A sheep that has been neutered can live as much as 60 percent longer than their intact counterparts by delaying the aging of DNA, a study shows.
And it is even possible that testicular removal may also offer the same benefits to human men, researchers led by the University of Otago have suggested.
It is well known that women and mothers tend to survive men and rams, respectively – and the new findings shed light on the role of male hormones in this phenomenon.
In addition to this, the team said that the methods they used could be used to give farmers the opportunity to tell which sheep are living longer and by extension be more productive.
It can also provide a DNA analysis-based means of determining when meat sold in the supermarket as juicy lamb is actually mutton in disguise.
Scroll down for video
Do you want to make that compromise? Sheep that have been neutered can live us much 60 percent longer than their intact counterparts by delaying the aging of DNA, a study shows – and removing testicles can also offer the same benefits to human males
AVERAGE LIFE EXPECTATIONS AROUND THE WORLD
- Japan – 84.3 years
- Australia – 83 years
- France 82.5 years
- Canada – 82.2 years
- UK – 81.4 years
- United States – 78.5 years
- Somalia – 56.6 years
- The world – 73.3 years
- Europe – 78.2 years
- Western Pacific – 77.7 years
- America – 77.2 years
- Southeast Asia – 71.4 years
- Eastern Mediterranean – 69.7 years
- Africa – 64.5 years
The study was conducted by epigeneticist Victoria Sugrue from the University of Otago, New Zealand and colleagues.
“Both farmers and researchers have long known that castrated male sheep on average live much longer than their intact counterparts,” explained Ms Sugrue.
‘However, this is the first time anyone is looking at DNA to see if it also gets older.’
To compare how DNA ages in different sheep, the team created a so-called epigenetic clock for the animal, which serves as a measure of biological aging based on the presence of chemical labels known as methyl groups.
After analyzing a large number of animals to calibrate their watch, the team was able to compare how neutered and intact males age.
They found that the epigenetic clocks of castrated sheep – or ‘skins’ as they are referred to by farmers, crossed more slowly than intact rams.
‘We developed a way to measure biological age in a wide variety of mammals,’ added paper author and inventor of the epigenetic watch Steve Horvath of the University of California, Los Angeles.
‘We have looked at over 200 species so far and discovered surprising generality in how animals get older.
‘But the sheep study was unique in that it specifically isolated the effects of male hormones on aging.’
According to study leader and epigeneticist Tim Hore from the University of Otago, the results could help pave the way for new studies of the mechanisms underlying male accelerated aging.
‘We found that men and women have very different patterns of DNA aging in sheep – and that the castrates (wethers), despite being men, had very feminine characteristics at specific DNA sites,’ explained Dr Hore.
Interestingly, the sites most affected by castration also bind to male hormone receptors in humans at a much higher rate than we would randomly expect.
They found that the epigenetic clocks of castrated sheep – or ‘skins’ as they are referred to by farmers, crossed more slowly than intact rams. The picture: Gus, an older weather
‘This provides a clear link between castration, male hormones and gender-specific differences in DNA aging.’
To investigate the effect of male hormones on tissues, the team studied the next mouse – to find large differences between DNA patterns in male and female mice in tissues where hormone receptors are found (as in skin, brain and kidneys).
In contrast, they found that tissues without expression of male hormone receptors tended to be the same in both male and female mice.
‘We found that men and women have very different patterns of DNA aging in sheep – and that the castrates (wethers), despite being men, had very feminine characteristics at specific DNA sites,’ explained Dr Hore. The image: an illustration of both intact and castrated rams as well as ewes. Neutered males have methylation patterns closer to females
‘Most researchers use blood to measure biological age, and so did we for sheep; however, it was not blood but skin where we found gender-specific aging effects in the sheep’s DNA, ‘said Dr. Hear.
He added that ‘this also seemed to be the case for mice, where we had data from many tissues and in both men and women.’
The full results of the study were published in the journal eLife.
MEET ‘SHREK’ – NEW ZEALAND’S TELL AND LONG-LIVING SHEEP
The picture: Shrek the sheep
A notable example of a neutered sheep that has had an unexpectedly long lifespan was ‘Shrek’ – which, thanks to his evasion of so-called ‘patterns’ (shepherds), has undoubtedly become New Zealand’s most famous sheep for six years.
When the ‘volatile’ ram was finally caught again, Shrek has grown a fleece that weighed a full 27 kg – much larger than an ordinary sheep.
While Shrek’s cunning disposition and habit of laying in caves in the winter helped him stay in the wild for so long, it is likely the fact that he was castrated, the researchers said, that ensured his ultimate longevity and survival to the mature age of 16.
‘When Shrek was captured, he was already 10 years old – about the maximum age of the most long-lived sheep on a commercial farm,’ explained Dr. Hear.
‘I think at least part of Shrek’s fame was simply that he lived that long. something that almost certainly would not have happened if he had not been castrated, ‘he added.