Twin lambs ease each other's pain
A little brotherly love between lambs can go a long way during the painful tail-docking season.
The presence of a twin sibling has been found to significantly decrease the pain lambs experience when the rubber rings used to cut off blood supply to their tails are put on, Massey University PhD student Mirjam Guesgen has found.
Previous studies in people show the touch of a mother eases babies' discomfort during painful procedures. Other primates and rats have also been shown to get by with a little help from their friends and siblings when hurt.
Guesgen wondered whether the same would apply to farm animals such as sheep, as they commonly undergo castration, cropping and docking without pain relief.
New Zealand's animal welfare codes allows lambs under six months old to be docked without pain relief, which can be costly and time-consuming for farmers.
"If we could have something that's a really easy form of pain relief, such as putting them with a particular social partner, that would be great," she said.
"There's a direct link between welfare and productivity."
In the soon-to-be-published research, Guesgen paired 44 lambs into three groups: siblings, strangers and "friends", where the duo were unrelated but grew up in the same paddock.
She then analysed the behaviour of lambs after a rubber ring was put on their tails. All the animals showed an increase in tell-tale pain behaviour, though the lambs paired with their twin siblings exhibited less discomfort than those paired with friends or strangers.
"We see an increase in abnormal posture - a weird way of lying or standing - and we also see a big increase in kicking or rolling around or jumping," she said.
Guesgen had initially expected "friend" lambs would provide some relief, but there was no significant difference between these animals and the stranger group. "Some showed a lot less pain, some a lot more."
One explanation for the difference was that the touch of sibling lambs released pain-soothing opioids in the brain - the phenomenon had previously been recorded in rats, Guesgen said. This would mean the company of siblings actually relieved pain rather than simply distracting the animal from it.
"We're not sure if it's the actual genetic relatedness of the lambs, or if it's because of their social upbringing together. By swapping twins lambs out, you could start to tease this apart."
The Dominion Post