Inclusion of lactose in dairy cow rations increases dry matter intake (DMI) and milk yield (Garnsworthy 1996). This may be due to the relatively slow rate of lactose fermentation ( Hussain and Miller, 1998) sustaining better regulation of rumen pH and also possible consequence for microbial protein synthesis (Chamberlain et al., 1993).This experiment was conducted to study the changes in rumen environment over the adaptation period and effect of these changes on the fermentation of lactose itself.
Three Suffolk wethers (b.wt 56± 7.36 kg) maintained on hay and concentrate (600:400) were offered 50g lactose per day for 16 days. Rumen liquor collected on dayO (before offering lactose), 4, 8, 12 and 16 was used to measure gas production from sucrose and lactose ( Menke et al., 1979). On these days rumen samples were collected at 0, 1, 2, 4, 6 and 8 hrs after the morning feed. Rumen pH, ammonia N (NH3 N) and volatile fatty acids (VFA) were measured. At 8 hrs time rumen samples were also taken for protozoa enumeration. Data obtained were analysed using ANOVA procedure of Genstat 5.