The impact of supplementation withRhagodia preissiiandAtriplex nummulariaon wool production, mineral balance and enteric methane emissions of Merino sheep

Abstract

The Australian perennial shrubs, oldman saltbush (Atriplex nummularia) and rhagodia (Rhagodia preissii), can complement the diets of sheep grazing moderate-quality cereal residues. We compared liveweight change, organic matter digestibility, nitrogen and mineral balance, wool growth and methane emissions of Merino wethers offered oaten hay (OMD 622 g kg−1 DM; N 9.74 g kg−1 DM) with and without shrub biomass (substituted at 25% of OM). Diets were fed at restricted levels for 1 month. Substituting hay with shrub biomass significantly decreased liveweight loss, increased clean wool growth and increased apparent absorption of phosphorus compared to the hay alone. Substitution of hay with both saltbush and rhagodia led to over 23% greater clean wool growth. Nitrogen balance and apparent digestion of organic matter, calcium and magnesium did not vary significantly between animals on the diets. Wethers on the rhagodia and hay diets had similar enteric methane emissions, while animals offered the saltbush diet had significantly higher emissions (L/OM intake). When methane is expressed in terms of wool growth, animals on the rhagodia diet produced 26% less methane for every gram of wool.