Evaluation of genetic non factors on characteristics of weight performance of Nelore and Guzerá breeds in the State of Rio Grande do Norte

Abstract

The purpose of this study was to estimate the effects of environmental factors that may affect the bodyweight of the cow herd at the ages of newborn (WN), 205 (W205), 365 (W365), and 550 (W550) days in Rio Grande do Norte State, Brazil. Total information assessed comprised 3,116, given that 2,017 were from Guzerat breed plus 1,099 from Nelore breed, born in 14 ranches from 1977 to 1997. Analyses were carried out with the aid of a statistic model considering breed invariable and specific characteristics, year and month of birth of the calf, gender of the newborn calf, dietary system, and age of cows at delivery as variable. Average and standard deviation for WN, W205, W365, and W550 were 29.72 ± 0.27 kg; 174.38 ± 2.59 kg; 261.37 ± 6.29 kg, and 336.09 ± 6.79 kg, respectively, for Guzerat breed, and 29.12 ± 0.28 kg; 171.76 ± 2.8 kg; 246.62 ± 4.61 kg, and 335.44 ± 5.76 kg, respectively, for Nelore breed. A significant effect was observed (P<0,01) for ranches, breeds, year and month of birth, newborn gender, and dietary system for all parameters considered (calf bodyweight was taken into account only after the end of sucking period). The variable breed presented a significant effect for WN (P<0.01) and W365 (P<0.05), but showed no significance for (P>0.05) W205 and W550, suggesting a superior performance by the Guzerat breed. Age of cow at delivery affected (P< 0.01) WN, W205, and W550. All of the effects were important sources of variation for most bodyweight and should be taken into account when selection and management strategies for cow herd are to be performed.