Читать книгу Farm Animal Medicine and Surgery - Graham R Duncanson - Страница 154

This condition may cause the highest mortality of all conditions in beef suckler cows. It is rare in dairy cows. Magnesium levels in most suckler cows are on a knife-edge. Any upset to the absorption of sufficient magnesium by the small intestine will bring on hypomagnesaemia. The laxative effect of lush grass is the normal cause. Other causes of stress, e.g. oestrus or weaning of a calf, are sufficient to trigger the condition. The almost pathognomic sign shown by cows with hypomagnesaemia is recumbency and convulsions. Diagnosis can be confirmed by measuring blood magnesium levels or at post-mortem by measuring magnesium levels in the aqueous humour of the eye.

At the very onset, the clinician should warn the owner that the cow could die at any moment and that any treatment will be hazardous. It should also be stressed that although the level of magnesium in the blood will be raised by the treatment, irreparable brain damage may already have occurred.

Historically, in a cow having convulsions, clinicians used to inject 10 ml of a small animal euthanasia triple-strength barbiturate solution iv to calm her so that treatment was not so hazardous for the cow or the handlers. However, with the current legislation on veterinary medicines, this practice is not advisable. The first treatment is to inject a 400 ml bottle of 25% magnesium sulfate (this normally has a black top) sub cut. This should be well rubbed in and then a 400 ml bottle of 20% calcium borogluconate with 5% magnesium hypophosphite and 20% glucose mono-hydrate (this normally has a blue top) should be injected slowly iv. Nursing is important in hypomagnesaemia cases. Trying to maintain the cow in sternal recumbency is difficult but worthwhile.