Le transit digestif chez le Lapin. VI. — Influence de la granulation des aliments

Abstract

An attempt was made to establish whether a modification of the digestive transit could account for the lower growth in rabbits fed with their feed in the form of meal as compared to that of rabbits receiving the same feed in the form of pellets. Retention in the digestive tract was studied by means of current methodology using 141Ce as a tracer, in thirty 8-wk old rabbits receiving ad lib either a standard feed (pellet A) or a simplified feed B (soyabean, maize and straw) offered either in form of pellets or meal. The lowest growth rate was found in rabbits receiving meal B (30.9 g/d [day] vs. 33.3 and 35.5 g/d, respectively, for pellets B and A). The intake of meal took place all along the 24 h period. The total feed intake represented 118 g on an average for pellet A, only 96 g for pellet B, but reached 114 g for meal B. The 24 h fecal excretion of dry matter was lower (meal B : 21.4 g, pellet B : 18.7 g) for feeds B (ADC of dry matter, 78%) than for pellet A (38.5 g ADC, 64%). Administration of feed B in the form of meal led to a 24 h-excretion rhythm very different from the normal one (2 maxima at 9.00 and 21.00 h) and with an average hour of hard feces excretion located 2 h earlier. Retention of radioactivity in the gut was longer for feed B than for pellet A. The residual radioactivity in the gut 72 h after the administration was lower for pellet A, but showed the same distribution pattern for the 3 diets. The effect of the composition of the diet can be summarized as follows: the most digestible feed led to a lower food intake level, a longer retention in the digestive tract and finally the same daily digestible dry matter intake; but the qualitative difference was responsible for the poorer growth performances observed with this feed (B). Comparison of the results obtained with pellet B and meal B, of the same composition, did not show any large difference in mean retention times. However, intake of a larger amount of meal resulted in daily digestion of a greater quantity of dry matter without improving the growth performance. This lower feed efficiency can only be explained by the disturbance in the rhythm of nutrient supplies reflected by the increased feed intake during the day and, parallel to that, the shifting in the average hour of hard feces excretion.