Why do we use sheep?
Sheep are large mammals that have many similarities to humans in terms of physiology and suffer from many diseases which affect humans. Because they have been used in farming for many decades, we know a significant amount about their care, handling and welfare that we are able to bring into the research field. They also have a shorter gestation period than us yet give birth to young of a similar weight to human babies, making them an ideal species for studying development and genetics. Sheep also live much longer than mammals such as mice and rats, enabling us to study diseases that affect humans in their adult lives, including neurodegenerative diseases such as Huntington’s disease.
They are also used extensively in veterinary research, studies of digestion in ruminants, and research on the impact of farming on the environment.
Information adapted from AnimalResearch.info
What do we study?
Development in the womb
We use sheep to help us understand the effects on an individual’s health in later life of poor oxygenation during development in the womb. We know that babies of low birth-weight are at a greater risk of developing diabetes and high blood pressure in later life, and have a greater chance of dying early from a heart attack or stroke as a consequence. Our researchers are investigating how and why this occurs, by looking at fetal development and early newborn life in a range of animals, from mice through to sheep. The ultimate goal of the research is to improve identification of individuals at risk of life-shortening conditions as a result of their early life environment and to offer potential therapeutic interventions to reduce this risk. This will have implications for both humans and veterinary medicine.
Sheep’s brains are much larger than those of rodents, similar in size to the brain of a rhesus macaque, and with the complex folds that are seen in primate brains. Crucially, their brains also have basal ganglia similar to ours – this is the area deep in the brain that, along with the cerebral cortex, is responsible for important functions such as the control of movement and ‘executive functions’ such as decision-making, learning and habit formation. It’s this that makes sheep a useful model for studying brain diseases such as Huntington’s disease and Batten disease that affect the basal ganglia and cerebral cortex.
Batten disease is extremely rare, and only a handful of infants or children are diagnosed each year in the UK. It is a genetic disease caused when a child carries two copies of an aberrant gene – one copy from each parent. But it is also extremely serious – symptoms include progressive blindness, severe seizures and the loss of language, swallowing and motor skills. Death at a young age is inevitable and there is no cure. Although Batten disease affects humans, it also occurs naturally in sheep.
Our researchers have used Batten disease sheep to validate behavioural tests which will now be used to investigate Huntington’s disease, a more common, but equally devastating disease. Unlike those with Batten disease, people – and sheep – with Huntington’s do not begin showing signs of disease until adulthood. We have good mouse models for studying Huntington’s disease, but mice are short-lived animals, whereas sheep can live to at least 12 years.
See also: Counting on sheep