Feeding willow to lambs: Results from Innovative Farmers field lab

Resource explained

This resource page presents the findings from a recent Innovative Farmers field lab trial conducted by Tom Fairfax at Mindrum Estate, which explored how feeding willow trees to weaned lambs could prevent nutrient deficiencies, improve health, and boost growth.

Cobalt is a trace mineral essential for synthesising vitamin B12 in ruminants. B12 supports energy metabolism and appetite in young animals, helping to promote high growth rates. Willow is known for containing high levels of cobalt, thus potentially cutting the need for supplements such as boluses and drenches. The study hypothesised that incorporating cobalt-rich willow into the lambs’ diet could provide valuable supplementary feed, in addition to offering benefits for shelter, shade, water retention and carbon sequestration.

• This short introductory video outlines the aims and objectives of the trial, and explains the benefits that the field lab model can provide to farmers.
• The final report, published in January 2025, provides a detailed explanation of the methodology, data collection process, and results of the trial.   
• In this end-of-trial webinar, Tom Fairfax discusses the findings of the project and outlines next steps, alongside researcher Dr Nigel Kendall, Soil Association Farming Advisor Tabitha Acton, and Soil Association Agroforestry Advisor Jon Haines.

Findings & recommendations

• The study found that feeding willow leaves weekly to lambs had no measurable impact on growth rates (DLWG) or vitamin B12 (cobalt) status compared to the control group. All lambs began the trial with B12 deficiency, but levels improved across both groups, regardless of willow supplementation.
• The lack of measurable benefits may be due to a range of confounding factors, including limited feeding frequency, pasture diversity, or insufficient quantities of willow.
• Nutrient levels and production outcomes are influenced by a broad mix of environmental, dietary, and management factors.
• Willow is still worth exploring as part of a diverse forage strategy, due to its ability to increase the resilience of marginal systems, high palatability, and rich micronutrient profile.
• Further research is needed to refine how willow can be best integrated into lamb diets. A particular focus should be placed on understanding optimal frequency, quantity, and delivery methods.

Find out more about agroforestry on Tom Fairfax’s farm here.

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