Making better use of dietary protein would reduce the environmental impact of dairy farming and increase farm profitability. One way to do this is to target supplemental protein at specific periods of the cow’s lactation cycle. Specifically, providing extra protein just in diets provided during the first few weeks after a cow has calved may have longer term benefits for the efficiency of protein use and the production of milk protein. This has been demonstrated under controlled experimental conditions, and we now plan to test this idea using feedstuffs that could be used in practice on UK dairy farms.