Egg Production and Biochemical Evaluation of Laying Quails Fed Diets Containing Phytase Overdosage Under Different Thermal Conditions

This study evaluated the effects of increasing phytase levels on serum biochemical parameters and renal and hepatic changes in Japanese quails (<i>Coturnix japonica</i>) under different temperature conditions. A total of 720 quails were distributed in a 5 × 3 factorial design with five phytase levels (0, 500, 1000, 1500, and 3000 FTU/kg) and three temperature ranges (24, 30, and 36 °C), totaling 15 treatments with six replicates of eight birds each. Data were collected in cycles 2 and 4. The parameters measured included eggshell thickness (ST), total egg production (TEP), liver weight (LW), gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (FA), phosphorus (P), calcium (Ca), urea (URE), creatine kinase (CK), and uric acid (UA). PRO was higher at 30 °C compared to 24 °C and 36 °C. EC showed a significant interaction between phytase levels and temperature, with phytase improving EC, especially at 1500 FTU and 36 °C. PF was not affected in the second cycle but had a quadratic effect in the fourth cycle. Phytase supplementation improved shell thickness and regulated biochemical parameters, especially at high temperatures. Based on these results, a phytase level of 1500 FTU/kg is recommended to optimize performance and mitigate the negative effects of high temperatures on quail health.