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This article was published in 1951
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

Nutritional Encephalomalacia in Chickens

K. V. BYRNE, B.V.Sc., Inspector of Stock, Young

This condition is the result of Vitamin E deficiency. It was first demonstrated in rats in 1922, and then in chickens in 1930. It was encountered under field conditions in 1935, and since then has been noted on a number of occasions in England and U.S.A. McClymont (1947) stated that it had not yet been detected in NS.W., but that it probably had occurred through the injudicious use of fish oils. It is understood that the disease has been encountered on a number of occasions since in this State, but no subsequent reference to it has been noted in Australian veterinary literature.

Hammond (1941) demonstrated that there is a factor in cod liver oil which hinders the utilisation of Vitamin E by the chicken, and as a result, Encephalomalacia may appear in chickens which apparently are receiving an adequate diet.

In 15 years' field experience, the writer has not seen this condition to his knowledge until April of this year (1951). He was then contacted by a poultry farmer, who reported a mortality in his chickens.

The history supplied was that 650 day-old, mixed sex, cross- bred chickens had been obtained from Sydney on 17th March, and that no trouble was experienced with them until 6th April, when half a dozen became sick. By the following morning 17 were dead, and another 14 affected.

It seemed fairly evident that the trouble was nutritional, but it was found difficult to obtain precise information about the diet. It was learned, however, that green feed was not being fed, and that the cod liver oil and a proprietary brand of Vitamin A oil in use were old stock. As it has been the writer's experience that considerable fluctuation of the vitamin content of oils may take place in such circumstances, it was considered that a vitamin deficiency was a distinct possibility. The owner was advised therefore to obtain a fresh supply of a reliable brand of Vitamin A-Vitamin D oil, feed it at double rate for two days, and then revert to normal rate.

He was advised also to forward some live chickens to Glenfield Veterinary Research Station, and within a few days a report was received from the laboratory. This stated:

"Post-mortem examination revealed oedematous brains and haemorrhages in the cerebellum. Three of them also showed greenish-yellow necrotic areas with haemorrhages in the cerebellum.

"The treatment of three chickens with alpha-tocopherol resulted in complete recovery.

"These chickens were affected with Nutritional Encephalomalacia."

An Immediate visit was made to the property, and an especial effort made to discover the precise diet up to the commencement of the mortality. This was found to be approximately as follows:

Pollard	20 lbs.
Meat Meal	2 lbs.
Bran	20 lbs.
Powdered Milk	1 lb.
A Propty. brand of Vitamin A Oil	1 pt.
Cod Liver Oil	½ pt.
Salt	1%

The cod liver oil at this rate had been given all the time, but the proprietary oil had been given for a fortnight only preceding the commencement of the mortality. (The standard rate at which Vitamin A oil at 1,000 Internat. units per gram should be incorporated in a battery ration is 1 pt. per 100 lbs.)

The owner also mentioned that the supply of powdered milk had run out four days before the losses commenced, and the ration did not contain any over that period.

Four-five feeds of the above mash were given daily; with in addition a feed of cracked wheat and maize meal at night.

When the property was visited following the receipt of the laboratory report, the owner stated that he had obtained a fresh supply of vitamin oil the day he contacted the writer, and commenced to feed it as instructed immediately. At the same time he had obtained also fresh supplies of powdered milk. This change in the diet had been followed by almost complete cessation of losses, as only two chickens died in the 24 hours following the change; and only two more chickens showing slight symptoms of Encephalomalacia have been seen since.

These symptoms as given in "Diseases of Poultry", edited by H. E. Biester and Louis Devries, are: "The chicks first appear droopy, their eyes are closed and the birds assume a fixed posture for long periods. This is followed by a nervous derangement, which often is intensified by excitement, or it might occur suddenly without apparent cause. The features most often observed are ataxia or lack of power to co-ordinate muscular movements, increased inco-ordination, a rapid contraction and relaxation of the legs, and finally complete prostration and death."

In cases seen in this instance, affected birds showed the typical "Crazy Chick" syndrome; tumbling over, and whilst on the ground demonstrating the rapid contraction and relaxation of the legs.

Discussion

The obvious conclusion here is that the mortality was due to "injudicious use of fish oils." The proprietary fish oil being used prior to the commencement of the losses is proclaimed by the manufacturer as equivalent in Vitamin A value to cod liver oil, and the owner was therefore feeding fish oil at thrice the usual rate. However, it would appear that quality as well as quantity enters into the matter; as the feeding at double rate of another (and in the writer's experience, more reliable) brand of oil did not produce a continuation of the losses.

Another point of interest is the frequency with which losses from this disease occur in this State. It is understood that it is not reported very frequently, and if that is so, it is felt that it does not occur very often unless it is not unusual for chickens to die of the disease without manifestation of the typical symptoms. This opinion held because these symptoms are so striking that they could not be overlooked by a field officer.

References

McClymont, G.L. (1947)—Aust. vet. J., 23:22
Hammond, J.C. (1941)—Poultry Science, 20:369
Biester, H.E., & Devries, Louis (1945)—"Diseases of Poultry", The Collegiate Press Inc., Ames, Iowa.