Low protein diets based on high protein forages

Rationale and aims

The combined effects of an increasing global price of soya bean meal and tighter regulations on the disposal of cattle manure and slurry has led to renewed interest in alternative dietary protein strategies for dairy cows. Previous studies (link) showed that, in maize silage-based diets, dietary protein levels can be reduced to around 140-150 g/kg DM without any major impact on performance, health or fertility if the diets are formulated appropriately to maximise ruminal microbial protein synthesis. An alternative approach to dietary protein reduction is to increase the utilisation of high protein home grown forages (i.e. legumes). Findings from AHDB-funded work (link) showed that milk performance was similar when lucerne replaced maize or grass silage. In combination, both sets of studies have demonstrated that significant savings in feed costs can be achieved without impacting on performance, health or fertility. However, the impact of low protein diets (e.g. 140 g/kg DM) based on high protein, home grown forages such as red clover, lucerne or good quality grass silage is not known. Such dietary conditions are expected to have an excessive degradable protein content and this imbalance may be particularly relevant to higher yielding cows where the dietary contribution of by-pass protein is more important. As a consequence, reducing the dietary protein concentration in legume based diets may decrease intake and performance compared to maize silage or lower protein grass silage based diets.

The aim of this research is to investigate

a)     The impact of reducing protein in diets based on high-protein legume silage (red clover and lucerne)

b)     The means to mitigate any reduction in performance and determine the effects on health and fertility.

Expected outcomes

  • Advice to dairy farmers on how to reduce the requirement for purchased protein such as soya bean meal by the combination of growing high protein forage and feeding lower protein levels.
  • The effect of these diets on intake, milk yield and composition and body tissue mobilisation, diet costs, N digestibility and efficiency of N use.
  • The efficacy of strategies to mitigate any reduction in intake or performance from feeding low protein/high forage legume diets.
  • Subsequent effects of low protein, high protein forage diets on health, fertility and lameness.
  • Cost-benefit analysis of low protein diets based on high protein forages, including a sensitivity analysis of the changes in purchased feed costs and fertiliser N, and breakeven points determined.

Start Date             

September 2018

Completion Date
September 2021

Lead Investigator
Harper Adams University


AHDB Dairy

For further information please contact: martina.dorigo@ahdb.org.uk or call 024 7647 8632


*This project is part of the Research Partnership II between AHDB Dairy and the University of Nottingham (Lead Contractor). Other subcontracted investigators and delivery partners within the Research Partnership are: Harper Adams University, SRUC, RVC.

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