Farm Animal Medicine and Surgery. Graham R Duncanson
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• There are many ideas put forward for fluid therapy. The author favours giving large volumes of electrolytes with an Agger’s pump.
• Prevention measures include dry cow therapy, teat sealants and vaccination against E. coli.
Summer mastitis
• This occurs in dry cows and in-calf heifers but rarely in maiden heifers.
• The author has on rare occasions seen it in the mammary tissue of bulls.
• The disease, which is bacterial, is spread by the fly Hydrotaea irritans, which has a predilection for trees.
• There is a sequence of events; initially the udder is colonized by S. dysgalactiae, there is a slight swelling and the animal will be only slightly ill with a pyrexia. If treatment with antibiotics, normally penicillin, is initiated immediately, the disease will not progress further and the infected quarter will be saved.
• If the animal is not treated, other bacteria, namely Arcanobacterium pyogenes, Peptococcus indolicus, Bacteroides melaninogenicus and Fusobacterium necrophorum will colonize and the animal will become ill and the quarter will be lost, even with antibiotic treatment.
• At this stage, the udder discharge will be creamy and malodorous, alerting the clinician to the poor prognosis for the udder.
• Animals will be stiff behind and often their hocks will swell so treatment with NSAIDs as well as antibiotics would be appropriate.
• Prevention is with dry cow therapy, teat sealants and fly control.
Mummified fetus
The aetiology of this condition is obscure; in fact, there may be two conditions with different causes. The most common manifestation is the cow which has been diagnosed as in calf but never develops normal udder enlargement, i.e. does not ‘bag up’ for calving at the expected date. Rectal examination of the uterus will reveal an enlargement but no cotyledons or fremitus. Only if clinicians are certain of service dates, and are 100% certain that there has been no subsequent unrecorded service, should prostaglandin injections followed by dexamethazone be given. These mummified chocolate non-malodorous fetuses of about the size of a hare are difficult to abort. After the abortion, the cow should be served at the first oestrus as this has been shown to be the most fertile. The second much more unusual manifestation -after a prolonged pregnancy – is felt on rectal examination as a bag of bones either in the uterus or actually in the vagina. This small calf is mummified but also purulent and malodorous. The calves can be pulled out of the vagina or are easily aborted with a prostaglandin injection. It is possible that the second scenario is just a sequel of the first scenario which has been invaded by pus-forming bacteria.
Pyometritis
This condition causes confusion as literally it means ‘pus in the uterus’, and might be muddled with endometritis which occurs post-parturition (see above). The main cause of pyometritis is Trichomonas fetus which is spread by the bull and results in death of the fetus. The fetus often remains dead in the uterus bathed in pus. Diagnosis is by rectal palpation or rectal ultrasonography. There is no serological test. Treatment is with prostaglandin injections. Prevention is by using artificial insemination (AI).
Udder oedema
This occurs in high-producing dairy cows and, particularly, in heifers immediately before calving. Inducing calving with a prostaglandin injection may be warranted to prevent damage to the udder.
Udder rot
The cause of this condition is not clearly understood, but it is associated with cows with enlarged mammary glands. Inflammation and infection occur between the udder and the hind leg. This irritates the cow which then starts to lick the area regardless of any creams or sprays applied. This licking becomes an obsession and can even result in the licking off of a teat if it becomes involved. Parenteral antibiotics and dexamethazone may be helpful, but the latter should be used with care as these animals are often pregnant.
Diseases of the Locomotory System
Viral diseases
Bovine ephemeral fever (BEF)
This is caused by a rhabdovirus and transmitted by Culicoides spp. and Anopheles spp. It occurs in Africa (where it is called ‘three day sickness’), Asia and Australia. Animals will be pyrexic and recumbent with a serous nasal, lacrimal and salivary discharge. There may be dyspnoea. Mortality is low and animals normally recover with good nursing. There is no treatment. Infection can be confirmed by paired serum samples.
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