Feeding straw to small ruminants: effect of amount offered on intake and selection of barley straw by goats and sheep

Abstract

The hypothesis that increasing the amount of straw offered and allowing animals to refuse proportionately more than 0·1 to 0·2 would increase intake and quality of the straw consumed was tested in two experiments with castrated goats (aged 6 to 31 months) and one with wether sheep (aged 6 to 18 months). Each trial (over 21 to 42 days following 14 to 35 days preliminary feeding) involved individually feeding long barley straw and concentrate supplement (15 g dry matter (DM) per kg live weight (M075) daily) and monitoring the quantity and quality of straw offered and straw refused. The results supported the hypothesis. In experiment 1, with 18 goats per treatment, those allowed to refuse 500 rather than 200 g straw per kg DM offered consumed more (18·9 and 14·4 g DM per kg M75 per day, s.e.d. 0·70) and their straw refusals contained more digestible organic matter (DOM) in vitro (347 and 320 g/kg DM, s.e.d. 7·7). For both treatments, refusals were less digestible in vitro than the straw offered (412 g DOM per kg DM). Thirty-six goats in experiment 2 (over 42 days) offered increasing amounts of straw (18, 54 and 90 g DM per kg M075 per day) consumed more (15·5, 22·8 and 26·2 g DM per kg M per day, s.e.d. 0·74), refused more (125, 566 and 703 g/kg DM offered) and the refusals were of increasing digestibility in vitro (354, 370 and 403 g DOM per kg DM, s.e.d. 14·5). All refused straw was inferior to that offered (443 g DOM per kg DM). The estimated intake of straw DOM was markedly improved by offering more straw (7·2, 12·8 and 14·5 g per kg M75 per day). Experiment 3, using 30 wethers over 21 days fed as in experiment 2, showed similar treatment responses, although absolute intakes of straw were lower. The responses observed are comparable to improvements in intake following treatment of straw with alkali. Further research is required to determine optimum feeding rates as affected by straw quality and animal productivity level. Practical feeding strategies will also need to consider utilizing refused straw.