Evaluation of Beef Fed Conventional or Organic Diets

Abstract: Feed consumption, bodyweight gain and carcass evaluation of Holstein bulls fed either conventional (CON) or organic (ORG) diets were compared. Animals were randomly assigned to either CON (n = 15) or ORG (n = 15) treatments when 6 months old. Inclusion rates of the ingredients were similar in CON and ORG diets formulated for growing (6-12 months of age) and fattening (13-18 months of age) periods. Ingredients of organic origin were used to formulate ORG growing and fattening diets. The bulls on the CON diet were vaccinated, de-wormed and treated conventionally (with antibiotics) against any sign of illness. No dietary or implant growth promotant was used. The bulls on the ORG diet were vaccinated although they were not de-wormed or treated against illness using conventional methods. Instead they were allowed to recover naturally from illness for 3 days. However, if the illness persisted beyond 3 days, they were treated using conventional methods. Consumption of concentrate and rice straw during growing, fattening and overall periods (6-18 months of age) was the same in bulls fed the CON or ORG diets. Bodyweight gain, total dry matter (concentrate and straw) intake and feed to gain ratio during growing and fattening were not affected by the treatments. Daily feed cost and feed cost for unit gain were greater in bulls fed the ORG diet than those fed the CON diet. Weight of cold carcass and different carcass cuts of the bulls were not affected by the treatment. According to the Korean beef grading system, the carcasses from bulls fed either CON or ORG diets were graded similarly but were of lower quality. The Korean beef quality grade is primarily determined by marbling score. The bulls in this study were slaughtered earlier (at 18 months of age) than the conventional slaughtering age of beef cattle (similar to 30 months) in Korea to produce highly marbled beef. It is concluded that the bulls fed ORG diets performed equally, and produced carcasses of similar quality, to those fed CON diets. However, feed costs for a unit bodyweight gain were significantly greater in the ORG diet compared with the CON diet.

Reference: Lee, W.S. et. al. (2009). Feed consumption, growth performance and carcass evaluation of Korean Holstein bulls fed either conventional or organic diets. Animal Production Science 49(4): 306-310. Available online at: http://dx.doi.org/10.1071/EA08229