标。结果低AFC奶牛（< 25）产后第一次排卵明显晚于高AFC奶牛（>= 25），但两组奶牛从产犊到最低体重的变化和产奶量相似。本研究结果还表明，低AFC和产后第一次排卵延迟的奶牛在产后第一次排卵后的第一个卵巢周期较短。在高AFC组和低AFC组中，首次产后人工授精（AI）的平均DIM和开放天数（从产犊到AI实现妊娠的天数）相似。结论高AFC奶牛产后第一次排卵明显早于低AFC奶牛。这一结果的假设原因是高AFC奶牛对促黄体激素的敏感性较高，卵泡中雄烯二酮和雌二醇的产量较大。因此，具有高AFC的奶牛可能比具有低AFC的奶牛更能生育，而它们的产奶量增加而体重下降，这意味着它们处于负能量平衡。(340/350字）
Background The timing of the first postpartum ovulation is an important factor affecting the timing of estrous resumption in dairy cows. The first postpartum ovulation is delayed in cows producing large amounts of milk with an intensive negative energy balance. The antral follicle count (AFC) and serum anti-Mullerian hormone concentrations are known to be indicators of the ovarian reserve, which is the number and quality of follicles left in a pair of ovaries and known as an indicator of female fertility. Cows with higher AFC have been proven to show higher pregnancy rate and shorter calving to conception intervals; however, the relationship between the timing of the first postpartum ovulation and ovarian reserve remains unclear. Therefore, this study examined the relationships between postpartum follicular dynamics, the ovarian cycle, nutritional status, and ovarian reserve. Methods Transrectal ultrasonography was conducted from calving to 70-120 days in milk (DIM) in 26 cows to monitor AFC, follicular dynamics and the ovarian cycle. Body weight (BW) and milk yield were used as indicators of nutritional status. Results The first postpartum ovulation was significantly later in cows with low AFC (< 25) than in those with high AFC (>= 25), while changes in BW from calving to the nadir and milk production were similar in both groups. The present results also suggested that cows with low AFC and a delayed first postpartum ovulation had a shorter first ovarian cycle after the first postpartum ovulation. The mean DIM of the first postpartum artificial insemination (AI) and days open (days from calving to AI with which pregnancy was achieved) were similar in high and low AFC groups. Conclusions The first postpartum ovulation was significantly earlier in cows with high AFC than in those with low AFC. The assumed reason for this result was higher sensitivity to luteinizing hormone and larger androstenedione and estradiol production in follicles in high AFC cows. Therefore, cows with high AFC may be more fertile than those with low AFC while their milk production increase and BW decrease; it means they are in negative energy balance. (340/350 words)