Dietary Energy and Protein for Growing Pigs: 1. Performance and Carcass Composition

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Abstract
In a joint Nordic project, four experiments with a total of 880 growing pigs following the same outline were conducted in Denmark, Norway, Finland and Sweden. In three of these experiments the animals were fed individually. Five dietary treatments were investigated with respect to effects on performance, carcass composition and leg condition by entire or partial dissection. The treatments were: (1) restricted standard feeding as a reference in all experiments; (2) ad libitum feeding with protein (amino acid) concentrations according to recommended allowances (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 restricted feeding scale recommended in the individual countries, thus being different from experiment to experiment. Compared with the restricted standard 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 (rel. value 100), the corresponding mean values for the ad libitum fed animals were 119 and 120, respectively (P < 0.001). Ad libitum compared with restricted feeding lowered carcass meat percentage by 1.5 percentage units (P < 0.05–0.01). Feeding regimen did not affect leg condition. In the weight range 23–60 kg, treatment RA - 10% resulted in a slight decrease in performance and also in a slightly lowered carcass quality at 100 kg. On restricted feeding, females and castrated males performed equally, but carcass meat percentage of the former exceeded that 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 affect feed efficiency of ad libitum fed animals. Castrated males showed a poorer hind leg condition than females (P < 0.01). Carcass meat percentage was higher in restrictedly fed than in ad libitum fed animals. The difference was 0.7 and 1.8 percentage units for females and castrated males, respectively. A main conclusion is that the daily feed intake is a major factor in the control of the development of the animals and also for the extent of fat deposition.