Luiz Anjos Lima ¹ Maria Isabelly Leite Maia ¹ Larissa Kellen da Cunha Morais ¹ Tarsys Noan Silva Veríssimo ¹ José Danrley Cavalcante Santos ¹ Adriano Leite Silva ² Nátali Rodrigues Santos ² Severino Guilherme Caetano Gonçalves Dos Santos ³ José Helder de Andrade Moura ⁴ Rannyelle Gomes Souza ⁴ José Humberto Vilar Silva ⁵ Fernando Guilherme Perazzo Costa ² Lucas Carvalho ^6* Edilson Saraiva ¹

• ¹ Research Group in Bioclimatology, Ethology and Animal Welfare (BioEt), Department of Animal Science, Federal University of Paraiba (UFPB), Areia-PB, Brazil
• ² Department of Animal Science, Federal University of Paraiba (UFPB), Areia-PB, Brazil
• ³ Department of Animal Production, National Institute of Semiarid - INSA, Campina Grande - PB, Brazil
• ⁴ Federal University of Tocantins (UFT), Palmas - TO, Brazil
• ⁵ Federal University of Paraiba, CCHSA, Bananeiras - PB, Brazil
• ⁶ Karolinska Institutet (KI), Solna, Sweden

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 121.48g ± 3.1g, 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 30ºC, 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 to 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.