Evaluation of in vitro energy distribution and methanogenic potential of two forages with the addition of condensed tannins

ABSTRACT.

The objective of this work was to analyze the effect of the addition of condensed tannins (CT) in the efficiency of digestion, methanogenic potential and energy distribution between the fermentation products of two forages. An assay was carried out using the in vitro gas production technique in which extracts of Quebracho (Schinopsis balansae) and Lotus corniculatus were evaluated with fermentation patterns of derived products from Ryegrass (RG, Lolium perenne) and a tropical forage, Megathyrsus maximus (MM). Tannins were added to the substrate at a concentration of 30 mg g^-1. MM presented higher and delayed gas production (GP), and in vitro dry matter, organic matter and fiber digestibilities (ivDMD, ivOMD and NDFD, respectively) were relatively high but lower than RG. In addition, MM presented higher CH₄ production (CH₄p) than RG in 24 and 48h. Even though CT of Quebracho induced a decrease in the NDFD, contrary to what was expected, CH₄p was greater, although this effect could not be attributed to the presence of CT. The stoichiometric evaluation indicated that while the highest CH₄p in Quebracho treatments were associated with acetogenic profiles, CH₄p with Lotus did not show any relationship with the volatile fatty acids (VFA) profile, but it did show a relationship with the highest total VFA production and the highest GP.

Keywords:
secondary compounds; methane production; in vitro gas production; ryegrass; Megathyrsus maximus