Hunter M G, Biggs C, Faillace L S
Department of Physiology and Environmental Science, University of Nottingham, Loughborough, Leics, UK.
J Reprod Fertil Suppl. 1993;48:261-70.
The enhanced early embryonic survival in Chinese Meishan compared with Large-White gilts may be due, in part, to differences in ovarian and endocrine function, particularly during the periovulatory period. The overall patterns of oestradiol, LH and FSH secretion were not different between Meishan and Large-White hybrid controls during this period, although circulating inhibin concentrations were higher in Meishan gilts. Thus, there appeared to be a decreased sensitivity to inhibin feedback on FSH secretion in Meishan gilts. Behavioural oestrus was exhibited earlier relative to the LH surge in Meishan gilts than in Large-White hybrid gilts, but the time interval from the oestradiol peak until the LH surge was similar in both breeds. This finding suggests that Meishan gilts are more sensitive in terms of initiating a behavioural response, but not in terms of positive feedback. Although preovulatory follicular characteristics were as variable in Meishan as in Large-White hybrid gilts, follicles from Meishan gilts were smaller, but contained a higher concentration of oestradiol in the follicular fluid. This was probably due to increased aromatase activity in both granulosa and theca cells of Meishan follicles. The enhanced maturation of the intrafollicular environment in Meishan gilts was reflected in the oocyte population which was at a more advanced stage of development in the period preceding ovulation. In addition to decreasing the time between onset of oestrus and ovulation, advancing the LH surge to coincide with onset of oestrus (via hCG administration) decreased embryo survival at day 30 of gestation. It is concluded that both endocrine and follicular mechanisms have a role in ensuring the prolificacy in the Meishan breed.
与大白母猪相比，中国梅山猪早期胚胎存活率的提高可能部分归因于卵巢和内分泌功能的差异，尤其是在围排卵期。在此期间，梅山猪和大白杂交对照母猪的雌二醇、促黄体生成素（LH）和促卵泡素（FSH）分泌的总体模式并无差异，尽管梅山母猪循环中的抑制素浓度较高。因此，梅山母猪对抑制素对FSH分泌的反馈似乎敏感性降低。与大白杂交母猪相比，梅山母猪的行为发情相对于LH峰出现得更早，但两个品种从雌二醇峰值到LH峰的时间间隔相似。这一发现表明，梅山母猪在引发行为反应方面更敏感，但在正反馈方面并非如此。尽管排卵前卵泡特征在梅山猪和大白杂交母猪中一样具有变异性，但梅山母猪的卵泡较小，但卵泡液中的雌二醇浓度较高。这可能是由于梅山卵泡的颗粒细胞和膜细胞中芳香化酶活性增加所致。梅山母猪卵泡内环境成熟度的提高反映在排卵前阶段发育更成熟的卵母细胞群体中。除了缩短发情开始到排卵的时间外，通过注射人绒毛膜促性腺激素（hCG）使LH峰提前与发情开始同步，会降低妊娠第30天的胚胎存活率。研究得出结论，内分泌和卵泡机制在确保梅山猪的多产性方面均发挥作用。
