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Milk Fever in the Dairy Cow

Also referred to as parturient paresis or hypocalcemia, milk fever is a common nutritional disorder generally affecting older, high producing cattle.

The demand for calcium in the body of a cow increases at the beginning of lactation, as large amounts of calcium are lost through milk and hence the need to replenish it. This may lead to a decrease in blood calcium levels if the cow is unable to replace the lost calcium fast enough, consequently leading to a disease called milk fever.

Most milk fever cases occur within 48 to 72 hours of calving when demand for calcium for milk production exceeds the body’s ability to mobilize calcium reserves. Fever is a misnomer as body temperature is usually below normal. Low blood calcium interferes with muscle function throughout the body causing general weakness, loss of appetite and eventually heart failure.

Signs seen in cows with milk fever

At first, the cow experiences muscle tremors, lack of appetite and unsteadiness. Eventually, the cow is unable to rise, body temperature falls, and constipation occurs. Cows go down to a sitting position often with a kink in the neck. Death may occur if the cow is not treated promptly.

Causes

The beginning of milk production causes a decline in the animal’s blood calcium levels. If the cow is unable to replenish this calcium quickly enough, milk fever occurs.

Some high producing multiparous (those which have calved before) cows will develop clinical hypocalcemia just prior to signs of parturition. This occurs when there has been changes within the dry cow ration.

Older cows are more susceptible as they produce more milk and are unable to replenish calcium quickly enough.

Prevention

Managing the diet can be a valuable aid in preventing milk fever. The key to prevention is managing a dry cow nearing parturition, which should be kept on a low calcium diet. Such a diet stimulates the calcium regulatory system to keep the blood levels normal by mobilizing the body stores from the bone. Lucerne, a feed high in calcium and potassium, should thus not be a major ingredient in close-up dry cow diets to avoid too high calcium levels before calving.

When the demand for calcium increases at calving, calcium can be mobilized much more rapidly thus preventing milk fever. In early lactation, high-yielding cows should receive as much calcium as possible. High-risk cows can be injected with vitamin D3 2–8 days before calving.

Diets providing less than 15 g of calcium per day per cow and fed for at least 10 days before calving will reduce the incidence of milk fever.


East Coast Fever (ECF)

East Coast fever (ECF) is a tick-transmitted protozoan disease of cattle characterized by high fever, dyspnea , lymphadenopathy and high mortalities. It affects cattle in East and Central Africa, particularly in Kenya, Uganda, Tanzania, Rwanda, Burundi and Malawi.

Etiology

The disease causing agent, Theileria parva is an apicomplex protozoan parasite. Classic East Coast Fever occurs in East Africa and is associated with T. parva transmitted from cattle to cattle by the brown ear tick, Rhipicephalus appendiculatus. ECF also occurs either as Corridor disease in eastern and southern Africa or as January disease in central Africa.

Occurrence

ECF affects mainly cattle but also buffalo, and occurs in countries in eastern, central, and southern Africa. Its occurrence is related to the distribution of the vector tick which has been recorded from large areas extending from southern Sudan in the north to western Zambia and eastern Zaire in the west, and to Mozambique and Zimbabwe in the south.

The disease is prevalent throughout the wetter areas favoring the development of the tick, but is absent from the wet highlands in the horn of Africa. It has been eradicated from southern Africa up to the Zambezi River. The endemic scenarios range from a stable situation with high prevalence of herd infection but low fatality rates (endemic stability), to a low prevalence/high fatality scenario (endemic instability).

Endemic stability develops in indigenous zebu cattle exposed to constant tick challenge as in wetter areas whereas endemic instability is seen with commercial production systems utilizing imported breeds or crossbreeds and in areas with a unimodal rainfall pattern that restricts tick activity. Epidemics occur when there is a breakdown in tick control especially during the rainy season or when susceptible animals are introduced into an endemic area.

Transmission

The vector of ECF is Rhipicephalus appendiculatus and in the field, the disease occurs only where this tick is found, save for Corridor disease which may be transmitted by R. zambeziensis. Other species of Rhipicephalus and Hyalomma spp. can transmit ECF experimentally, but they are not significant.

Economic Importance

ECF has a major impact on cattle production in eastern, central, and southern Africa. The disease is cause for death of large heads of cattle. Serious losses occur in exotic and indigenous cattle, mainly from reduced production of milk and meat due to morbidity and mortality, as well as from the heavy costs incurred in implementing effective tick control.

Clinical Signs

The first clinical signs of ECF in cattle appear 7 to 15 days following the attachment of infected ticks. These signs include:

  • Generalized lymphadenopathy involving superficial subcutaneous lymph nodes such as the parotid, prescapular and prefemoral lymph nodes.
  • One or 2 days later, there is fever, depression, anorexia, and a drop in milk in dairy animals. In later stages, there may be nasal and ocular discharges, dyspnea, generalized lymph node enlarge­ ment, and splenomegaly. In severe cases, cliarrhea occurs, sometimes with dysentery; but usually only late in the course of the disease. Emaciation, weakness, and recumbency lead to death from asphyxia in 7-10 days.
  • Terminally, there is often a frothy nasal discharge. Occasional cases of brain involvement occur and are characterized by circling, hence ‘turning sickness’ or cerebral theileriosis.

Differential Diagnoses

  1. Corridor disease
  2. Mediterranean or tropical theileriosis
  3. Heartwater
  4. Trypanosomosis
  5. Babesiosis
  6. Anaplasmosis,
  7. Malignant catarrhal fever

Control

  • Vaccination-Animals are inoculated with a potentially lethal dose of infective sporozoite stabilate prepared from ticks and treated either simultaneously with a drug.
  • Vector control using acaricides-Organochlorides, organophosphorus , Synthetic pyrethroids and Amitraz, are applied in dips, spray races, or by hand spraying.

Always Contact your veterinarian whenever your identify abnormal behavior in your cows. Timely consultation and prompt treatment ultimately influences the prognosis.