Improving protein utilization in silage to increase animal performance and reduce environmental burden

Silage normally contains between 12 and 22 % crude protein (CP). While such levels 5 should be adequate for most productive livestock, in silages they are not. This is because of poor 6 utilization of N in silage. Most silage-based production rations require supplemental protein to meet 7 requirements for growth or lactation in ruminants. Silage protein is highly degradable in the rumen and as 8 such is a poor supply of dietary protein and peptides to the small intestine. The situation is exacerbated by 9 a scarcity of available energy in the rumen which limits microbial protein synthesis. Associated with poor 10 utilization of silage N by ruminants are concomitant high losses of silage N to the environment. Poor 11 utilization of silage N by ruminants is attributed to proteolytic activity by crop enzymes shortly after 12 harvest and further microbial breakdown of protein during ensilage. The production of low molecular 13 weight nitrogenous compounds, including ammonia, amines and amides, has a negative effect on 14 voluntary intake of silages. This appears to relate to an ammonia burden in the blood stream as well as 15 specific appetite suppressing characteristics of certain compounds. The poor utilization of silage N in 16 combination with lower voluntary intake of silages can seriously limit ruminant production. Methods to 17 improve silage protein utilization exist, including improved crop drying rates, use of microbial and 18 chemical additives and use of, or selection for, crops having characteristics that reduce protein solubility. 19 In future, the emphasis will move away from additives and towards plant breeding and management 20