Organic matter digestibility of condensed tannin-containing Lotus corniculatus and its prediction in vitro using cellulase/hemicellulase enzymes

Three digestion experiments involving cryptorchid weaned lambs were conducted for 14-day periods in the spring, summer and autumn to determine the in vivo digestibility of dry matter (DMD), gross energy (GE), organic matter (OMD), digestible organic matter in the dry matter (DOMD) and estimated metabolisable energy (ME) concentration of Lotus corniculatus L. (birdsfoot trefoil; cv. Grasslands Goldie) at different stages of maturity. The experiments were carried out indoors at Massey University's Riverside farm, in the Wairarapa, North Island, New Zealand. In vivo digestibility samples were then used as standards to investigate if the enzymic in vitro system of [Roughan, P.G., Holland, R., 1977. Predicting in vitro digestiblities of herbages by exhaustive enzymic hydrolysis of cell walls. J. Sci. Food Agric. 28, 1057–1064] could predict OMD and DOMD of condensed tannin (CT)-containing L. corniculatus.Digestibility of L. corniculatus declined as it matured, but the rate of decline was much less than that which occurs for perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. It was concluded that the in vitro enzymic system of [Roughan, P.G., Holland, R., 1977. Predicting in vitro digestiblities of herbages by exhaustive enzymic hydrolysis of cell walls. J. Sci. Food Agric. 28, 1057–1064] can be used to predict OMD and DOMD of L. corniculatus with a high degree of accuracy, provided a standard curve involving in vivo data generated with L. corniculatus is used. Using a standard curve with in vivo data from perennial ryegrass/white clover pasture led to bias which increased at lower OMD values. Reasons for the differences between L. corniculatus and pasture standard curves are discussed, including possible effects of bound CT.