Effect of a reduction of dietary particle size by substituting a mixture of fibrous by-products for lucerne hay on performance and digestion of growing rabbits and lactating does

The effect of a reduction of dietary particle size by the substitution of a mixture of paprika meal, sugar-beet pulp and soya bean hulls for lucerne hay was evaluated in rabbits. Four isonutritive diets were formulated containing a decreasing proportion of large particles (> 0.315 mm) 24.1%, 22.0%, 20.6% and 18.9%. Nutrient digestibility, caecotrophy and caecal traits were determined using 9 growing rabbits per diet. Growth and lactation performance was determined in 45 weanling rabbits and 13 rabbit does per diet, respectively. The diet with the shortest particle size increased by 20% the weight of caecal contents and reduced feed intake of fattening rabbits, lactating does and suckling rabbits (21–30 d of age) by 7%, 10% and 30%, respectively, with respect to the average of the other three diets. It also decreased growth in fattening rabbits, milk production and litter weight at weaning by 6%, 13% and 18%, respectively. Feed efficiency decreased by 7% in rabbit does and was not affected during fattening, as the decrease in performance was parallel to a higher (+ 3%) digestible energy concentration in this diet. Reduction of particle size also increased NDF digestibility and caecal volatile fatty acid concentration. It is concluded that a minimal proportion of large particles (> 0.315 mm) of 20.6% is required to maximise growth and lactation performance in rabbits.