APPARENT DIGESTIBILITY OF HIGH-FAT RAPESEED PRESS CAKE IN GROWING PIGS AND EFFECTS ON FEED-INTAKE, GROWTH AND WEIGHT OF THYROID AND LIVER

Rapeseed from a winter variety of Brassica napus was pressed through a screw press. The press cake (321 g crude protein, 180 g crude fat, 10 2 g crude fibre, glucosinolates at 18 mmol kg(-1) DM (dry matter)) was tested either untreated or soaked (11 water kg(-1) rapeseed press cak e) and dried at 60 degrees C. Press cake contained 28% more glucosinol ates than the corresponding seed, Moist heat treatment caused a reduct ion of glucosinolate content to 0.3 mmol kg(-1) press cake DM. Glucosi nolate degradation products were not detectable (less than 0.1 mmol kg (-1) DM), In a digestibility experiment consisting of two periods in a 2 X 4 crossover design four pigs received barley or diets with rapese ed press cake 500 g kg(-1) as a replacement for barley, The digestibil ity of all measured parameters except fat was lower in the rapeseed pr ess cake than in barley (%): crude protein 68.5 vs, 77.8, crude fat 78 .4 vs. 46.4, crude fibre 14.7 vs. 42.2, N-free extract 83.8 vs, 92.4, organic matter 70.0 vs. 84.7, The differences were all significant (P < 0.05). A metabolizable energy (ME) of rapeseed press cake of 14.1 MJ kg(-1) DM was calculated, and this value was similar to that calculat ed for barley (14.6 MJ ME kg(-1) DM). In a further 16 week experiment with four groups of ten pigs, diets with 0, 50 g, 100 g or 150 g rapes eed press cake per kilogram were tested. In a final experiment the hig hest rapeseed press cake level (150 g kg(-1) diet) was also treated wi th moisture and heat. There was no significant effect of dietary level or treatment of rapeseed press cake on performance criteria. There wa s a trend (P < 0.1) for daily weight gain to decrease with increasing press cake level. The dietary rapeseed press cake level caused a signi ficant increase in thyroid and liver weights. In the group with untrea ted press cake at 150 g kg(-1) diet the thyroid weight was trebled and the liver weight increased by 20%. Treatment significantly lowered th e weight of organs. The weight of the thyroid, as well as of the liver , was significantly higher in this group with moist-heat treated rapes eed press cake at 150 g kg(-1) than in animals of the glucosinolate-fr ee control group.