The term ‘ball and chain’ may evoke images of a tedious relationship or prison sentence, but for caged mink, these are entertaining toys and lead to greater fertility, according to a new international study led by University of Guelph researchers.

Equipping a cage with a ball to chase and a plastic chain to chew led to major improvements in the mental well-being and fertility of female mink, as well as improvements in temperament in the animals, the scientists found.

Across the entire enriched population, the number of infertile females was nearly halved, and the total number of young mink produced grew by about 10 per cent.

Prof. Georgia Mason, Animal and Poultry Science, said the study shows practical ways for farmers to improve their breeding programs. As principal investigator, she worked with researchers from Guelph, as well as Denmark and Austria.

Referring to a 2013 study using “large super-enriched cages,” she said “these were great for creating big differences in phenotype and major effects on welfare, and showed super-enriched males were more successful with females. However, these setups were not remotely practical for mink farmers.”

For the new study, she said, “we worked closely with local farmers to pick enrichments that were cheap, robust, and small enough to work in a standard farm cage. The results have already helped changed Canadian animal care codes for mink.”

The researchers also found mink given simple toys were generally calmer and less aggressive when handled, and less prone to chew their own fur.

“We think the toys provide an outlet for natural predatory motivations — mink are naturally determined hunters — thereby reducing boredom and stress in a cage which otherwise offers very little to do,” said Mason, a member of the Campbell Centre for the Study of Animal Welfare at U of G.

These enhancements also make economic sense.

“For only a few dollars per cage spent on these simple additions, farmers can make tens of dollars back per cage, because the females are more fertile and each offspring she produces is worth money,” she said.

During years when pelt prices are strong, a farmer with 3,000 breeding females would make an estimated $25,000 more per year by providing small enrichments.

Animal care has to extend beyond meeting animals’ basic physical needs, said lead author Rebecca Meagher, who was a post-doctoral researcher at Guelph during the study.

“Focusing on food, water and veterinary care is good but not enough; we need to look after mental well-being also,” said Meagher.

“This work shows that improving welfare can be profitable. Making housing systems that are better suited to the animals’ natural behaviour is generally a win-win strategy – good for both animals and farmers.”

The paper, “Benefits of a Ball and Chain: Simple Environmental Enrichments Improve Welfare and Reproductive Success in Farmed American Mink,” was published in the journal PLOS One, an international journal published by the Public Library of Science.