ELECTROMETRIC TITRATION AS A METHOD OF PREDICTING THE CHEMICAL-COMPOSITION AND CORRECTED DRY-MATTER CONCENTRATION OF SILAGE

While near infra-red reflectance spectroscopy (NIRRS) has now been wid ely accepted as a technique for the routine prediction of some compone nts in grass silages, there is often a need for additional descriptive information on the products of fermentation and nitrogen fractions to give an overall measure of the silage quality. 136 silage samples whi ch had been obtained from farms across Northern Ireland over a 2 year period and which had been selected as representative of a broad spectr um of silage types, were analysed by normal wet chemistry techniques f or dry matter, nitrogen components, volatile fatty acids, lactic acid, and residual sugar concentrations. The silages were also assessed by titration of press-juice using an automatic computer controlled titrat ion system. The titres corresponding to fermentation products and nitr ogen fractions were extracted from the titration curves about the pK v alues of the component groups. Linear regression analysis of analytica l data against predicted component concentrations for Kjeldahl nitroge n, ammonia nitrogen, total volatile fatty acids and lactic acid gave R (2) of 0.91, 0.86, 0.88, and 0.87, respectively. Prediction of known v olatile corrected dry matter (kvcTDM) using volatilities of ammonia, v olatile fatty acids and lactic acid during oven drying from previous w ork gave R(2) = 0.95 and S.E. of prediction of 5.7 g kg(-1) fresh sila ge. The titration technique offers an alternative method for routine s ilage analysis in advisory work. The method has the benefit of being r apid, inexpensive to operate and it can be easily automated.