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This article was published in 1960
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

Suspected Dietary Deficiency of Selenium

PROBLEMS ENCOUNTERED IN THE FIELD

R. D. JOLLY, B.V.Sc., Faculty of Veterinary Science, The University of Sydney

Introduction

As the title indicates, this paper deals with Selenium deficiency as a field problem rather than with the pathology and chemistry involved. Many observations that have been made await verification by experiment, or if this has been done, the results have yet to be published. The idea of a dietary deficiency of Selenium is very recent and present knowledge far from complete. Present evidence suggests that it may not be a simple deficiency disease, but prove more complex; as with Copper deficiency. Despite these limitations to our understanding of the subject sufficient is known or suspected to build up a preliminary picture of the disease conditions; which, because they may be largely prevented by the administration of small amounts of Selenium, have come to be regarded as being caused by a dietary deficiency of Selenium. In view of the paucity of accurate information, any discussion of the subject must necessarily be tentative, but it is hoped that it might stimulate interest in investigating the possible importance of the condition in Australia.

CONDITIONS BELIEVED TO BE ASSOCIATED WITH SELENIUM DEFICIENCY

The following conditions are believed to be associated with Selenium deficiency:—

A Sheep

(i) Muscular dystrophy, "White Muscle Disease", or "Stiff lamb disease".

(ii) 111-thrift.

(iii) Infertility in ewes.

B. Cattle.

(iv) Muscular dystrophy - "White Muscle Disease".

(v) Ill-thrift of young stock.

In New Zealand these conditions are found generally on light silty or pumice soils of a highly leached-out type. Pasture is lush, green and with a predominance of legumes growing rapidly under the influence of superphosphate. However, this is not always the case; as White Muscle Disease has been described on stands of H1 rye grass and Algerian oats, as well as in circumstances where phosphate fertilisers have not been used as a routine. Seasonal variation of incidence occurs and it is thought that, in view of its effect on the growth rate of pasture, the weather plays an important part. The different conditions listed above do not necessarily all occur together, and this may indicate other complicating factors.

(i) Muscular Dystrophy or White Muscle Disease has been recognised for many years but has been of increasing importance in recent times. Lambs and calves usually are affected within the first four months of life, but it is not restricted to this age group. Symptoms include a stiff straddling gait and difficulty or inability in rising from the recumbent position. Appetite is maintained but the animals ability to suckle or feed is often impaired and death may occur from starvation or other secondary complications. The precipitating cause of an outbreak of White Muscle Disease in sheep is often exercise; as encountered in moving a flock from paddock to paddock or to the yards. Some lambs are born dead while others die shortly after birth from acute heart failure due to lesions in the heart muscles. It is possible that the diet of ewes as far back as before tupping may have an influence on the incidence of this congenital form of the disease, which may reach as high as 50 per cent. Muscular Dystrophy in calves, although recorded, is uncommon in New Zealand.

Pathology. Macroscopically, lesions are found in the heart musculature and in the skeletal muscles; where they are always bilaterally symmetrical. They appear as sharply outlined whitish patches or streaks involving part or whole of a muscle, and often contrasting with nearby normal muscle tissue. Microscopically, swelling of the sarcoplasm is seen with complete destruction of the fibrils but not the nuclei. There is little inflammatory reaction although monocytic infiltration may be seen and calcification sometimes is found in more advanced stages.

Aetiology. It generally has been agreed that the disease is of dietary origin and because of a similarity of lesions produced by deficiencies of Vit. E in certain experimental animals, an upset of Vit. E metabolism has been postulated. When fed to ewes during pregnancy, Vit. E has little effect in preventing the occurrence of the disease in young lambs. A reduction in incidence is seen when it is given direct to lambs and calves, but is not complete.

The discovery of an inter-relationship between the actions of Vit. E and Selenium has stimulated trials in sheep using this element. Muth et al. in America and Drake, Grant and Hartley in New Zealand have shown that the administration of small amounts of Selenium to pregnant ewes by mouth was effective in preventing White Muscle Disease in lambs. It has been shown also that when administered to lambs and calves it is an effective prophylactic agent. Field experience with the administration of Selenium prophylactically has proved successful and is complementary to the experimental data.

