Caecal Metabolites and Fermentation Pattern in Coypus ( Myocastor coypus ) and Rabbits ( Oryctolagus cuniculus )

Marounek M. , M.Skfiivan, P. Bfiezina, I . Hoza: Digestive Organs, Caecal Metabolites and Fermentation Pattern in Coypus (Myocastor coypus) and Rabbits (Oryctolagus cuniculus). Acta Vet. Brno, 2005, 74: 3-7. 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 μmol/g in coypus, and 103.7 and 25.5 μmol/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. Coypu, rabbit, weight, digestive tract, digestion, caecum, fermentation Coypus (Myocastor coypus) and rabbits (Oryctolagus cuniculus) are medium-sized herbivore animals with similar morphological features of the digestive tract. In both species the caecum is the primary site of digesta retention and microbial fermentation. Both coypus and rabbits practise caecotrophy, i.e. produce two types of faeces, soft and hard, and reingest soft ones. Soft faeces (fermented caecal material) are rich in nutrients, whereas hard faeces are basically a refuse. Comparative nutritional trials with coypus and rabbits are scarce, as well as with other non-ruminant herbivores. Hullár et al. (1992ab) found that coypus fibre requirement and the significance of caecotrophy were lower, probably due to continuous availability of low-fibre parts of aquatic plants in the coypu’s natural environment. A high-fibre feedstuff (lucerne) was digested less efficiently in coypus than in rabbits, but in case of feedstuffs low in fibre (maize, wheat), or containing the fibre in an easily digestible form (wheat bran) no difference in digestibility coefficients was observed. Caecal microorganisms of coypus produced more propionate and methane, and less butyrate than caecal microorganisms of rabbits (Marounek et al. 1999). This study has been aimed at extending our knowledge on comparative digestive physiology of herbivore animals. Thus, weights of digestive organs, acidity and dry matter (DM) concentration of their contents, and concentration of caecal metabolites were determined in coypus and rabbits fed the same diet ad libitum, as well as the stoichiometry of fermentation in cultures of caecal contents. ACTA VET. BRNO 2005, 74: 3–7 Address for correspondence: Prof. Ing. M. Marounek, DrSc. Institute of Animal Physiology and Genetics Czech Academy of Sciences, VídeÀská 1083 CZ 142 20 Prague 4, Czech Republic Phone: +420 267 090 507 Fax: +420 267 090 500 E-mail: marounek@iapg.cas. cz http://www.vfu. cz/acta-vet/actavet.htm Materials and Methods Six broiler rabbits, Hyplus breed, and six coypus were fed ad libitumacommercial granulated feed containing lucerne meal, wheat bran, sunflower meal, oats, barley, sugarbeet pulp, and soyabean meal as the main ingredients (Table 1). Rabbits and coypus were slaughtered at the age of 3 and 6 months, respectively, between 06:30 and 08:00 h. After slaughtering, the stomach, small intestine, caecum and colon were isolated by ligating organs with a string to prevent movement of the digesta. Digestive organs were weighed and their contents squeezed out into beakers. In all samples, the pH was measured and DM concentration determined by drying at 105 °C. The caecal contents (10 g) were added to 30 ml of water or Burroughs buffer (Burroughs et al. 1950) with yeast extract (1 g·l-1) and urea (0.5 g·l-1). To stop the fermentation in former samples, HgCl2 was added immediately. The latter samples were incubated with or without a substrate (0.6 g of wheat bran) in 100 ml serum bottles at 39 °C for 24 h. The bottles were thoroughly flushed with CO2 and hermetically closed with rubber stoppers. Sodium sulphide was added to the incubation fluid at 0.5 g·l-1 as a reducing agent. The pH (above 7 initially) fell by 0.7-0.9 in the course of the incubation.