Controllable Factors which Influence Wool Returns

New Zealand Journal of Agriculture, Volume 84, Issue 1, 15 January 1952, Page 61

Controllable Factors which Influence Wool Returns

QUALITY in wool commands a small but worthwhile premium at present— indeed, at most times—but weight of fleece has a more important effect on returns. Fortunately improvement in yield is usually accompanied by an improvement in quality. Factors affecting wool returns over which farmers can exercise some control were discussed by E. A. Clarke, Senior Research Officer, Department of Agriculture Animal Research Station, Ruakura, in a paper which he delivered to the 1951 Ruakura Farmers' Conference Week and from which this article is adapted.

AN understanding of the fundamental facts about the origin and growth of the wool fibre is helpful to an appreciation . of the factors influencing the development of the fleece. Development of Skin Follicles . The follicles in the sheep’s skin which produce the wool fibres are laid down early in foetal life, and by the fortieth day after conception a definite pattern of follicles has appeared. As in the growth and development of the body, the follicles develop in orderly fashion. A wave of development spreads from the head down the midline of the back to the tail and from the back toward the belly and down the limbs. By about the ninetieth day the whole body carries a clear-cut pattern of follicles, arranged .in trios. These, the earlyfounded or primary follicles, grow the coarsest fibres, which are usually hairy, and the kemps. They comprise the coarse outer coat of primitive sheep and are present in the improved breeds, particularly in the “halo hairs” which occur on many lambs and in the face and leg hairs. These fibres fall out of the fleece during the first few weeks after the lamb is born and are replaced in the same follicles by fibres which continue to grow indefinitely and otherwise generally resemble the fibres of the remainder of the fleece, but in some sheep they may be replaced by more coarse,. hairy fibres and kemps which constitute a fault in the wool by reducing its range of usefulness. Secondary Follicles From about the ninetieth day onward many smaller follicles are founded about the trio groups. These are the secondary follicles and produce the true wool fibres which in the primitive sheep make up the fine undercoat. In the improved sheep the secondary fibres make up the bulk of the fleece, and around each primary trio group from 30 to 100 secondary follicles > develop, according to breed and type of sheep. By the time the lamb is born its follicle arrangement and population are about complete. After . birth, but for only a short time, a few more secondary follicles are laid down, but for practical ' purposes the maximum number of fibres the sheep can grow throughout its life has been decided by then. Moreover, for all practical purposes the course of follicle development in the foetus cannot be influenced by man, so efficient is the “buffering” ability of the mother against environmental changes. Follicle development and pattern are predetermined by heredity.

Structure of Follicles The essential features of a primary follicle are shown in Fig. 1. The secondary follicle differs from the primary follicle chiefly in the absence of the sweat gland and the arrector muscle. The diagram also shows a medulla or spongy, air-filled core in the fibre; a true wool fibre lacks the medulla and is a solid fibre enclosed in the sheathing cuticle. , The workshop of the follicle is the papilla at its base. It is a region of active tissue well supplied with fine blood vessels and nerves, and by the budding off of new cells the fibre is pushed up and through the skin. The new cells have hardened and changed to keratin (the material comprising horn, hoof, fingernail, and wool) before the surface of the skin is reached. Once this has occurred the fibre is a dead structure and cannot be changed by the animal or improved by any practicable treatment of the growing fleece. Dipping, for example, can in no way improve it, but it may be damaged by such factors as dips, stains, sunlight, and micro-organisms.

Influence of Nutrition

Many factors, however, influence the activity of the follicles and hence the amount and kind of wool produced. Apart from inherent factors, including breed, sex, and age, the greatest single factor is the level of nutrition. Maximum nutrition enables each follicle to produce the greatest possible amount of keratin and results in the coarsest and longest fibre possible. Lowered nutrition causes the output of fibre material to be reduced and results in a finer fibre, and to a less extent a shorter fibre, and also causes some follicles to cease functioning, temporarily at least, and . thus to shed their fibres; this not only results, in reduced fleece weight but also affects wool quality. . Under • extreme conditions shedding of the fleece can occur because of almost complete cessation of follicle activity. Coarsest Fibres Least Affected All follicles do not respond similarly to lowered nutrition: The first fibres to be affected are the later-founded secondaries, and the coarsest (earlyfounded) fibres seem to have first call on available nutrients. This results in an unfavourable change in the quality of the fleece. Quality is also affected by breaks, tenderness, cotting, and uneven crimping caused by irregular growth of the fibres. Variations of Growth Rate Apart from the kemps in the fleece, the fibres normally continue to grow indefinitely and, if the level of nutrition is adequate, at a constant rate. Under experimental conditions fleeces have been grown for 3 to 4 years, weighing up to 701 b. and showing almost perfectly regular growth. Fig. 2 shows variations in the weight of wool grown per month by Romney ewes under conditions of unrestricted grassland feeding. Perfectly regular growth throughout the year is unusual, and a depression in growth rate corresponding with the end of pregnancy and the beginning of lactation occurs commonly, usually manifesting itself as a “break” in the staple. At present the cause of this break is not known, but a sudden drop in feed supply, a change to poor-quality feed, or illness is known to be capable of causing a severe break at any time.

