LAUSR

Abstract Despite substantial advances in animal production efficiency over the last 40 years, feed still represents the majority of production costs. The negative impacts of animal production on the environment must be reduced, which implies a reduction of nutrient losses to the environment associated with animal production. Feed efficiency, mostly expressed as feed conversion ratio (FCR), is a key indicator to judge the financial and environmental performance of a farming system. In intensive rabbit breeding, the average farm FCR (maternity + fattening units) in European farms improved from 3.8 to 3.4 during the past 15 years. This translates into a drop in nitrogen and phosphorus output of approximately 10%. This improvement can be attributed to progress in health control, nutritional factors and strategies, management and genetics. To optimize rabbit farm FCR, the reproducing stock as well as the fattening unit must be considered. This review summarizes the impact of different strategies to optimize FCR under intensive production conditions, where rabbits are exclusively fed a pelleted diet. High performing reproduction stock results in a lower FCR in maternity. The use of diets with nutrient levels to optimize digestive health, together with an appropriate feeding restriction after weaning, leads to minimal losses and has a large impact on the FCR. If the different fiber requirements are met, an increase of the dietary energy level, especially in the finishing stage, reduces the FCR by approximately 0.15 points, for an increase of 0.5 MJ DE. Future possibilities for genetic selection for feed efficiency are based on improvements to the residual feed intake. It seems possible to improve feed efficiency further by reducing feed intake without affecting weight gain. Such a genetic improvement would reduce both feed input (reducing costs) and output (reducing environmental impacts). An average farm FCR of 3.0, similar to that of pig breeding, can be reached in the next decade for rabbit meat production.