Several roads lead to Rome: about improving nitrogen efficiency in cattle

Intensive livestock production is facing important environmental and societal issues, which will force the sector into a transition towards better and more efficient use of nitrogen (N) in their production cycles. In ruminants, optimizing N and protein efficiency is about minimizing losses of N in the rumen. This can be done by reducing protein degradation in the rumen and/or increasing the utilization of N by the ruminal microbial population. There are several roads to do so: intelligent forage combinations, improving forage quality (selection, crop techniques), use of rumen escape protein sources, complementing low crude protein diets with rumen escape amino acids. Beside the nutritional strategies, the environmental challenges for livestock force the sector to further improve N efficiency by other means such as closing N loops at farm level, culturing more N efficient crops on their arable land and further improving overall productivity of the herd. Despite the importance of the N efficiency, the sector needs to be evaluated in a broader perspective by considering the human edible protein output in relation to the amount of human edible feed input. It is well-known that the transformation by ruminants of human in-edible feed into human edible food, valuable proteins and other nutrients, is an important step in the food chain. When evaluating the dairy sector one should look for an optimum combination of efficiencies at all levels (cow, farm and complete system).