|O'Kiely, Padraig - GRANGE RESEARCH INSTITUTE|
Submitted to: Grass for Dairy Cattle
Publication Type: Book / Chapter
Publication Acceptance Date: November 1, 1998
Publication Date: N/A
Technical Abstract: Ensiling is one of the principal means of storing grasses for later consumption by dairy cattle. The attractions of ensiling include reduced weather risk in harvesting, ease of mechanization, and lower potential crop losses between the field and animal. The crop is preserved in the silo by two primary mechanisms: anaerobic conditions and low pH. Anaerobic conditions prevent the growth of spoilage microorganisms. A low pH is created by fermentation of sugars by lactic acid bacteria and inhibits the growth of detrimental anaerobic bacteria. Key factors affecting the successful ensiling of grass are the water soluble carbohydrate content, the buffering capacity (or resistance to pH decline) and the number and type of lactic acid bacteria on the crop. The first two factors are influenced by the grass species and environmental conditions under which the grass is grown whereas as relatively little is known about bacterial variation. Losses for a silage harvesting system range from a minimum of 7 to more than 40% under poor management conditions. The minimum represents unavoidable harvesting losses, respiration losses during rapid filling, and fermentation losses. Aerobic deterioration during slow filling, storage and feedout make up the variable or avoidable losses. The nutritive value of silage may be affected by a variety of factors: quality of the harvested crop, degree of wilting, chop length, type of fermentation in the silo, length of storage, degree of oxygen exposure prior to feeding, silage additives, presence and growth of microorganisms deleterious to animal health, and the type and production potential of the animal being fed.