Environmental aspects of silage additives: Nutritent digestibility and nitrogen retention of inoculated alfalfa haylage in sheep

During ensiling process, naturally occurring enzymes (proteases) will cause the valuable true protein to break down (McDonald et al, 1991). Prolonged fermentation in uninoculated silage allows proteolytic bacteria (eg. Clostridia) to degrade high quality plant protein and convert it into ammonia and nitrates. Therefore, it is essential that the decline in pH is as rapid as possible in the first two or three days of ensilage to stem proteolysis as true protein rather than the products of proteolysis is more readily absorbed by the intestine (by-pass protein) than the products of protein hydrolysis (Webb and Matthews. 1998). In uncontrolled silage fermentation 45% of the protein will be broken down (Carpintero et al, 1979). The use of lactic acid producing bacteria inoculants can significantly reduce the breakdown of protein, leaving higher levels of true protein in the treated forage. Reducing soluble protein levels in the rumen has been reported to improve microbial protein synthesis (Sharp et al, 1994). This overall retention of nitrogen by the animal will lead directly to improved performance, be it live-weight gain in beef animals (Mayne and Steen, 1993), significant extra milk production in dairy cows and helps sustainable development in agriculture owing to lower nitrogen content of the manure. The authors studied the effect of a biological silage additive on apparent nutrient digestibility and nitrogen-retention of alfalfa haylage in whether.