Effect of length of ensiling on silo degradation and digestibility of structural carbohydrates of lucerne and orchardgrass

This study determined the extent of structural carbohydrate loss from lucerne (Medicogo sativa L.) and orchardgrass (Dactylis glomerata L.) after 5, 21 and 56 days of ensiling. About 70 and 60 kg fresh matter of lucerne and orchardgrass, respectively, were ensiled in nine silos of 120 l capacity. For each forage, the four treatments (i.e. fresh material and 5, 21 and 56 days silages) were fed to four male castrated sheep in a 4×4 Latin square design experiment to determine effects of ensiling on digestibility. The overall fermentation quality of the two forages was judged to be good and within acceptable guidelines. Dry matter (DM) and gross energy losses were small, confirming an acceptable fermentation process. Hemicellulose losses of 19.8 and 17.2% occurred in lucerne and orchardgrass, respectively, by 56 days of ensiling. Cellulose losses in both forages were small compared to those of hemicellulose. Pectin loss by 56 days of ensiling were similar to hemicellulose, being 17.3% in lucerne and 17.7% in orchardgrass. Hemicellulose digestibility decreased (P<0.05) in lucerne and orchardgrass as ensiling advanced, while cellulose digestibility was higher (P<0.05) in days 21 and 56 silages than in the harvested lucerne grass. An appreciable amount of structural carbohydrate (i.e. pectin+hemicellulose+cellulose) were degraded during fermentation.