Effect of indigestible sugars on nitrogen utilization in adult rabbits

To determine the effects of indigestible sugars on the digestibilities of nutrients and utilization of nitrogen (N) in adult male rabbits, 12 rabbits with or without a collar that prevented cecotrophy were fed experimental diets for 8 days, comprising 3 days for adaptation and 5 days for collection of feces and urine. The experimental diets were formulated by adding D-mannitol or citrus pectin to a commercial diet at 60 g/kg. In the rabbits allowed cecotrophy, mannitol increased the absorption of crude ash but did not significantly alter the digestibilities of crude protein (CP), dry matter and acid-detergent fiber. By contrast, the digestibility of CP was decreased by pectin. The ratios of retained N to consumed N and absorbed N were elevated by mannitol. In the rabbits prevented from cecotrophy, mannitol had no effect on N retention, but increased the N content of cecotrophs (soft feces) and the ratio of the N content of cecotrophs to consumed N. Pectin did not have any significant influences on N retention and the N content of cecotrophs. These results suggest that D-mannitol stimulates cecal microbial proliferation, thereby improving N utilization in rabbits.