DIGESTIBILITY AND FEEDING VALUE OF FROST-DAMAGED CANOLA SEED (LOW GLUCOSINOLATE RAPESEED) FOR GROWING PIGS

Abstract

Digestibility trials with 57-kg pigs were conducted on blended canola seed (B. napus 'Regent') containing 20, 45 and 65% frost-damage fed in conjunction with a barley, wheat, soybean meal basal diet, supplemented with minerals and vitamins. The seed was fed whole, ground, pelleted and ammoniated. The seed contained, per kilogram, 18–20% crude protein, 22–35% ether extract, and 21.7–24.5 MJ gross energy. Glucosinolate concentrations were 15–33 μmole/g, oil-free basis. Grinding improved energy digestibility of the seed per se from an average of 34.4 to 62.8% and protein digestibility from 17.0 to 65.3%. Pelleting improved energy digestibility of whole seed from 31.6 to 65.5% and grinding before pelleting gave 69.2%. Pelleting, in addition to grinding, did not further improve protein digestibility over grinding alone. Ammoniation improved the digestibility of energy in ground seed from 61.2 to 66.9% and in ground pelleted seed from 69.2 to 72.4%. Ammoniation increased protein digestibility in ground seed from 61.6 to 65.2% and in pelleted seed from 62.1 to 63.1%, corrected for ammonia intake which was assumed to be of little value to the pig. Digestible energy values of processed seed were 15.6 to 17.7 MJ/kg and digestible crude protein values were 12.3 to 14.0% of dry matter. Frost-damaged canola seed was shown to be worth 20–50% more than good barley. Key words: Rapeseed, frost damage, digestibility, pigs, feeding value