How many lambs per ewe?

Press, Volume CXII, Issue 33046, 13 October 1972, Page 10

How many lambs per ewe?

Dr K. T. Jagusch, senior lecturer in animal science at Lincoln College, wonders whether New Zealand farmers really want to have ewes that drop triplets and quadruplets at lambing.

He is not long back from spending three months in Britain studying methods of intensifying meat production from sheep. Dr Jagusch says that sheep in New Zealand are in the process of increasing in fecundity and moving from a one ewe and one lamb status to perhaps one ewe and two lambs. The first thing that had to be done was to utilise the capacity of sheep like the Coopworth and thereafter the next step would be to cross these sheep with a breed like the Finnish Landrace. when it had been introduced after an adequate quarantine period. It would then be a case of using the Finn crossbred ewes, and if twins were

going to become commonplace every year then some of these ewes would also be having triplets and quadruplets. But did farmers in this country want these sort of sheep under the existing system of shepherding and stock care? In the United Kingdom where these Finn cross sheep were used in intensive lamb production there was one shepherd to about 250 ewes, whereas in New Zealand one man looked after 1500 to 2000 ewes.

He was not too sure that New Zealand farmers wantedsheep with this level

of fecundity, as he did not think that one shepherd could handle them with the numbers of ewes currently being carried per shepherd. If fanners were running a heavy breed of sheep weighing about 160 to 1801 b at mating these animals were already likely to have twins and if these were crossed with the Finn it was possible that they would end up with litters at lambing, with a possible high death rate. It was his view that it might be moi'e desirable to use the Finn, not with heavy type sheep, but rather with those weighing about 100 to 1201 b improving their fecundity to the point where the crossbred ewe produced 150 to 170 per cent of lambs, which was comparable with what might be obtained with a heavy ewe. At the Rowett Research Institute at Aberdeen, Dr Jagusch said that, using Finn Dorset cross ewes, Dr J. J. Robinson had obtained eight lambs from these sheep in three lambings in two years and a half. To achieve this he had used artificial lighting control so that the ewes were indoors the whole time after the first mating, and also hormones to synchronise subsequent matings. All lambs had been weaned at four weeks. At a 100 per cent lambing Dr Jagusch said that in New Zealand ewes would have been 10 years old before they had eight lambs. Dr Robinson had been utilising the breeding season of about nine months of the Finn Dorset cross sheep. The Finn cross lambs, although light, survived well and showed excellent growth rate when reared away from their mothers (artificially). There had been criticism of the growth rate of these lambs left on the ewe, but it had to be remembered that this was a tripletbearing ewe and the milk supply had to be adequate if the lambs were to be left to be reared under the conventional system.

Dr Jagusch said that the Finn was a fecund sheep, regularly leaving triplets. With clean points, it, however, had a light fleece of only 51b or 61b and its feet had to be watched. When sheep of the breed like rams got heavy and they were running on wet soils footrot could be a problem. They had a fine, deep cleft in their cloven hoof. However, the Animal Breeding Research Organisation in Edinburgh claimed that with adequate care and good management this could be obviated. It, however, had poor meat » type conformation, and wether lambs tended to the Omega type. It tended to be rather weak in the loin with quite heavy deposition of fat around the kidneys and rather less in the subcutaneous area. If New Zealand was going to quarantine sheep breeds from overseas before testing their worth in the local situation, Dr Jagusch said that as well as looking at the Finn it should also be investigating the light-weight type of ewe.

A sheep in the latter category, he said, was the Welsh Clanwenog, weighing about 1001 b, which regularly had twins and was quiet in temperament, but with a low wool clip of 31b to 41b. If it was possible to run two of these light-weight sheep for one of the heavier sheep, then it might be relatively more efficient than the 1601 b ewe with triplets. However, the bigger sheep had the advantage of better weight gain in their progeny, fewer numbers per acre and better survival. Nevertheless it would be necessary to conduct trials in New Zealand to see whether the lighter weight ewes were more biologically efficient than the heavier weight sheep at the same levels of fecundity, particularly having regard to the fact that wool could contribute a significant proportion of the income from a ewe. Dr Jagusch said that great care would need to be taken with the quarantine of sheep brought in from Britain, as the

infective agent in scrapie disease was still unknown and could readily pass through a filter or membrane. This disease, which affected the brain, spinal cord and spleen, might not show up for four years, and there was even evidence it might be six years, after the initial contact, and when identified in a flock the only means of eradication was by complete slaughter of all stock. For a while Dr Jagusch worked in an artificial lamb rearing unit at the British Grassland Research Institute at Hurley. Here there are four houses each holding 120 lambs into which the lambs are introduced at about 24 hours after birth, first being fed for about four weeks on a milk replacer diet with access to a concentrate ration after about two weeks, and then from four to six weeks of 'age they are converted to a ration of about 15 per cent crude protein based on barley. From about two weeks they also have access to hay to facilitate rumen development. Gaining about 11b a day, the lambs are ready for slaughter at eight to 12

weeks at 331 b to 341 b carcase weight. Dr Jagusch said that the unit at Hurley, involving a capital investment of about $60,000, could turn off about 2000 lambs a year worth about $40,000, but at the prices lambs were bringing in Britain when he was there the return would only show a profit on labour and feed costs but not on fixed costs. And if it was not economic in Britain then it would not be an economic proposition in New Zealand. But in Britain the supply of such lambs to France might place a different complexion on the economics of the exercise.