Effect of sodium bicarbonate addition to alfalfa hay-based diets on digestibility of dietary fractions and rumen characteristics.

Three trials were to evaluate effects of sodium bicarbonate in alfalfa hay-based diets. In Experiment 1, four Jersey cows were fed diets of 40:60 chopped alfalfa hay:grain with either 0, .25, .5, and .75% sodium bicarbonate in a 4 X 4 Latin square digestion trial. Dry matter and fiber digestion were unaffected. Volatile fatty acids of ruminal fluid and milk fatty acids were not different. In Experiment 2, two rumen fistulated cattle were fed diets of Experiment 1 for changes of ruminal fluid characteristics at -1, 2, 4, and 8 h postfeeding. Volatile fatty acids of ruminal fluid and hydrogen ion concentration were not different across time with sodium bicarbonate. In Experiment 3, four Holstein cows with rumen cannulae were fed diets of 30:70 chopped alfalfa hay:grain with 0, .4, .8, and 1.2% sodium bicarbonate in a 4 X 4 Latin square. Dry matter and fiber digestion were unaffected. Ruminal fluid samples were collected at -1, 3, 6, and 9 h postfeeding. Volatile fatty acids were different only at 6 h with 0 and 1.2% sodium bicarbonate diets displaying lower concentrations. Rate of increase of hydrogen ion concentration was greater for diets containing 0 and .4% compared with .8 and 1.2% sodium bicarbonate between -1 and 6 h. Milk fatty acid composition, ruminal liquid dilution rate, and dry matter disappearance from nylon bags suspended in the rumen were not affected by sodium bicarbonate.