New research led by Queen’s University Belfast has found that total confinement systems may negatively impact the 'optimism' of dairy cows.
The research published in the journal Scientific Reports was funded by Northern Ireland’s Department for the Economy, as well as the EU's Horizon 2020 research and innovation programme.
This study is believed to be the first of its kind to investigate whether dairy cows have judgement bias, and questions whether optimistic judgements can be used as an indicator of psychological wellbeing, which is important for animal welfare.
The study found no difference in judgement bias between cows with and without pasture access. However, found that cows given access to pasture were less likely to hunt for rewards (which took the form of concentrate hidden in buckets).
It concluded: "Giving dairy cattle pasture access appears to induce more positive emotional states than cubicle housing. We previously showed that cows are more comfortable at pasture: They exhibit longer lying times, less restlessness, and greater herd synchrony.
"In our judgement bias task, however, the pasture treatment was slower to approach a known reward. This effect implies reduced reward anticipation, suggesting that cows in the pasture-based system had more rewarding lives. Collectively, our results indicate that pasture access improves emotional wellbeing in dairy cows."
Despite the fact that over 95% of British and Irish dairy cows are grazed outdoors, total confinement systems are rapidly becoming more popular overseas.
In Denmark, Greece, and Poland, less than a quarter of dairy cows went out to pasture in 2019. In the USA, the figure was just 20% for lactating cows and 34% for dry cows in 2013. However, other countries - Finland, Norway, and Sweden - have banned full-time housing.
Dr. Gareth Arnott, senior lecturer in Animal Behaviour and Welfare at Queen’s University and principal investigator on the research, said: “Animal welfare scientists and dairy consumers have long been concerned that depriving dairy cattle of pasture access harms their welfare.
Pasture access can promote natural behaviour, improve cows’ health, and cows given the choice spend most of their time outside.
"However, the effects of pasture access on dairy cows’ psychological wellbeing have been poorly understood – that is what our judgement bias study intended to measure.”
The study was carried out as part of a collaboration with the Agri-Food and Biosciences Institute, and saw researchers give 29 Holstein dairy cows 18 days of overnight pasture access (which previous studies suggest improves wellbeing) and 18 days of full-time indoor housing (which previous studies suggest harms welfare).
The cows had all been at pasture that spring but were cubicle-housed for eight weeks before the experiment began. Each cow was trained to approach a food rewarded bucket location, but not approach another, unrewarded bucket location.
After learning this task, to test judgement bias, the researchers presented cows with buckets in between the trained locations.
Approaching these intermediate buckets would reflect an expectation of reward under ambiguity – an “optimistic” judgement bias, suggesting positive emotional states. The researchers found cows kept indoors full-time were faster to approach the known rewarded bucket location.
The outdoor grazing group was brought indoors between 10:00am and 3:00pm when they were exposed to the stimuli.
Andrew Crump, a postdoctoral researcher from the School of Biological Sciences at Queen’s and lead author of the paper, said: “Increased reward anticipation suggests that an animal has fewer rewards in its life, so our results indicate that pasture is a more rewarding environment for dairy cows, which may induce more positive emotional wellbeing than full-time housing.
“Britain and Ireland have mostly resisted the trend towards housing dairy cows indoors full-time.
We hope that our research encourages farmers, retailers, government and consumers that pasture access is important for cow welfare, and should be protected.
"In countries where full-time housing is common, we hope that ours and other welfare studies challenge this trend."