Animal welfare officer and veterinarian at the University of Auckland, Dr Jodi Salinsky says euthanising laboratory animals takes a heavy toll on animal care technicians.
“People get choked up all the time,” she says.
“We want to talk about the fact that this is hard … We are trying to make the animals’ lives as good as they can be, use as few as we can, replace them when we can.”
Even when done as humanely as possible, ending the lives of laboratory animals is a challenging task for the people who’ve worked with them. It is particularly tough when it comes to otherwise healthy ‘surplus’ animals that have been bred for research but not used, as the technicians have cared for them since birth.
The issue of surplus animals has been garnering global attention thanks to the publication of five-yearly statistics in Europe. New data is imminent, with the last count revealing 12.6 million surplus animals were bred and killed in one year, substantially higher than the 9.4 million animals used in research.
In Australia, more than a million mice and other laboratory mammals are surplus — bred for research but never used — in New South Wales and Victoria alone.
There are no national figures, but state-based reporting shows the surplus is more than double the number used for science, education or product testing.
Most surplus animals are laboratory mice. The vast majority are humanely killed.
Professor Gilbert Schoenfelder is the head of the German Centre for the Protection of Laboratory Animals (Bf3R), an independent organisation of the German government that researches and advises on animal experiments and improving animal welfare.
He argues that reducing surplus animals is “the easiest way we have, in the short term, to reduce the numbers of animals used in the context of research”.
Yet doing so will require transparent statistics and addressing contributing factors — researchers’ bias towards using male animals, breeding to maintain genetic strains, and excess animals kept in reserve to meet short-term requests, or ‘just in case’.
How many surplus laboratory animals are there?
Australia’s code governing animal research requires breeding to be managed to avoid or minimise the production of excess animals.
The experience in Germany reveals the scale of the opportunity.
In 2021, Germany began publishing the number of surplus animals every year, exceeding European Union requirements to tally every five.
In one year — between 2021 and 2022 — Germany recorded a 31% decrease in the number of surplus animals, equivalent to 785,123 fewer animals overall.
A combination of reasons contributed to the dramatic drop — transparent statistics along with increased scrutiny and legal action by animal welfare groups about whether scientists had “reasonable cause” for killing surplus animals.
But as Schoenfelder says, the data shows what’s possible. “If we can do around 700,000, just in Germany, think about how many animals can you save worldwide.”
In New Zealand, where Salinsky is based, national statistics on animals in research have been published for more than a decade, including data on the number of animals “bred but not used”. In 2022, 58,193 mice, rats, guinea pigs and rabbits were used, compared to 116,078 bred but not used.
The RSPCA’s chief science officer, Suzanne Fowler says more transparent data and monitoring in Australia would promote greater scrutiny and awareness of animals used in research as well as surplus animals.
“More data analysis and reporting on the breeding of animals and the ratio of animals used versus those killed without use is needed in Australia and this should form a formal component of any project reporting that includes breeding and maintenance of specific research lines,” she says.
The RSPCA advocates for greater transparency, including consistent, accessible animal use statistics, published by institutions and collated at a state and national level.
Currently, available state data suggests the surplus of animals is significant, far outweighing the number of animals used in research.
The most recent data from NSW (2021) shows: that 263,767 laboratory mammals (mice, rats, rabbits and guinea pigs) were surplus — used for stock breeding and maintenance — approximately 2.3 times the number (114,071) used in research, education or product testing.
In Victoria in the same year, 945,096 ‘specified’ animals including laboratory mice, rats, rabbits, guinea pigs and non-human primates were held in breeding colonies, double the amount (458,462) used for research or education.
Addressing sex bias in animal research a win-win
One solution potentially has a “huge benefit” for improving the quality of the science as well as animal welfare, says Schoenfelder.
Male bias in biological sciences and clinical studies is well-documented and also extends to studies involving animals. “Most animals which are used in experiments are male animals,” he explains.
Excluding one sex has mostly been for convenience, he says. Mice and rats have an oestrous cycle of two to five days. In the past, scientists wanting to control for the variability and influence of hormonal cycles in their data opted to use only male animals. The practice became widespread and entrenched.
With mice producing offspring of both sexes in roughly equal numbers, the bias has contributed to the surplus, with the females mostly being killed as they were not used.
Practices are changing.
There is growing recognition of the problems arising from sex-based bias, such that major research agencies like the National Institutes of Health in the US, and the UK’s Research and Innovation now require experiments to use both sexes as a default.
Salinsky says at her institution, any researcher proposing to use only males in an experiment will be heavily scrutinised and questioned by the animal ethics committee, as well as asked to use both sexes. “As we go on, hopefully, this will become standard practice,” she says.
Even so, excess animals can arise because litters are unpredictable — you might only want six animals, but the animal breeds a dozen.
In addition, the nature of breeding to produce certain genetic strains also contributes to the surplus, creating excess animals that don’t match the required characteristics.
Where institutions don’t require specific strains of live animals over a significant period, technologies like cryopreservation and re-animation may provide a solution.
Schoenfelder says cryogenic conservation can limit the overall number of animals and strains being housed and bred in facilities, as an alternative to continually breeding to maintain certain genetic lines.
“You can cryo-conserve embryos, and keep them in fluid nitrogen. If you need the strain, you take them out, put them in a dam [a surrogate mouse mother] it’s raised, and you can breed.”
“This is not a grocery store”
Reducing surplus animals also requires a cultural shift in scientific practice.
A difficult issue to address is the way researchers, scientific journals and reviewers sometimes request animal experiments at short notice. This means facilities are sometimes breeding additional animals to have them on hand.
The profligate attitude towards using animals is something Salinsky is working hard to change.
“We do have some additional numbers so that we have diversity and timely supply for researchers. We very much try to engage the research community in the fact that this is not a grocery store, we don’t indiscriminately breed animals,” she says.
Researchers are expected to communicate their requirements with sufficient time to breed the animals, avoiding last-minute requests.
Fowler says “There should not be breeding done ‘just in case’ animals are required”.
“The RSPCA is opposed to animals being bred in excess, in order to meet fluctuating demands or for maintenance of lines if there is no clear intended usage of the animals,” she says.
Along with the obvious cost for the animals, dealing with the surplus affects staff too.
“Unfortunately for staff, this often means caring for animals for many weeks or months and then having to kill those same animals,” she says.
“This is definitely a challenge, in particular if they have not been used to contribute for their intended purpose, for example in biomedical research, which means there is little justification for their production in the first place. This can heighten the challenging aspects of the role and make it difficult for staff to rationalise and may possibly be a contributor to compassion fatigue.”
To manage these risks, Salinsky instils a ‘culture of care’ in the team, looking after the welfare of staff as well as the animals. For example, if someone feels they can’t euthanise animals on a given day, another person will step in — no questions asked.
“I try to make sure that whatever we are doing, we are doing the best we can — for the welfare of people, the welfare of animals, and the robustness and translatability of the research,” she says.
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