Estimate of biological and cultural energy efficiency in lean beef production

Abstract

Trials were conducted over 3 different years to determine the relationships in feedlot and carcass performance, cultural and feed energy requirements of different age groups of cattle. Treatments were calves, yearling and long-yearling steers and heifers of similar background and genetics, but managed under different finishing regimes. Initial feedlot weights were heavier (P $<$.05) for yearlings compared to calves during the three year period. In year I yearlings had heavier (P $<$.01) final weights when compared to calves. Feedlot gains were greater (P $<$.05) for calves compared to yearlings for the three year period. Calves had a lower (P $<$.05) daily feed intake and higher (P $<$.05) total feed consumption compared to yearlings in all three years. However, in year I there was no difference in daily feed intake for the heifer treatments. In year III both yearlings and long-yearlings had higher (P $<$.05) ADG compared to calves. In both years I and II there were no significant differences in ADG between the treatments. Calves also had lower (P $<$.05) initial hip height measurements compared to either yearling or long-yearlings. However, calves grew faster (P $<$.01) than either yearlings or long-yearlings. Yearling and long-yearling steers required 5.66% and 5.64% more cultural energy during the trial when compared to the steer calves. There were no differences in the heifer treatments. During the feedlot period, calves required approximately 18.41%, 24.59% and 21.26% more total cultural energy compared to yearling and long-yearling steers and yearling heifers. However, calves required fewer Mcal of cultural energy on a daily basis when compared to yearlings and long-yearlings. Steer calves were the most efficient when expressed as Mcal cultural energy:per HCWT ratio or Mcal cultural energy:per carcass energy ratio compared to yearling and long-yearling steers. Yearling steers were the least efficient compared to the other two steers. The heifer calves and yearling heifers were the least efficient in feed:gain ratio and cultural energy ratio when compared to the steer treatments.