(ii) II-thrift. McLean et al. in 1959 reported a weight response to the administration of Selenium by both oral and subcutaneous route in young lambs in the South Island of New Zealand. A very serious ill-thrift problem causing up to 4-5 per cent. loss of lambs and hoggets, and which fails to respond to conventional control measures, occurs in the Rotorua district of New Zealand. Diagnosis o Muscle Disease on some of these properties, coupled with the observation that some ill-thrifty lambs (although showing no clinical lesions on autopsy) prompted Wallaceville workers to initiate Selenium trials. Their results from eight farms over a ten week period may be summarised as follows:—

Figure 1

	No. lambs	Deaths	Av. wt. gain per farm of surviving lambs	Av. dif wt. gain per farm
Control lambs	201	27%	11.6 lbs.
Selenium treated lambs	201	8%	19.6 lbs.	+8 lbs.

Combining live-weight gains and deaths, the Selenium group as a whole gained 3,150 lbs. against a loss of 178 lbs. in the control group. Although surviving control lambs gained weight, the greater number of deaths actually caused a combined loss of weight in the group. The cost of Selenium for this difference was less than one shilling. The results of these trials have been duplicated in other parts of New Zealand and the general use of Selenium in the Rotorua area has provided confirmation.

A similar 1ll-thrift problem in dairy calves existed in the same area despite a fairly high standard of management. As part of a composite experiment on ill-thrift we were able to compare 116 approx. seven-month-old calves that received two doses of Selenium at a two-week interval, with 93 controls. Over a period of one month the Selenium-dosed calves gained 52 per cent. more live-weight than the controls. Once again general use of Selenium has given very satisfactory results in several thousand calves from eight weeks old to the adult stage.

Selenium-dosed calves and lambs showed an immediate response. Diarrhoea, a feature of the deficiency syndrome, often ceased within 48 hours and the animals appeared brighter and more inclined to graze. This led to a general filling out of their frame and marked improvement in appearance.

(iii) Infertility. Grant, Hartley and Drake have noted that certain properties with a high incidence of White Muscle Disease in sheep also had a high incidence of empty ewes. This was a feature of the syndrome in the Rotorua District but was found also on farms where White Muscle Disease was not pronounced, though ill-thrift was. Experiments have been carried out and although the figures are not yet available there is a strong indication that Selenium is efficacious in controlling the condition. Last season we used Selenium on 50 per cent. of approximately 12,000 ewes on fifteen farms and farmers reported a much lower incidence of empty ewes in dosed than in undosed sheep.

Although infertility of dairy cows has not been a feature of the type of country on which infertility of ewes occurred, it was felt that this aspect well could be looked at. Consequently, 2,500 dairy cows were randomised into two groups and half drenched with 15 mg. of Selenium on two occasions 3-4 weeks apart. As judged from their capacity to hold to the bull within a certain time limit, no advantage was shown in the Selenium-treated group. Where production figures were available these were compared also and showed no advantage to either group.

To summarise our observations on these conditions one would like to mention the case history of one farm as an example of what can happen, even under a high level of management.

In six years the owner, using good farming techniques involving the ploughing up and resowing of old pastures with good species of grasses and clover, reported that the infertility of his flock increased from 6 per cent. empty ewes to 18.5 per cent. Last season half the flock was given Selenium, and his figures showed approx. 9 per cent. empty ewes in the dosed group, compared with 20.5 per cent in the controls. Having suffered severely from ill-thrift, this property was selected as one of the eight on which the trials described above were carried out. Results are summarised in Figure 2.

Figure 2

	No. lambs	Deaths	Av. Wt. Gain	Diff.
Controls	25	15	4.8 lbs.
Selenium dosed lambs.	25	2	15.6 lbs.	+ 10.8 lbs.

Actual losses through White Muscle Disease have been recorded on this property but were not numerous.

In addition, trouble has been encountered each year in raising replacement beef cattle, which have had to be sent out of the district to "healthy country". These have shown a response to Selenium dosing and we hope, although it is too soon to tell yet, that this aspect of his trouble may be overcome as well.

