Effect of cereal sources and processing in diets for the growing rabbit. I. Effects on digestion and fermentative activity in the caecum

Abstract

-Four high-starch diets (20%) varying only by the source of starch (wheat = diet W; barley = diet B; maize = diet M; extruded maize = diet EM) were given ad libitum before weaning (at 29 d old) from 18 days of age, to 8 litters (2 litters per diet) of 8 rabbits caged separately from their mother. Starch concentration in the ileal digesta and caecal fermentative characteristics were assessed at weaning and at 50 d of age, while faecal digestibility was measured between 46 and 50 d of age. The energy digestibility coefficient was the highest for the barley based diet while the lowest were observed for wheat and maize based diets (P < 0.05). At weaning, the level of starch in the ileum was high and similar for W, B and M diets (meanly: 8.8% DM), but was 5 points lower for the EM diet. At 7 weeks of age, it remained high (>10% DM) with the maize based diet, while it decreased for the other groups (less than 6% DM). The faecal digestibility of the glucidic fraction (NNCC) was almost complete (> 92%) and significantly higher with the EM diet followed by the B diet. NNCC digestibility was negatively correlated with ileal starch concentration (r = -0.63, P < 0.001). The fibre and protein digestibility remained unaffected by the dietary treatment, and no significant correlation was detected between the ileal starch level and fibre digestibility (NDF or ADF). Caecal VFA concentration increased by 11 mmol (+20%) from weaning to 7 weeks of age, while ammonia level decreased by 15%. Compared to weaning, at 7 weeks of age, the butyrate proportions were 5 units higher. The starch source did not significantly affect the caecal traits or fermentations, except for a slight increase in the empty caecal weight for EM and B compared to the W and M diets (P < 0.05). The ileal starch concentration was not correlated with caecal fermentative activity. rabbit / digestion / starch nature / extrusion / caecal fermentation Résumé -Effet du type de céréale et de l'extrusion dans l'alimentation du lapin en croissance. I -Conséquences sur la digestion et l'activité fermentaire caecale. Pour étudier les effets de la nature de l'amidon alimentaire sur la digestion du lapin en croissance, quatre aliments riches en amidon (20 %) variant seulement de par l'origine de l'amidon (blé = groupe W, orge = groupe B, maïs = groupe M, maïs extrudé = groupe EM) ont été distribués à volonté avant le sevrage (29 j) à partir de 18 jours d'âge, à 8 portées de 8 lapereaux (2 portées par régime) logés séparément de leur mère. La concentration en amidon iléal ainsi que l'activité fermentaire caecale ont été mesurées au * Corresponding author: gidenne@toulouse.inra.fr 56 T. Gidenne et al.sevrage et à 50 jours d'âge, tandis que la digestibilité fécale des aliments a été mesurée entre 46 et 50 j d'âge. La digestibilité de l'énergie du régime à base d'orge (groupe B) est la plus élevée, alors que celle du régime à base de maïs est la plus faible (P < 0,05). Au sevrage, la concentration en amidon iléal est assez élevée et similaire entre les groupes W, B ou M ...

Effect of cereal sources and processing in diets for the growing rabbit. II. Effects on performances and mortality by enteropathy

“…The level of lignocellulose (ADF = 16.3%) was slightly below recent recommendations [4], while the level of starch was chosen about 5 points over the usual post-weaning recommendations [4]. The ingredients and the analytical characteristics of the experimental diets were reported in detail in the first part of this study [7]. The four diets were manufactured and pelleted at one time (CCPA, Osny), using the same batches of raw materials.…”

“…The nutritive value of the diets was determined in the first part of this study [7]. The digestible energy contents were 11.49, 12.24, 11.68, 11.97 MJ·kg -1 (air dry basis) respectively for W, B, M, and EM diets.…”

“…A concerted study associating a research centre (INRA), an extension centre (ITAVI) and five feed manufacturers was thus carried out to analyse the effects of varying the origin of starch (with similar fibre levels) on the digestion of nutrients (see part I of the study [7]), and on the performances and mortality of the fattening rabbits (present study). The concerted study consisted in managing repeated assays on a high number of animals, under various breeding conditions while using the same protocol, in order to obtain results transposable to commercial breeding.…”

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

“…Maize starch is less digested in the small intestine than wheat or barley starch in both young (Blas et al, 1994;Pinheiro and Gidenne, 2000) and older rabbits (Gidenne and Perez, 1993). However, recent works have shown that an increased starch flow through the ileo-caecal junction, modulated by the origin of cereals incorporated in diet, would not have any negative impact on post-weaning caecal fermentation and mortality (Gidenne et al, 2005a and2005b). The higher flow of proteins reaching the caecum in early-weaned rabbits resulted from a higher digesta flow, as the composition of the ileal content was not affected by weaning age.…”

“…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. However, the digestive response of the young rabbit to sharp changes in the feed intake (quantity and quality) was never studied at the ileal and faecal levels.…”