ESTIMATION OF THE NUTRITIVE VALUE OF SILAGES

Abstract

Forty-eight wethers were used to determine voluntary intake and digestibility of eight silages made from pure swards of legumes and grasses. Chemical and physical characteristics of silages were measured and related to dry matter intake, digestibility coefficients and digestible nutrient intakes by means of simple correlation and linear regression analyses. Intakes of dry matter (DM), digestible energy, digestible protein and total digestible nutrients were correlated negatively with percentage cell walls (r = −0.87) and positively with crude protein (r = 0.92). Lignin and the logarithm of (lignin × 100/acid detergent fiber) were highly correlated to cell walls digestibility (r = 0.98). There was a close relationship between protein digestibility and crude protein content (r = 0.99). Dry matter digestibility was accurately estimated by a summative equation (r = 0.74). The physical characteristics (packed volume and water solubility) of the silages were not well correlated to either digestibility coefficients or intake. The nutritive value of good quality, well-preserved grass and legume silages was satisfactorily predicted from laboratory analyses of crude protein and cell wall components. The applicability of the equations developed in this study should be tested using a larger number of silages. Key words: Nutritive value, forages, silages, sheep