Effects of pectin and cellulose on growth, feed efficiency, and protein utilization, and their contribution to energy requirement and cecal VFA in rats.

Graded levels of cellulose (0 to 20%) or of pectin (0 to 10%) were incorporated in purified diets with either 22 or 8.5% casein as the protein source. Weanling male rats were fed these diets for 4 weeks. Body weight gain, food consumption, feed efficiency, protein biological value, apparent digestion of food, fiber and protein, cecal weight and cecal volatile fatty acids (VFA) were recorded. Cellulose was largely and inert diet diluent causing increased weight gains when protein was limiting but not when protein was sufficient. The 25% disappearance in the gut was due, at least in part, to compaction in the ceca and in increased cecal VFA. Pectin caused progressively greater depressions in body weight gain, food intake and efficiency and protein digestion at both levels of dietary protein. At least part of the 75% disappearance of pectin during passage through the gut could be attributed to increased cecal VFA. However, a rat growth bioassay for energy showed that pectin as well as cellulose, agar and gum arabic contributed no measurable energy to young rats.