Effect of dietary supplementation with chestnut and grape pomace extracts on growth performance, nutrient digestibility and meat quality of rabbits

The present study aimed at evaluating the effect of the dietary supplementation with two high-tannin extracts (chestnut vs. grape pomace) at two inclusion levels (0.2% vs. 0.4%) on growth performance, nutrient digestibility, and meat quality in growing rabbits. A total of 270 crossbreed rabbits were randomly divided into 5 experimental groups and fed from weaning to slaughter (30 to 66 d of age) with: control diet (B); diets supplemented with 0.2% or 0.4% of chestnut extract (C2 and C4, respectively), diets supplemented with 0.2% or 0.4% of grape pomace extract (G2 and G4, respectively). The mortality rate was very low (0.4% on average) without differences among groups. Growth performance was not affected by the dietary treatments. In the post-weaning period, the digestibility of crude protein was higher in G2 and G4 groups compared to the C4 group (+2.9%; P<0.001). The digestibility of ether extract was lower in rabbits fed diet C4 compared to the others (P<0.001). In the fattening period, the digestibility of dry matter (+3.1%), fibre fractions and gross energy was higher in rabbits fed diet G4 with respect to the control group (0.05<0.001), whereas the digestibility of crude protein was the lowest with diet C4 (P<0.001). Slaughter weight, cold carcass, and dressing percentage averaged 2664 g, 1618 g and 60.8%, respectively, without significant differences among groups. Meat pH, colour indexes, and oxidative status were not modified by the dietary treatments. In conclusion, both chestnut and grape pomace extracts rich in tannins can be used as feed additives in diets for growing rabbits at inclusion levels ranging from 0.2% to 0.4% without negative effects on growth performance, slaughter results, and meat quality traits. However, the chestnut extract reduced nutrient digestibility at the highest supplementation rate during the postweaning period, whereas grape pomace extract increased nutrient digestibility at both rates in the postweaning and fattening periods.