DL-Methionine Supplementation in Japanese Quails under Different Thermal Conditions

Rannyelle Gomes Souza¹Isabelly Maia²Luiz Arthur Anjos Lima²Larissa Kellen da Cunha Morais²Severino Guilherme Caetano Gonçalves Santos³Tarsys Noan Silva Veríssimo⁴José Danrley Cavalcante Santos²Pavlos Vinícius Nascimento²Kilmer Oliveira Soares⁵Fernando Guilherme Perazzo Costa²Ricardo Romão Guerra⁶Lucas Rannier Ribeiro Antonino Carvalho^7*Edilson Paes Saraiva²

• ¹Universidade Federal do Norte do Tocantins, Araguaína, Brazil
• ²Research Group in Bioclimatology, Ethology and Animal Welfare (BioEt), Department of Animal Science, Federal University of Paraíba, Areia-PB, Brazil
• ³Department of Animal Science, Center for Agricultural Sciences, State University of Maranhão, São Luiz - MA, Brazil
• ⁴University Center UNIFIP, Centro Universitario de Patos, Patos, Brazil
• ⁵Technological Education Center Institute, Marco - CE, Brazil
• ⁶Universidade Federal da Paraiba, João Pessoa, Brazil
• ⁷Karolinska Institutet (KI), Solna, Sweden

This study investigated whether dietary methionine + cystine (Met+Cys) supplementation could mitigate the adverse effects of heat stress on the productive, physiological, and histomorphological parameters of laying Coturnix japonica during peak egg production. A total of 504 female quails were distributed across 12 treatments in a 3 × 4 factorial design, combining three Met+Cys levels (100%, 110%, and 120% of NRC recommendations) and four ambient temperatures (20, 24, 28, and 32 °C). Over an 84-day trial, productive performance, egg quality, physiological markers (cloacal temperature, respiratory rate), and tissue morphology (duodenum, jejuno, hepatic, uterine) were evaluated. Heat stress markedly impaired reproductive performance and egg quality, particularly at 32 °C, with no significant interaction between temperature and supplementation level. Principal Component Analysis revealed structural degradation in intestinal, hepatic, and uterine tissues under elevated temperatures, partially alleviated by 120% Met+Cys at 24 °C. However, increased supplementation failed to reverse thermal-induced production losses under severe heat. These findings demonstrate that ambient temperature exerts a stronger influence than methionine and cysteine supplementationon overall quail performance. While nutritional interventions may help preserve tissue architecture under moderate heat stress (up to 28 °C), strategic thermal environment management remains the primary tool to safeguard welfare and productivity. This integrative approach underscores the value of multidimensional analysis in poultry science and supports refined thermal-nutritional management in quail production systems.