The value of stubbles and chaff from grain crops as a source of summer feed for sheep

Abstract

Context Modern crop stubbles provide an important source of feed for sheep during summer but can vary widely in their feeding value due to Genetics × Environment × Management interactions during crop growth, and how chaff is managed at harvest. Stubbles are difficult to assess for grazing value, due to the heterogeneity of forage components (e.g. stem, leaf, grains), which means that livestock producers rely on their observations and experience to manage sheep grazing stubbles. Aims To provide current information on the feeding value of stubbles, and to establish better methods for estimating stubble feeding value. Methods In the present paper, we report the results of sheep grazing wheat-stubble paddocks and a survey of the nutritive value of standing stubbles and chaff lines and piles of grain crops (including wheat, barley, canola and lupins) from crop paddocks in the mixed-farming region of Western Australia. Key results Without supplementation, wheat stubbles provided 50–100 dry sheep equivalent grazing days per hectare, before the estimated metabolisable energy (ME) intake of sheep fell below maintenance. This was influenced by ewe body condition score, where sheep of lower body condition gained more weight on stubbles (89 g/day higher weight gain per unit lower body condition score). Estimated ME content of edible chaff (leaf, fine stem and seed sheath or pod, excluding main stem and grain) was 5% higher in barley, 19% higher in lupin, and 5% lower in canola, than in wheat chaff, which was 5.9 MJ ME/kg DM. Implications While the grazing value of modern stubbles is variable, they have an important role in the seasonal feedbase by providing several months of feed during summer. Chaff by itself does not meet the energy or protein requirements of livestock, so a high-protein grain supplement (e.g. lupins) is necessary to maintain non-lactating ewes fed only chaff. The increased use of chaff lines and piles at harvest, primarily for weed control, provides a new opportunity to fill feed gaps in sheep and cattle enterprises if the material can be transported and stored efficiently, or if grazed in situ, as is common practice.