Inter-relationship of microbial activity, digestion and gut health in the rabbit: effect of substituting fibre by starch in diets having a high proportion of rapidly fermentable polysaccharides

Abstract

Caecal microbial activity, digestion and gut health were analysed in the young rabbit, in response to fibre substitution by starch, in diets with high proportions of rapidly fermentable polysaccharides (pectins þ hemicelluloses:acid-detergent fibre (ADF) ratio of 1·7). A range of five diets corresponding to a 60 % linear reduction of the ADF level (230 to 92 g ADF/kg) without changes in the fibre quality, and to a corresponding linear increase in dietary starch, was given ad libitum to young rabbits from 18 d until 70 d of age. A one half reduction of the ADF level resulted in a sharp increase in energy digestibility (þ 25 units), associated with a lower feed intake ( -35 %) and to an increase of the mean retention time (þ 6 h) in the whole digestive tract. Despite large variations in the fibre intake (20 to 59 g ADF/d), the fibre digestive efficiency remained similar among the five diets. Starch ileal concentrations were low after 4 weeks of age (,5 %), and variations with age were significant when the dietary starch level was over 19 %. A 65 % lower biomass production was measured when the ADF level progressed from 230 to 165 g/kg, and no precise relationship was found with fermentative activity. Reducing the fibre intake led to a linear decrease of caecal volatile fatty acids concentrations, and to higher pH and NH 3 levels. An increased occurrence of mortality by diarrhoea was registered with the lowest fibre intake. It can be concluded that a sufficient supply of fibre, with high proportions in rapidly fermentable polysaccharides, stimulates the maturation of microbial activity and reduces the occurrence of diarrhoea.

Dietary fibres in the nutrition of the growing rabbit and recommendations to preserve digestive health: a review

“…The DgF fraction plays a key role in digestive efficiency and digestive health, as it is rapidly fermented (compared with Mortality after weaning % Dietary ADF concentration, % as fed Gidenne et al, 2004bGidenne et al, 2004aDebray et al, 2002Bennegadi et al, 2001Perez et al, 1996Perez et al, 1994Perez et al, 1994Blas et al, 1994Carraro et al, 2007 Tazzoli 2012 CP15 Tazzoli 2012CP17 De Blas et al, 1981Maître et al, 1990 Figure 4 The rabbit post-weaning mortality decreases when the dietary lignocellulose (ADF) concentration increases, but with a highly variable impact within the classical dietary ADF range (15% to 22%). Data from 12 studies and 46 diets, without antibiotics, and varying in their ADF concentration.…”

“…A similar relationship is obtained when we related the criteria 'TDF − ADF' to mortality. The favourable effect of DgF (compared with starch) on health would originate from a stimulated caecal fermentative activity (Garcia et al, 2002), and possibly from their moderate effect on the rate of passage (Gidenne et al, 2004a). This relationship between DgF and digestive health status is improved by using the HRi (more precise than mortality rate).…”

“…The HRi is improved, whereas the feed efficiency is weakly modified Gidenne et al, 2004b;Tazzoli et al, 2009;Trocino et al, 2011). Furthermore, a substitution of protein by DgF Health Risk index, after weaning % Ratio DgF /ADF in the feeds Gidenne et al, 2004bGidenne et al, 2004aDebray et al, 2002Bennegadi et al, 2001 lower HRi higher HRi Figure 7 The health risk index (HRi) of the growing rabbit depends on the balance between low-digested (ADF) and highly digested (DgF) fibre fractions. Data from five studies and 16 diets, without antibiotics, varying in their ratio DgF/ADF (within a study dietary ADF is varying).…”

“…However, to look more precisely at this effect, we should select studies comparing diets having a similar level of ADF (or NDF), as shown in Figure 9. However, even for the six studies selected (same data set as for Mortality, after weaning % Dietary SF*, % as fed basis Gidenne et al, 2013Trocino et al, 2010Soler et al, 2004Xiccato et al, 2011Xiccato et al, 2011Tazzoli et al, 2009Perez et al, 2000Gidenne et al, 2004aPerez et al, 1994Perez et al, 1996Gidenne et al, 2004bGidenne et al, 2001Bennegadi et al, 2001Debray et al, 2002De Blas et al, 1981Blas et al, 1994 [r² = -0.04] Figure 8 The post-weaning mortality of the growing rabbits is weakly related to the dietary soluble fibre (SF*) level. Data from 16 studies and 78 diets, without antibiotics, and without selection for the fibre level.…”

Adaptability of the digestive function according to age at weaning in the rabbit: II. Effect on nutrient digestion in the small intestine and in the whole digestive tract

“…For instance, ileal flow of nutrients through the ileo-caecal junction will subsequently influence the caecal microbial activity, and it would be related to the incidence of digestive disorders in the young rabbit (Gidenne et al, 2004). Although, amylase and disaccharidases activities are low until 35 days of age (Corring et al, 1972;Dojanȃ et al, 1998), it has recently been shown that a high ileal flow of starch did not disturb either the caecal fermentation (Gidenne et al, 2005a) or the digestive health (Gidenne et al, 2005b) in growing rabbits.…”