Evidence for a high efficiency of bacterial protein synthesis in the digestive tract of adult sows fed supplements of fibrous feedstuffs

Two experiments with adult sows were carried out to obtain data on the fermentation of wheat bran and alfalfa meal and on the effects of these feedstuffs on nitrogen turnover and bacterial protein synthesis. Wheat bran was provided at levels of 0 g, 225 g and 675 g per day and alfalfa meal was given in amounts of 0 g, 575 g and 1150 g per day both in addition to a basal diet covering maintenance requirements. Each treatment was carried out in eight replicates. Both supplements significantly impaired the digestibility of different carbohydrate fractions. The level of supply, however, had no effect on the partial digestibility of these carbohydrates as incorporated in wheat bran and alfalfa meal. A proportion of 40-46% of the non-starch polysaccharides from wheat bran and alfalfa meal was degraded which is similar to the level previously observed with purified cellulose. Fecal nitrogen composition was only slightly affected by the supplements, whereas the excretion of all nitrogenous fractions increased. With alfalfa meal, the fecal N per gram of N intake significantly increased at a cost of urinary N. Bacterial protein excretion per 100 g of fermented matter was 13 g, 20 g and 28 g for the basal diet alone, for wheat bran and for alfalfa meal, respectively. The values obtained with the supplements fall within the range estimated for the efficiency of microbial protein formation in the rumen of ruminants.