Influence of cotton-seed meal and barley grain supplements on intake, digestion, live-weight gain and wool growth in sheep fed NaOH-treated oat and wheat straw diets

Abstract

SummaryGrowth and digestibility trials were conducted to investigate responses of young cross-bred sheep to alkali-treated straws and supplements. Oat and wheat straws were coarsely milled, sprayed with NaOH solution and then sprayed with a solution containing N, S, P, Cu and Co, and mixed with powdered limestone. The treated straws were fedad libitumwith no supplement (0) or with 150 g/day of either cotton-seed meal (CSM) or whole barley grain (B). In a preliminary trial to study the effect of frequency of ort collection on intake of treated straw, consumption decreased (P< 0·05) when frequency of ort collection was reduced from once daily to once weekly. This was associated with an increase in the neutral detergent fibre content of the orts. During the growth trial, which lasted 105 days, intake of treated straw increased by 34%.When no supplement was fed, digestibility of treated oat straw was higher (P < 0·05) and dry-matter intake lower (P< 0·05) than that of treated wheat straw. However, calculated intakes of metabolizable energy (ME) and measurements of growth and wool production were similar on the two straws (P> 0·05).When supplements were fed, there was no effect on intake of the treated straws. Mean live-weight gains were 51·4, 80·2 and 77·3 g/day on treatments 0, CSM and B respectively (P< 0·01). This was associated with higher intakes of ME (P< 0·01) which accounted for 73% of the variation in live-weight gains. Mean clean wool growth was 7·6, 10·5 and 9·3 g/day on treatments 0, CSM and B respectively (P< 0·01). This effect was associated more with nitrogen (N) absorption than with ME intake (80 and 48% of the variation in wool growth respectively).It was concluded that the treated straws provided sufficient nutrients for modest growth in young sheep, that the supplements had no effect on intake of the treated straws and that additional live-weight gain and wool growth obtained by feeding CSM and B were associated with energy intake and nitrogen absorbed respectively.