DIAGNOSIS OF SELENIUM DEFICIENCY

Where any of the described conditions occur singly or together, particularly where soil and pasture types agree with those described above, the possibility of Selenium deficiency should be borne in mind. Sufficient evidence is not yet available to say whether the occurrence of White Muscle Disease is pathognomonic or not, but this well might be the case. The final diagnosis can be made only by carrying out well controlled trials, as analytical methods for determining minute amounts of Selenium in pasture, soil, and animal samples are not yet available.

TREATMENT

Drenching or injection of Selenium either as Sodium selenate or selenite is of benefit; particularly in the case of ill-thrift, where results may be seen within 48 hours. Nursing is important with lambs suffering from muscular dystrophy as they may be unable to feed and are liable to fly strike. Dose rates have not yet been accurately determined. Trials at Rotorua indicate a dose of 2.5 - 5 mg. of Selenium is effective in sheep three months and older. This should be given two or three times at two-weekly intervals, followed then by monthly dosing. No figures are available for cattle but experience indicates a dose of 5 mg. in eight-week-old calves; rising to 25 mg, in adult cattle to be an effective level.

PREVENTION

Where a Selenium deficiency is diagnosed a preventive program should be started, and only experience will indicate how wide this program should be. Once again lack of experimental data means we should accept arbitrary rules to begin with and build on them as experience dictates. The following recommendations are the ones we used satisfactorily in practice last season; and until more is known they must be recommended.

A. Sheep:—

Ewes:—

(i) 5 mg. Selenium orally as the rams are put out.

(ii) 5 mg. Selenium orally 4 weeks prior to commencement of lambing.

(iii) Additional doses four weeks after rams go out and at lamb marking may possibly have an added beneficial effect.

Lambs:—

(i) 1-2 mg. Selenium orally at lamb marking.

(ii) 2 mg. Selenium orally at 8-10 weeks.

(iii) 2.5 - 5 mg. at weaning.

(iv) As required, but should not be necessary more than once a month.

B. Cattle:—

Calves:—

(i) 10-15 mg. Selenium given at weaning.

(ii) 15 mg. as required — should not be necessary more often than once a month.

Solutions of Sodium selenate or selenite are made up so that the required dose of Selenium is contained in 1 ml. of solution for sheep and 3-5 mls. for cattle. This is too small an amount to be spat out and with automatic syringes it is possible to dose orally 400 or more sheep an hour.

PRESENT RESEARCH

Present research is aimed at a better understanding of the disease, at analytical methods of estimating small quantities of Selenium, and at easier and more effective preventive methods.

The development of Selenium bullets similar to those made with Cobalt, and top dressing techniques, are each receiving attention so that the regular handling of sheep for dosing may be done away with.

SUMMARY:—

Disease conditions which respond to small amounts of Selenium, such as White Muscle Disease, ill-thrift in sheep and cattle and infertility in ewes, are discussed. Where possible experimental data is given to support observations. Methods of treatment and prevention are suggested.

References:

Drake, C., Grant, A. B. and Hartley, W. J. (1960)—New Zealand Veterinary Journal, 8: 4
Drake, C. Grant, A. B. and Hartley, W. J. (1960)—New Zealand Veterinary Journal, 8 : 7
Grant, A. B. Hartley, W. J., and Drake, C. (1960)—New Zealand Veterinary Journal, 8: 1
Hartley, W. J. (1953)—New Zealand Veterinary Journal, 1 : 137
Hartley, W. J., and Dodd, D. C. (1957)—New Zealand Veterinary Journal, 5 : 61
Hartley, W. J., Grant, A. B., and Drake, C.—Pers. Com.
Jolly, R. D (1960)—New Zealand Veterinary Journal, 8: 11
Jolly, R. D (1960)—New Zealand Veterinary Journal, 8 : 13
Jolly, R. D.—unpublished
Marsh, H.—Newsom's Sheep Diseases: Williams and Wilkins Company, Baltimore: 2nd Ed. (1958) : 248
McLean, J. W., Thompson, G. C., and Claxton, J. H. (1959)—New Zealand Veterinary Journal, 7:47
Muth, O. H., Oldfield. J. E., Remmert, L. F., and Schubert, J. R. (1958)—Science, 128 : 1090
Sharman, G. A., Blaxter, K. L., and Wilson, R. S. (1959)—Vet. Rec., 71 : 536