In vitro gas production from buffel grass (Cenchrus ciliaris L.) fermentation in relation to the cutting interval, the level of nitrogen fertilisation and the season of growth

Microbial fermentation, measured by the gas produced in vitro incubation, was evaluated in samples of buffel grass (Cenchrus ciliaris) from a previous study performed in Maracaibo (Venezuela), where the effects of nitrogen soil fertilisation (0, 75 or 150 kg N/ha), age of cutting (21, 28 or 35 days) and season of growth (from September to November or from April to June) were studied in a 3×3×2 factorial design. Soil fertilisation had small effects on either forage chemical composition or microbial fermentation. Buffel grass grown in September–November had less N content (P<0.05), but promoted a higher gas production (P<0.05) and a faster rate of fermentation from 6 to 48 h (P<0.001) than that grown in April–June. Season of growth also influenced the comparison among cutting intervals. In September–November, N proportions diminished with the age of cutting, total gas production was lower at 21 days cut (P<0.05) and there were no differences in the rates of fermentation. However, in April–June, the cut at 28 days had a higher N content and lower rates of fermentation than the other cutting ages, and total gas production was higher at 21 days than at 28 or 35 days.