Evaluation of Bengal gram (Cicer arietinum) husk as a source of tannin andits interference in rumen and post-rumen nutrient digestion in sheep

Bengal gram (Cicer arietinum) husk (BGH) was evaluated for the content of t annin and its interference in digestion. The BGH contained (% DM) 76.0 NDF, 65.2 ADF, 6.1 ADL and 8.4 tannin, The gas production (ml/200 mg DM/24 h) f rom BGH incubated with rumen inoculum was 45.0, which increased to 61.3 whe n polyethylene glycol (PEG 6000) was added. The magnitude of the increase i n gas production was not explained by the quantity of tannin-bound protein (acid detergent insoluble nitrogen x 6.25) or the total protein. This sugge sted that carbohydrate could be the main substrate bound by tannin in BGH. The availability of tannin-bound substrate in the post-rumen digestive trac t was assessed through a metabolic. trial. Twelve male lambs aged between 6 and 8 months were divided into three groups of four animals in each group. BGH was incorporated in the diet at 0, 6.8 and 14% by replacing deoiled ri ce bran (DORB). Incorporation of BGH in the diet increased OM digestibility (P<0.002) from 63.3% (Group I) to 68.1% (Group Il) and 72.4% (Group III). The observed differences among the diets was quantitatively explainable by the difference in ME content (8.5 MJ) of BGH and DORB after PEG addition. T he faecal excretion (gl day) of organic neutral detergent solubles (ONDS) ( 54.5, 55.3 and 46.7), and neutral detergent soluble nitrogen (NDSN) (4.4, 4 .4 and 3.9) for the three groups were similar. Therefore, it is speculated that the tannin-bound substrate in BGH is carbohydrate, protected from rume n fermentation but digested in the small intestine. (C) 2000 Elsevier Scien ce B.V. All rights reserved.