Digestibility and metabolic utilisation of diets containing chestnut tannins and their effects on growth and slaughter traits of heavy pigs

This research aims at evaluating the effects of the dietary addition of a supplement containing 75% of chestnut tannins (CT) on growth performance, slaughter traits (Exp. 1) and on nutrient utilization (Exp. 2) of Italian heavy pigs. Experiment 1 compared a control (C) diet with diets containing 0.15 or 0.30% of CT supplement. Forty-two barrows (91±6 kg of BW) were divided into pairs and kept in 21 partially-slatted pens equipped with individual feeding (7 pens/diet). Animals were slaughtered at a BW of 174±6 kg. The CT inclusion did not modify the performance and the slaughter traits but lowered the intensity of red colour (P<0.05) and brightness (P<0.05) of the gastric mucosa. Experiment 2 measured digestibility of nutrients, N balance and energy utilization of a C diet compared with low protein diets containing 0 or 0.53% of CT supplement (LP and LPT, respectively). Eighteen barrows (BW 153±4 kg) were housed in 6 metabolic cages in 3 periods of 14 days, with 6 animals per diet. LPT pigs produced less urine than LP (2132 vs 2561 g/d, P<0.05) and both were lower than C (2978 g/d, P<0.05). LP and LPT diets had similar digestibility (87.6 vs 87.8 % for DM, and 85.1 vs 83.9 % for CP). N and energy balance were similar among all diets (34.8, 39.0, 39.2% retained N, and 37.6, 35.7, 37.3% retained energy, for C, LP and LPT, respectively). In conclusion, tannins do not exert anti-nutritional effect at the concentrations applied.