Effect of inclusion of distillers dried grains and solubles from barley, wheat and corn in isonutritive diets on the performance and caecal environment of growing rabbits

To evaluate how the dietary inclusion of distillers dried grains and solubles (DDGS) could affect the performance and caecal environment of growing rabbits, four experimental diets were formulated from a control diet without DDGS (C), including 20% of barley DDGS (Db20), 20% of wheat DDGS (Dw20) and 20 (Dc20) or 40% (Dc40) of corn DDGS. Animals had free access to medicated versions of the diets until 49 d, and then to unmedicated diets until 59 d of age. The performance trial was done using 475 three-way crossbred weaned rabbits of 28 d of age, individually housed in 5 batches. Caecal fermentation traits were determined in 20 animals per diet and at 42 d and at 59 d of age. No significant effect of the growing diet on mortality, morbidity or sanitary risk index was observed. In the whole period and respect to the control group, animals fed with Db20 showed higher dry matter (DM) and digestible energy (DE) intake (+6 and +12%, respectively; P<0.05), but similar daily weight gain (DWG) and increased feed conversion ratio (+9%; P<0.05). Similarly, and regardless of its inclusion level, the increase in DE intake of animals fed with corn DDGS (+9, respectively; P<0.05) did not increase DWG. In contrast, higher DM and DE intake of animals fed with Dw20 (+8; P<0.05) resulted in a higher DWG (+2.8 g/d; P<0.05) than those fed with C. Although inclusion of DDGS at 20% did not affected main caecal parameters controlled at 42 d, caecum of animals fed with the diet Dc40 was characterized by greater N-NH3 and valeric acid and lower total volatile fatty acids and acetic acid concentrations than the average of the other groups (on av. +5.2±1.7 mmol/L, +0.29±0.07 mol/100 mol, –17.17±4.41 μmol/L and –2.60±0.99 mol/100 mol, respectively; P<0.05). At 59 d of age, higher caecal DM, and propionic and valeric acid concentration and lower values of total volatile fatty acids and acetic/propionic rate were observed for DDGS inclusion at 20% compared to the control (+1.6±0.5%, +0.95±0.44 mol/100 mol, –9.3±4.3 μmol/L and –2.7±1.2, respectively; P<0.05). Linear inclusion of corn DDGS increased caecal DM, propionic acid proportion and total volatile fatty acids concentration and reduced acetate/propionic rate (+4.0±0.4%, +2.27±0.41 mol/100 mol, –21.27±3.9 μmol/L and –5.6±1.1, respectively for Dc40 compared to C; P<0.05). Rabbits given Dc40were also characterized for a greater caecum N-NH3 content than the other groups (on av. –8.7±1.7 mmol/L; P<0.05) at 59 d of age. The results of the present work reveal that inclusion of DDGS up to 20%, independently of the grain source (barley, wheat or corn), could be an interesting alternative in balanced diets for growing rabbits.