Feed the green for a sustainable and protein-efficient dairy production

Abstract

CONTEXTIn modern intensive dairy farming, cows are increasingly held indoors and fed arable crops instead of grass to maximize individual animal performance. This leads to environmental issues such as high farm-level nutrient surpluses and loss of grassland plant species diversity as well as a growing competition between food and feed. OBJECTIVEWe conducted this study to define a threshold of concentrate supplementation that ensures a net contribution to the protein supply and evaluate the environmental performance of dairy farms when this level of supplementation is shifted. METHODSIn a first step, we calculated the hePCR (human-edible protein conversion ratio) of 52 dairy farms across a pedo-climatic gradient with varying feeding strategies. Based on farm management data and vegetation surveys, we analyzed the relationship between hePCR and different components of environmental and productive performance, with special interest on farm nutrient balances, grassland biodiversity and grass-based milk production. RESULTS AND CONCLUSIONSOur results show that higher concentrate supplementation levels significantly reduce the efficiency of converting plant protein into food. A critical threshold was identified at a concentrate milk proportion of 30 % or 177 g of concentrate feed per kilogram of milk produced, beyond which net protein contribution shifts to net consumption. Furthermore, we show critical interlinkages between a high protein efficiency and an enhanced environmental performance of the farms, such as higher grassland Shannon diversity and reduced nutrient surpluses. Our study suggests grass-based dairy farming as an integrated solution for enhancing net protein output while simultaneously safeguarding critical ecosystem functions. SIGNIFICANCEWe are in urgent need of sustainable agricultural practices that align an efficient food production with the reduction of negative environmental impacts. Our study is the first that shows direct positive interlinkages between the protein conversion efficiency of dairy farms and their environmental outcome as based on multi-annual management data and comprehensive vegetation surveys.