Estudio de la vida productiva de vacas de diferentes genotipos en pastoreo en campo natural

In the present work, associations of the variables are described: number of births throughout the life of each cow and length of productive life. The quantification method that was taken was the number of calvings throughout the productive life of each cow and the number of years of permanence of the breeding cow in the herd, respectively.

The breeds evaluated in the work were: Hereford, Aberdeen Angus, their F1 crosses and their backcrosses. The analysis comprised the records during the period 1994 to 2005.

In this work, the database of the breeding herd of the Bernardo Rosengurtt Experimental Station of the Faculty of Agronomy, located at km 408 of National Route no. 26. They were subjected to similar management, with feeding purely in the natural field. For the analyses, the GLM procedure of the SAS program (V 9.4) was used, the frequencies of cows of each breed with the occurrence of calving only 1 year, 2 years, etc. were estimated. In a similar way, the productive life of different years of duration (1 onwards) was analyzed. The significance of this variable was analyzed using the chi square test (P<0.05).

Significant differences were found for the F1 cross genotypes, while the pure genotypes and the backcrosses did not present differences between them. This is mainly explained by the expression of Heterosis or hybrid vigor that the F1 genotypes have.