Washington State Univ. and USDA researchers used a statistical method, “survival analysis techniques,” to identify factors affecting the longevity of beef females. They used data from 1,379 composite cows, born from 1982 to 1999 at the Miles City research station.

Longevity was not affected by age at first calving or calf birth weight. Females that experienced dystocia were at 60% greater risk of being culled than those calving unassisted. Interestingly, as breeding value for cow weight increased, the risk of being culled decreased, whereas the risk of being culled increased with increasing maternal breeding value for preweaning calf gain. The authors noted that this likely due to the fact that cows with lower milk production may accumulate body energy reserves during lactation and therefore weigh more at weaning than contemporaries with higher milk production. Conversely, heavier-milking cows may expend more energy reserves and therefore not be in adequate condition to rebreed.

The analysis revealed that selection among heifers based on their birth weight, 200-day preweaning gain, or 365-day weight had no effect on subsequent longevity. Moreover, weaning weight and yearling weight of the cow are not predictive of her life-cycle efficiency.

The estimate of heritability for longevity was low (0.14). The authors stated that the relatively low heritability and the lack of indicators of longevity expressed early in life indicate that genetic improvement of longevity will be difficult. This suggests that longevity in the herd may be best ensured by matching the genetic potential of cows for size and milk production such that rebreeding performance is not compromised (Rogers et al. 2004. J. Anim. Sci. 82:860).