Methods for reduction of water soluble carbohydrate content in grass forages for horses

A large number of factors influence water soluble carbohydrate (WSC) concentration in forages. Four of these were studied; effect of conservation method (silage, haylage, hay); effect of using bacterial inoculants in silage and haylage; effect of storage time; and effect of soaking. Grass forage was harvested as silage (400g dry matter (DM)/kg) and haylage (600gDM/kg) in laboratory silos and as hay (840gDM/kg). Silage and haylage were preserved with and without a bacterial inoculant. All forages were sampled at 3, 6, 12 and 18 months of storage. Forages stored for 3 and 12 months were soaked in water for 12 and 24h to evaluate soaking as a method to reduce WSC concentration. Concentrations of glucose, fructose, sucrose and fructans were analysed using an enzymatic-spectrophotometric method and total WSC concentration calculated as the sum of these. Conservation method influenced concentration of WSC and its components, as silage had lower content of glucose, fructose and WSC compared to haylage and hay; and silage and haylage contained less sucrose and fructans compared to hay (P<0.001). Use of inoculants in haylage and silage resulted in lower fructose concentration in silage (P=0.03) but not in haylage. No consistent effects of storage time on concentration of WSC and its components were present. Soaking for 12h reduced concentration of fructose and WSC in silage to approximately half of the initial concentration before soaking (P=0.001). For haylage, soaking for 12h resulted in approximately half of the concentration of initial glucose, fructose and WSC (P<0.001), but no further reduction in these components was present after 24h soaking time. For hay, soaking for 12h resulted in 50% of glucose, 70% of fructose, 15% of sucrose and 40% of fructan concentrations compared to initial contents (P<0.02). Soaking hay for 24h resulted in further reduction of glucose and WSC concentrations (P<0.001). Concentration of WSC was lower in silage compared to haylage and hay due to the utilization of WSC components by lactic acid bacteria during ensiling. Concentration of WSC in silage before soaking (24g/kg DM) was also lower than in hay after soaking for 24h (38g/kg DM), meaning thatpreserving forage as silage was more effective in reducing WSC concentration than soaking of hay. If the goal is to produce forage with low WSC concentration, preservation as silage should be preferred over hay-making.