THE RESPONSE OF GROWING PIGS TO A CHOICE OF DIETS DIFFERING IN PROTEIN-CONTENT

An experiment was designed to test whether pigs can differentiate between two foods differing in their protein content. A control food (160 g protein per kg food) and six choice-feeding treatments, in which the diets differed only in their protein concentrations, were used in the experiment. Pigs were given the following choices of protein: 220 v. 180; 220 v. 140; 220 v. 100; 180 v. 140; 180 v. 100 and 140 v. 100 g protein per kg food. Group data were collected on 240 Landrace x Large White pigs during the growing phase (30 to 90 kg), all pigs used being of similar genetic background. A 2 x 7 factorial design was replicated twice, with 10 pigs per pen, and with barrows and gilts being penned separately. Food bins for the choice-feeding treatments were placed side-by-side and an 8-day training period, in which the pigs were allowed access to only one of the two foods on alternate days, was used at the beginning of the trial to allow them to learn the position, taste and physiological effect of each of the two foods. All pigs were weighed weekly, as was the amount of food consumed in each pen. The conclusion reached was that growing pigs were able to differentiate successfully between two foods on the basis of their protein content and to change the selected diet to match their changing requirement for dietary protein. As a result, there was a significant reduction in food intake (P < 0.001) and in the P2 backfat thickness (P < 0.01) and the food conversion ratio was significantly improved (P < 0.001) compared with the control treatment.