Factores que afectan la vida útil de vacas doble propósito.

Objective. Determine the effect of non-genetic factors and breed group, on the useful life (UL) of dual-purpose cows. Materials and methods. Records from 2098 cows were used in the analysis which included all the females who entered to the reproductive program and were culled or died. The data came from two dual-purpose commercial herds located in the basin of the Lake of Maracaibo in Trujillo State. The UL was quantified in number of calving upon culling. The parameters included in the model were: herd (H: AG, VV), year of the first calving (Y1C: 1995-2006), season of the first calving (S1C: January-March, April-May, June-August, September-December), breed group (BG: Zebu, 50%Zebu50European; ZE, Milking Crossbred; MC) and the interaction HxBG y Y1CxBG. Results. The UL average was 2.63 (0.07) calvings. All the factors had highly significant effects (p<0.01) on UL, however, H did not affect UL. It is interesting to highlight that HxBG and Y1CxBG interactions were highly significant (p<0.01) indicating that breed groups behave differently in every herd and during the course of the years. Conclusions. Non-genetic factors and breed group have a high influence on UL. [ABSTRACT FROM AUTHOR]