Comparison of different in vitro digestibility methods for nutritive evaluation of rabbit diets.

Seven simplified experimental diets for rabbits with a wide range of acid detergent fibre content (87 to 525 g kg· dry matter) were used to compare three different in vitro techniques for evaluating their dry matter and organic matter digestibilities, based on the use of mullienzyme, caecal or faecal inocula. The multienzyme method always resulted in higher in vitro dry matter digestibility values (P<0.001) than those methods based on the use of digestive tract inocula. The prediction equations for dry matter digestibility obtained with the multienzyme and caecal in vitro techniques showed higher precision (r2 = 0.95 and 0.88, respectively) and lower variability (se: 4.32 and 6.58, respectively) than that based on the chemical composition (r2 = 0.80 and se = 8.34), while the method using faecal inocula showed lower precision and variability (r2 = 0.68 and se = 10.64). Repeatability was good for the three techniques (0.38 to 1.05), although the multienzyme method was significantly better (P<0.05). However, the caecal and faecal in vitro methods showed clearly poorer results for reliability (P<0.001) than the multienzyme technique (2.61, 2.65 and 0.71 for dry matter digestibility prediction, respectively).