EFFECTS OF RAPESEED DOCKAGE CONTENT ON THE FEEDING VALUE OF RAPESEED MEAL FOR SWINE

Abstract

Five lots of fine rapeseed screenings were obtained from crushing plants, extracted in a pilot crushing plant, subjected to botanical analysis, and assayed for mycotoxins, protein, ether extract, ash, crude fibre, sand, amino acids, combustible energy and glucosinolates. Each screenings meal was substituted for 4, 8 and 12% of clean Tower rapeseed meal, incorporated into diets, pelleted and fed to swine over a weight range of 23–88 kg. The main finding in the feeding trial was a decline in efficiency of feed utilization as the level of screenings increased. Digestibility trials were conducted on the 12% screenings diets. Two of the screenings lots depressed protein digestibility from 78 to 73% and four of the screenings samples depressed energy digestibility. The lysine content of screenings tended to be lower than for Tower rapeseed meal and this, together with the lower protein digestibility, suggests that available lysine might be adversely affected by the inclusion of screenings in rapeseed meal. It therefore is nutritionally advantageous to ensure that rapeseed is relatively free of foreign matter prior to crushing.