Double-low rapeseed meal for pigs: ileal apparent digestibility of amino acids in diets containing various proportions of rapeseed meal, fish meal and soya-bean meal

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Abstract
In order to determine the relative nutritional value of rapeseed meal (var. Tandem) in comparison with soya-bean meal and fish meal, seven barley-based diets were formulated to provide 13·1 MJ digestible energy and 8·8 g total lysine per kg. They contained soya-bean meal (S), rapeseed meal (R) or fish meal (F) alone, or equal proportions (on a total nitrogen basis) of soya and rapeseed, soya and fish meal, rapeseed and fish meal or soya, rapeseed and fish meal. The study involved 14 pigs growing from 40 to 90 kg, each fitted with a T cannula in the terminal ileum. Dietary treatments were applied during 7-day periods according to a 7 × 7 Latin-square design, replicated twice. The pigs were fed at 12-h intervals. Ileal digesta were collected during two 12-h periods from each pig after adaptation to each diet. Nutrient apparent digestibilities were measured using chromium III oxide as a marker; for diets S, R and F, respectively, values were: dry matter, 0·58, 0·51 and 0·66 (s.e. 0·014); N, 0·72, 0·67 and 0·73 (s.e. 0·011); lysine, 0·79, 0·72 and 0·83 (s.e. 0·010), with a similar relationship between diets for most other amino acids. In general, values for diets containing combinations of the protein supplements were intermediate between those for diets containing the respective single supplements. Following the main trial, seven pigs were given a semi-purified diet containing rapeseed meal as the only protein source; this gave amino acid digestibility values similar to or slightly higher than diet R. Diet R, which contained 375 g rapeseed meal per kg, presented no palatability problem. Rapeseed meal of the quality used in this trial could contribute a substantial proportion of the protein supplement for growing pigs. Its value should be enhanced by formulating diets according to the ileal digestibility of the limiting amino acids.