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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
SOME FIELD OBSERVATIONS ON MINERAL IMBALANCE IN CATTLE
F. E. TREVITT, B.V.Sc., Inspector of Stock, Carcoar.
During the 1943 Spring there was an outbreak of mineral imbalance in cattle in the greater part of the Eastern and Central Divisions of New South Wales. The observations recorded in this article were made in the Carcoar Pastures Protection District.
WHAT IS "MINERAL IMBALANCE?"
This name refers to an imbalance in the animal's blood and was evolved principally because previous names such as Grass Tetany and Lactation Tetany led to confusion, in that they mentioned a symptom which was most inconstant in its appearance. The only constant symptom observed personally in mineral imbalance cases was paresis. Sera analysed showed the following conditions:-
1. Hypomagnesaemia and normal calcium level.
2. Hypocalcaemia and normal magnesium level.
3. Hypocalcaemia and hypomagnesaemia.
4. Hypocalcaemia and hypermagnesaemia.
5. Hypermagnesaemia and normal calcium level.
It was found that the symptoms shown by the affected cows gave no indication as to the particular imbalance in the cow's blood. The popular belief that a hypocalcaemia is indicated by a comatose state, and hypomagnesaemia is indicated by hypersensitivity (flicker reflex,etc.) was not borne out when the symptomatology of each case was examined in conjunction with the blood analysis.
PREDISPOSING FACTORS.
(a) The Pastures. The 1943 winter had been a particularly good one from the point of view of rainfall received, and much river flat country had been under water following flooding. As a result there was a lush growth of feed everywhere. The first cases of mineral imbalance were reported on the river flats where cows had been running on country which previously had been flooded. These cases were reported in July and outbreaks of the condition were investigated on a number of holdings on the Lachlan River flats between Cowra, Canowindra and Goolagong. At this time the feed was about three to four inches high and consisted principally of barley grass. As the weather became warmer in the higher country around Carcoar and Blayney, and there was a corresponding response in the pastures, cases of mineral imbalance came to be reported in these localities also.
(b) Type of Cattle. Only dairy cows were affected, and in every instance the cows were in milk. It was more common to see cows that had calved only a few days affected, but several cases were observed in which the condition had not developed until as long as three months after calving. All cases seen by the writer were cows producing over the average amount of milk. All dairy breeds were found to be equally susceptible.
SYMPTOMS.
Early cases of mineral imbalance show a disinclination to move, stilted gait, and a goose stepping action of the fore-limbs sometimes is observed. Frothing from the mouth and grinding of the teeth also may be seen in a number of cases. Cows usually go down a few hours after the onset of symptoms. At first they are able to sit up and may turn the head around towards the flank, but the commonest position in which to find a cow with mineral imbalance is lying on its side, with head strained back and legs extended. Bloating may or may not be present. The flicker reflex of the eye has been claimed to be a symptom diagnostic of hypomagnesaemia. In personal experience with fifteen cases from which blood analyses were made, it was found that the flicker reflex was a far too indefinite a symptom to give any guide as to the nature of the mineral imbalance in the cow's blood. Death does not usually take place in less than 24 hours after the onset of symptoms, and sometimes may take as long as seven days.
TREATMENT.
Best results were obtained when treatment consisted of an initial injection of a soluble calcium salt, followed by the injection of a magnesium salt if no response were obtained to the calcium injection.
Calcium borogluconate was found to be the best calcium salt. It is a wise precaution to inject a proportion, if not all subcutaneously, as when this is done in preference to giving the entire dose (2¼) ounces intravenously, there is less likelihood of a relapse. Calcium chloride is claimed by some to be a more potent drug, and in cases of extreme paresis its use has been recommended. The writer used it on several occasions and obtained good results, but its use is not favoured, firstly as it is so irritant if accidentally injected subcutaneously, and secondly it is likely to produce a cardiac spasm with immediate death if administered too quickly.
Magnesium sulphate is the commonest magnesium salt used. It usually is injected intravenously, and the amount used is 1 ounce in 10 ounces of water.
On a number of occasions the calcium and magnesium salts were combined to make a single injection. Combinations of this nature used were:—
| 1. | Calcium borogluconate | 2¼ ounces |
| Magnesium sulphate | 1 ounce | |
| Water ad | 12 ounces | |
| 2. | Calcium chloride | 1 ounce |
| Magnesium chloride | 1 ounce | |
| Water ad | 10 ounces |
There did not appear to be any ill effects from using the combined injection, even in one case in which a hypermagnesaemia was present at the same time as a hypocalcaemia.
When a relapse occurred it was found more difficult to obtain a response to injections of calcium and magnesium. In such cases it was found desirable to double the normal dosage, but even then the desired effect was not obtained always.
After the injection has been given, an important essential was found to be insistence on the cow getting up if she was at all able to do so. If the cow is given a few sharp strokes on the loins she often will make a greater effort to get up, and it is also of considerable value to assist the cow in getting up when she has been down any length of time. The heavier dairy breeds seem less inclined to get up than the lighter ones. It was found that when cows were left lying without making any attempt to make them get up, there was less likelihood of ultimate recovery.
Before passing over the subject of treatment it is proposed to make a brief mention of an unexpected response obtained on one occasion to the intravenous injection of tank water. Quite accidentally a recently calved cow in a comatose state was given an intravenous injection of about 900 c.c. of tank water, instead of, as was thought, a calcium chloride solution. The response to the water was very similar to that observed after an injection of a calcium salt, in that the cow was able to sit up about twenty minutes after the injection, and was able to stand up an hour after the injection. No sooner had she got on to her feet than she ran a distance of about 15 yards. It cannot be said whether the injection of water alone would have resulted in the cow's complete recovery, as it was followed up about an hour and a half later with the injection of calcium chloride.
PREVENTION.
Various wild statements have been made regarding the prevention of this condition by providing for the cattle licks containing dolomite and ground limestone. Quite obviously on first principles this could have little, if any, effect. It is recognised that mineral imbalance does not represent a shortage of calcium or magnesium in the cow's body, but it is a condition of the blood which develops, for some reason when the cow is unable to retain the levels of calcium and magnesium in the blood from the adequate reserves of these minerals in other parts of the body.
The provision of dry feed in the form of hay or dry grass is probably a preventative measure which has some merit.