Ileal apparent digestibilities of amino acids, growth and tissue deposition in growing pigs fed low glucosinolate rapeseed meals

Abstract

SUMMARYA factorially designed growth and carcass dissection experiment was made in which a low glucosinolate rapeseed meal (cv. Tower, TRSM) was compared with soya-bean meal (SBM) as the sole protein supplement in simple diets, containing barley and a vitamin and mineral supplement (to give 18 mg copper/kg air-dry diet) only, which were fed individually on a restricted scale of feeding to 72 pigs. The diets were of similar digestible energy (DE) content and were formulated to contain in each kg of air-dry matter 150, 170 and 190 g crude protein. In each crude-protein level the total lysine content was similar. Also experiments using 35 pigs were made to determine the ileal apparent digestibilities of amino acids in barley-based diets containing SBM, the low glucosinolate rapeseed meals Erglu (ERSM) and TRSM and a high glucosinolate British rapeseed meal (BRSM) and either 20 mg or 200 mg copper/kg air-dry diet.In the growth experiments there were no significant interactions for the variables considered. Pigs given TRSM diets, compared with those given SBM diets, had significantly poorer growth rates, conversion efficiencies and killing-out proportions but the proportions of lean and fat in carcasses and the backfat thicknesses (P2) were similar. There were no significant differences between protein levels in the killing-out proportions, the proportions of fat in carcasses and backfat thicknesses (P2) but pigs given diets containing 150 g, compared with 170 and 190 g, crude protein/kg air-dry diet had significantly lower growth rates and proportions of lean in the carcass and significantly poorer efficiencies of food conversion. The quantities of dietary crude protein used to produce units of live-weight gain, carcass weight and lean tissue increased progressively from the diets containing 150 to 170 to 190 g crude protein in each kg air-dry diet.In the ileal digestibility studies the results indicated that amino acids were of a lower digestibility in the rapeseed meal diets than in those based on SBM and that the copper content of the diet may have been important in this context.