Evaluation of life-cycle herd efficiency in cow-calf systems of beef production

A deterministic beef efficiency model (BEM) was used to evaluate life-cycle herd efficiency (LCHE) in cow-calf beef production systems using four bree d groups of beef cattle. The breed groups were Beef Synthetic #1 (SY1), Bee f Synthetic #2 (SY2), Dairy Synthetic (DS), and purebred Hereford (HE). The LCHE was defined over the lifetime of the herd as the ratio of total outpu t (lean meat equivalent) to total input (feed equivalent). Breed difference s in LCHE were predicted with the larger/slower maturing DS being most effi cient at each age of herd disposal and reproductive rate. This was mainly b ecause, at any average age at culling, the dams of DS breed group were less mature and so had been carrying relatively lower maintenance loads for sho rter periods and positively influencing LCHE. Higher LCHE was predicted wit h improvement in reproductive performance if there were no associated extra costs. However, this declined markedly if there was a delay in marketing o f offspring. As average age at culling increased from 4 to 6 yr, efficiency declined sharply, but it began to recover beyond this age in most breed gr oups. We concluded that the slower maturing DS breed group may be more effi cient on a herd basis in cow-calf systems and that improvements in reproduc tive rate not associated with extra costs improve lifecycle efficiency. Cul ling cows soon after their replacements are produced seems efficient.