Breeder Age and Zinc Source in Broiler Breeder Hen Diets on Progeny Characteristics at Hatching

Metabolic, immune, and physical status of chicks can impact the incidence of morbidity and mortality of broilers during the first week of production. Assessments of chick quality are made primarily by subjective observations with few quantitative measurements. Given a better understanding of how broiler breeder hen age and nutrient intake may influence progeny physiology, certain actions can be taken to improve chick quality. This experiment evaluated the effects of broiler breeder age, dietary zinc source, and their interaction on the physiological characteristics of chicks at hatching. Caged broiler breeder hens were provided 1 of 3 diets from hatch through 65 wk of age. All experimental diets consisted of 160 ppm supplemental zinc from inorganic ZnSO4, AvailaZn zinc-amino acid complex (ZnAA) or a mixture of ZnAA and ZnSO4 (ZnAA + ZnSO4, 80 ppm zinc from each). Incubation length, relative organ weights, and carbohydrate status were measured in chicks from hens at 29, 41, 53, and 65 wk of age. The variation in hatch time among eggs set together was not influenced by hen age, but mean incubation length decreased from 29 to 53 wk of age and subsequently increased from 53 to 65 wk. Seasonal temperature changes may have caused confounding effects on incubation length. Chick heart glycogen declined as hens aged, and liver lactate was lowest in progeny from 65-wk-old hens. Relative yolk sac weight and relative heart weight were lowest in progeny from 29-wk-old hens. These data indicate that underdevelopment of supply organs may limit the performance of some chicks from young hens. Supplemental zinc source in breeder hen diets did not influence chick physiology at hatching.