Losses from FACIAL ECZEMA Can Be Prevented

New Zealand Journal of Agriculture, Volume 91, Issue 6, 15 December 1955, Page 561

Losses from FACIAL ECZEMA Can Be Prevented

By

J. F. FILMER,

Director, Animal Research Division, Department of Agriculture, Wellington POURING the autumn of 1955 facial eczema caused serious losses of sheep and cattle in many districts; similar losses have occurred in a number of previous years. These could have been prevented and this article indicates how losses can be prevented in future.

TO do this it is necessary to answer A the following questions: — What is facial eczema? What causes facial eczema? Where does facial eczema occur? . When does facial eczema occur? How can facial eczema be prevented? Can facial eczema be cured? = What should be done when facial eczema occurs? What Is Facial Eczema? Facial eczema is a disease of the liver of sheep and cattle which may or may not be accompanied by skin lesions. The severity of the liver damage may vary considerably. In early, mild cases very little can be seen with the naked eye. Usually, however, the surface of the liver shows a fine mottling which may affect part or the whole of the liver. Often there are areas which are more seriously affected than the remainder, and this causes a blotchy appearance. In later stages of the more serious cases the liver becomes much harder than normal and its shape may be grossly distorted. The skin lesions affect only the uncovered white or light-coloured areas. Thus in sheep the most commonly affected parts are the ears, nose, and eyelids, and in shorn sheep the back. In dairy cows the udder and any other white or slightly coloured areas are affected. The first sign usually seen in sheep is a swelling of the ears. Closer examination shows that the nose and eyelids are also swollen and the whites of the eyes are usually inflamed and yellow. Later the affected areas become covered with scabs. In dairy cows soreness of the teats and udder is usually the first sign. What Causes Facial Eczema? The liver damage is caused by a substance which develops in perennial ryegrass, short-rotation ryegrass, and possibly other plants. This has been

proved quite conclusively. . Pasture from paddocks where facial eczema occurs has been : dried and forwarded to the Wallaceville Animal Research Station, where facial eczema does not occur. There it has been fed to lambs bred at Wallaceville and has produced characteristic liver damage. It has also caused typical liver damage in guinea pigs which have never come into contact with the disease. The skin lesions are caused by a substance known as phylloerythrin, which is formed from chlorophyll in

the gut. In normal sheep and cattle it goes from the gut to the liver and is then passed out in the bile. When the liver is damaged the phylloerythrin gets into the bloodstream and renders the uncovered, light-coloured skin sensitive to light. It is for this reason that sheep with facial eczema seek the shade. Photosensitisation does not always occur in facial eczema, because sometimes the liver damage is not bad enough or does not occur fast enough to interfere with the liver’s ability to excrete phylloerythrin. Other functions of the liver may, however, be impaired and many sheep which do not show any skin lesions may lose condition and even die as a result of liver damage. Where Does Facial Eczema Occur? Facial eczema has occurred in most North Island districts and occasionally in Nelson and Marlborough. Fat lamb and dairy farms are most prone to the disease, but it is not rare on hill

country. It has occurred at intervals for over 50 years, and in most districts the areas which have been affected are well known. All such areas should be regarded as potentially dangerous, as should any similar newly developed country. When Does Facial Eczema Occur? Facial . eczema occurs only in autumn. No cases have been reported before 1 February and no new cases after 30 April, though old cases may continue to show symptoms much later than this. Fortunately the disease does not occur every autumn. The most important feature of the dangerous years is that they are hotter, than normal; this may apply to the whole of the summer and autumn, as in 1937-38, or to a shorter period, as in 1955. In 1955 temperatures in most districts .were about normal up to the end of January. The first half of February was from 2 degrees to 4 degrees above normal and the second half of February from 4 degrees to 10 degrees above normal. The first half

