AN EVALUATION OF THE SUPPLEMENTARY PROTEIN AND METABOLIZABLE ENERGY VALUE OF RAPESEED MEALS FOR CHICKS

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Abstract
Eleven samples of commercially manufactured rapeseed meals were compared as sources of supplementary protein for chicks fed wheat-based diets. When the meals were used to supply 4% of protein to diets containing a total of 16% of protein, growth rate was inferior to that obtained when 4% of supplementary protein was supplied by isolated soybean protein or by soybean meal. Growth in these tests was severely limited by the suboptimal level of lysine present in the diets, even at the low level of protein fed. Growth response of the chicks fed the different meals was accordingly sensitive to the amount of lysine available to the chick from the diet. When the rapeseed meals were supplemented with lysine and tested under similar dietary conditions, i.e., to supply 4% of the supplementary protein, growth rate was enhanced from 60 to 90% above that of chicks fed the rapeseed meals without lysine supplementation. The range in protein supplementary value of the rapeseed meals was similar with and without lysine supplementation, but there was a shift in the ranking of the meals. Supplementation of rapeseed meal with methionine and/or arginine in addition to lysine did not elicit further response. When the rapeseed meals were used to supply 8% of protein to wheat-based diets containing a total of 17.5% of protein, some of the rapeseed meals gave a growth response equal to that obtained with soybean meal. Lysine supplementation stimulated growth of the chicks fed the rapeseed meal at the higher level, but to a lesser degree than when rapeseed meal supplied 4% of protein. The biologically-determined metabolizable energy values of rapeseed meal were approximately 60% lower than the estimated catabolizable energy values based upon the proximate analyses of the meals.

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