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Japanese quails (Coturnix coturnix japonica) are sensitive to zinc (Zn) deficiency, a mineral essential for growth, development, and bone health. This study evaluated the effects of different levels of Zn in the diet on zootechnical performance, organ and carcass weight, and tibial breakage resistance in quails from 1 to 42 days of age. A 5 × 2 factorial design was used, consisting of five Zn levels (30, 60, 90, 120, and 150 mg/kg) and two thermal environments (thermal comfort and heat stress), with five replicates of 10 birds per treatment. The results indicate an antagonistic relationship between high levels of Zn in the diet (150 mg/kg) and quail performance, where the addition of the highest Zn level impaired performance. On the other hand, supplementation with the available Zn from the basal diet (30 mg/kg) was sufficient to ensure satisfactory weight gain, better feed conversion, and appropriate carcass and liver weights of quails during the initial rearing phase. At 42 days, supplementation with 150 mg/kg of Zn provided greater resistance to tibial breakage, regardless of thermal conditions. These findings highlight the importance of adjusting Zn supplementation according to the needs of quails at different rearing stages. The study emphasizes the need for a balanced nutritional approach, considering both adequate Zn levels and the management of thermal stress. The combination of appropriate Zn levels in the diet and environmental management, especially concerning thermal stress, is crucial to optimizing productive performance, bone health, and the well-being of the birds. Furthermore, the nutritional Zn requirements for quails in the initial rearing phase may be lower than previously established, without compromising performance. Gradual Zn supplementation, according to the needs of the production stage and environmental conditions, is essential to ensure the health and productivity of the birds. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the effects of different nutritional plans on meat quails subjected to heat stress. A total of 324 quails male European quails (Coturnix coturnix coturnix) were used, with an average initial weight of 121.48 g ± 3.1 g, distributed in a completely randomized design with nine treatments and six repetitions of six birds each. The diets were evaluated from 22 to 42 days of age, according to the following treatments: T1 - Control diet; T2 - Moderate crude protein (CP) reduction, without amino acid supplementation (AA); T3 - Moderate CP reduction with supplementation of methionine (Met) and cystine (Cys); T4 - Moderate CP reduction with Met, Cys, and lysine (Lys) supplementation; T5 - Moderate CP reduction with Met, Cys, Lys, and threonine (Thr) supplementation; T6 - Severe CP reduction, without AA supplementation; T7 - Severe CP reduction with Met and Cys supplementation; T8 - Severe CP reduction with Met, Cys, and Lys supplementation; T9 - Severe CP reduction with Met, Cys, Lys, and Thr supplementation. The room temperature was maintained at 30°C, with relative humidity at 76.42%, and a black globe humidity index (BGHI) of 82.19. No significant (p > 0.05) effect of protein reduction or amino acid supplementation was observed on live weight, feed intake, carcass weight, yield, breast, legs, heart, and gizzard. However, significant effects were observed on weight gain (p < 0.04), feed conversion (p < 0.05), liver weight (p < 0.001), and liver yield (p < 0.001). In hot environments, crude protein in the diet of meat quails can be reduced from 22 to 17.6%, with adequate methionine supplementation to achieve 0.800% digestible Met + Cys during the growth phase (22–42 days). These nutritional strategies may optimize performance, reduce costs, and provide environmental benefits by decreasing nitrogen excretion. Future research should investigate the interactions between diet, heat stress, and quail performance, focusing on different amino acid combinations and their impacts on bird health and productivity under varied thermal conditions. [ABSTRACT FROM AUTHOR]