The main component affecting methane production is the type of carbohydrate and relative rate of fermentation. Kreuzer et al. (1986) found signi®cantly lower methane loss (total as well as % of GE) on rations with native starch than rations with cellulose. Johnson et al. (1993) showed that there was decreased methane production with increased energy intake, when expressed as percent of GE. Methane production do fall from a level of 6±7% of energy intake when forages are fed at maintenance to as low as 2±3% when high grain concentrates are fed at near ad libitum intake levels (Johnson and Johnson, 1995). Although fed approximately at maintenance during experimental study, the intakes were found to be exceeded far towards achieving positive balance. Van Soest (1994) indicated that a high grain diet and or the little addition of soluble carbohydrate with resulting shift in the fermentation pattern in the rumen are associated with a more hostile environment for methanogenic bacteria in which a passage rates are increased, ruminal pH is lowered and certain population of protozoa, ruminal ciliates and methanogenic
Table 5 Methane production in sheep fed on rations with varying roughage and concentrate (R : C) ratios
Methane production Treatmentsa SEMb
92R : 8C 50R : 50C 30R : 70C
As % of gross energy* 3.93 b 3.34 ab 2.98 a 0.12 As % of digestible energy* 7.02 b 5.62 a 4.87 a 0.18 l/day 14.8 15.7 13.6 0.52 g/day 10.6 11.2 9.7 0.37 g/100 g digestible DM* 2.10 b 1.76 a 1.46 a 0.06 g/100 g digestible OM* 2.20 b 1.84 a 1.54 a 0.06 g/100 g digestible CHO* 2.65 b 1.88 a 1.62 a 0.08
a Means bearing different letters in a row differ signi®cantly. b Standard error of means. * p < 0.05.
296 Chandramoni et al./Animal Feed Science and Technology 83 (2000) 287±300
bacteria may be eliminated or inhibited. In present study also total energy intake was signi®cantly higher in groups II and III than in