On the face of it, high prolificacy is a bonus for sheep producers, but in reality, triplets and quads are often seen as a nuisance.
Limited feeding windows permitted by the ewe, coupled with the fact there aren’t enough nipples to go around, means time-consuming hand-rearing is often a necessity.
However, a farmer in Devon has been working on a solution by selectively breeding for an extra pair of teats. Could the answer really be that simple?
The existence of sheep with four teats is not a new phenomenon; many producers of traditional breeds are likely to have come across some in their flock. These extra nipples are always anterior to the normal pair but, in the vast majority of cases, are non-functional.
However, Phillip Caunter from Stonehills Farm, Harbertonford, Totnes, has been selectively breeding four-teated ewes since the early 1970s. By crossing a mixture of four-teated Poll Dorsets, Lleyns and Border Leicesters, he now has a flock of 125 four-teated ewes. These are kept on his 100ha farm, along with 80 Zwartbles ewes, 210 Lleyns, and 50 Whiteface Dartmoors, as well as a suckler herd of 36 pedigree Hereford cattle.
We’ve measured the milk output and found that when functional, the extra two teats can equal the volume of one of the main teats
“We’ve measured the milk output and found that, when functional, the extra two teats can equal the volume of one of the main teats, so raising triplets is not a problem for the ewes,” says Mr Caunter. “It also reduces teat damage as the lambs are not fighting each other off at the udder.”
Another bonus is that if one of the main quarters is lost to mastitis, the ewe can still feed twins successfully. And Mr Caunter has not had to compromise on market price with his selecting either. “I’ve managed to work good carcass conformation, teeth and longevity into the flock, so there’s plenty of commercial benefit,” he says.
The ewes are fed 0.5kg of cake for singles, 1kg for doubles and 1.2kg for triplets, and the lambs usually finish at 19-21kg. “I don’t see any difference in the growth rates of the lambs or the condition of the ewe compared with my other flocks, so the system seems to be working,” he adds.
Alun Davies, a former lecturer in animal husbandry at Liverpool Veterinary School, spent a number of years researching the science of breeding four functioning teats into his own commercial flock, using animals from Mr Caunter’s farm. He found a direct correlation between longer extra teats and positive functionality.
“We found that when we crossed four-teated rams with four-teated ewes, all of the offspring had four nipples, though not all were necessarily functional,” he says. “When that next generation was crossed with another four-teated ram, the ewes were found to be generally more productive [more milk per working teat], so there appears to be a cumulative effect.”
However, there are potential problems with breeding for the phenotype, as lambs have a natural inclination to suckle from front nipples, which are generally less productive or, more commonly, completely blind.
“There is a lot more to be unpicked regarding the dominance of the trait, but for the right farming system, where multiple births are common, there is good potential to be found in this kind of selection,” says Mr Davies.
Samuel Boon, breeding specialist at EBLEX, agrees that the research is potentially useful to sheep farmers, but needs to be viewed in the wider context of optimising output.
“The whole issue of how we manage triplets and quads is far greater than the simple mechanics of how many teats are available,” he says. “Nutrition of the ewe pre- and post-lambing has a huge influence on the survival of larger litters, as do elements of fostering and lamb adoption policy, lamb health in early life and issues relating to lambing ease.”
Mr Boon believes that increasing productivity in the future will be more dependent upon analysing and identifying the genetics of ewes that can successfully rear larger litters.
“Having four teats might be a small but important part of this picture, but not if it is to the detriment of selection for other important traits, such as milk production, maternal behaviour and lamb vigour,” he says. “While output is important, enhancing lamb survival is every bit as important as increasing prolificacy.”
Sheep breeders at cutting edge of genetics