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Scientists based at Rothamsted have found a clear link between the weight of lambs early in their life and meat quality – which is good news for consumers, farmers, and the environment.

Currently, 35% of lambs going to market have meat that is considered too fatty, but this new study shows that it’s the lambs which are heaviest at the point of weaning – when they switch from their mother’s milk to grazing – that go on to produce the leanest, most sought-after meat at market.

This knowledge will allow farmers to concentrate on giving their flock the best start in life, as well as looking to breed for lambs that are heavier once weaned.

In addition to producing a better quality of meat, these heavier lambs are also ready earlier in the season when demand is highest and therefore attract premium prices at market.

According to lead author and PhD student Andy Jones, a greater understanding of how better-quality meat is produced would be beneficial to both our health and the livelihood of sheep farmers.

“More than a third of British lambs going to market are rated as overfat and we’ve shown that the leanness of lamb meat is determined very early in an animal’s life.”

“Given that the majority of lambs’ pre-weaning nutrition comes in the form of ewe milk, it is now likely that carcass quality is also affected by management of ewes during pregnancy and lactation. On the other hand, how to manage lambs once weaned may not be as important as those early life experiences.”

The NHS recognises red meat as a good source of protein, B vitamins, iron, selenium and zinc, but says its consumption should be limited to 70g per day. Excess consumption of lamb and beef is commonly associated with an increased risk of cardiovascular disease due to levels of saturated fat.

The study was carried out at Rothamsted’s ‘farm lab’, the North Wyke Farm Platform in Devon, where data was collected from 2,963 sheep. The facility, where all relevant environmental, economic, and animal welfare data are collected 24/7, is also home to a high-tech sheep shed which opened last year.

The research team found that the leanness and musculature of lamb meat can both be successfully predicted from the growth pattern of the animal before weaning.

Lambs heavier at weaning, typically at 13 weeks of age, were assessed to be the highest quality at market and as such returned significantly greater profits.

The study might also have implications for the climate change effects of livestock farming.

“At first glance, livestock’s impacts on environment and health may seem independent from one another,” says Dr Taro Takahashi, who led the research team.”

“But as we’ve demonstrated previously, the carbon footprint of a food item should be evaluated as the ratio between greenhouse gas emissions and the overall nutritional value of the product, rather than just the nominal weight of the product. Besides, if these lambs spend a shorter time on the farm, this can trim down emissions of both methane and nitrous oxide as well.”

“The production of leaner meat does contribute to climate change mitigation, provided that people don’t make up for the leanness with overconsumption.”

The study was published in the journal Animal and funded by the Agriculture and Horticulture Development Board and the Biotechnology and Biological Sciences Research Council.


Dr Taro Takahashi

Honorary Research Scientist


Rothamsted Research is the longest-running agricultural research institute in the world. We work from gene to field with a proud history of ground-breaking discoveries in areas as diverse as crop management, statistical interpretation and soil health. Our founders, in 1843, were the pioneers of modern agriculture, and we are known for our imaginative science and our collaborative approach to developing innovative farm practice.
Through independent research, we make significant contributions to improving agri-food systems in the UK and internationally, with economic impact estimated to exceed £3 bn in annual contribution to the UK economy. Our strength lies in our systems approach, which combines strategic research, interdisciplinary teams and multiple partnerships.
Rothamsted is home to three unique National Bioscience Research Infrastructures which are open to researchers from all over the world: The Long-Term Experiments, Rothamsted Insect Survey and the North Wyke Farm Platform.
We are strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC), with additional support from other national and international funding streams, and from industry. We are also supported by the Lawes Agricultural Trust (LAT).


The Biotechnology and Biological Sciences Research Council is part of UK Research and Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.
BBSRC invests to push back the frontiers of biology and deliver a healthy, prosperous and sustainable future. Through our investments, we build and support a vibrant, dynamic and inclusive community which delivers ground-breaking discoveries and develops bio-based solutions that contribute to tackling global challenges, such as sustainable food production, climate change, and healthy ageing.
As part of UK Research and Innovation (UKRI), we not only play a pivotal role in fostering connections that enable the UK’s world-class research and innovation system to flourish – we also have a responsibility to enable the creation of a research culture that is diverse, resilient, and engaged.
BBSRC proudly forges interdisciplinary collaborations where excellent bioscience has a fundamental role. We pioneer approaches that enhance the equality, diversity, and inclusion of talent by investing in people, infrastructure, technologies, and partnerships on a global scale.


The Lawes Agricultural Trust, established in 1889 by Sir John Bennet Lawes, supports Rothamsted Research’s national and international agricultural science through the provision of land, facilities and funding. LAT, a charitable trust, owns the estates at Harpenden and Broom's Barn, including many of the buildings used by Rothamsted Research. LAT provides an annual research grant to the Director, accommodation for nearly 200 people, and support for fellowships for young scientists from developing countries. LAT also makes capital grants to help modernise facilities at Rothamsted, or invests in new buildings.