Bovinos da raça Canchim submetidos a dois períodos de monta: Estudo comparativo das taxas de fertilidade e desmama

Reproductive performance of Canchim cows bred from October to January (breeding season A) as compared to cows bred from April to July (breeding season B), were studied in a three-year period beginning October 1970. The observed calving, survival to weaning and weaning rates were, respectively, 67.73%, 80.31% and 54.40% for breeding season A and 71.17%, 88.21% and 62.77% for breeding season B. Chi-square tests showed that breeding season affected (P < 0.05) only survival and weaning rates. Analyses of variance with effects of year, breeding season, year by breeding season interaction and bull or sire of calf were also utilized to analyse the results. None of the effects included in the statistical model had significant effects on calving rate and on weaning rate. Survival rate was affected significantly by breeding season (P < 0.01). Calves conceived during breeding season B survived more than those conceived during breeding season A. Since the bull or sire of calf effects were confounded with the effects of year and breeding season, no conclusions can be draw with respect to the effects of breeding season on calving and weaning rates.