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This article was published in 1955
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Digestive Disturbance in Sheep—An Effect of Pellet Concentrates
C. D. Gee, B.V.Sc., Inspector of Stock, Braidwood
INTRODUCTION
During the drought months of 1954, a number of mortalities in sheep were found to have been due to sudden changes in the feeding of pelletted concentrates or sheep nuts.
The losses in some cases were of much greater severity than would have been expected from such a comparatively minor change in feeding as the switching from one type of nut to another.
This matter was first brought to the notice of the writer in August, 1954, when mortalities occurred almost simultaneously on five properties in the Bungendore area of the Braidwood District.
All the sheep lost on the five properties showed similar symptoms, the two most common being inappetence and scouring. The highest of the five mortality rates was about 2% but up to 20% of the affected flocks showed sufficient digestive disturbance to cause a definite set back in condition.
The first action taken by the owners concerned was to call in a practising Veterinary Surgeon, who carried out a post-mortem examination and made a diagnosis of Entero-toxaemia. This was based on the history and postmortem findings. No specimens were forwarded to a laboratory for confirmation. Following this investigation, the writer was called in and the mortalities were investigated on 4th August, 1954
HISTORY
The property of Owner A was visited. In conversation with this owner, the information was obtained that the only factor common to the five mortalities was that, within the few days prior to the onset of the losses in each case, the affected sheep had been put on to a brand of nuts ("X"), derived from a single truckload.
Details of the mortalities are as follows:
OWNER A.
The affected sheep were a mob of 500 in-lamb Merino cwes. These sheep went on to supplementary feed for the first time on 29/7/54, when they were fed "X" nuts from the particular truckload at the rate of about six ounces per day per sheep.
On the 31st ten or so were found sick. On 2nd August, four were dead and another four died between then and the time of the investigation on the 4th. Five others were very sick and were not expected to live. At least twenty sheep had shown definite symptoms with obvious scouring. A further hundred, approximately, had suffered a set-back and appeared hollowed-out.
The scour was quite fluid and varied in colour from a dark slate to almost black. The sick sheep were easily picked out from the mob as they stood apart from the healthy animals with their heads down and their noses nearly touching the ground. A sick sheep from this mob was selected for postmortem.
OWNER B.
The sheep affected on this property were originally a mob of 690 in-lamb Merino ewes. These sheep had been fed for about six weeks on a well-known brand of nuts ("Y") without any losses. About a week before the mortality, two hundred of the sheep were run off because of the water position in the paddocks. On 27/7/54 all these sheep were fed a three day supply of "X" nuts instead of the brand "Y"; at the feeding rate of about 9 ounces per sheep per day. This was repeated on the 30th. According to the owner, the "X" nuts were fed at about the same feeding level and in the same manner as the original variety ("Y").
Of the mob of 490 ewes, nine died between 30th July and 3rd August None of the mob of 200 died, although some of these sheep were noticed to have scoured.
OWNER C.
This owner was feeding two hundred hoggets on "Y" nuts. The sheep in this case were switched on to "X" nuts from the particular truckload; and two sheep were lost within a few days.
OWNER D.
This owner was feeding "Z" nuts. He lost one sheep after changing to, and feeding out two bags of, the "X" variety.
OWNER E.
Two mobs of sheep were affected on this property. The first was a lot of 440 ewes in lamb. These were fed on 27/7/54 and again on the 30th; with a three days' supply of the "X" nuts at a rate of about three ounces per sheep per day. On 3/8/54 a couple of ewes were seen scouring and obviously sick.
The second was a mob of 530 two-tooths fed on the same days at the rate of about 2 ounces per sheep per day. On 3rd August one sheep was dead and several others were scouring. These sheep had been fed "Z" nuts lightly since about 1st June.
Post-mortem.
A sick sheep from the property of Owner A was destroyed and examined post-mortem.
The animal was in fairly poor condition. There was evidence of a dark, quite fluid scour, but there were no other discharges. The lungs were normal; heart was very soft and flabby; liver apparently quite normal and free of fluke. The spleen and kidneys also were apparently normal. The rumen contents had a very pronounced unpleasant sour smell somewhat similar to the smell of sour ensilage. There was some sand and other evidence that the sheep had been feeding on nuts.
The abomasum showed mild congestion, particularly towards the pylorus The contents of the alimentary tract from the abomasum on were all quite fluid. There were very few worms. The blood vessels of the intestine were injected, but there was no significant congestion of the mucous membrane.
DIAGNOSIS.
The first and foremost thought at this stage of the investigation was that the particular truckload of sheep nuts had somehow been contaminated by some poisonous material.
It was thought to be less likely, but still a possibility, that the losses were due to a severe digestive disturbance resulting from the sudden change in the feeding. At the time it seemed unlikely that such minor changes in feeding as switching from one nut to another could have caused such severe symptoms.
The third possibility considered was Entero-toxaemia. It was not thought that this was a likely cause of the mortality, but as an experienced Veterinary Practitioner had made this diagnosis, appropriate specimens were submitted to Glenfield for examination.
A full range of specimens was submitted also for examination for an irritant poison. Pending the report from Glenfield on the specimens submitted, the owners were advised to discontinue feeding the nuts. Losses ceased on all properties almost immediately.
LABORATORY REPORT.
In the laboratory at Glenfield it was found that the bowel smears submitted were not suggestive of Entero-toxaemia, while toxin could not be demonstrated in filtrates of the ingesta. The nuts gave an HCN reaction with the picrate test. The nuts were fed to six mice for three weeks without producing any ill-effects.
In his summing up of the mortalities, the Director of Veterinary Research advised that mortalities in sheep other than those described in these cases had been reported about that time following feeding on nuts. In all cases losses had occurred within three weeks of the commencement of feeding and had been about 1% of the total flock.
He considered that the three likely causes suggested by the writer covered the possible aetiology. These were:—
1. Irritant poisoning.
2. Digestive disturbance.
3. Entero-toxaemia.
Entero-toxaemia was not confirmed in this case and, as many sick sheep were observed, it seems unlikely to be responsible.
Irritant poisoning might have been considered if certain bags of pellet became contaminated in trucks or storehouses, but this also was considered unlikely.
It was thought that the losses were due to digestive disturbances in sheep which had over-eaten before being fully accustomed to that type of feed. In small preliminary trials at Glenfield, where sheep had been fed nuts at a fairly rapid rate of daily increase, the sheep finally had shown complete inappetence and probably would have died unless removed from the trial. The cause of such indigestion could have been the excessive production of lactic acid in the rumen. On most of the properties mentioned, sufficient nuts had been put out to allow the greedy feeders to consume more than one pound of the nuts at the one feed.
It is understood that "Y" nuts contain about 15% lucerne meal and also cocoanut meal, while it is possible that other nuts may not contain anything other than grain by-products. If such were the case, one might expect the more concentrated nuts to be more likely to cause gastric derangement.
If this assumption were correct, then prevention would lie in accustoming the sheep gradually to nut feeding. No more than one or two ounces should be offered daily; each day in a thin trail to prevent gorging, and at least three weeks allowed before nuts are fed at high levels. It may be unwise even to feed more than one day's supply of nuts on the one day, even when sheep are accustomed to the nuts.
CONCLUSION.
Sheep nuts, which have been considered in the past to be a safe drought feed, can cause serious losses in sheep under certain conditions.
As much care should be exercised in the feeding of sheep nuts as in the feeding of wheat grain.