THE EFFECT OF AN ACID SALT-TYPE ADDITIVE ON THE FERMENTATION OF GRASS SILAGES MADE IN BUNKER SILOS ON COMMERCIAL DAIRY FARMS IN WALES

The fermentation characteristics and chemical composition of 57 first-cut and 30 second-cut samples of grass silages, made in bunker silos on commercial dairy farms in Wales in 1990, and treated with a nominal 6 1 t-1 of an acid salt-type additive at ensilage, is described. Typical chemical composition of grass cut for ensilage was 156 g kg-1 dry matter (DM) and 28 g kg-1 water soluble carbohydrate (WSC), with 181 g (kg DM)-1 crude protein (CP) and 232 g (kg DM)-1 modified acid detergent fibre (MADF). The effect of additive use was to produce silages with DM 230 g kg-1 pH 3 . 93, ammonia N 70 g kg-1 total N, with residual WSC 35 g (kg DM)-1, lactic acid 83 g (kg DM)-1, total acids 118 g (kg DM)-1 and butyric acid 0.7 g (kg DM)-1. No significant differences were found between first- and second-cut silages. Silage fermentation was restricted (i.e. lactic acid less than 60 g kg DM-1) in only 20% of the samples. It is suggested that on commercial farms the application rate achieved may be insufficient to produce a restricted fermentation.