Protein efficiency in intensive dairy production: a Swedish example.

BACKGROUND: Animal agriculture has been criticised in terms of its sustainability from several perspectives. Ruminants such as dairy cows can transform inedible, low-quality protein in roughage and by-products from the food industry into the high-quality protein found in milk and meat. Evaluation of the protein conversion efficiency of dairy production from a sustainability and resource perspective must be based on the proportion of the animal feed edible to humans. A relevant metric is thus edible feed protein conversion ratio (eFPCR), i.e. human-edible protein output in cow's milk per unit human-edible protein input in feed. In this study, eFPCR was calculated for five regionally adapted and realistic feed rations fed to Swedish dairy cows producing different annual milk yields typical for high-yielding, intensive dairy production. RESULTS: All scenarios except one showed a protein efficiency ratio of >1 for human-edible protein. Thus, depending on the composition of their diet, most Swedish dairy cows can convert human-inedible protein into edible, high-value protein. However, higher milk yield led to a decrease in eFPCR, regardless of diet. CONCLUSION: Dairy cows in high-yielding, intensive production systems such as those used in Sweden have the capacity to convert low-value inedible protein into high-value edible protein. However, a minor part of the dairy cow diet is edible for humans and this fraction must be minimised to justify dairy production. These results are in line with previous findings on protein conversion efficiency and add scientific input to the debate on sustainable food systems and sustainable diets. © 2017 Society of Chemical Industry.

A systems approach to assess farm-scale nutrient and trace element dynamics: a case study at the Ojebyn dairy farm.

A systems analysis approach was used to assess farmscale nutrient and trace element sustainability by combining full-scale field experiments with specific studies of nutrient release from mineral weathering and trace-element cycling. At the Ojebyn dairy farm in northern Sweden, a farm-scale case study including phosphorus (P), potassium (K), and zinc (Zn) was run to compare organic and conventional agricultural management practices. By combining different element-balance approaches (at farmgate, barn, and field scales) and further adapting these to the FARMFLOW model, we were able to combine mass flows and pools within the subsystems and establish links between subsystems in order to make farm-scale predictions. It was found that internal element flows on the farm are large and that there are farm internal sources (Zn) and loss terms (K). The approaches developed and tested at the Ojebyn farm are promising and considered generally adaptable to any farm.