Ruminants have the advantage of converting cellulose and food processing industry by-products into valuable products and are thus not serious competitors for human food.
However, they also have the well-known drawback of being inefficient processors. For every 100 g of protein consumed by a dairy cow, no more than 25 to 28 g make their way into the milk. This is a much lower yield compared with other types of livestock, or in relation to the efficiency of nitrogen fertilizer applied to pasture in good conditions. Ruminants are therefore a weak link in the production system. And, unfortunately, that's not all, as ruminant farming is also criticised for the greenhouse gas emissions it produces, methane in particular. So how can the environmental impact of dairy farming be lessened while at the same time producing higher quality milk?
This is the issue addressed by CRA-W and UCL (Professor Y. Larondelle, Professor M. Focant) in the context of a cooperative project with three private-sector companies, subsidised by the Regional Government of Wallonia. The first avenue explored is that of specifically formulated feed that provides exactly what the animal really needs. The use of minor natural ingredients thought to optimise the digestive process or to interact favourably with the digestive microflora is a second line of research. Three rations were therefore tested in a trial aimed at optimising the feed efficiency of dairy cows in full production (30 l/day). Limiting the ration protein content to 13% (as against 16 to 18% in practice) has already increased the cows’ nitrogen efficiency by more than 25% in relation to on-farm observations, and the 35% threshold has been reached. The addition to the ration of two specific plant ingredients duly selected following a battery of in vitro tests has raised the nitrogen efficiency to over 37%. That makes the dairy cow just as efficient as a pig in terms of protein. And those are not the only improvements. It was found that replacing the beet pulp in the control ration with cereals and extruded linseed (with the aim of increasing the health value of the milk via fatty acids) cut the methane emissions by 16% per litre of milk produced, for the same nutritional contribution. These results suggest that there is significant scope for improving ruminants’ nitrogen efficiency and energy efficiency and that there are still good prospects for research in this area, with both economic and environmental benefits to be expected.