Compost-sourced substances (SBO) as feedstuff additives in rabbit production

• SBO feed addition improve eco-friendly practices.
• Effects on live and slaughtering performance were determined.
• SBO addition increase intestinal absorption area and do not affect meat quality.
• Low level of SBO supplementation affect digestibility and caecum microbiology.
• SBO promote aggregating effect on feed particles.

Acid soluble bio-organic (SBO) substances have been extracted from plant bio-waste. The SBOs have been tested as feed additives for reared animals. Two trials (T1 and T2, lasting 63 and 56 days, respectively) were carried out to evaluate the effect of different doses of SBOs as feed additives in diets for fattening rabbits (131 and 120 animals from 35 days of age, respectively) and as binders for the manufacturing of diet pellets to improve their physical properties. The effect of different SBO doses (0, 0.5, 2.5 g/kg for T1 and 0, 5, 10 g/kg for T2) on the growth performance, health status, diet digestibility, carcass and meat traits of rabbits was studied. The aggregating effect of SBOs on feed particles during pelleting was studied by adding 50 and 100 g/kg of SBOs to a feed, and then measuring the shear and compression force on the pellets. The results have shown that SBO supplementation of rabbit diets at a concentration of 0.5–10 g/kg does not affect the live and slaughtering performances, except for the intestinal tract absorption area (higher in the intestines of rabbits fed with a high supplementation of SBO; P < 0.05) or the dry matter, organic matter, ether extract, fibre and gross energy apparent digestibility of the feed (lower in diets with low or no supplementation of SBO; P < 0.05). The rabbits fed with the lower SBO dose showed higher values of total anaerobic bacteria and Bacteroides (P < 0.05) and a higher cadmium meat content (P < 0.05) in T1 and T2 than all others groups. SBOs included at concentrations of 10 and 20% were also found to affect the physical properties of the pelleted feed. These pellets are more resistant to shear (P < 0.05) and compression force (P < 0.01) in the presence of added SBO. It can be concluded that SBO may be used as a feed additive for rabbits, without any adverse effects on animal productivity and health, as well as to improve the physical properties of pelleted feeds.