Effect of type of lucerne hay on caecal fermentation and nitrogen contribution through caecotrophy in rabbits.

Seventy-five New Zealand White x Californian rabbits were used to study the influence of the chemical composition of lucerne hay on caecal and caecotrophy characteristics. Five lucerne hays varying in chemical composition were ground and formed into pellets. These were the sole form of nutrition during the experiment. The type of lucerne hay did not affect caecal volatile fatty acid concentration, pattern of fermentation of pH. However, the caecal ammonia concentration decreased linearly (by 30% between extreme diets, P = 0.002) when dietary fibre proportion increased. The weight of caecum and caecal contents increased linearly (by 12%, P = 0.010, and 35%, P < 0.001, respectively, between extreme diets) with dietary fibre proportion. Soft faeces excretion and contribution of soft faeces to dry matter intake were not influenced by the type of lucerne hay. The proportion of caecal content that appeared daily as soft faeces and the total and microbial nitrogen concentrations in soft faeces were higher (42, 14 and 39%, respectively) for the lucerne hay with the lowest dietary fibre proportion than for the average of the other hays.