As the warmer summer weather dries-out the ground soaked by heavy UK rainfall during May, cattle producers are being urged to be vigilant for any coccidiosis outbreaks in calves around weaning.
The summer months are a peak risk period for coccidiosis outbreaks in spring-born calves, typically affecting animals between three weeks and six months of age.
“Coccidiosis breakdowns in young calves are common during the summer, particularly around weaning,” warned Dr. Kat Baxter-Smith, veterinary adviser with MSD Animal Health.
Calves’ immunity to the Eimeria parasite is quite variable at this time of year and the climatic conditions have been perfect for coccidial oocysts to remain viable in the farm environment.
Dr. Baxter-Smith explains that any passive immunity to coccidial oocysts gained from dam colostrum starts to wear off once the calves reach three weeks-of-age.
The majority of spring-born calves are well beyond that age now, so are particularly vulnerable over the next few months.
“However, while most ruminant animals excrete some coccidial oocysts in their faeces most of the time, not all farms see clinical disease,” the veterinary advisor said.
“The outcome of any infection in calves is a balance between the infection pressure from coccidial oocysts in the environment, calf immunity and stress factors such as overstocking, poor hygiene or adverse weather events.”
Management of coccidia
She added that good management of coccidia means helping calves to avoid disease and any growth setbacks while ensuring youngstock get enough exposure to the parasite to develop good immunity.
“In ideal conditions, sound hygiene and management practices can control the level of oocyst challenge in the environment.
However, on most farms, strategic use of anticoccidial treatments will be required to manage the challenge and allow immunity to develop without loss of performance or disease.
“With most immune adults excreting only a very few oocysts into the environment, it is infections in calves that result in very high levels of oocyst output.
“This causes heavy potential infectivity in the environment, leading to higher challenges and clinical disease in subsequent groups of youngstock.
“Anticoccidial treatments should therefore be targeted at youngstock; to allow exposure, but also to remove the parasite before there is any impact on productivity – and before further environmental contamination occurs,” said Dr. Baxter-Smith.
“Timing of coccidiosis treatment is therefore crucial,” she stressed.
“You have to treat only once the calf is infected but before its gut is damaged.
This means detailed historical records of previous disease outbreaks are valuable, so always try to keep calves in age-related groups and treat all calves in those groups at the right time.”
She added that treatment options for youngstock include triazinone derivatives such as diclazuril (oral drench).
Calves with clinical signs of disease may also need other supportive treatments until the gut damage has had time to heal.
