The voluntary intake and digestibility of straw diets and the performance of wether sheep as influenced by formaldehyde treatment of soya-bean meal

ABSTRACT In two experiments, straw diets were supplemented with a concentrate mixture containing either untreated or formaldehyde-treated soya-bean meal. In experiment 1, adult wether sheep were given straw/concentrate mixtures in a 3:1 ratio (air-dry basis) in restricted amounts. In experiment 2, these proportions were adjusted to 3:2 and the growing lambs were offered straw at proportionately 0·05 to 0·1 greater than that eaten daily. In experiment 1, formaldehyde treatment of soya-bean meal depressed apparent nitrogen (N) digestibility (P < 0·001) although diet organic-matter digestibility was not affected. Formaldehyde treatment also tended to reduce N retention in experiment 1, whereas with growing lambs in experiment 2, it led to improved N retention. Plasma urea concentrations were reduced as a result of formaldehyde treatment of soya-bean meal. Digested N was more efficiently utilized by sheep given the treated soya-bean meal diet in experiment 2 but not in experiment 1. Lambs given the treated soya-bean meal diet tended to gain more live weight with marginally superior food conversion ratios while consuming similar amounts of dry matter as those given the untreated soya-bean meal-supplemented diet.