Calcium requirements for Japanese quail in the early growth period.

This study aimed to determine the optimal dietary calcium (Ca) requirement for quail chicks by evaluating its effects on growth performance, carcass characteristics, serum biochemical parameters, immune responses, and bone development. Quail chicks were fed diets containing varying levels of Ca (0.60-1.00 %) in a completely randomized design from 11 to 24 days posthatch. Growth performance data indicated that weight gain was influenced by dietary Ca (P = 0.006), with the highest gain observed at 0.80 % Ca. Feed conversion ratio (FCR) tended to follow a quadratic trend (P = 0.092), with optimal efficiency estimated at 0.80 % Ca. Carcass analysis showed that thigh meat yield (TMY) was affected by dietary Ca levels (P = 0.012), whereas breast meat yield (BMY) and overall carcass yield remained unaffected. Serum biochemical parameters, including Ca, phosphorus, alkaline phosphatase (ALP), and insulin-like growth factor (IGF), did not show differences among dietary treatments (P > 0.05). Immune responses were not markedly affected, although total immunoglobulins (Ig-Total) and IgY exhibited slight improvements at 0.80 % Ca. Bone parameters, including bone diameter and thickness, demonstrated robust responses to dietary Ca, with the highest R² values observed at approximately 0.80 % Ca. Two-slope broken-line regression models estimated the Ca requirement for optimal gain and FCR at 0.788 % and 0.800 %, respectively. The best estimate for BMY and TMY requirements was 0.809 % and 0.748 %, respectively, while bone density suggested an optimal requirement of 0.835 %. Immune responses indicated a higher Ca requirement of approximately 0.852 %, which was greater than the requirements for performance and other physiological traits. Based on the combined highest R² and lowest standard deviation of residuals (S), the overall optimal dietary Ca requirement for quail chicks was estimated at 0.800 % for growth and efficiency, but higher levels may be needed to support bone density and immune function. These findings provide valuable insights for optimizing Ca nutrition in quail production.