EFFECT OF HERBAGE WATER-SOLUBLE CARBOHYDRATE CONTENT AND WEATHER CONDITIONS AT ENSILAGE ON THE FERMENTATION OF GRASS SILAGES MADE ON COMMERCIAL FARMS

A total of 1009 samples of silage made in bunker silos on commercial farms between 1972 and 1978 was analysed to investigate the effect of herbage water‐soluble carbohydrate content (WSC) and weather conditions at ensilage on fermentation as measured by ammonia‐N concentration and pH of first‐cut grass silages. Silage dry matter (DM) content had the major effect on fermentation. Factors influencing silage DM were rainfall and hours of sunshine during silage making, and DM content of the grass cut. WSC content of herbage ensiled also had a significant effect on subsequent fermentation. The major influences on herbage WSC were hours of sunshine and rainfall during the growing season. The effect of chemical additives, albeit at poorly defined and often inadequate rates, was small in comparison to that of silage DM. The minimum DM necessary to produce well‐fermented silage without additive was approximately 260 g kg−1. Use of formic acid significantly reduced this requirement to 240 g kg−1 and to 252 g kg−1 for sulphuric add + formalin. The results indicate that the minimum herbage WSC necessary to prevent a clostridial fermentation developing in silage with a DM content of 230 g kg−1 is approximately 37 g kg−1 without additive and 30 g kg−1 with formic acid. It is concluded that on commercial farms, weather conditions i.e. amount of rainfall and sunshine prior to and at ensilage, have a greater effect on subsequent silage fermentation than additive use. Copyright © 1990, Wiley Blackwell. All rights reserved