EFFECT OF TANNIN CONTENT IN TWO ISOSYNTHETIC STRAINS OF BIRDSFOOT TREFOIL (Lotus corniculatus L.) ON FEED DIGESTIBILITY AND RUMEN FLUID COMPOSITION IN SHEEP

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Abstract
Low tannin (LT) and high tannin (HT) isosynthetic strains of birdsfoot trefoil containing 1 and 3% condensed tannins on a dry matter (DM) basis were cut fresh daily and fed to eight ruminally cannulated Suffolk wethers. Rumen fluid samples were collected before feeding and 3 and 6 h after feeding for pH, chlorophyll, supernatant protein nitrogen (N), ammonia nitrogen (NH3-N) and volatile fatty acids (VFA) determinations, and protozoa counts. Daily samples of the forage fed to the animals, and of feces, were analyzed for crude protein (CP) content, acid detergent fiber (ADF) and organic matter (OM). Results from rumen fluid analyses indicated that sheep receiving the HT strain had lower (P < 0.01) supernatant protein N and NH3-N concentrations, and consistently but not significantly lower VFA and chlorophyll concentrations. Animals fed HT showed higher (P < 0.05) protozoa counts than LT-fed animals, but only in the samples taken 3 h postfeeding. Ruminal pH was similar on LT and HT diets. Apparent digestibility of CP was 9% less (P < 0.05) in sheep fed the HT strain. However, apparent digestibilities of DM, OM and ADF were not affected by the tannin level. Key words: Lotus corniculatus L., birdsfoot trefoil, tannin, digestibility, rumen, sheep

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