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

Two feeding systems (L, ad libitum vs. R, feed restriction) were combined with three 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 week) of ad libitum intake, thereafter R rabbits had free access to feed. The three feeding plans were: MM plan, M diet with moderate digestible energy (DE) content, 10.6 MJ/kg, during the whole trial; HH plan, H diet with high DE content, 11.1 MJ/kg, during the whole trial; MH plan, M diet during the first three weeks and H diet during the last two weeks. Feed restriction did not affect nutrient digestibility, growth rate on the whole trial and slaughter results, but improved feed conversion (2.96 vs. 2.89 in L and R rabbits, respectively; P<0.01) and reduced N excretion (2.16 vs. 2.07 g excreted N/d, in L and R rabbits; P<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 high energy feeding plan (HH) improved feed conversion (2.97 vs. 2.89 for MM vs. HH; P<0.05), but increased excreted N (2.03 vs. 2.17 g/d; P<0.001) in comparison with the moderate-energy feeding plan (MM) because of the higher DP/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. Besides, N excretion was confirmed to depend largely on dietary nitrogen content.