Effect of polyethylene glycol on in vitro gas production of some non-leguminous forage trees in tropical region of the south of Mexico

The objective of the current study was to evaluate the chemical composition and the in vitro gas production (GP) of some non-leguminous forage trees in presence or absence of polyethylene glycol (PEG). Guazuma ulmifolia, Crescentia alata, Ficus glabrata, Ficus cotinifolia, Spondias purpurea, Mangifera indica, Licania arborea, Simira mexicana were collected during the rainy season, in the Bejucos locality, State of Mexico. Metabolizable energy (ME), partitioning factor (PF24h), in vitro organic matter digestibility (OMD), short chain fatty acids (SCFA) and microbial biomass production (MBP) were estimated as tools to detect the adverse effects of tannins in tree foliage. The chemical composition data were analyzed in a random design, and the in vitro digestion parameters on a randomized design with 8 × 2 factorial arrangement. Chemical composition showed a wide variation (P < 0.05) between species. The use of PEG increased (P < 0.05) GP from the foliage of S. purpurea, L. arborea, F. glabrata and G. ulmifolia, showing activity of total phenolics and condensed tannins. Similarly, ME (5.9 MJ kg−1 DM), OMD (354.5 g kg−1 DM) and SCFA (2.3 mol/150 mL) increased (P < 0.05); it was higher for S. purpurea, because of the PEG addition effect. The PF24h and MBP were different between species (P < 0.05), and decreased due to PEG addition (P < 0.05); the species with lower production was S. purpurea. It could be concluded that S. purpurea and F.cotinifolia represent important sources of fodder for livestock in the south region of Mexico.