DIVERGENT SELECTION FOR WEIGHT AND FEED-E FFICIENCY IN CHAROLAIS BREED - EFFECTS ON BODY-COMPOSITION AND MEAT QUALITY TRAITS (1ST RESULTS)

This study was conducted to measure the differences in carcass and mea t quality traits as responses of progeny performance to the selection of Charolais bulls for weight and feed efficiency. During 3 index that combined final weight and feed efficiency. The same number of bulls ( 18) were selected among the best and worst ranking bulls, after semen quality had been tested. The selection differential between the two gr oups was 3.4 standard deviations. From 9 months of age entire male pro geny calves were raised and intensively fattened in a single experimen tal unit and slaughtered at 15 or 19 months of age. At slaughter, carc ass composition was estimated using a prediction equation based on the dissection of the 6th rib and the weights of the internal fat and can on bones. Meat quality traits determined on the longissimus muscle wer e: hydroxyproline, heme iron, intramuscular lipids contents, pH and th ermal solubility of collagen. Selection tended to improve slaughter ( 12 kg), carcass (+8 kg), muscle (+ 7 kg) and bone (+ 1 kg) weights wi thout change in fat depots. Dressing percentage (+ 0.41) carcass lengt h (+ 1.9 cm) were significantly increased by selection. On meat qualit y traits, selection induced a decrease in heme iron content (- 0.6) an d a tendency to reduce intramuscular lipid content (- 0.2) and to impr ove the thermal solubility of collagen (+ 1,5).