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Table 3 Mean dates ± S.E.M. in days, for onset and end of ovulatory activity in Black-Belly ewes maintained under two different photoperiodic conditions.

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

  1st breeding season 1998–1999 2nd breeding season 1999–2000 3rd breeding season 2000–2001
  onset end onset end onset end
Temperate regimen NA 22/04 ± 7 15/09 ± 3 25/04 ± 12 22/09 ± 5 NA
Tropical regimen NA 09/04 ± 4 05/08*** ± 5* 22/04 ± 4* 13/09 ± 3 NA
  1. 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, ***: P < 0.001). NA: not available.