The growth of the world’s population, combined with increasing prosperity, has resulted in greater demand for animal protein. As suppliers of milk and meat, ruminants are an important factor in supplying that demand. However, their digestive process, which includes fermentation, results in the production of the greenhouse gas methane. It is therefore necessary to be able to estimate the amount of methane they produce, in order to formulate fodder rations for ruminants that reduce the amount of methane emitted. Veterinarian and PhD Candidate Felicidade Macome has used an existing laboratory technique to study the possibility of estimating the amount of methane production, and she compared the results to experiments using dairy cattle.
Macome wanted to know the degree to which methane production in the lab (in vitro) could predict methane production by dairy cattle. Her lab experiments were unique in the sense that they were conducted in conjunction with experiments involving dairy cattle, which meant that the actual methane production was a known factor. In total, the PhD Candidate conducted four in vitro experiments, involving tests of various types of raw fodder: grass silage, fodder maize and common sainfoin (Onobrychis viciifolia, a plant in the legume family).
However, none of these experiments confirmed a relationship between in vitro methane production and the actual methane production observed in the cattle. The combination of in vitro methane production, the chemical composition of the fodder and the various parameters of the total gas production measured in vitro also did not provide an adequate explanation of the dairy cattle’s actual methane production. This means it is not possible to accurately predict the production of methane by dairy cattle based on current in vitro techniques. A new in vitro technique is therefore needed, but it will have to be developed first.