This work was carried out to estimate stability parameters of milk production using data from "Associação de Criadores de Gado Holandês de Minas Gerais (ACGHMG)". Animals from different genetic groups of the Holstein breed (31/32, GC1, GC2 GC3, >GC4 and PO), with different regions (15, 25, 35, 45, 55, 65 and 75) and with two management systems. The database was defined by 22560 animals milk production up to 305 days, from 1989 to 1996.The following animals criteria was used to discord animals for the analyses: suckling smaller than 150 days or production up to 305 days, smaller than 750 kg of milk, or animals with abnormal drying were eliminated. The TOLER (1990) methodology was applied to study the genotype x environment interaction. The genotype 31/32 and GC1 (1st controlled generation) presented linear patterns of response across environments. Both were separated as genotypes of low milk production level, and they were classified according to Toler (1990) in the groups D and C, respectively. The genotypes GC2 (2nd controlled generation), GC3 (3rd controlled generation), >GC4 (of the 4th to 11th controlled generations) and PO (pure of origin) presented bi-segmented models with different inclinations. All of theses genotypes were separate as of high production level. According to TOLER (1990), they were classified as belonging to the groups A, F, E and G, respectively. The results allowed that genotype GC2 (2nd controlled generation) was included in the group A, with high milk production, and it could be recommended for favorable or unfavorable environments.
phenotypic stability; Holstein breed animals; milk production
