AGE-DEPENDENT VARIATION OF CECAL CONTENTS COMPOSITION OF YOUNG-RABBITS

In order to study the age dependent variation of caecal contents compo sition, a young rabbit was slaughtered out of 6 conventional litters a t the age of 22; 25; 28; 32; 36; 42 and 56 days. Rabbits were fed a st andard diet before and after weaning (at 28 days of age). Daily growth and caecum size were determined. Caecal contents were analyzed for dr y matter (DM), pH, crude protein (CP), neutral detergent fibre (NDF), ribonucleic acid (RNA), lactate, ammonia nitrogen and volatile fatty a cids (VFA). Between 22 and 25 days of age, a highly significant drop i n CP content was found, associated with an increase in NDF content. RN A Values tended to decrease with age, but it is striking that the RNA/ CP ratio suggests that about 50% of CP is microbial N, very early in t he development (22 days). No significant changes of ammonia nitrogen c oncentration with age were observed, and lactic acid concentration sho wed some significant changes, suggestive of a decrease after weaning. Total VFA concentration is suggestive of a progressive and significant (P<0.01) increase reaching a plateau after 42 days (83.7 mmoles/kg). Molar proportions of propionate and butyrate varied significantly (P<0 .001) and inversely with age. Propionate drops by nearly 50% while but yrate proportion doubles between 22 and 56 days of age. The shift from a propionic to a butyric pattern occurs already at day 25. Correlatio n analysis revealed significant associations between CP-NDF and RNA. T he significant negative correlation between pH and daily weight gain r eflects the relation caecal pH-animal health. PH was correlated with l actate and VFA concentration.