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

Animal performance in organic and conventional beef production systems was evaluated using preconditioned crossbred steers from conventional (C, n = 2 4) and low-input (O, n = 30) farming systems that were randomly divided int o two groups and assigned to either organic (o) or conventional (c) feedlot systems. C calves were vaccinated, implanted and creep fed with a commerci al feed that included lasalocid, while O calves were only vaccinated prewea ning. Postweaning treatment c included vaccination, deworming, implants, io nophore and conventional corn and soybeans. Postweaning treatment o include d vaccination and organic corn and soybeans. All steers received organic gr ass-clover hay during the finishing period. Individual dry matter intake (D MI) was measured daily and animals weighed monthly. To analyze the producti on system from birth to slaughter, the model included fixed treatment effec t and age at the beginning of the feedlot phase (AGE) was fitted as a covar iate. Cc steers had higher (P < 0.01) rates of gain than all other treatmen t groups and better (P < 0.01) feed efficiency than Co and Co steers. Altho ugh Co steers had higher (P < 0.05) DMI than Cc and Co steers, feed efficie ncy was similar for the three groups. Cc steers required the least (P < 0.0 1; 163.6 days) and Co 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 Cc steers had similar DOF. To analyze the feedlot phase only, the model included fixed effect of finishing treatment (c vs. o) with AGE and initia l weight as covariates. Conventionally finished steers had similar (P > 0.0 5) 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 f ewer DOF (P < 0.01) than steers finished on the organic treatment. Feed cos ts were the major determinant of total cost of gain. Feed cost of gain was similar (P > 0.05) for Cc and Cc steers and lower (P < 0.05) than for Co an d Co steers, which also were similar (P > 0.05). Using total cost of gain f or conventionally finished steers as the basis for comparison, it cost 39% more (P < 0.001) to finish steers organically. (C) 1999 Elsevier Science B. V. All rights reserved.