Effects of Breeder Age and In Ovo Administration of Vitamin D3 Metabolites on Hatchability, Growth Performance, Bone Quality, and Leg Health in Broilers.

This study evaluated the effects of breeder age (BA) and in ovo (IO) administration of vitamin D3 metabolites on hatchability, body weight, bone traits, and leg health in broiler chickens. A total of 640 eggs obtained from young (YB; 29 wk) and old (OB; 52 wk) Ross 308 broiler breeder flocks were assigned on day 18 of incubation to four treatments: 25(OH)D3, 1,25(OH)2D3, diluent, or non-injected. Chicks were reared under standard conditions until market age. Hatchability was not affected by BA or IO treatments. Birds derived from OBs exhibited greater hatch weight and final body weight than those derived from YBs. At market age, BA effects on bone traits were limited to greater femur length in OB birds. In contrast, IO administration of vitamin D3 metabolites significantly enhanced bone mineralization and mechanical competence, as evidenced by higher tibial Ca, P, and Mg concentrations; increased bone ash content; a higher Seedor index; and greater breaking strength. Treated birds also exhibited shorter, narrower, and heavier long bones, indicating altered bone geometry. Furthermore, the incidence of gait abnormalities and tibial dyschondroplasia was markedly reduced, whereas femoral head necrosis remained unaffected. Among the metabolites evaluated, 25(OH)D3 produced the most consistent improvements in final body weight, bone traits, and leg health. Overall, IO administration of vitamin D3 metabolites, particularly 25(OH)D3, improved bone traits and leg health at market age and may represent a practical strategy to enhance broiler welfare and production performance.