An extreme case of irregular growth rate is illustrated in Fig. 3. During 14 weeks of winter growth almost ceased, resulting in an extreme break, much shedding, and extreme cotting. The cotting is caused primarily by fine shed fibres becoming entangled among the growing fibres and the mass felting so tightly that it cannot be separated without much fibre breakage. Pre-lambing and Double Shearing Pre-lambing shearing results in a fleece of full 12 months’ growth free from the pre-lambing break. Experiments at Canterbury Agricultural College, Lincoln, showed no increase in wool production from winter shearing, but the wool was cleaner, brighter, and free from breaks and cotts. Such wool might be expected to be more valuable, but in general it does not seem to have brought increased prices. That has been the experience of many South Island farmers. Double shearing results in two short fleeces which total little more than< the weight of the normal 1-year fleece. Experimental results indicate that the increased wool growth seldom exceeds a couple of ouncesinsufficient to cover the extra cost of a second shearing. Furthermore, the short wool is of restricted usefulness and unsuited for specialty uses such as in paper felts, spinners, and preparing. It meets a much poorer demand and the price is ' usually disappointing. Many farmers claim marked increases in wool production as a result of both pre-lambing shearing and double shearing, but wool production is very closely associated with seasonal conditions, and the average fleece weight of a flock can vary appreciably from season to season. Controlled experiments have shown that time and frequency of shearing have little effect on the wool yield. Condition and Fleece Weight The effect of level of nutrition on the growth rate, fatness, and wool production of two similar groups of ewe hoggets: is shown in Table 1. These hoggets were shorn as lambs in late January and divided into two groups of about 200 each in March. Thereafter they were run separately until they were shorn. The striking feature of the figures is the big drop in fleece weight (about 27 per cent.) associated with a comparatively small drop in liveweight, which allowing for wool carried is only 4.51 b., or less than 6J per cent. Had both groups been

heavier throughout, a difference in liveweight of this order might have produced little effect on fleece weight, but such information has yet to be obtained. The lower average fleece weight of the second group may also be associated with greater irregularities in the shape of the growth curve between weighings. The effect of level of nutrition on the wool production of 5-year-old breedings ewes is shown in Table 2. In these mature animals, each of which reared a lamb, the effect of low-plane feeding on wool production, though substantial, was less ’ marked than in the hoggets. The greatest effect of poor nutrition on wool growth of breeding ewes occurs during pregnancy rather than during lactation, but the effect on lamb growth is the reverse. A ewe has remarkable powers of preserving the developing foetus and in times of lowered nutrition suffers heavy loss of body weight and greatly reduced wool production to produce a normal full-term lamb. A lowered level of nutrition during pregnancy of breeding ewes in the South Island was responsible for a reduction in fleece weight of the .order of 1 to IJlb., but a similar change after lambing caused a reduction of only % to Jib.

The effect on wool growth of plane of nutrition in 5-year-old ewes for short periods beginning on the average about 50 days before lambing is shown in Table 3. The high-plane ewes gained at about 5.21 b. per week and the medium-plane ewes at 2.91 b.; the lowplane animals were maintained at a constant mean liveweight of 1241 b. The medium- and high-plane ewes differed little in either fleece weight or quality, but these two groups showed marked improvements over the ewes kept at constant body weight. This points to the desirability of maintaining an optimum liveweight increase rather than aiming at the maximum. The precise definition of this optimum is not yet possible, nor can the most economic feeding level be described.

Weight and Quality The fact that weight greatly overshadows quality in effect on wool returns has always been obvious. Crossbred wool is second in grade to Merino types in world trade and is used in articles in which quality in its broadest sense is less important. Such wool is often used only because better wools are more costly, but there is some premium for quality. The main quality considerations (within fineness grades) affecting the price per pound of fleece wool are as follows; originating from the days of wartime control, these types are now more .or less generally recognised in the trade in New Zealand: Good-super (A): Good colour, well grown, sound, well skirted, free, may contain very slight fault, suitable spinner. Good (BB): Good colour, well grown, well skirted, free from seed, may contain slight tender. Good-average (B): Good topmaking, fair to good colour, skirted, may contain odd cott and/or very slight seed. / , . Average (C): Topmaking, fair colour, may contain few odd cotts, may be unskirted and/or bush stained and/or .part seedy. Average-inferior (D) : Average to inferior topmaking, may be poor colour, may be cotty and/or seedy, unskirted and/or bush stained.

