EVALUATIONS OF RAPESEED AND SOYBEAN MEALS AS PROTEIN SOURCES FOR SWINE: APPARENT DIGESTIBILITIES OF AMINO ACIDS

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Abstract
Semi-purified diets containing either soybean or rapeseed meal were fed to four barrow pigs of 60-kg liveweight in balance study cages. Comparison of feed intake and feces and urine output showed that the apparent digestibilities and biological values of the soybean meal-containing diet were 87.8 and 84.0%, respectively; the corresponding values for the rapeseed meal-containing diet were 78.4 and 78.9%. Samples of feed and feces were hydrolyzed and the n-propyl N-acetyl esters of the amino acids were prepared and separated by gas-liquid chromatography. Apparent digestibilities of the amino acids in the two protein sources were calculated; for soybean meal the values ranged between 85 and 92%, with the exception of methionine, for which the value was only 79%; the value for lysine was 90%. The corresponding values for rapeseed meal were 74 and 86%, with values of 87% for both methionine and lysine. An attempt to use polyethylene glycol as a digestion indicator failed, because rapeseed meal appeared to contain material which interfered with the development of turbidity; however, for the soybean meal-containing diet there were no significant differences between the apparent digestibility values determined with the indicator and those determined using total feces collection.