In vitro buffering capacity changes of seven commodities under controlled moisture and heating conditions.

Effects of adding 0 or .25 g of water/g of feed and heating for 0, 20, or 40 h at 100 degrees C on buffering capacity of beet pulp, almond hulls, alfalfa hay, oat hay, wheat bran, oat bran, and barley were determined in vitro. Feeds were examined for ash, N, NDF, ADF, acid detergent lignin, total buffering capacity (pH 4 to 9), and physiological buffering capacity (pH 5.5 to 7). Minerals were measured at 0 g of water/g of feed, 0 h of heat and at .25 g of water/g of feed, 40 h of heat; differences were negligible. Total buffering capacity was high for alfalfa, oat hay, and almond hulls; low for barley and oat bran; and intermediate for beet pulp and wheat bran. Physiological buffering capacity was consistently lower than total buffering capacity, but differences varied among and within feeds. Moisture had little effect on buffering capacity, NDF, ADF, or lignin. Time of heating had a significant effect on buffering capacity, NDF, ADF, and lignin but not on N or ash. Heating increased buffering capacity in most cases. Lignin was a poorer predictor of buffering capacity than total ash across feeds but a better predictor within feed across treatments. Large errors could occur when using total ash to predict buffering capacity for feeds subjected to heat.