The effect of including palm oil sludge in cattle diet (silage) was conducted in vitro in order to ascertain the suppressing effect on ruminal methanogenesis. The silage used for the study was Panicum maximum, Centrocema pubscens, Bracharia decumbens and Andropogon gayanus. The silage were cut into an average size of 3 to 5 cm and ensiled for 21 days. Four treatment diets were formulated with the silage by including palm oil sludge at 0, 10, 20 and 30%, respectively. Treatments were subjected to anaerobic digestion in 10 L bio-digesters. Total gas production, percentage methane production, volatile fatty acids and microbial population of the substrate were measured. Total gas production was significantly suppressed in the treatment having 30% palm oil sludge for about 25 days while a lag phase of 16 days was observed before a significant amount of methane was detected. Acetic acid production increased only in T1 on the first week while T2, T3 and T4 decreased after which their production remained irregular until the end of the experiment. Propionic acid production also increased in T1 and T4 on the first week while T2 and T3 decreased after which their production maintained an undefined pattern as the experiment progressed. Butyric acid production increased in T1, T2, and T4 on the first week while T2 decreased after which an undefined trend of production was established. Microbial population especially methanogens also reached its peak around the same period when there was maximum gas production. It was concluded that ruminal methanogenesis can be suppressed in-vitro by the inclusion of 30% palm oil sludge in the silage.

 

Key words: Bio-digesters, fermentation, in-vitro, methane, silage.