True Amino Acid Availability Values for Soybean Meal and Tower and Candle Rapeseed and Rapeseed Meals Determined in Two Laboratories

Abstract

True availabilities of amino acids (AA) in soybean meal (SBM), unprocessed, whole Tower and Candle rapeseeds (RS), and meals derived from these two cultivars were determined in two laboratories, the University of Guelph (UG) and Canada Packers Ltd. (CP). The method involved analyses for AA in samples of feed and excreta obtained from a 24-hr true metabolizable energy (TME) assay of these feedstuffs fed alone or mixed with a basal diet. Reasonably good agreement was obtained between the two laboratories for the true amino acid availability (TAAA) values for both the SBM and RS products when fed as the sole feed. The TAAA values, except those for cystine and tryosine, ranged from 90 to 97, 82 to 94, 84 t o 95, and 86 to 96% for SBM, Tower RSM, Candle RSM and Tower, as well as Candle RS, respectively, However, the TAAA values for the RS products varied greatly between laboratories when they were fed in conjunction with a basal diet. There did not appear to be any correlation between TAAA values and the TME values of the respective test ingredients. Further work using an excreta collection period longer than 24 hr is recommended to check the accuracy of the TAAA values determined for the rapeseed products.