Effect of inclusion of Mucuna pruriens and Dolichos lablab forage in napier grass silage on silage quality and on voluntary intake and digestibility in sheep
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Two high protein legume forages were added to Napier grass silage to determine their effect on silage quality. Each silage was also assessed for its intake by and digestibility in sheep. Napier grass regrowth was harvested at 8 weeks, wilted and chopped. The two legumes, Dolichos lab/ab and Mucuna pruriens, were harvested at 12 and 17 weeks, respectively, and were wilted and chopped. Napier grass was ensiled alone or mixed with either legume (at 20% of total weight) to make three treatments: Napier ensiled alone (NO), Napier ensiled with D. lab/ab (NOD), and Napier ensiled with M. pruriens (NOM). During ensiling, molasses was mixed at 3% w/w to each of the 3 silages. To determine intake and digestibility, the 3 diets were fed to 6 male Dorper sheep housed in metabolic crates in a double Latin-square design. The crude protein content of the Napier silage alone was 97g kg" OM, which was improved with the addition of legumes to 112 and 113 g kg' DM for NOD and NOM, respectively. Silage pH was 4.6 for NO alone, compared to 4.5 and 4.3 for NOD and NOM, respectively. There was a trend towards improved dry matter intake (OMl, P=0.229) and organic matter intake (OMI, P=0.157) of the silages containing legumes. Inclusion of legumes had no effect on dry matter (OM) digestibility (P=0.069) but organic matter (OM) digestibility tended to be higher in NOD than in NO and lower inNGM than in NO. The OM digestibility of NOD was significantly higher (P50.05) than NOM. Metabolizable energy (ME) content (estimated via both gas production and digestible nutrients) was not altered by inclusion of legumes (7.4 MJ kg") but nitrogen (N) balance was improved by the legumes (5.5, 9.2 and 8.3 g u' for NO, NOD and NOM, respectively). It was concluded that inclusion of the legumes in Napier grass silage increased the protein content of the silage and improved the nitrogen balance in sheep.