Effect of different combinations of light and dark regimes on the performance of egg lay events, fertility and plasma steroid hormones, during the ovulatory cycle in Peking ducks

Abstract

SummaryDifferent photoperiodic treatments within 2 types of light dark cycles ranging from 24 to 30 h were applied to Peking ducks. The first consisted of constant photoperiods (1, 8L: 16D; 2, 14 L: 10D; 3, 18L:6D; 4, 14L: 13D; 5, 14L: 16D and 6, continuous light) and the second of intermittent cycles (1, 6L:2D:2L:14p; 2, 6L:4D:2L:12D; 3, 6L:6D:2L:10D; 4, 6L:8D:2L:8D and 5, 14L:½D:3½L:6D). The traits studied varied in response according to the photoperiodic regimes used. Rate of lay and eggs laid in the modal 8 h period increased with the duration of the light period in the cycle. Sequence lengths of 1–3 eggs were most frequent under all photoperiodic regimes (constant and intermittent). Length of intra-sequence interval (h) showed an inverse relationship with length of inter-sequence interval. A pause length of 2–4 days was the most frequent for all the different light-dark cycles. Egg weight was heavier in the second season than in the first when the light period of the photoperiodic regime was long. Weights of albumin and yolk showed similar trends to egg weight. The latter differences were significant, while shell weight differences were not significant. Plasma progesterone lvels were lowest in non-laying ducks. The highest values in laying ducks were before ovulation. The highest level of cortisol was shown during the last hours of the dark period. Differences from ovulatory cycle to another were observed.