Produtividade de vacas mestiças leiteiras em sistema semi-intensivo nos municípios de Irituia e Mãe do rio do nordeste paraense

Abstract

Check the influence of environmental factors on reproduction and production traits in dairy cattle genetic groups exploited in some farms in the municipalities of Irituia and Mother of the river in northeastern Pará. We used an average of 454 animals lactating crossbred Holstein, Brown Swiss and Girolando belonging two farms to system with the semi-intensive in the less rainy season. The mean and standard deviation for total milk production was equal to 1097,36 ± 330,47 kg, with a coefficient of variation equal to 25,64% and the group genetic Holstein, the less rainy season of birth and year of 2007 produced more. The period of lactation had an effect on the linear and increasing total milk production. The lactation period showed a mean and standard deviation equal to 218,17 ± 43,17 days, the highest average for the period of lactation was observed in the rainiest season and the average lactation period decreased over the years 2007 and 2008. The mean and standard deviation of calving interval found in the herd was equal to 398,975 ± 60,85 days. The least rainy season had an average calving interval of less than rainiest season and the average interval between births was reduced from 2006. The average age at first calving was found to be 38,57 ± 5,81 months. The coefficients of determination were greater than 0,85 (R2 a> 0,85), and genetic group for Holstein, the settings were better than those other two settings of genetic groups. For the genetic group Girolando, the shape of the lactation curve differed from the other two genetic groups difficult adjustment for the functions Gamma incomplete, Linear hyperbolic and Polynomial inverse. The adjustments made by the function Polynomial inverse showed slight deviation from the other two functions. The group presented genetic Holstein production peak and persistence slightly higher compared to other genetic groups.