The effects of geographical area, rearing method, caging density, and lymphoid leukosis infection on adult performance in egg stocks of chickens.
Birds were brooded reared, and laying house-tested at two widely separated sites: Animal Research Centre (ARC) and North Central Region Poultry Breeding Laboratory (NCRPBL). Two strain and a commercial stock were included only at NCRPBL. At ARC, all birds were brooded, reared, and laying house-tested in cages. At NCRPBL, half of the chicks were brooded and reared on floor and half in cages, and all hens were laying tested at one or two birds per cage. Most hens housed one per cage were tested for lymphoid leukosis virus (LLV) infection by the complement fixation test for group specific antigen in egg albumen. When all hens tested at NCRPBL were considered, the method of brooding and rearing affected only egg weight and body weight in favor of the hens reared in floor pens. The commercial stock and the strain crosses performed better than the control strains. Despite very similar genetic backgrounds, there were large differences between control strains 10 and NCR. Hens housed one per cage had lower mortality and higher egg production than those housed two per cage. Average performance of birds at ARC was somewhat better than that at NCRPBL, but there were genotype-site interactions for mortality, egg production, and sexual maturity. The frequency of shedders in the crosses (17.2%) was the same as that of the control strains (20.8%), but the frequency of shedders in the commercial stock (4.5%) was much lower. The method of brooding and rearing had no effect on the frequency of shedders. The LLV infection was associated with significant reductions in egg production and egg quality. For example, the difference between test-positive and test-negative hens was 25 eggs per hen housed and 16 eggs per surviving hen.
D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D001353:Avian Leukosis / Q000503:physiopathology*; D002645:Chickens / Q000235:genetics / Q000502:physiology*; D002980:Climate; D003433:Crosses, Genetic; D005260:Female; D005838:Genotype; D006799:Housing, Animal; D008297:Male; D008954:Models, Biological; D010058:Oviposition