Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

The aim of this experiment was to assess, using sheep, the nutritive value of lupin seed transgenically modified to contain sunflower seed albumin. Ei ghty Merino wether sheep of mean live weight 32.3 kg were divided into two groups and fed 796 g dry matter (DM) day(-1) of a cereal hay-based diet con taining 350 g kg(-1) of either the transgenic or parent (unmodified) lupin seed for 6 weeks. Measurements were made of wool growth and live weight gai n. After 6 weeks, half the sheep in each group were selected for a urine an d faeces balance study in which organic matter (OM), nitrogen (N) and urina ry purine metabolites were measured. Blood samples were taken fr om all she ep at the beginning and end of treatment and analysed for amino acids and p lasma metabolites. A comprehensive chemical analysis of the grains showed t hat there was little difference between them in terms of most nutritional c omponents, but the transgenic lupin seed contained a 2.3-fold higher methio nine concentration and 1.3-fold higher cysteine than did the parent. There were no significant differences between grains in OM digestibility, rumen m icrobial protein synthesis or in sacco degradability of dry matter. Sheep f ed the transgenic lupin grain had an 8% higher rate of wool growth (P < 0.0 1) and 7% higher live weight gain (P < 0.05) than sheep fed the parent grai n. The sulphur (S) concentration of wool and the cysteine concentration of plasma were also higher in the sheep fed the transgenic lupin by 2.7% and 1 1.5% respectively (P < 0.05). Plasma methionine was increased by 10%, but t he differences were not statistically significant (P > 0.1). Plasma urea N was lower in the sheep fed the transgenic grain than those fed the pai ent grain (6.5 vs 6.8 mmol l(-1), P < 0.05). The results show that genetic modi fication of a feed grain can improve its;nutritive value for ruminants. The size and nature of the responses were consistent with the transgenic :lupi ns providing more methionine to the tissues, a first-limiting amino acid fo r sheep. (C) 2000 Society of Chemical Industry.