Influência das condições meteorológicas sobre a produção de vacas mestiças criadas em sistema de pastejo irrigado em ambiente tropical semiárido

Abstract

Animals under heat stress tend to have affected their productive and reproductive capacity , based on this, the objective of this study was to evaluate the influence of climatic variables on the production of crossbred dairy cows reared in semi-arid environment in Northeast Brazil . Data were used for the production of 497 crossbred cows ( Holstein x Gir ) , between the years 2008 to 2012 , created in rotational grazing system using Guinea grass as pasture , with water ad libitum and supplemented with feed at 18 % protein . Meteorological data were collected at the Federal Institute of Ceará weather station, located in the Apodi Plateau, in the city of Limon Northern 500m from the farm where the cows are raised The animals were classified as lactations (1-5) and according to days in milk (DIM - 0-300), were divided into 10 groups every 30 days. Thus the average production was evaluated according to lactation and time in lactation (DIM). Analysis of variance was based on the least squares method and the correlation analysis , the Pearson method , where data of milk production and all environmental variables used for each lactation and DIM were analyzed each was used. The average production grew as increased lactation order. Regarding environmental variables, it was observed that there was a positive correlation between the air temperature and production (P < 0.05), and precipitation and relative humidity were inversely proportional to production (P < 0.05). In semiarid region crossbred cows have increased production to 5th lactation and peak occurs between 60 and 90 days of lactation. The daily milk yield was correlated with meteorological variables. Negatively with relative humidity and mainly with rainfall and positively but low, with the air temperature