Effect of fiber source on cecal fermentation and nitrogen recycled through cecotrophy in rabbits.

Abstract

The influence of fiber source on fiber digestion in rabbits was investigated. Six fibrous feedstuffs with wide differences in chemical composition and particle size were selected: paprika meal, olive leaves, alfalfa hay, soybean hulls, sodium hydroxide-treated barley straw, and sunflower hulls. Six diets were formulated to contain one of these ingredients as the sole source of fiber. To avoid nutrient imbalances, fiber sources were supplemented with different proportions of a fiber-free concentrate, based on soy protein isolate, wheat flour, lard, and a vitamin and mineral mix, to obtain diets containing at least 3% nitrogen and 5% starch. Daily soft feces excretion, and its NDF, and total and microbial nitrogen content were determined in 60 fattening rabbits (10 per diet). Seven days after the last cecotrophy control, the same animals were used to determine weight of stomach, cecum and their contents, and cecal fermentation traits (pH, VFA and ammonia concentrations, and buffer properties of cecal contents). Stepwise regression analysis showed a positive effect (P < .001) on soft feces excretion, total and microbial nitrogen concentrations in soft feces, cecal acidity, and total VFA in the cecum of dietary pectic constituents (2.9, 3.5, 2.5, .9, and 6.6%) and proportion of fine particles (< .315 mm) (1.8, .9, 1.3, .15, and .9%) per each increment of one percentage unit of the independent variables. Proportion of fine particles also increased weight of cecal contents (P < .001). Soft feces excretion and weight of stomach and of its contents increased (P < .001) by 5.2, 2.8, and 10.2% per each percentage unit increment of proportion of large particles (> 1.25 mm). Degree of lignification of NDF decreased total nitrogen concentration in soft feces and cecal VFA concentration (P < .001). Source of fiber affected cecal pH not only by its influence on the cecal concentrations of the final products of fermentation, but also through its effect on the pH of dry cecal contents (P < .001). The latter was negatively correlated with dietary proportion of fine particles, degree of lignification of NDF, and base-buffering capacity of dry cecal contents (r = -.52, -.37, and -.49, respectively). From these results, we conclude that pectic constituent concentration, degree of lignification of NDF, and particle size are the variables that best characterize the influence of the source of fiber on soft feces excretion and cecal fermentation traits in rabbits.

Influence of Dietary Supplementation of Coated Sodium Butyrate and/or Synbiotic on Growth Performances, Caecal Fermentation, Intestinal Morphometry and Metabolic Profile of Growing Rabbits

“…The decreased in caecal pH, the decreased in ammonia-N concentration and the higher VFA concentration suggest high fermentation activity, caecal microbial synthesis, gut health and high nitrogen retention. This observation is consistent with the growth performance result discussed above, and is also in agreement with the results of Garcia et al (2000).…”

New trends in rabbit feeding: influence of nutrition on intestinal health. A review

“…Several studies (Nicodemus et al, 2004;Gidenne et al, 2004a,b;Gidenne and Licois, 2005) have shown a significant increase of mortality in fattening rabbits when NDF levels were decreased below 30-32%. Insoluble fibre might be necessary to decrease mean retention time of digesta in the gut, dilute dietary and ileal starch and protein content and reduce total microbial growth (García et al, 1995(García et al, , 2000De Blas et al, 1999b).…”

Effects of type and level of fibre on digestive physiology and performance in reproducing and growing rabbits.

“…However, it also increased total mean retention time and reduced feed intake (Pairet et al, 1986;Fraga et al 1991, García et al, 1993, Carabaño et al, 1997Falcao-e-Cunha et al, 2004). The opposite effect has been observed with the dietary inclusion of insoluble and low fermentable fibre (Fraga et al, 1991;Motta-Ferreira et al, 1996;García et al, 2000) or by increasing ADL content Nicodemus et al, 1999;García et al 2002a). Accordingly, a balance between soluble and insoluble fibre seems to be advisable to maximize fattening performance.…”

“…Insoluble fibre is the dietary fraction most related to digestive troubles in rabbits, as it is the most important factor in regulating rate of passage and microbial growth García et al, 2000;Gidenne, 2003). A minimum level of 34% of NDF is recommended to minimize the accumulation of digesta in the caecum and maximize performance during the whole fattening period (De Blas and Mateos, 1998).…”