Satheshkumar S, Brindha K, Roy A, Devanathan T G, Kathiresan D, Kumanan K
Department of Animal Biotechnology, Madras Veterinary College, Chennai, Tamil Nadu, India.
Department of Animal Biotechnology, Madras Veterinary College, Chennai, Tamil Nadu, India.
Theriogenology. 2015 Jul 1;84(1):19-23. doi: 10.1016/j.theriogenology.2015.02.010. Epub 2015 Feb 13.
The study was aimed at investigating the effect of seasonal changes on follicular and luteal dynamics in vivo in normally cycling crossbred cows during summer and winter months of the year. Six healthy regularly cycling Jersey crossbred nonlactating pluriparous cows were used for the study. Follicular and luteal developmental pattern was studied every other day throughout the estrous cycle by scanning the ovaries during two periods of a year viz., hot season (April to June; n = 16) and cold season (December to February; n = 12). Plasma progesterone (P4) concentrations were measured on Days 0 (estrus), 6, and 12 of the estrous cycle. Among the 12 cycles studied during the cold season, 11 (91.7%) had three waves and one had two waves. Of 16 cycles studied during the hot season, eight (50%) had two waves, four (25%) had three waves, and the remaining four cycles had single (n = 2) and four waves (n = 2). High P4 concentrations during the midcycle would have suppressed the dominant follicle of the second follicular wave and induced the emergence of the third wave during the cold season. The first follicular wave (wave I) of the cycle emerged much earlier (Day 0.5 ± 0.3) during the cold season than that in the hot season (Day 1.7 ± 0.4). The ovulatory wave emerged significantly earlier during the hot season (Day 11.5 ± 1.3) than in the cold season (Day 14.8 ± 0.4), and hence, the growth phase of ovulatory follicle significantly increased during the former season (11.0 ± 1.4 days) than the latter (5.8 ± 0.2 days). The ovulatory follicle attained a significantly larger diameter (12.8 ± 0.8 mm) to express the estrus during the hot season when compared to the cold season (11.3 ± 0.4 mm), which might be indicative of alterations in steroidogenic activity within the follicular microenvironment. During the midphase of the cycle, a period critical for embryonic sustenance, the P4 level was significantly reduced in the hot months indicating suppression of luteal activity during hot period of the year. Thus, it could be concluded that increased incidence of two follicular waves associated with a prolonged growth phase of the ovulatory follicle, and altered luteal endocrine activity during the hot season might be associated with decreased fertility in crossbred cattle.
本研究旨在调查一年中夏季和冬季正常发情周期的杂交奶牛体内季节性变化对卵泡和黄体动态的影响。选用6头健康、发情周期规律的泽西杂交非泌乳多胎奶牛进行研究。在一年中的两个时期，即炎热季节（4月至6月；n = 16）和寒冷季节（12月至2月；n = 12），通过扫描卵巢，每隔一天研究一次卵泡和黄体的发育模式。在发情周期的第0天（发情期）、第6天和第12天测量血浆孕酮（P4）浓度。在寒冷季节研究的12个周期中，11个（91.7%）有三个卵泡波，1个有两个卵泡波。在炎热季节研究的16个周期中，8个（50%）有两个卵泡波，4个（25%）有三个卵泡波，其余4个周期有单个卵泡波（n = 2）和四个卵泡波（n = 2）。寒冷季节周期中期较高的P4浓度可能抑制了第二个卵泡波的优势卵泡，并诱导了第三个卵泡波的出现。与炎热季节（第1.7±0.4天）相比，寒冷季节周期的第一个卵泡波（波I）出现得更早（第0.5±0.3天）。排卵波在炎热季节（第11.5±1.3天）比寒冷季节（第14.8±0.4天）出现得明显更早，因此，排卵前卵泡的生长阶段在前一个季节（11.0±1.4天）比后一个季节（5.8±0.2天）显著延长。与寒冷季节（11.3±0.4毫米）相比，炎热季节排卵前卵泡达到显著更大的直径（12.8±0.8毫米）以表现出发情，这可能表明卵泡微环境中类固醇生成活性的改变。在周期的中期，即对胚胎维持至关重要的时期，炎热月份的P4水平显著降低，表明一年中炎热时期黄体活性受到抑制。因此，可以得出结论，炎热季节两个卵泡波的发生率增加、排卵前卵泡生长阶段延长以及黄体内分泌活性改变可能与杂交奶牛的繁殖力下降有关。
