Nutritive value of on-farm common vetch-oat hays. II. Ruminal degradability of dry matter and crude protein

Abstract

Rumen degradation characteristics and effectivdegradabilitye degradabillty (ED) of dry matter (DM) and crude protein (CP) of 11 samples of common vetch-oat hay were determined using the nylon bag technique in three rumen fistulated wethers. Animals were fed at an intake level of 40 g DM·kg-1. BW0.75 with a mixed diet of vetch-oat hay and concentrate (2:1 on DM). Mean values of ED of DM and CP, calculated for rumen outflow rates determined in each sheep, presented a moderate variation (mean = 65.8%; CV = 7.9% for DM and mean = 79.3%; CV = 4.7% for CP). Vetch proportion in hay was positively correlated with ED of DM (r = 0.412; P < 0.05) and ED of CP (r = 0.583; P < 0.001). Predictive equations of ED from chemical composition were obtained using the step .wise procedure. The contents of neutral detergent fibre and acid detergent lignidegradabilityn explained 79.4% of the total variation of ED of DM. The best prediction of ED of CP was obtained with the concentration of cellulose as an independent variable (r2 = 0.839). Degradation studies in these hays also indicated that the content of bypass protein, potentially digestible in the small intestine, was low. Thus, most N available to animals was derived from rumen microbial synthesis.