DIETARY ENERGY AND PROTEIN FOR GROWING PIGS .1. PERFORMANCE AND CARCASS COMPOSITION

In a joint Nordic project, four experiments with a total of 880 growin g pigs following the same outline were conducted in Denmark, Norway, F inland and Sweden. In three of these experiments the animals were fed individually. Five dietary treatments were investigated with respect t o effects on performance, carcass composition and leg condition by ent ire or partial dissection. The treatments were: (1) restricted standar d feeding as a reference in all experiments; (2) ad libitum feeding wi th protein (amino acid) concentrations according to recommended allowa nces (RA); (3) as in (2) but RA increased by 10% (RA + 10%); (4) as in (2) but RA lowered by 10% (RA - 10%), or (5) the most common restrict ed feeding scale recommended in the individual countries, thus being d ifferent from experiment to experiment. Compared with the restricted s tandard feeding, for which daily feed intake and daily weight gain in the weight range 23-100 kg averaged 2.07 kg and 750 g, respectively (r el. value 100), the corresponding mean values for the ad libitum fed a nimals were 119 and 120, respectively (P < 0.001). Ad libitum compared with restricted feeding lowered carcass meat percentage by 1.5 percen tage units (P < 0.05-0.01). Feeding regimen did not affect leg conditi on. In the weight range 23-60 kg, treatment RA - 10% resulted in a sli ght decrease in performance and also in a slightly lowered carcass qua lity at 100 kg. On restricted feeding, females and castrated males per formed equally, but carcass meat percentage of the former exceeded tha t of the latter by 2.3 percentage units (P < 0.001). Daily feed intake and weight gain of ad libitum fed castrated males exceeded the values of females by 11% and 9%, respectively (P < 0.001). Sex did not affec t feed efficiency of ad libitum fed animals. Castrated males showed a poorer hind leg condition than females (P < 0.01). Carcass meat percen tage was higher in restrictedly fed than in ad libitum fed animals. Th e difference was 0.7 and 1.8 percentage units for females and castrate d males, respectively. A main conclusion is that the daily feed intake is a major factor in the control of the development of the animals an d also for the extent of fat deposition.