Effect of dietary soluble fibre and n-6/n-3 fatty acid ratio on growth performance and nitrogen and energy retention efficiency in growing rabbits

• Published in: Animal feed science and technology 2018-05, Vol.239, p.44-54
• Main Authors: Delgado, R., Nicodemus, N., Abad-Guamán, R., Sastre, J., Menoyo, D., Carabaño, R., García, J.
• Format: Article
• Language: English
• Subjects: Digestible energy and nitrogen retention efficiency; n-6/n-3 fatty acid ratio; Rabbits; Soluble fibre
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/j.anifeedsci.2018.03.006

•Soluble fibre improved the health status of rabbits.•Soluble fibre increased nitrogen and energy retention efficiency.•The reduction of n-6/n-3 ratio had no influence on the health status of rabbits.•Reduction of n-6/n-3 ratio improved nitrogen and energy retention efficiency. The aim of this work was to study whether the dietary supplementation with soluble fibre (SF) and the reduction of the n-6/n-3 fatty acid ratio or the combination of both influence the growth performance and digestible nitrogen and energy (DN and DE) retention efficiency in rabbits from 27 to 62 d of age. Four diets in a 2 × 2 factorial arrangement were used with two levels of SF (7.8 vs. 13.0%, on DM basis, LSF vs. HSF) and two different n-6/n-3 ratio (13.4/1 vs. 3.5/1, Hn-6/n-3 vs. Ln-6/n-3). Nitrogen and energy retention in the body and in the carcass were determined by bioelectrical impedance. The increase of SF reduced the mortality (38.3 vs. 24.1%; P = 0.018), with no effect of the n-6/n-3 ratio. The feed efficiency in the whole experimental period (27–62 d of age) improved with the increase of the level of SF (+3.5%; P = 0.003) and the reduction of the n-6/n-3 (+2%; P ≤ 0.048). The increase of SF decreased the ratio DN/DE (-2%; P = 0.035). The increase of SF and the reduction of the n-6/n-3 ratio reduced the DN intake (-4%. P ≤ 0.030). However, the amount of nitrogen retained in the body or in the carcass was not affected by treatments (P ≥ 0.26). Consequently, the increase of dietary SF and the reduction of the n-6/n-3 ratio improved the retention of DN in the body and in the carcass (between 3.4 and 5.4%. P ≤ 0.017). It was associated with a reduction of the urinary nitrogen excretion in HSF respect to LSF groups (−13%; P = 0.004) and in Ln-6/n-3 respect to Hn-6/n-3 groups (-12%; P = 0.006). In contrast, the increase of SF increased the faecal nitrogen excretion (+5%; P = 0.004). Treatments had no effect on DE intake and on body and carcass energy retention (P ≥ 0.13). The increase of SF improved the body and carcass DE retention efficiency (+3%. P ≤ 0.042). It was mainly due to the impairment observed in rabbis fed LSF_Hn-6/n-3 respect to those fed LSF_Ln-6/n-3 diet (P = 0.071). In conclusion, the increase of SF improved the survival of fattening rabbits, with no influence of the n-6/n-3 ratio, and both factors especially improved the efficiency of DN but also the DE retained in the body and in the carcass.