REPLACEMENT OF STARCH BY DIGESTIBLE FIBER IN FEED FOR THE GROWING RABBIT .2. CONSEQUENCES FOR MICROBIAL ACTIVITY IN THE CECUM AND ON INCIDENCE OF DIGESTIVE DISORDERS
N. Jehl et T. Gidenne, REPLACEMENT OF STARCH BY DIGESTIBLE FIBER IN FEED FOR THE GROWING RABBIT .2. CONSEQUENCES FOR MICROBIAL ACTIVITY IN THE CECUM AND ON INCIDENCE OF DIGESTIVE DISORDERS, Animal feed science and technology, 61(1-4), 1996, pp. 193-204
Caecal fermentative activity and daily bacterial biomass production we
re compared for two groups of nine rabbits, fed a diet rich in starch
(ST, 266 g starch kg(-1) dry matter (DM)) or a diet rich in digestible
fibre (DF, 271 g hemicellulose + pectin kg(-1) DM), but which were si
milar in acid detergent fibre (ADF) content (205 g kg(-1) DM). Caecal
volatile fatty acid (VFA) concentrations, measured in vivo in healthy
rabbits fitted with a caecal cannula, were significantly higher in the
DF group (85.1 mmol l(-1)) than in the ST group (67.7 mmol l(-1)). Be
tween 44 and 72 days of age, no change in in-vivo VFA level was record
ed for the two diets. Acetate molar proportion decreased from 86 to 72
% mostly between 44 and 53 days of age (P = 0.05), and was balanced by
a slight increase of both propionate and butyrate proportions. The co
ncentration of diaminopimelic acid (DAPA) was two-fold higher in soft
than in hard faeces, and was not significantly affected by diet compos
ition. The mean level of DAPA in bacteria was similar for the two grou
ps of rabbits (19.8 mu mol g(-1) DM). The mean bacterial biomass produ
ction was two-fold higher in the DF group (13.3 g DM day(-1)) and acco
unted for 13% of the feed intake. Although ADF intake was similar for
the two groups of rabbits, the animals fed the starch-rich diet showed
a higher incidence of digestive disorders (diarrhoea). The partial re
placement of starch by digestible fibre improved the health status wit
hout major impairment of growth performances.