RELATIONSHIPS BETWEEN BROODINESS EXPRESSION LAYING PERSISTENCY AND CONCENTRATIONS OF HORMONES DURING THE FIRST PRODUCTIVE PERIOD IN TURKEY HENS (MELEAGRIS-GALLOPAVO)

The changes in egg production, in broodiness index and in plasma conce ntrations of LH, prolactin, oestradiol and progesterone were monitored throughout the first period of laying in turkey hens. The hens were s ubsequently classified according to their ability to express broodines s (33%) and their laying persistency; 25% were out-of-lay by the end o f the experiment. A high percentage (67%) of the hens that went out-of -lay had previously been identified as broody. Altogether, a significa nt (p < 0.05) physiological stage effect was found when comparing prol actin, oestradiol and progesterone data obtained from short and long l aying persistency hens and this stage effect was also significant for oestradiol and progesterone data obtained from broody and non-broody h ens. Otherwise, plasma LH concentrations decreased slightly but signif icantly throughout the laying year in all hens but no significant diff erences between physiological states were observed, although the decre ase was more pronounced in the hens that went out-of-lay. Plasma proge sterone concentrations remained stable throughout in laying hens but d ecreased significantly in broody and/or out-of-lay hens. Plasma prolac tin concentrations were maximal between the 5th and 12th week of egg p roduction and the levels observed in laying hens that did not become b roody or had a long laying persistency were twice those measured in br oody and/or out-of-lay hens. In the meantime, plasma oestradiol concen trations were lower and stable in laying hens, whereas they were highe r during the first half of the productive period in broody and short l aying persistency hens. These results suggest that, under our experime ntal conditions, the hormonal profiles of prolactin and oestradiol for a given hen during the first 10 weeks of the laying cycle may provide predictive information for future changes in its physiological status . The inverse relationship that was observed here between high early p lasma concentrations of oestradiol and laying persistency is original. In addition, the relationship between the ability to express broodine ss and high and low early plasma concentrations of oestradiol and prol actin, respectively, in hens submitted to preventive broody treatment has not been reported previously. Furthermore, it seems clear that hig h initial concentrations in prolactin, far from exerting any deleterio us effects on egg production are closely associated with a longer pers istency of egg laying.