Effect of Water Soluble Carbohydrates on Fermentation Characteristics of Ensiled Perennial Ryegrass

Well-preserved silage is characterized by reduced pH, greater lactic acid concentration, and reduced ammonia (NH3) concentration compared with silage that did not ferment well. Water soluble carbohydrates (WSC) are the primary fermentation substrate. In temperate grass forages, glucose, fructose, sucrose, and fructans are the primary WSC. New varieties of ryegrass have been developed in the United Kingdom to express high levels of WSC.The objective of this trial was to determine differences in fermentation characteristics of grasses with different WSC levels cut and processed as silage. Four perennial ryegrasses, 3 cultivars with a relatively greater WSC concentration (AberAvon, AberDart, and Elgon) and 1 cultivar commonly grown in Oregon, the control WSC (Linn), were planted. Three replicates of each grass were ensiled after morning and afternoon harvests. Each sample was packed, vacuum sealed, and ensiled for 60 d at 10°C. Fresh grass samples were taken from each cutting and analyzed before ensiling. Fresh grass WSC was greater in the 3 high WSC grass cultivars vs. Linn. Final pH was less, total acids were greater, and lactic acid tended to be greater for the high WSC grass silages. Final pH, lactic acid, acetic acid, total acids, and NH3 were less for the afternoon vs. morning cutting. Ensiling was most efficient for high WSC grass varieties harvested at the afternoon cutting.