Comparison of conventional and organic beef production systems I. feedlot performance and production costs

Abstract

Animal performance in organic and conventional beef production systems was evaluated using preconditioned crossbred steers from conventional (C, n=24) and low-input (O, n=30) farming systems that were randomly divided into two groups and assigned to either organic (o) or conventional (c) feedlot systems. C calves were vaccinated, implanted and creep fed with a commercial feed that included lasalocid, while O calves were only vaccinated preweaning. Postweaning treatment c included vaccination, deworming, implants, ionophore and conventional corn and soybeans. Postweaning treatment o included vaccination and organic corn and soybeans. All steers received organic grass-clover hay during the finishing period. Individual dry matter intake (DMI) was measured daily and animals weighed monthly. To analyze the production system from birth to slaughter, the model included fixed treatment effect and age at the beginning of the feedlot phase (AGE) was fitted as a covariate. Cc steers had higher (P<0.01) rates of gain than all other treatment groups and better (P<0.01) feed efficiency than Co and Oo steers. Although Co steers had higher (P<0.05) DMI than Oc and Oo steers, feed efficiency was similar for the three groups. Cc steers required the least (P<0.01; 163.6 days) and Oo the most (P<0.01; 225.8 days) days on feed (DOF) to reach target end points (567 kg body weight and 0.75–0.90 cm backfat). Co and Oc steers had similar DOF. To analyze the feedlot phase only, the model included fixed effect of finishing treatment (c vs. o) with AGE and initial weight as covariates. Conventionally finished steers had similar (P>0.05) DMI, more rapid (P<0.001) weight gains (1.66 vs. 1.40 kg/d), better (P<0.01) feed conversion (6.09 vs. 7.58 kg DMI/kg gain) and required 27.7 fewer DOF (P<0.01) than steers finished on the organic treatment. Feed costs were the major determinant of total cost of gain. Feed cost of gain was similar (P>0.05) for Cc and Oc steers and lower (P<0.05) than for Oo and Co steers, which also were similar (P>0.05). Using total cost of gain for conventionally finished steers as the basis for comparison, it cost 39% more (P<0.001) to finish steers organically.