Prediction of the energy value of rabbit feeds varying widely in fibre content

Digestibility trials of 23 pelleted diets, with one or two ingredients and having 8.7 - 53.5% acid detergent fibre (ADF) on a dry matter (DM) basis, were carried out in adult rabbits fed ad libitum. Using a step-wise linear regression approach, the relationship between the digestible energy content (DE) or the coefficient of digestibility of gross energy (dGE) and the chemical composition of diets was established. Excluding beet pulp, with a very high crude fibre digestibility (54.8%), the prediction equations obtained were: DE (MJ kg(-1) DM) = 14.2 - 0.205 ADF + 0.218 EE + 0.057 CP (R(2) = 0.965, RSD = 0.494) and dGE (%) = 83.2 - 1.07 ADF (R(2) = 0.951, RSD = 3.15) where ADF, ether extract (EE) and crude protein (CP) are expressed as a percentage on a DM basis. When diets with level of EE or CP higher than 6% or 18% respectively (grape marc, olive oil cake, brewer's grains, sunflower meal) were also removed, the prediction equations became: DE = 15.9 - 0.219 ADF (R(2) = 0.974, RSD = 0.391) and dGE = 85.6 - 1.20 ADF (R(2) = 0.977, RSD = 2.02). The contents in DE, digestible crude protein and undigestible crude fibre of 21 ingredients are presented and discussed in comparison with other studies.