The potential of canola to decrease soybean meal inclusions in diets for broiler chickens

Feedstuffs derived from canola, predominantly canola meals plus whole, "full-fat" canola seed, and even canola protein isolates and/or concentrates, have the potential to decrease soybean meal inclusions in diets for broiler chickens. The protein content of soybean meal exceeds that of canola meal; however, canola meal contains more methionine and cysteine in absolute and relative terms. The purpose of this review is to explore this potential as Australian chicken-meat production is uniquely positioned to take advantage of this opportunity to the extent that it can be realised. Australia harvests ample quantities of canola, the bulk of which is exported as seed; alternatively, soybean production is very limited; therefore, large quantities of soybean meal are imported as the principal source of dietary protein for broiler chickens. This importation of soybean meal is not sustainable; however, canola meal inclusions in broiler diets do not usually exceed 100 g/kg. Regression equations derived from 15 recent studies indicate that dietary inclusions of 150 g/kg solvent-extracted canola meal would compromise weight gain by 4.04% and feed conversion ratio (FCR) by 4.72%. The foremost factors driving these depressions in canola meal are probably (1) high fibre contents coupled with low energy densities and (2) the presence of glucosinolates, which may be converted into toxic metabolites including thiocyanates. Moreover, regression equations from nine studies suggest that calculated dietary glucosinolate concentrations of 2.00 μmol/g would compromise weight gain by 5.72% and FCR by 6.56%. The nutritive value of canola meal could be enhanced by improvements in canola breeding programs, processing methods in canola meal production, and dietary formulations including judicious application of exogenous enzymes. Consideration is given to these aspects in this review as any improvements would increase the extent to which canola meal can feasibly replace soybean meal in broiler diets. An additional pathway to decrease the reliance on soybean meal could be the adoption of reduced-crude protein (CP) diets containing canola meal. The combined strategy of canola meal replacing soybean meal in reduced-CP diets, if successful, would tangibly decrease soybean meal requirements in global chicken-meat production.