Seasonal ovulatory activity exists in tropical Creole female goats and Black Belly ewes subjected to a temperate photoperiod

Table 4 Mean durations in days ± S.E.M. of anovulatory and ovulatory seasons in Black-Belly ewes maintained under two different photoperiodic conditions.

	1^st anovulatory season (1999)	2^nd anovulatory season (2000)	2^nd breeding season (99–2000)
Temperate regimen	134.2 ± 14.0	134.3 ± 14.0	237.8 ± 13.3
Tropical regimen	118.4 ± 7.5*	144.3 ± 5.8*	260.6 ± 6.7*

Two groups of Black-Belly ewes were maintained in light-proof rooms and subjected to either simulated temperate photoperiodic conditions (TE, 12 ewes, 8 to 16 hours of light per day from winter to summer solstice) or simulated tropical photoperiodic conditions (TR, 12 ewes, 11 to 13 hours of light per day from winter to summer solstice) for 25 months. Ovulatory activity was assessed by determinations of plasma progesterone by radioimmunoassay. Means and variances were compared between groups within each column. Significant differences between means and between variances are indicated by asterisks (*:p < 0.05).

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