DIGESTIBILITY AND EFFECTS OF CONDENSED TANNINS ON DIGESTION OF SULLA (HEDYSARUM-CORONARIUM) WHEN FED TO SHEEP

Sulla (Hedysarum coronarium) is a short-lived perennial legume with an erect growth habit which is grown as a fodder crop in Mediterranean r egions but is not common in New Zealand agriculture. Recent experiment al work has shown potential benefits of sulla for reducing the impact and numbers of intestinal nematodes in sheep and possible benefits for wool production, so that a feeding trial was undertaken to determine its digestibility. Twelve sheep aged about 6 months were held in metab olism crates and fed sulla as a sole diet for the 20-day experimental period. Sulla contains condensed tannins (CT) so that one group of 6 s heep were given twice-daily oral drenches of polyethylene glycol (PEG) to bind with and deactivate the CT (PEG group) enabling a comparison with the undrenched Tannin group. The dry matter (DM) content of the s ulla was 15.5%, comprising (DM basis) 33% leaf, 41% stem, and 26% flow er, and all portions of the plant were eaten. The DM contained about 7 .2% CT and 3.0% nitrogen (N). DM intakes averaged 1160 g/day and DM di gestibility was lower in Tannin animals (70.5%) than those given PEG ( 72.5%; P = 0.015). Condensed tannin substantially reduced N digestibil ity (63.1%) relative to those given PEG (77.1%; P < 0.001) and this wa s associated with a reduction in rumen ammonia concentration ((mol/ml) in Tannin (155) versus PEG (259) animals. Plasma urea concentrations (mu mol/ml) were also lower (P < 0.001) in Tannin sheep than in those given PEG (7.4 vs 8.8) which suggests that the CT affected the digesti on, absorption, and metabolism of nutrients.