The use of recycled oils from the food industry in growing rabbit feeds in substitution of fresh oil does not affect performance

The effects of including 30 g of recycled frying oil per kilogram of diet on the performance of growing rabbits were studied. A batch of vegetal oil was used, fresh (FO) or recycled (RO) after being used in industrial frying, and then heated at 165–170 °C for 8 h. In Experiment 1, 24 rabbits aged 42 days were used to determine apparent digestibility coefficients (CTTAD) of main nutrients (dry matter, organic matter, crude protein, ether extract, neutral detergent fibre and acid detergent fibre). In Experiment 2, 230 weaned rabbits were used to record rabbit performance between 28 and 63 days. In Experiment 3, 16 rabbits were slaughtered at day 63 to study caecal fermentation traits (pH, dry matter content, NH3 and volatile fatty acids) and serum markers of hepatic (gamma glutamyl transferase, aspartate aminotransferase, alanine transaminase and alkaline phosphatase) or renal (urea and creatinine) damage. The inclusion of RO in the diet in substitution of FO did not affect nutrient digestibility, growth performance, fermentation pattern in the caecum or concentration in serum of diverse enzymes and metabolites related to hepatic or renal functioning (P>0.10). Nevertheless, the use of RO increased the CTTAD of the aNDFom and ADFom (P<0.05), the acetic to propionic ratio in the caecum (from 18.1 to 26.1; P<0.10) and the concentration of creatinine (from 0.75 to 82 mg dl−1; P<0.10). Therefore, recycled frying oil can be used at levels of up to 30 g kg−1 in substitution of fresh oil in diets for fattening rabbits.