High grain rations reduce rumen Ph, which creates an environment conducive for bacteria that produce more propionic acid and less acetic acid. Ph tends to reverse this process and increase fat percent. Finely chopped or shredded silage is commonly observed in herds that have low fat percents. Lush pasture in early spring tends to reduce fat percent. Long hay tends to increase fat percentage because of the increased chewing required to break the feed down for digestion.
Sodium bicarbonate is a natural ingredient found in saliva.
In high forage rations they probably have little beneficial effect except as sources of sodium and magnesium. Buffers should not be used as cure-alls in feeding programs. The original nutritional problem should be corrected, if possible, before resorting to the use of buffers. Control the amount of grain fed. In other words, fiber that does not stimulate adequate chewing.