Life Cycle Efficiency of Beef Production: IV. Cow Efficiency Ratios for Progeny Slaughtered3

Weight and individual feed consumption data collected on 160 beef, dairy and beef × dairy dams and their progeny were used to estimate postweaning feed efficiency of progeny and several measures of lifetime cow efficiency for cows fed either a high or a low energy diet. Cow efficiency was expressed as the ratio of output to input where output included relative values for either progeny slaughter weights, carcass weights or trimmed wholesale cut weights plus cow weight; and input included pre- and postweaning feed consumption of progeny and lifetime feed consumption of the dam. In the first approach, life cycle cow efficiency was estimated by expressing output as a ratio to input when weight and feed consumption were weighted by their expected occurrence in a theoretical herd consisting of 100cows and 20 replacement heifers. Expected occurrence was a function of the age distribution of the cow herd and percentage calf crop. In the second approach, actual lifetime cow efficiency was estimated by expressing output as a ratio to input when all components were weighted equally. Both approaches included efficiency estimates calculated with and without cow calvage value. Diet of dam had little effect on efficiency of postweaning gain when progeny were slaughtered at age-constant end points. Dams fed low energy diets generally were equal or superior to those fed high energy diets in lifetime efficiency. Straightbred Holsteins mated to Hereford sires were less efficient than straightbred Herefords mated to Holstein sires, even though they produced progeny with heavier slaughter weights, carcass weights and trimmed wholesale cut weights, lower preweaning feed consumption and more efficient postweaning gains, in addition to possessing greater salvage value. The low efficiency ratios of Holstein dams were associated with their large metabolizable energy intake. Progeny of Simmental X Holstein and Chianina X Holstein dams tended to be more efficient than progeny of Hereford X Holstein and Angus X Holstein dams in the conversion of feed to postweaning gain. Hereford X Holstein and Simmental X Holstein dams were nearly equal in lifetime efficiency, while Angus X Holstein and Chianina X Holstein dams were slightly less efficient. Efficiency of production improved as number of progeny slaughtered increased.