Abstract

País Grape (Vitis vinifera L.) is an ancestral variety used in Chilean wine industry. It has a higher content of proanthocyanidins than commercial varieties such as Carmenère or Pinot Noir, resulting in País grape marc (PGM) with high contents of condensed tannins. As such, PGM inclusion in ruminant diets would have the potential to reduce enteric methane (CH4) emissions and decrease urinary N excretion. The objective of this study was to evaluate the effects of substitution of mixed hay (MH) with PGM in a high concentrate diet [65% dry matter (DM)] on in vitro dry matter disappearance (IVDMD), ruminal fermentation parameters, gas and CH4 production. Treatments were: T1 (Control) = 20% MH, 15% corn silage, 65% concentrate; T2 = 10% MH, 10% PGM, 15% corn silage, 65% concentrate; T3 = 20% PGM, 15% corn silage, 65% concentrate. The study was a randomized complete design with 3 treatment and 3 replicates, incubated for 24 h at 39º C. Data were compared by Tukey test and polynomial contrasts. There was a linear reduction in NH3-N (P = 0.001) as dietary PGM increased. Inclusion of PGM reduced NH3-N by 50% when added at 10% DM, and 71.7% at 20% DM. However, there also was 4% reduction in IVDMD (P ≤ 0.001) and gas production (P = 0.012) in the 20% GM diet. There were no treatment effects (P ≥ 0.05) on CH4 production or yield. Fermentation efficiency determined by the partition factor increased linearly (P = 0.013) as PGM inclusion increased, suggesting that it increases organic matter to be degraded. Based on this study it could be concluded that PGM is an alternative source of fiber for ruminants on concentrate diets, as it can result in improved rumen fermentation efficiency and a substantial reduction in ruminal ammonia nitrogen concentration (NH3-N).