Broodiness instinct in farm poultry: realization and methods of suppression

Many hens of gene pool populations along with their breed features are characterized by the manifestation of such a trait as broodiness which has been lost in commercial lines and breeds. This trait has some negative impact at commercial farming, because during the nesting period the hens stop egg laying that leads to decreasing in egg performance and the number of progeny. Predisposition to the broodiness is an inherited trait and its eradication can be achieved by use of selection methods. But elimination of the families with high levels of nesting will lead to the destroying of the genetic structure in the gene pool population. Hormonal methods and technological shocks (electric current, high-intensity light and transfer to the new environmental conditions) may also be used to suppress broodiness instinct. But some of them could be not available technically and other ones should not be applicable ethically. In our research, the Chinese silky chickens ( Gallus gallus ) from the gene pool collection of All-Russian Research Institute of Farm Animal Genetics and Breeding which are characterized by highly developed broodiness served as a model. In individual cage batteries the occurrence of broodiness instinct resulted in specific behavioral reactions and refusing in the majority of cocks to give sperm to massage. In the group keeping of birds on the floor, the presence of cocks to some extent stimulated the hens to lay eggs. But during the entire productive period about 70-75 % of hens demonstrated nesting behavior and did not lay eggs. Most part of cocks also showed specific behavior and did not mate with hens. This led not only to the low yield of hatching eggs from a pen, but also to the loss of a large number of genotypes of both hens and cocks in the reproduction of the flock. In order to suppress the broodiness instinct in Chinese silky hens, contained in individual cages, we used injection of native mixed sperm of cocks into the oviduct or cloaca of the hens. The insemination of the hens (three inseminations with 4-day intervals) started four weeks prior to the breeding season. During two experiments about 70 % of all hens responded to the stimulation by restarting of oviposition or increasing of egg performance. The frequency of occurrence of individuals with a high laying intensity (51-60 % and higher) increased, while frequency of hens with low egg laying rate went down. This method of broodiness suppression is more preferable and more physiologically acceptable in comparison to the traditional shock methods, but with the same efficiency.