Abstract

The objective of the present work was to analyze the evolution of the productive indicators over time in Nelore cows of the Bolivian tropics. The period between 1991 and 2016, corresponding to 3899 calvings of Nelore cows were used for the research work which belong to the Technology Center on Agriculture and Livestock in Bolivia belonging (FUNDATION CETABOL) and the Cooperativa Agropecuaria Integral San Juan de Yapacaní were used. Cows were ordered by birth period into three groups (1991-2000; 2001-2010; 2011-2016). The following variables were analyzed: Age at first calving in days, Live weight of cow in kg, Calf weight at birth in kg, Calf weight at weaning in kg, Calving interval in days, Longevity in days, Accumulative Productivity in kg Total calf production (CP) in kg. The age at first calving has decreased compared to the decade of 1991-2000, however the last period (2011-2016) has increased one more month compared to the period (2001-2010) showing significant differences (p≤0.05). The weights of the cows and the calving interval followed the same behavior in the sense of decreasing, showing that in the period 2011-2015, the cows had the lowest live weight and the lowest calving-calving interval. The calf weight at birth showed an increase in the last two periods with significant difference (p≤0.05) with the period 1991-2000. That the longest-lived cows were those from the 1991-2000 period, showing significant differences (p≤0.05). The cows of the period 2001-2010 presented the best value of the Accumulated Production (p≤0.05), although the highest production of kg of weaned calf was for the cows of the period 1991-2000. It was concluded of the evolution of the productive indicators over time in Nelore cows from the Bolivian tropics individually showed an improvement in their indicators, although the analysis of the more complex indicators did not show an improvement in the results.

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