Abstract
Retrospective data corresponding to the period between 2002 and 2018 were used, belonging to the Cooperativa Agropecuaria Integral San Juan de Yapacaní, Santa Cruz, Bolivia. Data corresponding to 663 male and female calves born to primiparous and multiparous cows were used. The calves had 13 individual weight controls. The calves had 13 individual weight controls. Variables used: Date of birth, Calf live weight at birth in kg, Calf live weight at weaning in kg, Average daily gain in kg, Live weight of cow in kg, Number of calving of cows.
 
 The mean values and standard deviations of the weights at birth were 35.1 ± 4.6 kg for males and 32.3 ± 4.7 kg for females, at 240 days (weaning) the weight of the males was 229 ± 35.8 kg and for females 206 ± 31.5 kg. The mean values and standard deviations of the weight increases were 0.807 ± 0.14 kg for males and 1.0 ± 0.13 kg for females. The selected model with the regressor variables: Year, Sex of the calf, Number of calving and Live Weight at Birth, all significant (p ≤0.001). No interaction was significant to be considered in the model (p≥0.05). The live weight at birth, the sex, the years and the number of deliveries of the mothers showed in this work and for the animals analyzed to be the factors affecting the increase in live weight in the rearing stage (from birth to weaning) in Nelore calves in the Bolivian tropics.
Highlights
An objective to be met by any livestock system is that it generates efficient productive results that allow maximizing economic returns (Damasceno Carvalho et al, 2015).The production of beef cattle has calves as one of the main stages in the production chain
The live weight at birth, the sex, the years and the number of deliveries of the mothers showed in this work and for the animals analyzed to be the factors affecting the increase in live weight in the rearing stage in Nelore calves in the Bolivian tropics
This does not always generate the highest income as if it does the fattening stage, it is still the main link for the maintenance of the meat production chain (Chiristofari et al, 2008; Gomes et al, 2013).An economic indicator in the beef cattle industry is birth weight, this being the first variable to be measured in a calf (Utsunomiya et al, 2013)
Summary
The production of beef cattle has calves as one of the main stages in the production chain This does not always generate the highest income as if it does the fattening stage, it is still the main link for the maintenance of the meat production chain (Chiristofari et al, 2008; Gomes et al, 2013).An economic indicator in the beef cattle industry is birth weight, this being the first variable to be measured in a calf (Utsunomiya et al, 2013). The growth phase until weaning in beef cattle is considered very important. The stage from birth to weaning in beef cattle is considered of utmost importance. During this phase there are several factors that must be taken into account, among them: maternal aptitude, genetics, sex, month and year of birth, the age of the cow and the age of the calf. During this phase there are several factors that must be taken into account, among them: maternal aptitude, genetics, sex, month and year of birth, the age of the cow and the age of the calf. (Paro de Paz et al, 1999)
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