ASSAYING FEEDSTUFFS FOR AVAILABLE LYSINE CONTENT USING A FEATHER MEAL BASAL DIET

Abstract

A feather meal basal diet with adequate supplementation of methionine, histidine and tryptophan was used in chick growth assays to estimate the availability of lysine in five feedstuffs. When a slope-ratio technique was applied, estimates of lysine availability were: meat meal 51.9%, fish meal 90.0%, blood meal 70.2%, rapeseed meal 90.1%, and soybean meal 96.6%, when calculation was based on weight gain versus the actual lysine consumed (method A). When the response was measured as weight gain versus dietary lysine concentration (method B), the available lysine values determined were uniformly lower, being 43.1, 86.6, 64.8, 81.5 and 94.5%, respectively, for the above feedstuffs. Feeding tests confirmed that the values obtained by method A, with the exception of soybean meal, were the more reliable of the two methods. Availability figures determined by method B resulted in growth responses superior to those of the control group, suggesting that this method underestimated the availability of lysine.