Parâmetros genéticos de características reprodutivas de touros e vacas Gir Leiteiro / Genetic parameters for reproductive traits of bulls and cows Dairy Gyr breed

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Data of 2,274 semen output from 200 sires, 7,055 measurements of age at first calving (AFC) from females and 141 measurements of scrotal circumference (SC) were used to determine genetic parameters for reproductive traits of males and females of Dairy Gyr breed. Were studied physical aspects such as volume (VOL), concentration (CONC), vigor (VIG), motility (MOT), and morphological aspects as major defects (MAD) and minor defects (MID). The statistic model for seminal traits included the fixed effect of AI company-year-season at semen output and age as covariate, with linear and quadratic effects. For scrotal circumference, the statistic model included the fixed effects of season and year of birth, age class at measurement and AI company. For AFC in females, the statistic model included herd- year-season of birth. The models also included the random effects of animal and residual, and permanent environment effect for seminal traits model. Covariance components were estimated by REML, in single trait analyses. The genetic trends for AFC were estimated by linear regression of the breeding values on year of birth of the animals. The estimates of heritability of seminal traits were low to moderate (0.03 to 0.27), the genetic correlations were low to high (0.01 to 0.88), and generally favorable. The SC presented favorable genetic correlation with seminal traits. The heritability for SC and AFC were, respectively, 0.37 and 0.22. The genetic trend were significant, with value estimated of -0.018 kg/year and shows that has not occurred genetic progress in this trait over the years studied. The genetic correlations between SC with volume, concentration, vigor, motility, major defects, minor defects, total defects, doses number, total number of feasible spermatozoid and AFC, were 0.33; 0.22; 0.91; 0.86; -0.07; -0.03; -0.04; 0.30; 0.23 and -0.37, respectively. Strategies should be set for seminal traits selection, toward gains in reproduction. The SC can be used for selection of higher quality semen in Dairy Gyr bulls. These results suggest that genetic gains should be realized in reproductive efficiency of females when bulls with greater SC were used in herds.

ASSUNTO(S)

genetic correlation correlação genética scrotal circumference perímetro escrotal semen genetica e melhoramento dos animais domesticos sêmen

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