Influence of genetic increases in egg production on traits associated with broodiness in turkeys

Egg production, nesting frequency, and serum levels of prolactin, estradiol, and total phosphorus were monitored in relatively nonbroody (egg) and relatively broody (RBC1) strains of turkey hens during a reproductive period. In the egg strain, prolactin levels were increased in a group with a relatively high frequency of nesting in comparison to a group with a relatively low frequency of nesting. No differences between these two groups were detected for serum estradiol, total phosphorus, or egg production. In the RBC1 strain, prolactin levels did not differ between a group of hens that did not exhibit broodiness and a group that exhibited one or more bouts of broodiness. A broodiness treatment was used for the latter group. The broody group exhibited extremely variable levels of prolactin. In individual broody hens, the levels of prolactin were relatively high. After broodiness in 12 of 13 hens, the level of prolactin fell to relatively low levels. In the one hen not responding to broodiness treatment, the level of prolactin became low levels. In the one hen not responding to broodiness treatment, the level of prolactin became extremely high. Nesting frequency, total serum phosphorus, and egg production were generally not different between the two groups. The level of prolactin showed seasonal changes in both strains of hens, starting low, increasing to maximal levels between 40 and 80 days of production, and then declining to low levels late in the reproductive period. Laying hens always had higher levels of prolactin than nonlaying, nonbroody hens.