Challenging the growing rabbit with a moderately pathogenic E. coli under ad libitum or limited feed intake conditions: impact on digestive physiology, bacterial communities, and on post-weaning growth

[EN] The impact of a challenge with moderately pathogenic Escherichia coli O128:C6 on the digestive physiology and gut bacterial community of growing rabbits under two feeding programmes was analysed. Upon weaning (28 d old), 180 rabbits were allocated to four groups (9 cages of 5 rabbits per group) for two weeks: group C100 was non-inoculated and fed ad libitum; C70 was non-inoculated and feed intake was limited to 70% of C100; I100 and I70 were inoculated and fed ad libitum or restricted to 70%, respectively. At the age of 31 d (D0), rabbits were orally inoculated with E. coli (2.2×108 colony forming units/rabbit). The effects of inoculation spiked on D4, with a 28% lower growth rate for I100 than for C100. Limited feed intake reinforced the inoculation’s effects on growth: I70 had a 66% lower growth rate than C70. The morbidity rate peaked at 42% between D4 and D7 for inoculated groups, without significant effect of the feed intake level. E. coli concentration peaked on D5/D6 in the caecum of the I100 and I70 groups. Inoculation reduced by 30% (P<0.05) the villus height/crypt depth and villus/crypt area ratios in the ileum, with no significant effect of the intake level. Inoculation was associated with a tenfold increase in serum haptoglobin (P<0.001) for both ad libitum and restricted rabbits. On D5, the inoculation modified the structure of the ileal bacterial community (P<0.05), but not that of the caecum. The feed intake level did not affect either the structure or diversity of the bacterial community, both in the ileum and caecum.The authors would like to thank Alain Milon and Stéphane Bertagnoli (ENV Toulouse) who provided the E. coli O128:C6 strain we used. We are also grateful to ANSES staff in the “Service d’Elevage et d’Expérimentation en Pathologie Aviaire” (M. Amelot, L. Le Moal, T. 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