Pinealectomy delays puberty in ewe lambs

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Abstract
Fifteen pinealectomized and 15 unoperated ewes were exposed to constant light for 3 wk before and 10 wk after lambing. Fourteen pinealectomized and 15 unoperated ewes were allowed to lamb outdoors. Five ewe lambs born in constant light to the 2 groups of dams were pinealectomized at 10 wk of age. Ewes and lambs were then returned to the field. Puberty (determined by weekly progesterone analysis) was significantly delayed (P < 0.05) in the pinealectomized ewe lambs. Median pubertal age in pineal-intact ewe lambs was 37 wk compared to 49 wk in pinealectomized lambs. Constant light during the first 10 wk of life had no effect upon puberty onset nor did the pineal status of the dam. Control lambs entered seasonal anestrus at the time pinealectomized ewe lambs were entering puberty. Pinealectomized lambs entered anestrus at the same time as control lambs were beginning their 2nd breeding season. Pineal-mediated hormonal signals have a key role in the control of puberty in the sheep.

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