Farm Animal Medicine and Surgery - Graham R Duncanson

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too low an energy diet. It may be secondary to some other condition, e.g. a left hand displacement of the abomasum (LDA). The normal signs are lethargy and poor appetite with a sweet-smelling breath which can only be smelt by some people. In unusual cases, nervous signs will be shown. Treatment is with dexamethazone together with treatment of the underlying cause.

      Acidosis

      This may be acute in cases of grain overload, or chronic with a diet low in fibre. The pH of the rumen will be low and this will depress food intake. This chronic form tends to occur in high-producing dairy cows or beef-fattening cattle fed entirely on grain. Diagnosis can be confirmed by measuring the pH of a sample of the rumen contents. Treatment is by adding bicarbonate to the food in the short term and by adding more fibre in the long term. In acute cases, animals should be given high volumes of electrolytes spiked with bicarbonate using an Agger’s pump, with supportive injections of vitamin B. In peracute cases, e.g. when an animal has broken into a grain store, a rumenotomy should be performed to remove the rumen contents and replace them with electrolytes.

      Hypocalcaemia

      This is a disease of adult cows called ‘milk fever’. Classically it occurs around parturition when there is a sudden drop in blood calcium levels. The case may be a true ‘milk fever’ around parturition, or in Jersey cows it may be brought on by oestrus. Feeding excess root crops, particularly the tops, will cause hypocalcaemia in growing and adult animals. Also, poisonous plants containing oxalates, e.g. rhubarb, will cause hypocalcaemia. Diagnosis can be confirmed by measuring blood calcium levels. One 400 ml bottle of 40% calcium into the vein should be sufficient for treatment except in a very large cow. There is no evidence to confirm that the solution is better given at blood heat and slowly, but taking these precautions is prudent. If the cow is staggering but not recumbent, it is advisable not to try to give large volumes of fluid iv, and obviously it should not be put in a crush. Trying to inject a staggering cow is difficult and dangerous. The worst scenario is that some fluid will be injected perivascularly. This will make the cow move her head violently, and will either result in injury or the needle will come out of the vein. It is preferable to give the dose sub cut as this will achieve the same blood levels of calcium within half an hour. It is important that after treatment the cow is moved either on to deep muck or out on to the pasture and then propped up on to her brisket in sternal recumbency.

      Hypomagnesaemia

      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.

      Hypophosphataemia

      This is an overdiagnosed condition of adult cows. The classical signs are recumbency, pain in the lumbar region and, on some occasions, there is haemoglobinuria. Diagnosis can be confirmed by measuring blood phosphorus levels. Treatment is 25 ml of 20% w/v of sodium toldimphos injected iv daily for 2 days.

      Common trace element deficiencies

       Cobalt deficiency

      Cobalt is an ingredient of vitamin B12 which is synthesized in the rumen. Lack of cobalt is rare but will result in a vitamin B12 deficiency which in turn causes ill thrift and anaemia. Diagnosis can be confirmed on a heparinized blood sample. Cobalt is readily given in the diet or as a drench. Vitamin B12 is readily given by injection.

       Copper deficiency

      True copper deficiency is very rare but secondary copper deficiency due to high levels of molybdenum or sulfur in the diet is common. The signs seen are multiple. Initially, black animals will take on a ginger colouring and the hair will rough, then erosions on the mouth and diarrhoea will occur, and eventually animals will die. Diagnosis can be confirmed on a heparinized blood sample. As copper is stored in the liver, low copper blood samples will only be seen in cases of severe deficiency. Liver samples give a more accurate picture. Treatment is with boluses containing copper oxide needles, which are licensed in the UK, or with copper injections, which are licensed in other parts of the world.

       Iodine deficiency

      This condition, called goitre, is extremely rare but is still seen in calves in goitrogenic areas worldwide. The pathognomic sign is a swollen, non-neoplastic thyroid. Low-grade deficiency may result in sub-fertility or the birth of weak calves. Prevention by adding iodized salts to the diet is preferable to treatment.

       Selenium deficiency

      Selenium deficiency will readily occur in selenium-deficient areas. The deficiency can be linked to vitamin E deficiency. Equally, calves can be affected by vitamin E deficiency when selenium levels are normal. The deficiency is manifest as ‘white muscle disease’, which may give signs of muscular weakness or, if the heart is affected, sudden death. Treatment in the short term is with injections of selenium and vitamin E. In the long term, there are long-acting selenium injectable preparations.

      Diseases of the Respiratory System

      The predominant signs

      • Dyspnoea

      • Pyrexia

      • Coughing

      Diagnosis

      • Age

      • History

      • Clinical signs

      • Nasopharyngeal swabs

      • Serology

      • Faeces sample (70 g minimum is required for lungworm larvae)

      Causes of respiratory disease

      • Viruses

      • Bacteria

      • Fungi

      • Parasites

      • Miscellaneous factors

      Respiratory diseases caused by viruses and bacteria, and their treatment

       Bovine respiratory disease (BRD)

      BRD is a syndrome affecting calves and growing cattle. Good animal husbandry is vital for its

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