Behavioral Genetics

In groups selection theory, my research has shown that the current practice of selecting for improved productivity based on production in single cages, as is the procedure of all breeders of layer type birds, is detrimental to production if the birds are housed in multiple bird colony cages due to competitive interactions. I has shown that a new selection procedure called 'group selection' can overcome this problem and will also greatly reduce mortality due to cannibalism. These results were of tremendous value to primary breeders and have caused some breeders to change their selection methods.

After 6 generations of selection, rate of lay increased from 52 to 68% while percent mortality decreased from 30.6% to 8.8% in the selected line. The combination of these factors resulted in an average increase in days survival from 160 to 348 and an increase in total eggs per hen housed from 91 to 237. In comparison with a commercial line, the selected line was superior for eggs per hen housed, egg mass, and eggs per hen per day. The most remarkable difference was for mortality. The commercial line had an 89% mortality at 58 wk of age as compared to the selected line with 20% and the control at 54%. During cold stress the commercial and control lines showed an increase in heterophil to lymphocyte ratio in 12-bird cages while the selected line did not. Egg production before, during, and after thermal stress indicated that the selected line withstood social, handling, and environmental stress better than the control and in some cases the commercial line. Similar observations with heat stress showed that the selected line withstood heat stress better as indicated by a lower mortality than the control or commercial lines. Egg production before, during, and after heat stress indicated that the selected line withstood social, handling, and environmental stress better than the control line and in some cases the commercial line.

Taken as a whole, these results present strong evidence that group selection on the traits rate of lay and longevity is effective in improving well-being of layers in a relatively short period of time without sacrificing productivity. This research has shown that commercial breeders can develop birds which do not need beak trimming and without sacrificing production. Further, because group selection is shown to improve well-being in multiple-bird cages, alternatives such as redesigning cage environments, or housing such as floor pens or free ranges, may not be needed.

Group Selection for Adaptation to Multiple-Hen Cages: Selection Program and Direct Responses

manuscript [PDF]

Incorporation of Competitive Effects in Breeding Programs

manuscript [PDF]