Face Cover and Productivity in Sheep

New Zealand Journal of Agriculture, Volume 91, Issue 6, 15 December 1955, Page 605

Face Cover and Productivity in Sheep

Powerful Selection Tool in Hands of Farmer

"THE relationship between the amount of wool on the face of a Romney ewe and her ■ production of lamb and wool has recently been given some publicity by workers at Massey Agricultural College. This article adapted from a paper given at the Ruakura Farmers' Conference this year by I. J. Inkster, Research Officer, Department of Agriculture's Ruakura Animal Research Station, Hamilton, introduces io sheep farmers the concept of face cover, shows some of the effects of face cover on the productivity of ewes, particularly under hill country conditions, and discusses what use farmers can make of this information.

pACE cover refers to the area of the * face actually growing wool; the length of the wool is not considered, nor whether wool has been shed from the face. To describe face cover four different classes are used. At left in the illustration on page 607 is an “open”-faced sheep. There is no wool growing forward of the eyes and such a sheep could never become wool blind. In contrast at right in the illustration on page 607 is a sheep with a face described as “very covered”. Sheep of this face-cover class have a complete ring of wool round the eyes, but the eyes are not always covered. This, of course, is an extreme case of wool blindness. This is the sort of

sheep which is difficult to muster and work and which must be wigged at crutching. Most farmers will have literally “damned the eyes” of sheep such as this. The intermediate grades of the classification system are: Sheep in the “slightly covered” grade, with wool on the face growing forward of the eyes, and sheep of the “covered” grade, in which the wool grows well forward on the face and down the nose, but does not completely encircle the eyes. The grades are quite distinct, though the differences between them are not large. This should be borne in mind when the productions obtained from ewes of these different face-cover grades are presented.

Most farmers recognise that woolblind sheep are at a disadvantage and they endeavour to minimise the effects of face cover by clipping the wool from the eyes or wigging at crutching. However, data obtained from widely differing sets of conditions indicate that face cover has a more profound effect on sheep than just causing wool blindness. The first suggestion that face cover could affect productivity, particularly fertility, came from the United States. The sheep studied were fine-woolled ewes of the Rambouillet breed (a breed of Merino origin) running under range . conditions. When the lifetime productions of these ewes were considered the following differences between open- and covered-faced sheep were found: — 1. Open-faced ewes had more twins. 2. They were better mothers and their lambs were weaned at heavier weights. 3. There were fewer dry ewes among open-faced ewes than among covered-faced ewes. 4. Open-faced ewes produced l/51b. less wool than covered-faced ewes.

The net effect was that during their lifetimes open-faced ewes produced 11.21 b. more lamb per year and l/51b. less wool per year than did coveredfaced ewes. These differences were present in spite of the fact that wigging was practised three times a year. It should be emphasised that these differences were obtained with sheep of the Merino type under range conditions in the United States. However, similar results have been obtained in New Zealand with the Romney breed. At Massey College on flat country of quite high carrying capacity it has been found that openfaced ewes have over 20 per cent, more lambs than woolly faced ewes and have lambs which are heavier at weaning. The fleeces of open-faced ewes were Jib. to Jib. lighter than those of covered-faced ewes. On a cash return basis the college has calculated that open-faced ewes return about 6s. a head per year more than covered-faced ewes. In addition there was some evidence that unshorn wether lambs with open faces grew more rapidly than those with covered faces.

Results at Ruakura Hill Station Some data on the effects of face cover on the production of ewes under hill country conditions follow. In 1950 all the ewes on the Ruakura Hill Country Station were described for face cover, and the productions of these ewes were recorded throughout their lifetime (Table 1).

These figures mean, comparing the extremes, that on the average there were 15 more barren ewes in 100 covered-faced ewes than in 100 openfaced ewes. Though the differences in average weaning weights are not very great, there is a steady increase from 47.31 b. in the very covered group to 51.61 b. in the open-faced group. These figures suggest, as do the American and Massey College figures, that openfaced ewes are better mothers than

covered-faced ewes. The figures for the net production of lamb per ewe show that on the average each year open-faced ewes produced over half as much lamb again as ewes with very covered faces. Though the average fleece weights of ewes from the different classes do not show the regular differences of

the measures of fertility above them, these figures show that ewes with covered faces clip a slightly heavier fleece than those with open faces. Part of this difference would be due to the greater incidence of dry ewes in the covered classes. In considering wool returns per ewe, however, the wool from the lambs must be credited to the ewes, and on this basis openfaced ewes surpass those in the very covered category.

A conservative calculation of the gross returns per ewe shows that on an average taken over 5 consecutive years ewes with open faces return nearly 7s. more per head per year than ewes with very covered faces. These are average results taken over 5 seasons. When the performances of the ewes were examined season by season it was found that the differences in average per-year production between ewes of the different facecover groups were due almost entirely to the very large differences which occurred when the ewes were 2-tooths (Table 2).

