In vitro Estimation of Gas and Methane Production from Locally Available Feed Stuffs and Rumen Content

Enteric fermentation is a major source of greenhouse gases emission from ruminants. Among other factors, the nature of the feed consumed by ruminants determines the amount of gas produced. In vitro gas production techniques simulate the rumen fermentation process and they have been used to evaluate the gas production potential of feedstuffs. Thus, an in vitro based gas production technique was employed to estimate overall gas and methane production potential of 12 commonly available local feedstuffs in and around Mekelle, and rumen content inoculum collected from Abergelle export abattoir. Both feed and rumen content substrates were inoculated with strained rumen fluid from slaughtered cattle and an equal amount of tap water was added, then follow-up was made for 24 hrs to measure gas production. A sequence of gas measurement was taken at 3, 6, 9, 12, 15 and 24 hrs post incubation by observing the calibrated syringes. The gas production showed a declining trend as the time of incubation increased. In feed substrates, a relatively high amount of gas production was observed at 6 hrs of incubation (9.27+1.92) followed by 3 hrs (7.03+1.71). The overall mean gas and methane produced from rumen content samples was higher at 12 hrs of incubation (6.57+15.15) and (2.57+5.92), respectively. The mean gas produced from each of the feed substrates showed a statistically significant variation (p=0.0012), where there was a relatively high amount of gas production in wheat bran (48.33+18.35) followed by commercial alfalfa hay (42.50+26.61). On the contrary, pods of Faidherbia (F.) albida scored the least gas production (0.83+2.04) followed by molasses (4.17+ 10.21). The incubation time effect on total gas and methane production was apparent at 6 hrs being the maximum, (p=0.0097). The mean gas production of young animals was higher (30.73±21.99) than that of adult animals (18.00±20.18). Feed manipulation is one strategy to mitigate emission of greenhouse gases from ruminants. Thus, it is recommended to supplement ruminant feed with seeds of F. albida and molasses to reduce the emission of gases as the gas production from these feed sources is low. Further experiments should also be conducted using in vitro and in-vivo techniques to better understand the emission potential of locally available feedstuffs.