SEASONAL EFFECTS AND HORMONAL PATTERNS RELATED TO PUBERTY IN EWE LAMBS
SEASONAL EFFECTS AND HORMONAL PATTERNS RELATED TO PUBERTY IN EWE LAMBS
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DOI：
10.1095/biolreprod27.4.853
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发表时间：
1982-01-01
影响因子：
3.6
通讯作者：
BUTLER, WR
中科院分区：
文献类型：
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作者：
FITZGERALD, J;BUTLER, WR
研究人员对 3 月、7 月和 8 月出生的母羊羔羊进行了研究，旨在区分季节对从生命早期到第一次排卵期间血清黄体生成素 (LH)、(FSH)、雌二醇、催乳素和黄体酮浓度的持续成熟变化的影响。每周采集两次血样，并根据 2 个或更多连续样本中血清孕酮 (> 1.0 ng/ml) 的增量来评估排卵。从 10 月到 1 月，81% (21/26) 的羔羊进入青春期。大多数 (16/21) 动物在排卵前观察到黄体酮短暂上升，持续 4-7 天。在青春期，3 月的羔羊比 7 月或 8 月的羔羊（170.0 .+-. 12.9 和 153.0 .+-. 7.1 天）大（220.9 .+-. 5.8 天，P < 0.01），也更重（P < 0.05，40.8 .+-. 1.9 kg，38 .+-. 1.9 kg，38 .+-. 1.5 和 35.7.+-1.9）。青春期前发育期间，3月和7月出生的羔羊血清LH、FSH和催乳素浓度高于8月出生的羔羊，秋冬季节羔羊进入青春期时，各组血清催乳素浓度均最低。进入青春期的羔羊和未能排卵的羔羊的循环激素浓度模式非常相似。唯一注意到的例外是，在青春期羔羊和一些非青春期羔羊中检测到的血清雌二醇等量增加，随后仅在一些羔羊中黄体酮增加。母羊羔羊的性成熟显然最早可在 150 天龄时达到，但季节决定了第一次排卵的时间，并将春季出生的羔羊的第一次排卵推迟到秋季。青春期羔羊的体重表明，最小阈值体重而不是临界体重可能是一个因素。秋季血清催乳素下降，与光周期减少同时发生，可能是排卵季节性调节的一个组成部分，但直接的因果关系尚未确定，必须考虑其他因素。
Ewe lambs born in March, July and Aug. were studied in an effort to separate the effects of season from the ongoing maturational changes affecting serum luteinizing hormone (LH), (FSH), estradiol, prolactin and progesterone concentrations from early life through 1st ovulation. Blood samples were collected twice weekly and ovulation was assessed from increments in serum progesterone (> 1.0 ng/ml) in 2 or more consecutive samples. Puberty was attained in 81% (21/26) of the lambs from Oct. through Jan. A small transient rise in progesterone of 4-7 days duration was observed prior to ovulation in most (16/21) of the animals. At puberty, March lambs were older (220.9 .+-. 5.8 days, P < 0.01) than either July or Aug. lambs (170.0 .+-. 12.9 and 153.0 .+-. 7.1 days) and also heavier (P < 0.05, 40.8 .+-. 1.9 kg, 38 .+-. 1.5 and 35.7 .+-. 1.9, respectively). During the prepuberal development period, serum concentrations of LH, FSH and prolactin were higher in lambs born in March and July than in those born in Aug. Serum prolactin concentrations were uniformly lowest in all groups during the fall and winter when the lambs reached puberty. The pattern of circulating hormone concentrations was very similar in lambs which reached puberty and in those which failed to ovulate. The only exception noted was that equivalent increments in serum estradiol, detected in both puberal lambs and in some of their nonpuberal counterparts, were followed by increased progesterone only in some lambs. Sexual maturity in ewe lambs apparently can be attained as early as 150 days of age, but season dominates the timing of 1st ovulation and delays its occurrence in spring-born lambs until the fall. Body weights of lambs at puberty suggest that a minimum threshold weight rather than a critical weight may be a factor. The decline in serum prolactin during the fall, coincident with decreasing photoperiod, may be one component of seasonal regulation of ovulation, but a direct causal relationship is yet to be established and other factors must be considered.