Effectiveness of photoperiod stimulation on reproductive performance of sheep housed continuously indoors on an accelerated breeding schedule.

Over five breeding periods, the reproductive performance (fertility, prolificacy and fecundity) of three strains of sheep housed continuously indoors was measured. The sheep were maintained as two separate flocks, A and B, with similar genetic background on an eight month accelerated breeding schedule under one of three lighting regimes, abrupt, contracted or constant, to induce ovarian activity. Overall fertility to one estrus was 59%. For flock A, fertility was greatest under the contracted lighting regime and lowest under the constant lighting regime; the opposite was true for flock B. Among the three strains, fertility was lowest for the Dam 2 strain in flock A. Prolificacy averaged 1.8 lambs per ewe lambing and was similar under each of the three lighting regimes. Fecundity (averaging 106%), the number of lambs born per 100 ewes exposed to rams, generally followed the pattern of fertility.