Calf scour is the most common cause of disease and death in calves during the pre-weaning period.
In a 2018 survey 82 percent of farmers had seen scour in calves during the previous 12 months and 48 percent had lost animals to the disease over the same period1.
Scour can be due to both infectious or non-infectious causes. Poor nutrition can cause non-infectious scour. Viruses and bacteria are the major causes of infectious calf scours but infectious scour can also be caused by parasites.
The biggest viral causes are rotavirus and coronavirus but bacteria such as E.coli K99 and protozoan organisms like cryptosporidia also cause infectious scour.
A number of these pathogens, particularly rotavirus and cryptosporidia, are present on most farms. Inexpensive diagnostics are available to identify pathogens which cause scour on farm.
Some viral causes of scour, such as rotavirus and coronavirus, destroy the gut lining of the small intestine, reducing the digestive and absorptive capacity of the intestine and causing diarrhoea.
Other infectious causes, such as E.coli, produce toxins which can lead rapidly to fatal disease. Even if calves recover from these infections they may never perform as well as non-affected animals.
The cost of treating scours in individual herds can be easily established. ADAS estimates the total cost of a scour outbreak in a 100-cow suckler herd (assuming 90 calves born) is £5,794.
The longer-term impacts on performance and profitability are harder to measure, but it’s important to take these other costs into account when analysing the total cost of scour on your farm.
Whatever the cause of infectious scour, good hygiene, colostrum provision and biosecurity practices are critical to minimising the chances of an outbreak occurring. Calves are most at risk from infectious scour in the first 3-4 weeks of life and need a continuous source of protection through the passive transfer of antibodies in the colostrum. On many units, normal colostrum may not provide enough antibodies. Giving the calf’s mother a single shot vaccination 12-3 weeks before calving boosts colostrum quality, allowing high levels of antibodies against rotavirus, coronavirus and E.coli K99 to be fed in early life.
Viruses like rotavirus and coronavirus cannot be cured with antibiotics so prevention, through vaccination, is the only effective way of controlling these scours. There is currently no vaccination available to prevent scour caused by cryptosporidia but there are other available prevention and treatment options.
Cryptosporidiosis is a common cause of scour, occurring in calves around 2-10 days old due to infection with Cryptosporidium parvum. Once infected, it takes approximately four days for scour to develop, usually lasting up to 14 days.
Humans are also susceptible to infection, usually by handling infected animals or drinking contaminated water.
Cryptosporidia destroy cells lining the villi of the small intestine, reducing its digestive and absorptive capacity and causing profuse watery diarrhoea. The onset of diarrhoea usually coincides with the shedding of fully developed and infectious oocysts (eggs). At peak shedding, millions of oocysts are excreted for 7-10 days but only five oocysts are needed to cause infection, so a single calf can easily infect other calves.
Prevention of cryptosporidiosis relies on good management practices and excellent hygiene. Calves should be born and reared in a clean, dry environment and, ideally, housed in individual hutches or boxes. Healthy calves need to be separated from sick calves and cared for by different people using different equipment. Calf-rearing areas should not be occupied continuously and must be thoroughly cleaned between batches of calves.
- National Youngstock Survey 2018 (MSD Animal Health May 2018)
- ADAS Report: Economic impact of health and welfare issues in beef cattle and sheep in England (p. 35/36)