Digestive organs, caecal metabolites and fermentation pattern in coypus (Myocastor coypus) and rabbits (Oryctolagus cuniculus)

Abstract

Six coypus and six rabbits fed the same granulated feed ad libitum were slaughtered, digestive organs with their contents weighed and digesta samples analyzed. The caecum was the largest digestive organ in both animal species. Its weight averaged 170 g in coypus and 157 g in rabbits (4.1 and 5.5% of the total body weight, respectively). In rabbits, the weight of stomach was greater and that of the small intestine smaller than in coypus (135 and 89 vs 85 and 111 g). Gastric acidity, caecal and colonic dry matter concentration were significantly higher in rabbits. Total volatile fatty acids (VFA) and ammonia concentrations in the caecal contents of coypus and rabbits were similar (100.1 and 23.3 mu mol/g in coypus, and 103.7 and 25.5 mu mol/g in rabbits, respectively). Molar percentages of acetate and propionate, however, were significantly higher and percentage of butyrate lower in caecal VFA of coypus than in rabbits (P < 0.002). The caecal contents were diluted with buffer and incubated anaerobically to determine the caecal fermentation pattern. Caecal microorganisms of coypus produced more propionate and methane, and less butyrate and valerate than caecal microbes of rabbits (P < 0.05). Thus, different major hydrogen sinks exist in the coypu and rabbit caecum. In conclusion, there are both differences and similarities in parameters of digestion in both animal species. Caecal fermentation pattern differed more than other parameters investigated.