Coccidiosis – Looking after your calves!

Coccidiosis has been seen on several farms around the district, renewing our need to ensure calves are protected! There are several ways this can be done, including medicated feeding, pasture management and proper hygiene.

The Disease

Coccidiosis is caused by a protozoal parasite that invades and multiplies in the cells lining the intestine. It causes severe, often blood-stained diarrhoea, and usually occurs in calves over three weeks of age.

Factors that predispose to the development of coccidiosis include those of nutritional, climatic or management stresses, as well as other diseases. It is important to remember that coccidia can survive on pasture from year to year, so prevention is necessary every year!

It is commonly associated with overstocked paddocks, or where there is poor pasture management.
Calves become infected by licking the coats of infected herd mates or from the ground, walls or other contaminated surfaces. Calves usually contract the resilient and highly infectious coccidia in times of stress, such as when calves are weaned onto pasture.


The disease is most commonly controlled with the use of a preventative (coccidiostat), such as Rumensin (Monensin), Lasalocid, or Decoquinate. These are usually added to calf pellets or as an additive in milk replacers.

Monensin is required at a dose rate of 1mg/kg of body weight (BW) as a preventative, and is usually found in pellets at a dose of 50-100mg/kg of feed. This means that a 50kg calf needs to eat ½ to 1kg of pellets a day, depending on what pellet you are using.

The most important note to take is that in order to be protected, calves need to be eating a required amount of pellets, this is often a big ask for small calves, thus it is vital that calves are started on pellets from day 1.

cross_bred_calves_webAnother form of prevention is with the use of Baycox (Toltrazuril) which requires a once-off oral dose, which is given ONE week prior to expected exposure, so before calves are to be placed on pasture.

This is a very useful product as it is easy to use and is extremely effective at protecting calves and will work along side but not disrupt the development of natural immunity to the disease. It can also be used as a treatment in the event of an outbreak, and is given at a dose of 3ml/10kg.


As often stated in our newsletter, bigger heifers make you more money. Studies have shown that for each 1 kg increase in live weight attained before a heifer has her calf, equates to 7 litres of milk per lactation after calving. A 50 Kg increase in live weight can result in an increase of 350L of milk in the heifer’s first lactation or 1,000 L during her lifetime.

As an aside, most cases of scours are not caused by coccidia. If calf scours is a problem on your farm, or you would like any more information, give us a call, and one of our vets will be more than happy to do an investigation for you.