Estimation of some productive and reproductive effects on longevity of beef cows using survival analysis

Longevity of beef cows defined as the length of productive life from first calving to culling was estimated in this study. Data from 1800 cows belonging to Hereford, Angus, Simmental, Charolais, Limousin and Blonde d' Aquitaine breeds were analysed using survival method. The results indicate effects of breed, calving season, and calving difficulty on longevity (P < 0.05); however, herd, age of the cow at first calving, sex and weaning weight of their calves did not affect (P > 0.05) the length of productive life. Hereford had significantly greater (10.3 years) estimated length of productive life than Angus (8.1 years), Simmental (7.9 years), and Charolais (7.1 years), which had similar estimated longevity. Limousin (5.9 years) and Blonde d' Aquitaine (5.2 years) were similar in estimated longevity, but less than the other breeds studied. Cows that calved first in spring or summer were estimated to have longer productive life (7.2 years and 9.9 years) and less risk of early culling than those calving in autumn (5.7 years) and in winter (5.1 years). Longer productive life (6.2 years) was estimated across breeds for cows calving without assistance or with a little assistance (6.9 years) compared to those needing veterinary assistance (2.8 years) or having stillbirth (4.6 years). The results highlight that breed, calving season and calving difficulty of beef cows may have important effects on length of productive life. Special attention should be devoted to these effects.