ESTUDO RETROSPECTIVO DE FATORES QUE INTERFEREM NA FERTILIDADE DE VACAS GIROLANDAS PRODUTORAS DE LEITE

Abstract

The aim of the study was to identify critical points that interfere with fertility of milking cows Girolando. At the experiment, were used 7134 reproductive and productive data of cows in a dairy farm located in the state of Minas Gerais during 2009-2012. Statistical analysis was performed using the Statistical Analysis System for Windows (SAS, 2001) by multivariate logistic regression using the LOGISTIC procedure of SAS. Variables were removed by reverse elimination, according to the statistical criteria of Wald with stipulated value P > 0.20. The final statistical model included the variables of season [winter (May to August) and summer (November to March)], days in milk (DIM; 50 days, between 50 and 90 days, 90-150 days and above 150 days), number of inseminations (repeat breeder, > 3 IA and not repeat breeder), production of milk in 305 days of lactation (up to 4000 Kg, between 4000 and 6500 Kg and above 6500 Kg) and animal category (primiparou or pluriparou). After this initial analysis, the variables were analyzed for the binomial distribution using the GLIMMIX procedure of SAS. There was no interaction between these variables (P > 0.05). In the study, the pregnancy rate was influenced by the season [summer (34.6%, 797/2301) and winter (45.0%, 1510/3347); P=0.001], number of inseminations [repeat breeder (34.7%, 543/1563) and not repeat breeder (41.7%, 2354/5642) , P=0.001], days in milk [DIM < 50 (38,7%, 313/809)bc, 50 < DIM < 90 (42.3%, 977/2311)ab, 90 < DIM < 150 (44.0%, 896/2035)a and DIM > 150 (35.5%, 702/1979)c; P=0.003], production of milk [milk < 4000kg (43.8%, 295/673)a, 4000kg < milk < 6500kg (39.9%, 1738/4360)b and milk > 6500kg (39.7%; 857/2159)b; P=0.04]. However, there was no difference in pregnancy rate between animal categories [primiparous (41.6%, 981/2359) and pluriparous (39.5%, 1916/4846); P=0.18]. We conclude that the fertility of crossbred cows (Girolanda) of media/high milk production is influenced by multiple factors, in which it was found lower pregnancy rate in the summer, in repeat-breeder cows, in extreme DIM and cows production up to 4000 Kg of milk in 305 days of lactation.