THE NUTRITIVE-VALUE OF LUPIN-SEED AND DEHULLED LUPIN-SEED MEALS AS PROTEIN-SOURCES FOR GROWING PIGS AS EVALUATED BY DIFFERENT TECHNIQUES

Four experiments were conducted to determine the effect of dehulling l upin-seed meal (Lupinus angustifolius cv. 'Gungurru') on its nutrition al value, relative to soya-bean meal, for growing pigs. In addition, a number of different techniques for assessing nutritional quality were compared-ileal digestibility by cannulation and slaughter techniques, total tract digestibility by total collection and partial collection using a marker and amino acid utilisation by nitrogen balance and slau ghter techniques. In all experiments, the meals were fed as the sole p rotein concentrate in sugar-based diets. Compared with lupin-seed meal , the dehulled lupin-seed meal (kernel) had a higher (g kg(-1)) crude protein (405 vs. 311), lysine (20 vs. 16), ileal digestibility of amin o acids (lysine, 0.88 vs. 0.82) and digestible energy content (16.3 MJ kg(-1) vs. 13.1 MJ kg(-1)) but lower crude fibre (51 g kg(-1) vs. 172 g kg(-1)). In the growth experiment, diets were formulated to 0.36 g ileal digestible lysine MJ(-1) digestible energy. Six diets were compa red: lupin-seed meal, kernel, soya-bean meal, soyabean meal plus lupin hulls, and lupin-seed meal and soya-bean meal supplemented with lysin e (to confirm that lysine was first limiting in the first four diets). Diets were given at three times energy requirements for maintenance t o growing pigs over the 20-45 kg growth phase. Growth response of the pigs given the lupin-seed meal diet was greater than those given kerne l or soya-bean meal (P<0.05). The addition of hulls to the soya-bean m eal diet improved (P<0.05) growth response and there was no significan t difference between the lupin-seed meal or soya-bean meal plus hulls diet (P>0.05). Protein deposition rates were similar to the growth res ponses. Lysine retention as a proportion of ileal digestible intake wa s: lupin-seed meal 0.70, kernel 0.68, soya-bean meal 0.64, soya-bean m eal plus hulls 0.69. Ileal digestibilities were similar with the two t echniques although the slaughter technique was unsuitable with the hig hly digestible soya-bean-sugar diets. Lysine retention was higher with the nitrogen balance technique, relative to the slaughter technique. Overall the results indicate that L. angustifolius cv. 'Gungurru' lupi n-seed meal is of high nutritional value, and that dehulling the meal lowered the nutritional value for growing pigs.