of March was 3 degrees to 7 degrees above normal and the second half of March was about normal, but temperatures in the first half of April were again about 1 degree to 4 degrees above normal. Facial eczema is most common in an autumn which follows a hot, dry summer in which grass dries off or remains green but makes little growth. The disease seldom occurs after a cool, wet summer in which pasture grows rapidly throughout. It has never been known to occur in a late, cold autumn. In some years the outward signs of facial eczema may occur within a few days of the eating of dangerous pasture. More usually, however, skin lesions are not seen for 2 to 3 weeks after the pasture first becomes dangerous, by which time it has usually become safe. J'. '■ : How Can Facial Eczema Be Prevented? Precautionary measures for the prevention of facial eczema must be based

on the principles which have been outlined. Because the disease is caused by a liver-damaging substance in the pasture, it can be prevented only by ensuring that sheep and cattle do not eat this pasture. The method of doing this will vary from farm to farm and will be different for different classes of stock. However, no method can hope to be successful unless it prevents stock from eating pasture containing the liver-damaging factor. To do this it is necessary, in an area where facial eczema occurs, to make careful plans not later than January. At this time each farmer should ask himself the following questions:— 1. Is facial eczema likely to occur this year? ' 2. If so, what paddocks on my farm are likely to be dangerous? 3. Are there any paddocks which I know will be safe? 4. When will I take precautions?

5. What precautions am I going to take? r 6. For how long will I apply them? Is Facial Eczema Likely to Occur This Year? If the weather is hotter than normal, and particularly if it has been dry enough to depress the growth of pasture even though it has remained green, the answer is “Yes, facial eczema may occur this year”. If the temperatures have not been above normal and sufficient rain has fallen to keep pastures growing well, the answer is “Facial eczema will not occur if this type of weather continues for the rest of the summer. If an unusually hot period occurs later, however, facial eczema may still occur.” What Paddocks Are Likely to Be Dangerous? Only two grasses have been proved to cause facial —perennial ryegrass and short-rotation ryegrass. The disease has occurred, however, in many paddocks in which these grasses were present in only small quantities, if at all. Any paddock in which facial eczema has ever occurred is potentially dangerous and on most farms all pasture paddocks should be regarded as suspect. Lucerne paddocks have often proved dangerous, though it is not known whether this is due to lucerne or to grass weeds. Are There Any Safe Paddocks? The only pasture species known to be safe is white clover. In Poverty Bay, where this can be grown as a pure stand, no cases of liver damage have ever occurred in lambs grazing it. It must not be concluded, however, that a clover-dominant pasture is safe. Such pastures may contain significant amounts of ryegrass and may be very dangerous. The brassica crops rape, chou moellier, kale, and turnips are safe provided they are reasonably free from weeds, particularly grasses. When Should Precautions Be Taken? In a dangerous year precautions must be taken as soon as sufficient rain falls in autumn to start the pasture growing. Obviously every farmer must answer this question for himself. , , Temperatures do not vary greatly within a district, and Departmental officers and other professional advisers can indicate if the season is likely to be dangerous. Rainfall, however, can vary greatly in small areas. Farmers would be well advised to keep rain gauges, which can be bought quite cheaply. Precautions should be taken

as soon as Jin. of rain has fallen, unless this is accompanied by a really cold change. What Precautions Should Be Taken? The object must be to ensure that stock do not eat dangerous pastures. Three classes of stock should be considered separately; ewes and other mature sheep, hoggets, and cattle. Safe crops will not generally be available in sufficient quantities to permit their being used for ewes and other mature sheep. The most practical method of protecting these is to concentrate them in such small areas that their consumption of pasture will

be negligible. This will mean a concentration of at least 100 sheep per acre. In many cases this will not be enough. Pasture can grow at the rate of 5001 b. of green grass per acre per day, and 51b. of toxic grass per day can produce serious liver damage in sheep. After sheep have been shut up for 24 hours there should be no grass left in the paddock; if there is, the concentration is too low and should be increased at once. Provided adequate water is available, the concentration cannot be too high. Hay should be fed at the rate of 21b. per sheep per day to prevent loss of condition, but even if no hay is available, the above rules governing rate

