Almost all cattle will be infected with coccidia during calfhood but disease only occurs if they are exposed to a heavy parasite challenge or if their resistance is lowered through stress, poor nutrition or concurrent disease. Calves between 3 weeks – 6 months of age are most at risk. Over 95% of the losses associated with coccidiosis are not immediately obvious:
→ reduced feed conversion efficiency and reduced growth rate
→ Delayed time to service
→ Reduced conception rate
Cocci oocysts (eggs) can survive for over 1 year in the environment between -30 and +40°C and are resistant to most disinfectants. Only a few oocyts need to be ingested to cause disease and the parasite multiplies rapidly in the gut. A single infected calf can shed millions of oocysts in its faeces therefore the environment can become heavily contaminated very quickly.
Effective control relies upon treating infected animals during the early stages of parasite development. This allows calves to acquire immunity to the parasite whilst avoiding the negative consequences of disease. Good hygiene practices alone are insufficient to manage coccidiosis as environmental contamination is inevitable. However, improving shed hygiene can aid in reducing the infection pressure.
Control of Coccidiosis:
- Dosing calf groups 10-14 days after they have been moved to contaminated pasture or housing. This prevents disease and reduces oocyte shedding. Treatment during an outbreak is of limited value as the damage to the small intestine has already occurred.
- Minimise oocyst intake. Prevent feed and water sources becoming contaminated with faeces. Feed from clean, elevated troughs. Avoid the transfer of faeces between older and younger groups of calves.
- Ensure calves have a healthy immune system. Provide optimal nutrition and prevent concurrent disease (pneumonia, BVD, salmonella) which will make them more likely to succumb to coccidiosis.
- Minimise stress such as re-grouping, dietary change and overstocking.
A single treatment with Tolracol (toltrazuril) is effective against all stages of the parasite. Products containing diclazuril (Vecoxan, Dycoxan) only treat certain stages of the parasite. These products are usually slightly cheaper, but calves may need to be dosed twice. Alternatively, decoquinate can be used as an in-feed medication. Decoquinate must be fed continuously for as long as calves are at risk as it only stops the initial phase of the coccidia life cycle. Calves may succumb to coccidiosis once they stop receiving the medicated feed. Lick buckets containing decoquinate are not recommended as not all animals will consume the required amount to be effective.