This study aimed to estimate genetic and phenotypic parameters and trends for adjusted 305 days milk yield of Murrah buffaloes, which were born from 1982 to 2003. Variance components, genetic parameters and breeding values were obtained using the MTDFREML program. Genetic trends were estimated by regression of breeding values on birth year of the animals by two methodologies: 1) linear regression and 2) articulated polynomial regression using a spline smoothing function. Heritability and repeatability estimates were 0.20 and 0.36, respectively. Phenotypic and genetic trends (by linear regression) were significant and equal to 32.86 and 0.85 kg/year, respectively. The genetic trend was positive but very unstable during the period. Most of the gain observed was due to environmental improvements.
articulated polynomial; buffaloes; genetic gain; heritability; selection