Effects of the main wool qualities on price are shown in the following figures; they can be only approximate because of the instability of wool values and the consequent difficulty of deriving valid average values:—

Grade and . count (fineness) are shown to have an appreciable effect on values, and yield influences price at the rate of about 2d. per pound for each 1 per cent, change in yield. With wool at 140 d. per pound, however, an increase in fleece weight of a few ounces can offset much loss of quality. Fortunately, all work on wool improvement tends to demonstrate that increased fleece weight, whether achieved by breeding or by feeding, is accompanied in some degree by improvement in quality. Benefits of Culling Worthwhile . increases of wool production can be achieved by culling. The rate of culling of hoggets varies considerably with such factors as the lambing percentage and the death rate in all classes of stock, but usually it ranges from 30 to 40 per cent, of the hoggets available and under most favourable conditions may reach 60 per cent. Much of this • culling can have the aim of raising wool yield. Considerable evidence shows that of the increase in average wool production per head achieved by culling hoggets at least’ half remains in each

subsequent year the selected animals stay in the flock. Thus, if by culling 40 per, cent, of hoggets the wool production of the remainder is increased by an average of 2/31b. per head, at least l/31b. per head of increase is to be expected from these selected sheep in each subsequent year, or during their - productive life a total increase of 1 to l|lb. of wool per head. In many flocks the increase has been greater. Only half the increase is realised in the 2-tooth and older ewes because hoggets vary considerably in age, size, and development, they are relatively immature and the weight of

wool carried has been influenced greatly by environment. Therefore the weight of a hogget’s fleece is not a perfect index of production capacity at maturity. In the selection of hoggets for heavy wool production a few important, principles must be kept in mind. By and large, the stronger is the wool the heavier is the fleece. ,At present .there is little premium for fineness, so in general the stronger types are more profitable. Wool surveys have shown that the better is the country the better is it able to grow stronger wools, as is illustrated in Fig. 4. Therefore the finest wools in the flock are not the most profitable. Rather the aim should be, in moderation, to produce the stronger types which careful inspection indicates can be well . grown on the country. Selection of hoggets for heavier wool production is neither difficult nor very time consuming. The decision having been made on the count range to be aimed at, culling consists essentially of

eliminating hoggets outside the : range, those with short, dense, fuzzy fleeces (“down type”), and those with markedly faulty fleeces showing break, cutting, and weak open backs. The ideal is a long, well-grown, “meaty” staple, evenly and clearly crimped over the whole fleece, with belly and points well covered. Such a simple ideal, conscientiously aimed at by anyone with even a meagre knowledge of wool quality, cannot fail to achieve worthwhile results for the expenditure at the outset of no more than 1 day per 200 to 300 hoggets. Moreover, the efficiency of the work can be tested immediately by shearing the culled -and selected sheep as two mobs and comparing mean fleece weights. Fleece weight is only weakly inherited and the improvement achieved by culling largely disappears in the following generation. For example, if culling results in an increase in fleece weight of lib., only 10 to 15 per cent, of this increase can be expected in the progeny of these sheep. Greatest scope for permanent improvement lies in the selection of the flock sires.

* 1 = fat, 10 emaciated.

* Excluding belly wool and locks.

16 March 1 June 26 September 28 September \Group Body weight \ (pounds) Body weight (pounds) *Grade Body weight ♦Grade (pounds) Body weight (pounds) *Grade Body weight ♦Grade (pounds) Body weight (pounds) ::: Grade Fleece weight ♦Grade (pounds) Fleece weight ‘ (pounds) 1 53.1 6.5 53.8 6.7 71.7 5.8 4.8 2 52.4 6.6 58.7 5.3 78.0 4.9 6.6

Table 1-Effect of Condition on Fleece Weight of Ewe Hoggets

Group Feb. May Liveweight (pounds) Aug. Oct. - Dec. *Fleece weight (pounds) Yield (per cent.) 1 100.5 113.0 135.3 129.2 127.5 9.3 71.0 2 97.7 111.4 . 126.4 124.5 119.3 8.8 70.2 3 98.8 101.4 108.7 107.9 109.4 7.4 71.2

Table 2—Effect of Plane of Nutrition on Fleece Weight of Breeding Ewes

High Medium Low plane plane plane Average fleece weight (lb.) 9.0 8.9 8.5 Fleeces graded very good (%) 12.4 8.6 5.3 Fleeces graded good (%) 33.0 33.3 12.6 Fleeces graded medium - and poor (%) .. .. 54.6 58.1 82.1 Fleeces with break (%) 6.2 8.6 31.2 Fleeces cotted (%) 2.1 3.2 8.3

Table 3—Effect of Nutrition on Fleece

Approximate price per pound Grade Count Nov. 1950 Nov. 1950 Jan. 1951 Jan. 1951 f 52 110 151 50 109 148 BB 48/50 106 140 . 46/50 105 138 46/48 107 140 : 52 * 106 149 50 103 143 B 48/50 103 . 140 46/50 101 135 46/48 103 135 ' 52 101 .140 50 97 133 C 48/50 96 131 46/50 95 129 46/48 96 131