Impact of Selection Decisions on Cow Efficiency  
     Two widely held contentions are that a beef animal’s “type” affects its ability to convert feed to weight, and that a direct relationship exists between an animal’s size and its efficiency. U.S. Meat Animal Research Center scientist Tom Jenkins says studies have demonstrated how production traits may contribute to differences in biological efficiency.
     For example, cows representing breeds that exhibit moderate growth and milk production were more efficient when subjected to limited feed availability because of higher conception rates. Under the same circumstances, breeds with higher genetic potentials for growth and milk production were less efficient because females did not cycle or conceive while nursing a calf. With high levels of feed, however, those higher potentials for growth and milk production are expressed more efficiently than among cows representing more “moderate” breeds, which became fat.
     Hence, cow-calf producers have sought to reduce energy requirements for cow maintenance, through genetic selection. According to Jenkins, however, stabilizing energy requirements over a wide range of nutritional scenarios may be more desirable.
     “Enhancing an animal’s genetic potential [to] conserve energy under sparse energy environments (feed resources and/or body fat) could be counterproductive to developing and efficient cow,” Jenkins suggests.
     A cow that is efficient for one producer may be ineffective under a different management system, but Jenkins predicts that genomic information will aid producers in identification of heifers that are suited to producing a calf every year, within a defined production environment.
— Troy Smith