Statut nutritionnel du lapereau : maturation des structures et des fonctions digestives et sensibilité à une infection par une souche entéropathogène d'Escherichia coli.

La comprehension du role de l'alimentation sur le fonctionnement du systeme digestif autour du sevrage s'avere essentielle afin de definir des strategies alimentaires permettant de reduire la frequence des episodes diarrheiques en elevage cunicole. L'objectif de ce travail est d'etudier l'implication des facteurs nutritionnels, via la modulation de l'âge au sevrage (3 vs. 5 semaines), sur le developpement des structures et fonctions digestives et sur la sensibilite du lapereau a une infection experimentale par une souche enteropathogene d'Escherichia coli (EPEC) du serogroupe O103. Suite a l'arret premature de l'allaitement, un sevrage a 3 semaines induit une augmentation de l'ingestion d'aliment granule des 2 jours post-sevrage. Les consequences sur le developpement morphologique de la muqueuse intestinale sont faibles, alors que les fonctions digestives endogenes (hausse des activites des enzymes intestinales) et microbiennes s'adaptent rapidement. A 28 jours, la capacite des lapereaux sevres a valoriser l'aliment leur permet d'atteindre un ingere d'energie digestible equivalent a celui fourni par la ration mixte lait/aliment des lapereaux allaites. Cependant, lors d'une infection experimentale a 28 jours par une souche EPEC O103, les lapereaux sevres a 3 semaines s'averent tres sensibles : taux de 50% de mortalite atteint en 8 jours. Les lapereaux allaites resistent temporairement a la colibacillose, qui se developpe apres leur sevrage a 5 semaines : 50% de mortalite 17 jours apres l'inoculation. Ce temps de reponse a l'infection differentiel selon que les animaux sont sevres ou allaites au moment de l'inoculation suggere que le lait maternel joue un role majeur dans la resistance a la colibacillose a EPEC O103. Les triglycerides du lait de lapine sont riches en caprylate (C8) et en caprate (C10) (65% des acides gras), a activite potentiellement antimicrobienne. Cependant, leur incorporation (2%) dans l'aliment de peri-sevrage ne permet pas de prolonger la protection conferee par le lait maternel vis-a-vis de la colibacillose. En conclusion, l'adaptation a l'aliment solide des lapereaux sevres a 3 semaines est rapide. Cependant, l'absence de lait maternel les rend vulnerables vis-a-vis d'une infection a EPEC O103, suggerant un role majeur de certains composes lactes non specifiques dans la resistance a la colibacillose. Ces travaux ouvrent de nouvelles perspectives quant aux strategies alimentaires du lapereau autour du sevrage. ABSTRACT : To understand the role of feed on the development of the digestive system around weaning is essential to define feeding strategies improving the digestive health in the young rabbit. This work aimed to study the impact of nutritional factors, by modulating the weaning age (3 vs. 5 weeks), on the development of the digestive structures and functions, and on the sensitivity of the young to an experimental infection with an enteropathogenic strain of E. coli (EPEC) from O103 serogroup. A weaning at 3 weeks of age led to a significant increase in solid feed intake from 2 days post-weaning. The morphologic development of the intestinal mucosa was weakly affected by weaning, whereas intestinal enzymes activities and microbial digestive functions adapted quickly. At 28 days of age, the capacities of young to digest the solid diet allowed them a similar digestible energy intake compared to still suckling rabbits fed a mixed milk/solid feed diet. Rabbits weaned at 3 weeks were very sensitive to an experimental infection with a strain of EPEC O103 at 28 days of age: 50% of dead rabbits 8 days after the inoculation. Suckling rabbits were temporarily protected against colibacillosis, which developed after their weaning at 5 weeks: the level of 50% of mortality was reached 17 days after the inoculation. This differential response time to the infection between weaned and suckling rabbits suggested that maternal milk was essential to protect kits against colibacillosis. Triglycerides of the doe's milk contain mainly caprylate (C8) and caprate (C10) (65% of fatty acids), which have a potential antimicrobial activity. However, their addition (2%) in a diet given around weaning did not extend the protection confered by maternal milk against colibacillosis. In conclusion, the digestive adaptation of rabbits weaned at 3 weeks was rapid. However, the lack of maternal milk made them vulnerable to an infection with EPEC O103, suggesting a major role of some non-specific milk components in their resistance to colibacillosis. This work gives new perspectives for feeding strategies adapted for young rabbits around weaning.