Trace Mineral Deficiencies and Current Stock Health Investigations

New Zealand Journal of Agriculture, Volume 99, Issue 5, 16 November 1959, Page 433

Trace Mineral Deficiencies and Current Stock Health Investigations

FOR some years deficiencies of three trace elements, cobalt, copper, and iodine, have played a relatively important role in animal health in parts of New Zealand. More recently evidence has been found of a probable soil deficiency of a further trace element, selenium. Incidence, symptoms, and control of these deficiencies and intensive research info the possibility of the use of selenium in the control of white muscle disease, ill thrift, and the barren ewe problem associated with white muscle disease were discussed in a paper, an adaptation of which follows, given by I. M. Cairney, Veterinarian, Department of Agriculture, Dunedin, to the second annual Invermay Farmers' Conference at Mosgiel this year.

COBALT SEVERE cobalt deficiency causes relatively rapid loss of condition and death in young sheep and cattle. Severely cobalt deficient areas are now known and preventive management practices are adopted in them. The main problem today is borderline or slight cobalt deficiency, which can be difficult to diagnose and requires careful investigation. In general this borderline deficiency shows itself by lambs not thriving after weaning. Frequently there are

no spectacular death rates or symptoms. There are two reliable methods of diagnosis. A liver from a typically affected lamb may be examined for the presence in normal amounts of vitamin 812B 12 (cobalt deficiency is in fact vitamin 812B 12 deficiency), or a cobalt dosing trial may be carried out. Farm Dosing Trial The method chosen in most circumstances is a cobalt dosing trial. Draft off 50 or 60 of the tail-end lambs and

sort them into two groups at random. Eartag each lamb, weigh and record! individual weights, and administer cobalt to one group only. Keep both groups under identical. conditions and finally weigh each lamb at the conclusion of the trial; that is, at one to three months old. . If cobalt is deficient, there will be a significant • difference in weight in favour of the cobalt group; this difference is frequently not apparent without weighing. The ideal method of supplying cobalt for these trials is by a cobalt bullet administered to the appropriate group of lambs at the commencement. If drenching is used, it must be done weekly.

Farmers suspecting cobalt deficiencyshould consult officers of the Department, as such aids as soil survey maps and the knowledge of specialist staff are useful in interpretation of cobalt trials. The deficiency may vary from year to year and trials may have to be repeated. On farms which are topdressed, cobalt deficiency is best remedied by using- cobaltised superphosphate, which is made by most fertiliser works. Where topdressing is not done cobalt bullets or licks containing, adequate cobalt may be used. ' Licks have disadvantages. Another satisfactory

alternative is spraying pastures with a cobalt solution. IODINE lodine deficiency causes goitre in sheep, cattle, and pigs. It is relatively common, particularly in river valleys. The deficiency effect most commonly seen is congenital goitre in young lambs, a percentage of lambs being born dead or dying within a few days of birth. In severe cases the dead lambs may not be properly covered with wool. Thyroid glands are generally enlarged, shown by swelling about the throat. Goitre may occur in two ways; it may be due to soil deficiency of iodine or by feeding ewes during pregnancy on crops such as brassicas which interfere with the use of iodine by the animal. Both types of goitre are readily prevented by giving iodine to pregnant ewes. If this is done by licks, they should contain potassium iodate, which does not deteriorate when put out. Licks containing potassium iodide . must be - renewed every week or so. The best method of supplying iodine is to drench the ewes with potassium iodide two months before lambing and again one month later. When this is done all ewes get sufficient iodine. COPPER AND MOLYBDENUM Copper deficiency also occurs on particular soil types. Peaty and sandy soils are always suspect; some river

and marine silts may also cause trouble. On other soils a slight copper deficiency may be accentuated by a high level of molybdenum in. the pasture, which causes further loss of the already low copper supply in the animal. Some lambs from copper deficient ewes show brittleness of bones and swayback, a type of paralysis of the hindquarters. Merino and half-bred sheep run on copper deficient country show steely wool, which has a characteristic appearance with all crimp lost. Copper deficiency in calves causes unthriftiness, brittleness of bones, and loss of coat colour. Copper deficiency associated with excess molybdenum causes unthriftiness in dairy cattle, severe scouring, and loss of coat colour. The scouring occurs with the flush of spring grass. This type of copper deficiency frequently does not show in such a spectacular manner with sheep. There may be a few cases of swayback in lambs or merely unthriftiness. Diagnosis of copper deficiency may be confirmed by chemical analysis of livers or by a copper dosing trial carried out in a similar way to the cobalt trial. Copper deficiencies are best corrected by topdressing with bluestone (copper sulphate) at 5 lb per acre or copperised superphosphate. Another satisfactory method is by the use of copper cerate

