Effect of fibre level reduction and gluco-oligosaccharide addition on the growth performance and caecal fermentation in the growing rabbit

The effect of reducing the level of fibre in the diet (15.8 to 10.6% ADF) was tested in combination with the effect of a supplementation (0 or 1.5%) with a mixture of gluco-oligosachharide (GOS), on the zootechnical performances and on the caecal parameters and health status of the growing rabbit during a complete fattening period (28-77 d of age). A 2 x 2 factorial design using 40 animals per treatment was used. The reduction of the fibre level resulted in a significant reduction (-10%) of the feed intake. The addition of GOS tended to increase the feed intake (P = 0.11), but only in the low fibre group (LF), thus an interaction (P = 0.067) between the effect of fibre level and GOS was detected, Daily weight gain was not affected either by fibre level or by addition of GOS, consequently the feed conversion followed a similar trend to that observed for the feed intake. Between weaning (28 d) and slaughtering (77 d), the LF diet was associated with an increase of the mortality (n = 3/40 vs. n = 7/40 for control and LF resp,). Supplementation with GOS significantly increased the mortality and morbidity. The concentration of the VFA in the caecum of healthy rabbits, measured at slaughtering, was significantly increased (+10%) when reducing the fibre level, and was associated with a higher molar proportion of the butyrate (meanly 20.4 vs, 17.8%). The caecal VFA pattern did not differ according to the addition of GOS. The weight of the caecum wall and of the caecal digesta were not affected either by the fibre level or by the addition of GOS.