Caecal microflora and fermentation pattern in exclusively milk-fed young rabbits

Thirty-two SPF New Zealand White rabbits of both sexes were used in this experiment. They were sequentially slaughtered at 22, 29, 35 and 42 days of age. The rabbits were only milked by their mother and by foster mothers (no access to solid food) throughout the experiment. They exhibited a caecal fermentation pattern that turned towards a proteolytic metabolic activity (high levels in NH 3 and in branched-chain fatty acids and valeric acid: 17 mmol ' L ' ' and 1 mmol-L-', on aver- age, respectively). The absence of caecal cellulolytic microflora and the low concentration of the total volatile fatty acids (tVFA) could be explained by the lack of substrate that would have been brought by a solid feed. From day 29 onwards, the low tVFA (12.5 mmol-L-1 ) and high NH 3 concentrations (16.5 mmol-L-1 ) explained the high pH value (6.8 on average). This could be considered as a patho- logical value in weaned rabbits, but in our case no clinical signs of diarrhoea were observed. The evo- lution of the colibacilli flora according to age was similar to that usually described and thus was not correlated with pH, tVFA or cellulolytic flora. The evolution of the colibacilli population (from 10! bact/g on day 22 to 10 3 on day 42) seemed dependent on ontogenic factors rather than on the com- position of the caecal media (pH, etc.). © Inra/Elsevier, Paris. rabbit / milky diet / caecal microflora / caecal fermentation / pH Rsum ― tude de la microflore et de l'activit fermentaire caecale chez le lapereau nourri exclusivement avec un rgime lact. Trente-deux lapins No-Zlandais, SPF ont t utiliss et abattus 22, 29, 35 et 42 j d'ge. Le maintien d'une alimentation uniquement lacte jusqu' 42 j, four- nie par leur mre et par une femelle nourricire, a conduit un profil fermentaire orient vers une activit mtabolique protolytique (teneur leve en NH 3 et en AGV mineurs : respectivement 17 mmol!L-! et 1 mmol!L-! de contenu caecal, en moyenne). L'absence de flore cellulolytique et la