Caecotrophes intake in growing rabbits estimated either from urinary excretion of purine derivatives or from direct measurement using animals provided with a neck collar: effect of type and level of dietary carbohydrate

The present study compares estimates Of caecotrophes production from urinary purine derivatives (PD) excretion with that from preventing caecotrophy by using a neck collar. A total of 64 New Zealand growing male rabbits were used to study the effect of diet composition on caecotrophes production. Diets were formulated using two sources of structural carbohydrates (fibre): alfalfa hay (AH) and sugar-beet pulp (SBP), mixed at two constant proportions, (0.75 : 0.25) AH diets and (0.25 : 0.75) SBP diets. Both diets included either barley or maize grain at two fibre : grain ratios (FIG, 80: 20 and 45: 55). Diets were given ad libitum. Growth rate, dry matter intake and digestibility were not modified by the grain source, although high FIG diets resulted in a lower growth rate (19.8 v 26.4 g/day; P < 0.001). Between fibre sources, dry-matter intake and growth were higher in AH than in SBP diets (122.5 and 25.6 v. 101.6 and 20.4 g/day, respectively, P < 0.001 and P < 0.01). Rabbits given high FIG ratio and AH diets excreted more caecotrophes than those given low FIG ratio and SBP diets (19.5 and 20.9 v. 16.3 and 14-85 g/day, respectively). Microbial-N recycling through the caecotrophy process was higher when considering data from PD excretion (1/33 g/d) than when estimated by preventing caecotrophy (0.72 g/day).