injections, which are also useful for trials. Copperised licks have the disadvantage common to all licks that not all stock take them. Copper poisoning can readily be caused by excessive concentrations of topdressing or licks. SELENIUM Many farmers will be aware that in recent research the mineral selenium lias given most promising results in the prevention of white muscle disease in lambs and has also caused an increased growth rate in lambs on some properties where trials have been conducted. White muscle disease has shown up in several forms in a number of districts in the South Island. The condition was first recognised in hoggets when they were driven to grass after being, wintered for several months on turnips; those affected became stiff and “stilty”, went down, and died within a few days. Experience has shown that the condition rarely occurs if hoggets can be allowed to wander quietly on to an adjacent crop of green feed for a few days before being driven any distance. However, the heaviest losses from white muscle disease have occurred in lambs. Some of these losses occur within one or two days of birth and frequently immediately after birth or within an hour or two. In these lambs the heart muscle is affected and before death breathing is rapid and difficult. There is frequently excess fluid in the body cavities. In older lambs, 3 to 12 weeks of age or more, deaths may occur suddenly due to white muscle heart lesions or several days after the lambs have shown stiffness and become “stilty” and unable to walk. Affected muscle, whether in the heart or in the body or limbs, is white like fish flesh or has white areas in it. White muscle disease in lambs occurs most frequently on light land which has been developed rapidly. Usually it is seen on paddocks in which lush clover is dominant.

Research with selenium in the United States suggested that it might prove valuable here and trials with it were begun. In carefully controlled trials carried out last season in Otago and Canterbury by the Department of Agriculture the most minute amounts of selenium gave good protection against white muscle disease in lambs. Many of the farms affected are on similar types of soil and from the evidence it appears possible that on some soils white muscle disease is due to a deficiency of selenium. A major difficulty in rectifying selenium deficiency is that this substance is highly poisonous, even in relatively small amounts, and there are very great dangers in the misuse of it. The highly poisonous nature of selenium has been well known for many years in America and Europe, where soils high in selenium cause serious diseases called “blind staggers” and “alkali disease”. Pasture containing five parts per million has been proved dangerous. For this reason selenium should be used only under direction of officers of the Department of Agriculture or veterinarians. A great deal of research remains to be done; for instance, to

find whether selenium can be used safely as a pasture topdressing, the rate at which it can be applied, and the uptake by plant and animal tissues. There is evidence that selenium has in some cases caused a substantial improvement in growth rate of unthrifty lambs. It is possible that it will play an important part in the prevention of some types of ill thrift. Investigation of the flock histories of properties where white muscle disease has occurred in lambs shows that most of them have an abnormally high percentage of barren ewes4o to 50 per cent on the worst affected farm. This infertility also may possibly be due to a soil deficiency of selenium. Extensive trials are planned to begin immediately to investigate this problem further. . Serious Losses The following figures from a group of properties affected with white muscle disease illustrate the very serious loss for which it has been responsible. . Lambs surviving Ewes to after all Barren Farm Year rams ’ losses ewes A . . 1957 1,000 330 400 1958 1,050 527 480 B .. 1957 1,500 . 800 100 . 1958 2,000 540 1,250 C .. 1958 700 350 300 D .. 1958 640 640 140 E .. • 1958 800 300 370 F .. 1958 640 100 400 G . . 1958 650 509 150

Severe losses in Otago have occurred on properties with a similar soil type, but trouble has seldom been experienced until a level of development permitting two ewes to the acre has been reached. Most of this land has a history of. intensive cereal cropping. Use of Selenium The present position with regard to selenium can be summarised as follows: @ It is highly poisonous; it has caused serious stock losses in some countries, even in relatively minute amounts. • Research carried out in New Zealand recently has shown selenium to be promising for: (a) Prevention of white muscle disease in lambs. ■ ■ (b) Prevention of some types of ill thrift. • Selenium is being investigated, for prevention of the high rate of barren ewes on farms which have experienced white muscle disease.

Covering Silage Clamps with Sawdust

By

G. B. HADDOW,

Farm Advisory Officer, Department of Agriculture, Auckland

SAWDUST has been used for covering silage clamps by farmers near Whenuapai aerodrome, Auckland, for over six years. Properly used, sawdust eliminates surface wastage of silage, but losses due to leaching and heating still occur. A SAUCER-SHAPED clamp comZx pletely covered with 9to 12 in. of sawdust immediately after the last load of grass had been spread had no surface wastage when opened a year later. This contrasts with the usual

waste of 3 in. under any other type of cover tried. Advantages of Sawdust Besides eliminating surface waste of silage, which is rarely less than 20 per cent, sawdust is light and clean to handle. It can be used for more than one season, though fresh sawdust is preferable because it makes a better seal. Waste sawdust remaining after the silage has been fed can be spread without harm to stock or pasture. Sawdust also provides a cover that deters biting flies which breed in early cut, warm, moist silage.

Disadvantages of Sawdust The farm should be handy to a sawmill to reduce cartage costs. Owing to the shortage of sawdust at local mills during harvesting time it has proved necessary to begin stock piling sawdust in August or September. The sawdust is left in heaps beside pits or the sites of proposed clamps until it is needed. It is most important to cover the silage with plenty of sawdust as soon as the stack is finished; otherwise surface wastage . occurs. Wider use of sawdust is recommended where it can be obtained cheaply and in quantity.

General Features of Deficiencies of Trace Mineral Elements

Deficiencies of various trace elements are frequently related to particular soil types. By the use of proper diagnostic methods it is possible to prove the existence of a deficiency. It is always preferable to have a thorough investigation made before applying minerals.