Effect of feed restriction and feeding plans on performance, slaughter traits and body composition of growing rabbits

Abstract

Two feeding systems (L, <em>ad libitum vs. </em>R, feed restriction) were combined with 3 feeding plans (MM, MH, HH) to evaluate the effects on performance, slaughter results, body composition and nitrogen balance of 300 commercial crossbred rabbits kept individually from weaning to slaughter (34-70 d of age). The R rabbits were fed from 80% (first days on trial) to 100% (end of 3rd wk) of <em>ad libitum </em>intake, whereafter R rabbits had free access to feed. The 3 feeding plans were: MM plan, M diet with moderate digestible energy (DE) content, 10.6 MJ/kg, throughout the trial; HH plan, H diet with high DE content, 11.1 MJ/kg, throughout the trial; MH plan, M diet for the first 3 wk and H diet for the last 2 wk. Feed restriction did not affect nutrient digestibility, growth rate on the whole trial and slaughter results, but improved feed conversion (2.96 <em>vs. </em>2.89 in L and R rabbits, respectively; <em>P</em>&lt;0.01) and reduced N excretion (2.16 <em>vs. </em>2.07 g excreted N/d, in L and R rabbits; <em>P</em>&lt;0.05). At the end of the first period (55 d), R rabbits showed lower empty body protein, lipid, and gross energy gains than L rabbits, but differences disappeared within the end of the trial. The HH plan improved feed conversion (2.97 <em>vs. </em>2.89 for MM <em>vs. </em>HH; <em>P</em>&lt;0.05), but increased excreted N (2.03 <em>vs. </em>2.17 g/d; <em>P</em>&lt;0.001) in comparison with the MM plan due to the higher digestible protein/DE ratio of H diet, whereas the MH plan showed intermediate results. In conclusion, a moderate feed restriction during post weaning improved feed conversion and reduced N excretion without negative effects on growth or slaughter results. Moreover, N excretion was confirmed to depend largely on dietary nitrogen content.