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Phil Garnsworthy

Head of Division of Animal Sciences and Professor of Dairy Science, Faculty of Science



Prof Phil Garnsworthy

Head of Division of Animal Sciences and Professor of Dairy Science

Phil's research encompasses all aspect of dairy science with particular emphasis on nutrition.

Current research projects include:

  • Feed efficiency and sustainability of dairy systems
  • Variation in methane emissions by individual dairy cows measured on-farm
  • Nutritive value of co-products from the bioethanol industry
  • Rumen function in relation to the microbiome, the cow genome, and digestive efficiency
  • Manipulation of milk fatty acid profile by nutrition and genetics
  • Nutritional strategies for enhancing dairy cow fertility

Research Summary

Nutrition of Dairy Cows

Phil's main area of interest lies in the nutrition of dairy cows and how to maximise efficiency of feed utilization for milk production without compromising reproductive performance, thereby minimising environmental impact.

Phil leads a £2.5m Research Partnership funded by DairyCo, the UK dairy industry body, investigating Animal Health, Welfare and Nutrition. Partners in the project are the Nottingham Vet School, Harper Adams University College, RVC, Bristol University, SAC and IBERS. For information, see

Phil sits on the management committee of the methane programme within the Agricultural Greenhouse Gas Research Platform project. This is a new research programme with a total investment of £12.6 million, funded by Defra and the devolved administration governments. It seeks to improve the accuracy and resolution of our reporting system by providing new experimental evidence on the factors affecting emissions and statistics relevant to changing farming practices in the UK. See

Phil is a partner in the 7.7m Euro EU FP7 project RuminOmics, which will connect the animal genome, gastrointestinal microbiomes and nutrition to improve digestion efficiency and the environmental impacts of ruminant livestock production. See

Phil is on the management committee of the £2.7m LINK project ENBBIO (Environmental and Nutritional Benefits of BIOethanol co-products), which involves 25 industry and academic partners, sponsored by Defra through the Sustainable Livestock Production LINK programme. The aim of the project is to quantify sources of variability in wheat DDGS a co-product of the modern bioethanol and distilling industries, identify opportunities to enhance its value, to consider innovative processes to reduce fibre content (for non-ruminants) and to quantify the contribution of the co-products to the overall GHG balance of UK crop, livestock and ethanol production. See

Phil has presented invited papers and lectures in more than 30 countries around the world. Current research links are with collaborators in USA, Canada, Mexico, Brazil, New Zealand, Australia, Malaysia, China, Finland, Sweden, Italy, Czech Republic, France, Germany, Switzerland and Ireland. Phil represents the UK in the Global Research Alliance on Agricultural Greenhouse Gases in the rapid-techniques group.

Selected Publications

Phil is (since 1992) Secretary of the Nottingham Feed Conference. This meeting has been held annually since 1967 and is the premier event of its kind in the UK. Each year, between 12 and 15 international experts are invited to present papers on topics of current relevance to the Feed Industry. Phil edits the proceedings - Recent Advances in Animal Nutrition, which are sold throughout the world. See

Phil is (since 1996) on the organizing committee of the Nottingham Cattle Fertility Conference, which is a one-day international conference held annually in collaboration with British Cattle Veterinary Association. See

Phil is leader of the DairyCo Research Partnership on Health, Welfare and Nutrition. He regularly gives talks to advisors and farmers about the findings of the research.

Past Research


In collaboration with Bob Webb at Nottingham, the Roslin Institute and SAC Aberdeen, Phil demonstrated that nutrition has major influences on fertility in dairy cows and beef heifers. Diets designed to increase blood insulin concentrations led to earlier resumption of cyclic activity and improved conception rates in postpartum dairy cows. However, although pregnancy rates are increased by a high-insulin diet, very high concentrations of insulin may be detrimental to embryo development. The project also investigated effects of individual dietary components on plasma insulin in dairy cows, in order to develop models to predict the implications of different feeding strategies for reproduction. Using this information, dietary strategies were designed to alter blood insulin at critical stages of the reproductive cycle resulting in significant improvements in pregnancy rate.

Methane and ammonia emissions

Phil developed a model to calculate the impact of dairy systems on environmental emissions, which is based on nutritional and physiological principles, rather than standard values per animal. The primary driver of total emissions at the herd or national level is the number of animals per unit of output. This is heavily influenced by fertility and the model shows that if fertility of UK cows was improved to the level achieved by the best herds, national methane and ammonia emissions would be reduced by approximately 20%.

In 2007 Phil and his team developed a novel method for measuring methane emissions by individual dairy cows during milking. This involves sampling the breath of cows and recording how often they belch. With funding from Defra, the method was calibrated against daily methane output by cows in respiration chambers. The method is currently being used to assess variability among thousands of cows on commercial dairy farms to inform the national greenhouse gas inventory.

Body condition score in dairy cows

Interest in body condition score of dairy cows started when Phil was registered for a PhD at Aberdeen University. Whilst studying voluntary food intake, he tried to explain why dairy cows have a delay between peak milk yield and maximum appetite. At that time, advisers recommended calving cows with a condition score of 3.5 to allow them to "milk off their backs". In two experiments, he demonstrated that body fat inhibits food intake so the delay was actually caused by management practices. Thin cows (condition score 2 at calving) had greater appetites and produced milk directly from food, which is more efficient. Maximum appetite of thin cows coincided with peak milk yield. In later experiments at Nottingham Phil showed that body fat mobilisation is dependent not only on the degree of fatness, but also on dietary protein and energy concentrations. As a result of this series of experiments, recommended condition scores at calving have been reduced. The work has been replicated and inspired novel research and updated recommendations throughout the world.

Milk composition

Phil has conducted several large studies on nutritional and genetic factors influencing milk fatty acid composition. The primary aim is to improve the fatty acid profile of milk by reducing the proportion of saturated fatty acids and increasing proportions of monounsaturated and polyunsaturated fatty acids. Of particular interest is conjugated linoleic acids (CLA), which potentially have tremendous health benefits for humans. They are anticarcinogenic, anti-diabetic and anti-atherogenic; they alter nutrient partitioning away from body fat and improve the immune system. A major source of CLA is cow's milk. Phil led studies looking at seasonal variation in the CLA content of milk and mechanisms by which CLA is produced by cows in the rumen and mammary gland. This work showed that 80% of CLA is synthesised in the mammary gland via the desaturase enzyme system. In a study of 10,000 cows, it was shown that desaturase activity has a heritability of 30%, so there are opportunities to breed cows for healthier milk.

Food intake prediction

The main limitation to milk production by dairy cows is food intake. Phil investigated the use of alkanes for measuring food intake of cows fed under group conditions. Alkanes are inert waxes found naturally in plants and have been used for predicting intake in grazing sheep. Phil developed the technique for cows fed on silage so that intake can be predicted from a sample of faeces from representative cows. Subsequently, he found that near-infrared spectroscopy can also provide accurate measurements of food intake from faecal samples.

Rumen synchrony

Studies of rumen fermentation have concentrated on synchronising the supply of energy and nitrogen to rumen microbes. A computer model was developed that predicted the hourly supply of nutrients from degradation characteristics of feed ingredients. In sheep, synchronising energy and nitrogen supply leads to significant increases in microbial efficiency of nitrogen capture. The work was extended to lactating dairy cows, but it was found that these animals have various strategies for overcoming the effects of asynchronous diets. Diet selection and control of meal size and feeding pattern are two strategies. Recycling of nitrogen in the rumen is doubled with asynchronous diets and the rumen microbes increase their storage of polysaccharides.

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