The effect of protein levels on the response of weanling rats to dietary pectin.

We have previously proposed that the inhibiting effects of pectin on feed consumption and growth might be due in part to the reduction it causes in protein digestibility. The present work was intended to test this hypothesis by feeding higher levels of protein in order to compensate for the lower digestibility. We fed diets containing 10, 20 and 30% casein (initial levels) and 0, 4.8, 16.7 and 28.6% pectin (by diet dilution). Despite the higher casein levels, pectin strongly inhibited the animals' feed intake, growth, protein efficiency ratio (PER), net protein ratio (NPR) and net protein utilization (NPU) as well as protein and energy digestibilities. Apart from determining the base (zero pectin) level of the various parameters measured, the dietary casein level in itself did not influence the effect of pectin on feed intake, digestible energy intake, protein digestibility, body weight growth or parameters of protein utilization such as PER, NPR and NPU. We thus cannot conclude that these effects of pectin were to any major extent secondary to the reduction in protein digestibility observed in these animals.