Environmental factors that influence the weaning weight, year weight and weight at 18-months in Nelore Mocho cattle in the southwest of Mato Grosso do Sul - Brazil

Abstract

Animals of the race Nelore hornless (mocha = sem cornos) in regime of pastures in
the three territorial units of the Southwest region of Mato Grosso do Sul, Brazil, in the period of 27
years, were analyzed with the objective of evaluating the environmental and genetic effects on the
weight of these animals. Relative data to 21,919 observations of weights at the weaning (W205), at
the year (W365) and at 18-month (W550) have been considered. Analyses were accomplished by
the method of the minimum squares, to verify the influence of some environmental factors. The
statistical model included the fixed effects of year and month from birth, sex, area and the covariable
of age of the cow to the childbirth (lineal and quadratic). The observed average of the weight to the
205 days of 9,256 observations was of 181,30 ± 23,29 kg, for weight to the 365 days with average
of 7,786 observations was of 244,51 ± 35,49 kg and for the weight to the 550 days of 4,877
observations was of 327,54 ± 47,80 kg. The effects of them were half significant (P <0,001), the
differences between the years and months from birth and areas were evident for the three
characteristics. The age of the cow at the childbirth (lineal and quadratic), only influenced the
weights to the 205 and 365 days, with maximum weights reaching at the ages of 8,8 and 8,54 years,
respectively. The difference between sexes increased gradually with the age, being the superiority
of the males in relation to the females of 9,36% (W205), 13,09% (W365) and 18,56% (W550).