EFFECT OF STOCKING RATE AND PERIOD OF SUP PLEMENTATION AT PASTURE ON ANIMAL PERFORMANCE OF BULLS FINISHED INDOOR

Two trials were conducted with fattening bulls grazed with different m anagements and then finished indoor. A total of 48 bulls of the Belgia n Blue breed dual purpose type were used in trial 1. They were divided in 6 groups from wich 3 were grazed at an average stocking rate of 7 bulls per ha (low stoking rate) and 3 groups at an average stocking ra te of 9.8 bulls per ha (high stocking rate). Futhermore, a supplement made of sugar beet pulp and barley was offered to one of the groups in each stocking rate from the beginning of the grazing season, to anoth er group from mid-June and to the last group from early August. On the end of the grazing season, the bulls were kept indoor in order to be finished on a concentrate diet, The trial was repeated over 2 consecut ive years. There were 36 bulls in trial 2 to compare 4 periods of supp lementation. The bulls were divided in 4 groups and grazed at an avera ge stocking rate of 7.8 bulls per ha. The supplement was given to the first group from the beginning of the grazing season, to the second fr om mid-June, to the third from early July and from early September to the last group. The trial was repeated over 4 consecutive years. There were only slight differences in the chemical composition of the grass according to the treatment groups. By contrast, the grass produced in the plots with the low stocking rate was characterized by a height of 7.35 cm and a proportion of refusal of 24.36 % as opposed to 4.84 cm and 10.76 % with the hight stocking rate. The delay of the supplementa tion reduced grass height and the proportion of refusal. During the gr azing season the average daily gains of the bulls were reduced with th e increase in stocking rate (1.269 vs 1.001 kg/d; p<0.001) wile the ga in per ha and the energy balance of the pasture were improved (1.270 v s 1357 kg/ha; 6322 vs 6932 UFV/ha. The increase in stocking rate reduc ed also the profit expressed both per bull or per ha. Average daily ga in and total gain per ha were slightly reduced when the supplement was offered lately but there was an improvement of energy balance of the pasture. When finished indoor, the bulls which had low daily gain at g rass because either they were grazed at the high stocking rate or they were offered the concentrate lately exhibited compensatory growth as indicated by large average daily gains or low food conversion ratio. T here were no effects on the killing- out proportion but the carcasses from the bulls which were grazed at the high stocking rate had a large proportion of muscle and a lower proportion of adipose tissue.