Comparison of conventional and organic beef production systems II. Carcasscharacteristics

Carcass characteristics were evaluated as part of a comprehensive study com paring organic and conventional beef production systems. Preconditioned cro ssbred steers from conventional (C; n = 24) and low-input (O; n = 30) farmi ng systems were randomly divided into two groups and assigned to either org anic (o) or conventional (c) feedlot systems. Conventionally fed steers rec eived an ionophore, implants on day 0 and 70, and an anthelmintic on day 0. Steers were fed individually using Calan Feed Access Doors. Each calf was fed to reach target end points of 567 kg body weight and 0.75 to 0.90 cm ba ck fat measured between the 12th and 13th ribs using real-time ultrasound w hen steers approached the target weight. Fixed effect of production system was fitted with age of steers at the start of the feedlot phase as a covari ate. Steers in the Cc system had the heaviest (P < 0.05) hot carcass weight s and Oo steers the lightest (P < 0.01). Ribeye areas from Cc steers were l arger than those from Oo (P < 0.01) and Cc steers (P < 0.05). Steers in gro up Cc had less back fat than Oc (P < 0.01) and Co steers (P < 0.05). There was no effect of production system on kidney, pelvic and heart fat or dress ing percentage. Fixed effect of finishing system only was also analyzed. St eers in conventional finishing had heavier (P < 0.01) carcasses, larger (P < 0.01) ribeyes and less (P < 0.05) marbling than steers in organic finishi ng. (C) 1999 Elsevier Science B.V. All rights reserved.