The role of condensed tannins in the nutritional value of mulga (Acacia aneura) for sheep

Abstract

Sheep were fed mulga (Acacia aneura) ad libitum and supplemented with 0, 12 or 24 g/day of polyethylene glycol molecular weight 4000 (PEG), with or without an additional supplement of 1.5 g/day of each of nitrogen (N), phosphorus (P) and sulfur (S) (NPS). Supplementation with either 12 g/day PEG or 24 g/day PEG increased dry matter intake by 56 and 78% respectively and clean wool growth per unit surface area by 166 and 178% respectively. Supplementation with 24 g/day PEG increased wool fibre diameter, linear growth rate and volumetric growth rate by 32, 29 and 143% respectively. Sheep receiving 24 g/day PEG retained more N (1.80 g/day) and S (254 mg/day) and digested more N (218 g/kg) and S (229 g/kg) when compared with non-supplemented animals. These parameters were further enhanced when NPS was supplemented in conjunction with 24 g/day PEG. Maximum precipitation (77%) of mulga condensed tannins (CT) occurred at a PEG to CT ratio of 0.7:l.