of stocking should be strictly observed. Fourteen days’ complete starvation will do no serious harm. During this period the ungrazed pasture grows rapidly and when sheep are turned on to it they soon regain any lost condition. Shutting up during tupping will reduce the number of twins, but usually results in a short lambing period. An outbreak of facial eczema in ewes will cause a far greater reduction in the number of lambs reared than will a period of starvation during tupping. This valuable method of preventing facial eczema has been criticised because it has failed when not properly applied. Three things are essential for its success: It must be applied immediately rain falls; the concentration must be high enough to ensure that no grass is left in the paddock 24 hours after sheep go into it; sheep must be kept shut up in the same paddock until pasture becomes safe. On no account must sheep be allowed out for short periods while the pasture remains dangerous. Unfortunately this method cannot be recommended for hoggets, unless very good hay is available. Though shutting up without hay will prevent facial eczema in hoggets, they receive such a severe check that they remain unthrifty for the rest of autumn. The only satisfactory method of protecting hoggets is to graze them on pure white clover, rape, chou moellier, kale, or turnips. Clean crops of maize are usually safe, but lambs do not do very well on them. Lucerne stands are not safe. If safe crops are not available in a dangerous season, lambs should be sent to. the works as soon as they are killable. It is better to accept light weights than risk facial eczema. If lambs are not killable and neither good hay nor safe crops are available, they should be turned into the paddocks which appear safest. Every farmer must learn these from experience; usually they will be the roughest pastures and will contain little ryegrass. Hill pastures are usually safer than flats, but gullies containing ryegrass are very dangerous and lambs tend to concentrate in them. Though cattle are less susceptible to facial eczema than sheep, in really bad years like 1938 and 1955 they have been affected. The principle underlying protective methods is still the same. Consumption of dangerous grass must be prevented. Probably the only satisfactory way to protect dairy cows and at the same time maintain their milk production is to feed them .on safe crops and silage. Dry cows, calves, and bulls should be concentrated in small areas and fed hay or silage. The concentration should be not less than 40 cows or 80 calves per acre. Bulls should

be kept in yards and allowed no pasture. Beef cattle, if they are killable, should be sent to the works before facial eczema occurs; ,if they are not killable, they can be protected in the ways indicated for dairy cows. If crops, hay, or silage are not'available, cattle should be grazed on the safest pasture, but full protection may not be achieved by this. How Long Should Precautions Be Maintained? Precautions must be maintained until there is a marked change in the weather and the pasture hardens. The change may be a pronounced fall in temperature or a change from warm, showery conditions to hot, dry weather. The hardening of the pasture is not easy to describe, but can usually be detected. There is usually a darkening in the colour of the grass and it appears to become tougher. Precautions should not be relaxed until at least 24 hours after the pasture appears to be safe. It must be realised that pasture may become dangerous several times in one autumn and precautions must be repeated as often as appears necessary. Experience has shown that it is not possible to tell with certainty when facial eczema will occur. If the advice given is strictly followed, stock will be protected against facial eczema, but precautions will sometimes be taken when no facial eczema occurs in freegrazing stock. At present there is no way of avoiding this without running considerable risks. Every effort is being made to isolate the liverdamaging substance in dangerous grass; when this has been done it will be possible to determine its concentration in grass at any time and this should make it possible to forecast dangerous periods much more accurately. Experience with Prevention Methods at Ruakura The methods recommended in this article for preventing facial eczema have been used at the Ruakura Animal Research Station during the last 12 years with the following results: — In 5 of these years it was not considered necessary to take any precautions. In each of the remaining 7 years precautions were taken, but on each occasion some test sheep were allowed to graze freely to determine whether the pasture was really dangerous. During 3 of the 7 potentially dangerous seasons no facial eczema occurred either in the test sheep or in the main flocks. : Thus on approximately half the occasions the precautions were needless. On the other hand, during the remaining 4 seasons at least some test sheep contracted facial eczema, but it was pre-

vented in the main flocks in which the recommended precautionary measures were taken. Over these periods 2000 to 3000 sheep were run on Ruakura each year in 5 to 8 separate flocks on separate, self-contained farms:

