R. Bras. Zootec.29/set/2025;54:e20240129.
Genotype × environment interaction in milk traits of Guzerá cattle using reaction norm models
Tainara Luana da Silva Soares
, Maria Gabriela Campolina Diniz Peixoto
, Eula Regina Carrara
, Delvan Alves da Silva
, Fernanda Larissa Cesar Santos
, Frank Angelo Tomita Bruneli
, Renata Veroneze
, Paulo Sávio Lopes
ABSTRACT
This study aimed to evaluate genotype × environment (G×E) interactions in Guzerá breed animals for 305-day first-lactation cumulative yields (kg) of milk (MY305), fat (FY305), and protein (PY305). We used 6823 records of MY305, 2466 records of FY305, and 1870 records of PY305. The contemporary groups (CG) were created considering herd and year of calving. The analyses were performed in two steps. In the first step, environmental effects on phenotypes were estimated by using a multi-trait model ignoring G×E interactions. In the second step, G×E interactions were evaluated by using single-trait analyses with the reaction norm model and considering heterogeneous residual variance divided into five classes. The CG solutions obtained in step 1 were used as an environmental gradient in step 2, representing low to high management environments. We observed increasing genetic variance estimates along the environmental gradient for all evaluated traits. Residual variance showed the same pattern, except with class 5 of FY305 and class 4 of PY305. Heritability estimates increased slightly as the management level increased. The correlation estimates between the intercept and the slope of the reaction norm curve were 0.998 for MY305, 0.989 for FY305, and 0.987 for PY305. The genetic correlation among the low (5% quantile), medium (55% quantile), and high (95% quantile) management level environments was high, with values higher than 0.99, 0.97, and 0.70 for MY305, FY305, and PY305, respectively. The breeding values of the animals changed along the environmental gradient, even those classified as robust. These results demonstrate a G×E interaction with scale effect for the evaluated traits that affects the breeding values.
Palavras-chave: cattle; contemporary group; environmental sensitivity; heritability; random regression; zebu
