Nutrient losses during deterioration of hay in relation to changes in biochemical composition and microbial growth

Abstract

Dry matter losses in moist hay (56, 63, 67, 70 and 72% DM) were measured in 7 separate runs by storing the hay in respiration chambers. Samples were collected during the storage period of each run, and the dry matter loss was measured from the carbon dioxide production ( R-loss) and by balance studies ( W-loss). The dry matter losses were related to changes in chemical components and microbial growth. The preservative effect of urea was investigated in hay stored at 56% DM. Dry matter losses during storage of moist hay are primarily caused by growth of storage fungi. Under similar storage conditions, total dry matter losses were closely related to initial dry matter contents ( r = 0.97). This relationship was affected by different aeration rates and by the urea treatment. In the urea-treated hay, the dry matter loss was less than in untreated hay. The high nitrogen content of the urea-treated hay and the single clover hay used seemed to favour the extensive growth of Scopulariopsis brevicaulis, which was frequently observed in these hays. The relative increase in acid detergent fibre (ADF) concentration during storage was highly correlated with dry matter losses. The linear relation between ADF and R-loss was described by the following regression equation; % R-loss = −58.2 + 0.59 × relative increase in ADF concentration when initial value is set to 100 ( n = 88, r = 0.89, sd = 2.8, cv = 36.4). The equation makes it possible to predict the dry matter loss by performing a few simple chemical analyses. This means that the difficulties of measuring storage losses under practical conditions can be easily overcome.