In 1955 precautions were taken on three separate occasions; on 5 days in February after 1.5in. of rain, 8 days in March after 1.3in. of rain, and 6 days in April after Jin. of rain. The following precautions were taken: Flock 1 (400 ewes), Flock 2 (300 ewes), Flock 3 (300 ewes), and Flock 4 (200 ewes) were all shut up at the rate of 200 per acre. The only cases of facial eczema in any of these flocks were two which occurred in Flock 1 after the third danger period. After the second danger period the 300 ewes in Flock 2 were killed, and examination showed that no damage had occurred in any of their livers. Flock 5 (120 ewes) was shut up at the rate of 65 per acre. Six cases occurred in this flock during the first two danger periods and a further 3 cases during the third danger period.

During the first two danger periods 240 hoggets were confined to a crop of chou moellier. As the crop was finished when rain fell in April, they were shut up during the third period, except for 88 which were used as test animals. No cases occurred in the hoggets while they were on chou moellier or when they were shut up. When the 88 test hoggets were slaughtered 60 per cent, of them were found to have severely damaged livers and 25 per cent, were badly jaundiced.

Thirty-six 2-tooth wethers which had been allowed to graze freely showed 30 per cent, of damaged livers when they were slaughtered in May. It is thus obvious that Ruakura pastures were dangerous when precautionary measures were taken, and that when these were properly applied they were very successful.

The lower stocking rate of 65 per acre did not give complete control, though the incidence of facial eczema was low. An explanation for the 2 cases in the 400 ewe flock after April is necessary. The April rain at Ruakura began on the 17th, when Jin. fell. The temperatures on that day and for several days previously had been extremely low, so that precautions were not considered necessary. A rise of 12 degrees in the minimum grass temperature, 4 degrees in the soil temperature, and 16 degrees in the minimum air temperature occurred on 18 April and conditions became extremely humid. Conditions looked dangerous again and sheep were shut up on 20 April; this was apparently a little late for complete control in one of the flocks.

Experience at Ruakura over the past 12 years thus indicates that if recommended precautions are

applied thoroughly whenever they appear necessary, almost complete protection can be obtained against facial eczema. Precautions will probably be taken approximately twice as often as facial eczema actually occurs. This is regrettable, but is surely better than permitting even one bad outbreak of facial eczema. Can Facial Eczema Be Cured? No drug is known which is likely to have any effect on the liver damage which occurs in facial eczema. In severe cases many of the smaller bile ducts are destroyed, the walls of the larger ducts become thickened and their bore is greatly increased, much of the liver tissue is destroyed, and the whole organ becomes fibrous and distorted. No treatment could possibly restore such a liver to normal. Less severely damaged livers recover without treatment sufficiently to function normally, provided no more toxic grass is eaten. The skin lesions recover without treatment if the affected animals are placed in the shade. Veterinary treatment may sometimes hasten the recovery of skin lesions, and this may be worth while for valuable animals. Cows with facial eczema affecting the udder should be dried off at once, as if this is not done a very severe form of mastitis may occur. What Should Be Done When Facial Eczema Occurs? Animals affected by facial eczema, should always be placed in the shade; if this is done as soon as the ears become swollen, swellings will subside quickly, and no scabbing will occur. Usually by the time outward symptoms appear the pasture has become safe, but if a further dangerous period occurs, precautions already outlined should be taken with both affected and non-affected animals. The disposal of affected sheep calls for considerable judgment. Sheep which lose condition very rapidly, even if they show no skin lesions, may not recover and are probably best slaughtered. Generally, however, a conservative policy pays. If sheep are given ample shade until skin lesions heal and they are not allowed to eat any more toxic pasture, most of them will recover condition. Even if they do not lamb, they will grow a fleece and become fat enough to kill in the following summer. The value of wool and carcass will greatly exceed the salvage price which can be obtained by sacrificing them in the acute stage of the disease. Ewes which lamb after an attack of facial eczema should be watched carefully; those which lose condition after lambing should be culled. They can sometimes be fattened if the lamb is weaned, and they should then be sent to the works, as a further lambing

