Effects of Moisture Determination Method on Estimates of Digestibilities and Intakes of Conserved Alfalfa

Abstract

Digestibilities, nitrogen balances, and voluntary intakes of six silage-hay diets fed to sheep were used to contrast different methods of determination of dry matter. All wet samples of feed, feed refusals, and feces from 24 wethers were analyzed in triplicate for dry matter by: forced air drying at 90C for 24h; vacuum oven drying at 70C under pressure of less than 75mm mercury for 24h; toluene distillation (uncorrected); toluene distillation (acid corrected); and by a chemical saponification method. There were significant differences in dry matter between methods. Dry matter digestibility of hay was overestimated by 6.8% when forced air drying was used rather than the chemical method whereas that of a formaldehyde-treated silage was underestimated by 5.5%; the digestible energy intake of the formaldehyde-treated silage was underestimated by 15.1%, and that of the hay overestimated by 6.9%. Nitrogen balance was 75.9 and 7.4 g/head per day for hay and untreated silage when forced air dry matter and Kjeldahl nitrogen on the dried sample were combined while values were 25.6 and −42.1 g/head per day when data by chemical method were used with Kjeldahl nitrogen on the wet sample. Differences in estimates of dry matter may explain some of the anomalous dietary comparisons for silage and hay.