Some 3.4 million scientific testing procedures were carried out on living animals in Britain last year – a decrease of 3% from 2018, official figures show.
Data from the Home Office revealed testing on live animals by researchers at universities, companies and government laboratories has fallen to its lowest level in England, Scotland and Wales since 2007.
Around half (1.73 million) of procedures were experimental, while the rest (1.67 million) were for the creation and breeding of genetically altered animals.
A majority of these procedures (93%) involved mice, fish and rats, which have been the most used for the past decade.
Professor Dominic Wells, of the Royal Veterinary College and chair of the Animal Science Group at the Royal Society of Biology, said: “We have seen a steady decline in the number of procedures involving experimental animals, particularly during the last four years.
“This may reflect the increased use of alternatives to animals or a reduction of funding for animal research.
“It is also important to note that the majority of procedures (approximately 80%) are either mild, sub-threshold or non-recovery, which indicates minimal animal suffering in the majority of cases.”
Some animals may be used more than once in certain circumstances so the number of procedures carried out in a year does not equal the number of animals used, the report said.
More than half (57%) of experimental procedures were carried out for basic research, mostly focusing on the immune system, the nervous system, and cancer.
The use of rats in experimental procedures fell by 5% since 2018 and has almost halved compared with their use a decade ago, according to the statistical release.
There were 130 experimental procedures that used cats in 2019, a decrease of 18% in the last year and 30% compared with 10 years ago.
But the most notable decreases in procedures involved primates (39%) and dogs (27%), the report said, with a majority of them being used in testing the safety of products and devices for human medicine, dentistry, and veterinary medicine.
The number of experimental procedures involving horses has remained at a similar level to 2017, with the majority (77%) of procedures being carried out for the routine production of blood-based products used for a variety of diagnostic purposes.
Cats, dogs, horses and primates are “specially protected species” in scientific research, subject to additional protection under Section 5C of the Animals (Scientific Procedures) Act 1986.
Licence holders using these animals must demonstrate no other species are suitable for their research and must adhere to additional licence conditions.
Specially protected species accounted for 1% (18,000) of experimental procedures last year.
Since 2014, the Home Office, which is responsible for regulating animal experiments, has classified testing according to the amount of suffering it causes.
Around 91% of all experimental procedures and 98% of all breeding procedures being performed last year were assessed as sub-threshold (discomfort measured as less than a needle prick), mild (equivalent to a needle prick) or moderate in severity, and the remainder were severe or non-recovery (where the animals does not wake up after anaesthesia).
Meanwhile, Understanding Animal Research, which promotes openness about animal research, released data showing 10 organisations account for nearly half of animal research in Britain.
They include the Francis Crick Institute (258,557), Medical Research Council (241,577), University of Oxford (229,163), University of Edinburgh (198,517), University College London (186,424), King’s College London (131,999), University of Glasgow (118,139), University of Cambridge (114,640), University of Manchester (97,506) and Imperial College London (80,799).
They carried out 1.66 million procedures, nearly half of the 3.52 million procedures in Britain in 2018.
More than 99% of these were carried out on rodents or fish.
Although the figures are from a pre-Covid-19 period, Wendy Jarrett, chief executive of Understanding Animal Research, said the pandemic has highlighted how important animal research is for the development of new drugs and vaccines.
She said: “Over the last six months, we have witnessed researchers from across the world work tirelessly to develop new treatments and vaccines for Covid-19, which it is hoped can prevent thousands of further deaths.
“Existing drugs, developed using animals, have also been found to be effective against the virus: Remdesivir, an anti-viral drug that was initially developed using monkeys to treat Ebola, is being used to treat severe cases of Covid-19, and dexamethasone, a steroid originally developed using animal research to treat rheumatoid arthritis, has been found to save the lives of some patients on ventilators.
“Research involving commonly used animals like rodents, and more unusual animals like llamas, alpacas, bats, and hamsters has also yielded important information on how Covid-19 can be treated.”