would be a poor risk. Ewes which lamb normally, without losing condition, can be kept, as their livers are obviously functioning effectively. As already indicated, dairy cows should be dried off as soon as their udders become affected. They, too, should be provided with ample shade and should be prevented from eating any further dangerous pasture. If affected cows are in calf, they should be kept until calving, unless they lose condition badly before this. Many cows have milked satisfactorily for several seasons after recovering from an attack of facial eczema. Intensive research work on facial eczema has been conducted since 1938. ——— ; ; j

Bv

RIDGE design and construction, •“-* like any other design and construction involving the strength of materials, is a problem which can be approached only by those having a knowledge of the forces involved and the strength of the materials it is proposed to use. To approach such problems without this knowledge is dangerous in that it may result in loss of life or limb and considerable material loss. The farmer can, however, provide within reason the bridges he requires if he receives from engineers information that will enable him to choose the materials he needs to provide satisfactory bridges for the spans he requires. The farmer need not concern himself with problems of design, provided he is assured that materials specified for fixed loads and spans will carry those loads safely. Range of Spans Ministry of Works engineers have prepared plans for single-span stringer bridge construction using either timber or rolled steel joist stringers. The dimensions and numbers of stringers required for spans of 6ft., Bft., 10ft., 15ft., 20ft., 25ft., and 30ft. are given in table form for Bft. and 12ft. width roadways. Full details are given of reinforced concrete abutments, decking, handrails, and all auxiliary equipment required for the complete construction of the bridges. Schedules of material quantities are also available. All bridges must be designed for specified loadings, and a total loaded weight of 6 tons is the maximum safe working load for which the spans are designed. If this loading is exceeded, the strength of the bridges cannot be guaranteed.

This work will continue until the liver-damaging factor is isolated. It should then be possible to say definitely which plants can become dangerous ' and so indicate more accurately when this is likely to happen. It may be possible to provide pastures which will remain safe during dangerous autumns. In the meantime farmers can avoid serious losses from facial eczema if they plan intelligently and act incisively to prevent sheep and cattle from eating pastures which contain the liver-damaging substance which causes this disease. r

Plans of Farm Bridges

H. W. T. EGGERS.

Engineer, Department of Agriculture, Wellington \A/ELL-CONSTRUCTED bridges which will ensure access to all parts of the farm are ▼▼ essential to the efficient operation of watered farm properties. Plans of bridges and information on different types for different spans are available from the Department of Agriculture.

Special design is necessary for bridges requiring spans of over 30ft. and farmers should not contemplate building them without first having proper plans and specifications prepared by a competent person, preferably a registered engineer. Any plans and specifications for bridges must be closely adhered to during construction if the conditions of design are to be fulfilled. Alternatively spans, up to 200 ft. may be catered for by the use of all-steel truss bridges built from prefabricated parts. These bridges are provided in standard sections numbers of which can be added together to give various spans. They are supplied at a fixed price per ton, which includes all steel work and bolts and nuts for fastening, but does not in some cases include decking. There is a farm version of these bridges suitable for a 12-ton loading. Culverts For bridging a very short span the use of a culvert may be more economical than a bridge. Reinforced concrete pipes are available up to 6ft. .in diameter and these, if bedded correctly, make very satisfactory culverts. Plans for bridges using either timber or rolled steel joist stringers can be obtained direct from the Engineer, Department of Agriculture, Box 2298, Wellington— must state for which type of stringer (timber or steel) the plans are required—or from . the Machinery Instructor, Department of Agriculture, Auckland, Palmerston North, Christchurch, or Dunedin.