FOUR TEATS GOOD, SAYS UNIVERSITY
Four-teated ewes can rear triplets without causing extra
shepherding according to research at one university.
Jeremy Hunt reports
FOUR-TEATED ewes and their ability to feed triplet-born lambs, but not necessarily through extra milk, are under ongoing evaluation at Liverpool University.
Alun Davies, well known for his work with the prolific Cambridge breed, is based at the universitys Leahurst Veterinary Centre on the Wirral, Merseyside, where a flock of around 60 four-teated ewes has been established.
"The present population of four-teated sheep has been derived from individuals of a number of breeds and crossbreds including Dorset Horn, Border Leicester, Lleyn, Welsh Mountain, Suffolk and Cambridge, although four-teats do occur in ewes of many other breeds," says Mr Davies.
His own research began 10 years ago in conjunction with Prof John King. They acquired four-teated foundation ewes from Philip Caunter, a farmer in Totnes, Devon, who had been selecting for the trait in his own flock for about 20 years.
Three rams and 10 Border Leicester x Dorset Horn ewes were bought from Mr Caunter who had also been using rams showing four nipples in an effort to increase the trait in his flock.
"Our aim was to bring together four-teated ewes and four-nippled rams and create a population at Leahurst but we had very little initial information at the start, other than the physical traits of the sheep," says Mr Davies.
Udders of four-teated ewes appear elongated and extra teats only occur in front of the normal teats. A comparison between the front and rear teats varies from just discernible to almost as long, according to Mr Davies research.
To complement the Devon-bred ewes, the Liverpool team bought an additional ram and three ewes from a Suffolk cross flock in Penrith.
"With the foundation females established at Leahurst, we set about measuring milk yield from the front teats after the first lambing. We noted that whereas the average was about 7%, some ewes produced 20% of their total milk yield – equivalent to 150ml/day – from their two front teats," says Mr Davies
"In the present flock front teat yields vary from 0-32% and averages 15% of the total. These figures equate to an average daily yield of 450ml and a maximum of one litre. If front to rear teat length ratio is below 0.7, the front teats produce no milk. Fore udder development is a major factor in influencing front teat yields.
"In dairy cows a 40:60 front to rear teat ratio has been quoted, but I am not aware of any current research with cattle. It would be interesting to hear whether cattle breeders are aware of differences in yield between front and back teats."
Some of the rams produced in the four-teated flock have been mated to Cambridge ewes with four teats, despite these ewes showing little milk in the additional teats. But the resulting four-teat Cambridge cross ewes all showed good fore-udder development and yields. Some of these ewes have produced 25% of their milk yield from the front teats.
"When ewes with four teats are mated with rams showing four nipples most of the progeny will have four teats but some will have five or six," says Mr Davies.
The main selection criteria used in the present breeding programme at Leahurst involves evaluating the physical development of udder and teats and milk production.
"Within the four-teated flock, selection is based on front to rear teat length ratio at puberty; fore udder development at mid-pregnancy; and milk yields at two to four days after lambing.
"Rams are selected on dam and half-sister figures for the first two selection criteria mentioned above," says Mr Davies.
Observations at Leahurst have shown that lambs will suck all four teats if all produce reasonable quantities of milk. Twins suck both front and rear teats on their side. When rear teats are large, new-born lambs prefer to suck only the front teats, so selection against large teats is necessary.
"Four-teated ewes do not necessarily have more milk, but if a ewe is rearing three lambs the existence of four teats means less competition," Mr Davies adds.
Some work on prolificacy of four-teated ewes at Leahurst has shown that a 180-230% lambing percentage can be achieved.
The main commercial advantage of ewes with four functional teats is their ability to rear triplets more efficiently by allowing all lambs to suck at the same time.
If four-teated rams were used on commercial ewes with two-teats almost all the offspring – 95% – would have four teats.
"The length of the front teats will, on average, be relatively shorter and more variable than in the parent population. Milk production from the front teats will be lower, with a maximum expectation of 12-15% of the total, and many ewes will not produce measurable quantities," says Mr Davies.
He adds that the only management disadvantage with four-teated ewes is their large rear teats. "Four-teated ewes are capable of rearing three lambs and that would reduce shepherding time and labour costs in flocks with high lambing percentages."
And it is not uncommon. Many commercial flocks contain four-teated ewes but their existence goes unnoticed. A good time to check is during shearing or foot- trimming, when ewes have to be up-turned. *