Objective

:To evaluate the in vitro methane production in forage resources and their mixtures, used in cattle feeding in the high Andean tropic of Nariño, Colombia.

Materials and Methods

:Three forage shrubs, from a forage bank of Tithonia diversifolia (Hemsl.) Gray, Sambucus nigra L. and Smallanthus pyramidalis (Triana) H.Rob (70 days old); two grasses, Cenchrus clandestinum (Chiov.) and Lolium perenne L. (37 and 28 days), and four mixtures of these forage shrubs and grasses, were evaluated. Representative samples of the forages and their mixtures were analyzed, at 24 and 48 hours of incubation, to evaluate the methane production, dry matter degradation and production of volatile fatty acids. The information was processed through a variance analysis and by Tukey’s mean comparison test.

Results

:The concentration of secondary metabolites and tannins was numerically higher in the forage species S. nigra (22,1 g/kg DM) compared with the grass C. clandestinus (8,9 g/kg DM). The highest DM degradation percentages (p< 0,01) were obtained in S. nigra (70,6 %), T. diversifolia (70,2 %) and L. perenne (71,6 %). C. clandestinus (87,2 mL) recorded the highest methane production and T. diversifolia, the lowest one (34 mL CH4/g DM). In the mixture of L. perenne + S. nigra the highest degradation was found (78,3 %). The lowest methane production was for C. clandestinus + S. nigra (p < 0,01).

Conclusions

: Higher concentration of secondary metabolites was found in the forage shrubs with regards to the grasses. When 20 % of the forage species was included in the mixtures, methane production decreased and substrate degradability increased.

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