N.Z. LAMBING PERCENTAGE

Press, Volume LXXXIX, Issue 27065, 13 June 1953, Page 5

N.Z. LAMBING PERCENTAGE

Steady Rise For Thirty Years EFFECTS OF WEATHER, AGE, AND MANAGEMENT In no department of sheepfarming is there less agreement than on the method of computing lambing percentages, and when any farmer mentions his percentage, it is necessary to ask him on what basis he calculates it. This point, as well as many others brought out an intensive study of New Zealand lambing percentages, was made by Mr P. G. Stevens of Lincoln College, in a paper to the Lincoln College Farmers’ Conference.

Mr Stevens began by quoting an actual instance of an Otago ffock which from the beginning of tupping to the end of lambing was reduced by ewe mortality from 2000 head to 1875 head, a mortality figure of 6 per cent. If the lambing percentage was based on the number of ewes that went to the ram, it would have been 92 per cent., but if on the number of ewes at the finish of lambing, the figure would have been 99 per cent. But among the ewes at the end of lambing there were 80 dry, so on the number of ewes with lambs (1795) the percentage was 103 per cent., a variation of 11 per cent, from the number of ewes at tupping time. In this case, ewe mortality was six per cent., and dry ewes were four per cent, of the flock, so that 10 per cent, of the ewes in the flock failed to breed.

“Even when figures are comparable, caution is necessary in interpreting the final figure, because a lambing percentage is a measure of a lot of unrelated features,” said Mr Stevens. “It is the end result of prolificacy in the ewes, fertility in the rams and the general management of the flock. Although management is placed last, It is of prime importance, as it includes feed supplies during the autumn, winter and spring, and general weather conditions, particularly during the peak of lambing in the spring. High lambing percentages result from a favourable combination of all factors, but low percentages may result from any one of them being unfavourable.” Million Lambs

The New Zealand lambing percentage had shown a steady rise over the last 30 years, said Mr Stevens. In the six five-year periods from 1921-25 to 1946-50, the Dominion percentage had risen from 85.5 to 94.9. In the five-year periods, there were considerable annual variations, as high as seven per cent, between two consecutive years in some instances, and could amount to a difference of a million lambs. Weather during the autumn and spring studied over a number of years, showed that in years of high percentages, there was abundant feed in the autumn, and mild weather in the spring, Mr Stevens said. Years of low percentages were always ones in which the weather in spring was bad, but in which the autumn weather had not necessarily been unfavourable. It appeared that lambing percentages were very much at the mercy of the spring weather, but at the same time the autumn was a not unimportant contributor to the general situation. Mr Stevens said he was at a loss to account for the steady improvement in the national lambing percentages in the last 30 years, but it had been suggested to him that either the farmers of today were better shepherds than their fathers, or that they were getting the benefit of the shelter their fathers planted for them. A point of interest was that the number of ewes rearing twins in the Lincoln College flocks had shown a steady increase also. Using four-year averages to even out yearly fluctuations again, the average number of ewes rearing twins had risen from 37 per cent, in 1936-39, to 46.7 per cent, in 1948-51. A study of the autumn and spring weather in these years showed again that the best years had a good spring. A study of the lambing percentages by counties throughout the Dominion showed that about a third of the total ewe flock was in areas that returned a lambing percentage of more than 109 per cent., he. said. The higher percentages were in areas where sheer farming was intensive, and where mature ewes were in the majority ir the breeding flocks. The importance of intensive farming as a factor ir securing higher percentages was generally recognised, but the age of ewes was recently shown to have an important bearing on prolificacy, and therefore could affect lambing percentages. Careful Records Carefully-kept records qf lambing performances over a number of years on the farm of Mr E. T. Topp, of Waipara, were now available to show the influence of age, and whether ewes were born twins or singles, on lambing percentages were quoted by Mr Stevens. The following tables summarise the results. (Group A are ewes born singles, and Grcflip B ewes born twins):—

The following table shows the lifetime breeding performance of the two groups, expressed as a percentage of each flock which had varying numbers of sets of twins during the five breeding seasons:—

“If the hill-country man takes three lambs from his ewes under conditions similar to those on the Waipara farm of Mr Topp, his anticipated prolificacy would be 1.3 for the ewes born singles, and 1.47 for the twin ewes,” said Mr Stevens. “But the fat-lamb raiser who has the ewes for two or three years of their mature life can anticipate a prolificacy rate of 1.5 for the single ewes and 1.7 for the twin ewes even if the conditions are no better than those under which the ewes spent their first three breeding seasons. This age difference in prolificacy is of considerable practical importance, and any work which aims at prolonging the breeding life of the ewe must be rated as of considerable national importance. Where twins' are available it is obvious that they, too, cari contribute to high prolificacy.”

SHEEP AND WOOL Members of the administrative staffs of woolbroking firms, and practising woolclassers, met at Lincoln College recently to discuss sheep breeding in relation to wool production. Members of the animal husbandry and of the wool departments of the college outlined the way in which the sheep industry in New Zealand is organised, and discussed the prevailing methods employed in sheep breeding. These methods were critically examined in the light of available knowledge of inheritance, particularly the inheritance of fleece and wool characteristics. Demonstrations on several breeds of sheep, and judging, wool on the sheep, occupied a large part of the two days. During these demonstrations the importance of a critical assessment of the characteristics likely to be of the most economic importance was emphasised. This conference was the third to be held at the college, and the continued support indicates a very healthy interest on the part of an important section of those engaged in the wool industry.

Age Lambs Group A per ewe Group B One-shear .. 1.25 1.3 Two-shear .. 1.3 1.4 Three-shear .. 1.45 1.7 Four-shear 1.55 1.73 Five-shear .. 1.54 1.68

No. of Twins Group A Group B Five sets .. 0 4.6 Four sets .. 8.7 ' 17.6 Three sets .. 28.2 44.4 Two sets .. 37.0 25.5 One set .. 17.4 5.9 No sets .. 8.7 2.0