The first line shows how striking the differences were in the percentage of ewes which lambed. Those figures show that there were 51 more barren ewes per 100 2-tooths with very covered faces than per 100 2-tooths with open faces. The average weaning weights of the lambs from ewes of the different facecover classes do not show such a big variation, but the lambs from openfaced ewes were heavier at weaning than those from covered-faced ewes. The third line shows that the average weight of lamb weaned per ewe put to the ram is 16.91 b. for ewes with very covered faces and 38.31 b., or more than twice as much, for openfaced ewes. The three measures of productivity increase regularly from the more covered to the less covered classes, showing that what are really quite small differences in face cover are associated with quite large differences in fertility.

When the returns from ewe and lamb wool are included 2-tooth ewes with open faces grossed a little over 15s. more per ewe per year than 2-tooths with very covered faces. Open-faced Ewes More Profitable Summarised, the results of the American, Massey College, and Ruakura observations on the effects of face cover on the lifetime productivity of ewes show, that open-faced ewes, in ■' spite of slightly lower fleece weights, are more profitable than covered-faced ewes because of their higher fertility. Whereas the American and Massey College results show that

face cover affects the production of ewes in all age groups, under Ruakura hill country conditions the predominant effect was found on 2-tooths. Estimates from both Massey College and Ruakura indicate that over their lifetime open-faced ewes return at least 6s. per ewe per year more than covered-faced ewes. There are obviously large differences in production between sheep with different degrees of face cover, but the reason for these differences is not quite so apparent. Wool blindness cannot be the only explanation, because in the results just cited all the sheep requiring it were wigged three times a year. Nor does wool blindness appear to explain the differences in fertility between ewes of the open and slightly covered classes, in neither of which are sheep with any wool round the eyes. Whether face cover has its effects through interference with the vision of the sheep or whether it is a reflec-

tion of some other quite different factor is not at present the important point. . If the normal farm practice of wigging does not eliminate the effects of wool cover on the face, what can the farmer do to obtain the enhanced fertility associated with the openfaced condition in sheep? This problem would appear to be answered easily in theory, but perhaps with more difficulty in practice. Just as wool has methodically been bred on to the face of the Romney in the past, it seems now that it must just as methodically be bred off. Inheritance of Face Cover With most characters of economic importance in sheep, such as fleece weight and body type, there is only a slow rate of improvement through breeding, because these characteristics are weakly inherited. How strongly is face cover inherited? Though there are no published data on the strength of inheritance of face cover in New Zealand Romney sheep, there are firm indications that it is strongly inherited. Estimates obtained in the United States show that in the fine-woolled Rambouillet breed face cover is the most strongly inherited character of economic importance. Professor A. L. Rae of Massey College is at present working on the problem and it seems likely that face cover in the Romney breed is at least as strongly inherited as it is in the Rambouillet. This means that rapid progress can be expected in breeding for the openfaced condition in sheep by the use of straightforward selections for it. The hill country farmer, however, can begin such a programme only when he can procure open-faced rams and these are not readily available in the industry. Most Romney rams bred today have extensive face cover. In fact, since the breed was introduced into New Zealand there has been a steady trend in stud sheep fashions toward increasing rather than decreasing face cover. The first step in the process. of reducing face cover in New Zealand Romney sheep . must, therefore, be taken by the stud breeder. However, the stud breeders will not breed open-faced rams unless their customers, the hill country farmers, demand them. Knowledge of the effects of face cover on the fertility of ewes places a powerful selection tool in the hands of the farmer. He can now recognise easily in sheep a strongly inherited character which can markedly affect productivity. It is hoped that the information presented will, at least give the hill country farmer food for thought, and it is suggested that his thinking be clear headed, not woolly headed.

TABLE I—AVERAGE YEARLY PRODUCTION OF EWES WITH DIFFERENT DEGREES OF FACE COVER, 1950-54 Very Slightly covered Covered covered Open Percentage of ewes lambing .. .. .. .. 74 82 88 . 89 ' Average weaning weights of lambs (lb.) .. .. 47.3 49.1 51.1 51.6 Average weight of lamb weaned per ewe mated (lb.) 24.7 30.2 36.8 39.1 Average fleece weight (lb.) .. .. .. .. 7.9 7.6 7.7 7.3

TABLE 2—PRODUCTIONS OF THE SAME GROUP OF EWES AS IN TABLE I AS 2-TOOTHS ~ Face-cover class Very Slightly covered Covered covered Open Percentage of ewes lambing .. .. .... 35 66 73 86 Average weight of lambs at weaning (lb.) .. .. 48.3 48.8 49.5 . : 51.8 Average weight of lamb weaned per ewe mated (lb.) 16.9 26.0 31.2 . 38.3 Average fleece weight of ewes (lb.) .. .. ..6.7 6.2 6.3 6.0