Colon passage time in rabbits in relation to the formation of caecotrophes.

The mechanisms which lead to a diurnal variation in the formation of hard and soft faeces in the rabbit are still to a great extent not known. Both types of faeces originate from caecal contents (BONNAFOUS and RAYNAUD, 1967; YOSHIHARA and KANDATSU, 1960). It is therefore presumed that differentiation occurs during the passage through the colon. This results in the hard faeces, with a low concentration of nutrient substances, and the caecotrophes, with approximately the same composition as the caecal contents (ELSDEN et al., 1946; FRANK et al., 1951; HARDER, 1949; SCHEUNERT and ZIMMERMANN, 1952). Several phenomena which may play a part in the formation of the two types of faeces are discussed: the rapidity of passage through the colon of that material destined for caecotrophic formation (THACKER and BRANDT, 1955), an increased absorption of water, protein and soluble substances during the hard faeces period (BONNAFOUS and RAYNAUD, 1967, 1970) and a different form of transport of the fluid and solid phase of the caecal contents (BJORNHAG, 1972). So far no actual figures for the colon passage time in relation to the type of faeces are available. In 1:he present investigation the passage time from ileum or caecum to excretion was determined under consideration of the formation of hard and soft pellets, with different markers for the fluid and solid part of the digesta being used. Furthermore, the passage time of already formed hard and soft faeces through the distal colon was measured.