In vitro fermentation of diets incorporating carob pulp using inoculum from rabbit caecum

Abstract

The aim of this work was to evaluate the nutritive value of carob pulp for rabbits using the in vitro digestibility and gas production techniques with inocula from caecal content of rabbits. Experimental diets contained 0% (D1), 10% (D2), 20% (D3) and 100% (D4) carob pulp on a dry matter (DM) basis and were incubated in glass syringes for 72 h at 39ºC. Carob pulp contained 313 g neutral detergent fibre/kg DM with a high acid detergent fibre (263 g/kg DM) content, resulting in a low hemicellulose content of 50 g/kg DM. Potential gas production ranged from 123 (D1) to 179 (D4) mL/g DM and was similar for the D1 (123 mL/g DM), D2 (126 mL/g DM) and D3 (130 mL/g DM) treatments. The lowest pH value of 6.47 and the highest organic matter degradation (OMD, 64.3%) were observed in the 100% carob pulp (D4) treatment, while its inclusion at 10% and 20% tended to improve the OMD of the diets. These results show that carob pulp is well fermented by the caecal micro-organisms of rabbits. Although its inclusion at 20% did not improve in vitro fermentation and degradation of the commercial concentrate, it was concluded that carob pulp has potential as an unconventional feed resource for rabbits. Its utilization could have a positive effect on intestinal microbiota owing to its high content of soluble fibre.

Keywords: Ceratonia siliqua, by-product, chemical composition, gas production, organic matter degradation