Energy, protein and fibre digestibility of sunflower hulls, olive leaves and NaOH-treated barley straw for rabbits

Abstract

One hundred and sixty nine New Zealand White x Californian rabbits were used to determine the nutritive value of sunflower hulls, olive leaves and NaOH-treated barley straw. These feedstuffs were substituted at 6, 12, 18 and 24% in a basal diet formulated for a high energy and protein content. Digestible energy (DE) values calculated by difference for the highest substitution levels (18 and 24%) were 4.77(±0.32), 6.16(±0.37) and 4.10(±0.32) MJ kg· DM for sunflower hulls, olive leaves and NaOH-treated barley straw, respectively. Standard errors of these estimations decreased with level of substitution (by 83% on average from 6 to 24% of inclusion level). Crude protein digestibility values obtained were not consistent due to its high standard errors (±48 as average). The values estimated for neutral detergent fibre digestibility (%) were relatively low and had also high standard errors: 10.7(±5.70); 7.76(±7.89) and 5.76(±6.14) for sunflower hulls, olive leaves and NaOH-treated barley straw, respectively. An stepwise regression equation to predict DE value of fibrous feeds was developed from data of this work and from literature using as independent variables ash, CP, crude fibre (CF), ether extract (%DM) and gross energy. The equation obtained was: DE (MJ kg^-1 DM)= 14.46 (±1.10) - 0.23(±0.032) CF (R²=0.781; RSD=1.43; P<0.001 ).