Individual ovulatory activity in Creole goats maintained under two different photoperiodic conditions. Two groups of Creole female goats were maintained in light-proof rooms and subjected to either simulated temperate photoperiodic conditions (TE goats 1-16 at the bottom of the figure, 8 to 16 hours of light per day from winter to summer solstice), or simulated tropical photoperiodic conditions (TR goats 17-33 upper part of the figure, 11 to 13 hours of light per day from winter to summer solstice) for 33 months. Ovulatory activity was assessed by twice-weekly (first 25 months) then once-weekly (last 8 months) determinations of plasma progesterone by radioimmunoassay. One line represents one female goat. A single dot represents one progesterone measurement above 1 ng/ml of plasma and is considered as indicative of the presence of at least one corpus luteum. Female goats which died or were excluded from the experiment are indicated by an "x".