Effect of Photoperiod on the Seasonal Changes of Laying, Plasma PRL and LH in Magang Geese

The present study examined the effect of photoperiod on the seasonal changes of laying,plasma PRL and LH in Magang geese.Adult breeding geese were either exposed to natural photoperiod(controls),or subjected to treatments of long and short photoperiods throughout the experiment.Plasma PRL concentrations increased in non-breeding season from April to July,and remained low in the rest of the year,while LH concentrations decreased in April to July and peaked in August to September.Increasing photoperiod increased PRL and decreased LH secretion,terminated lay and induced moulting in treated geese.These results demonstrated that long photoperiod directly inhibited reproductive activities in Magang geese while short photoperiod stimulating effect.The effect of photoperiod was mediated via the secretions of PRL and LH,whose seasonal secretions coordinated the breeding seasonality of this bird.