Calf scour is the most common cause of disease and death in calves during the pre-weaning period.
In a 2020 survey, 81 percent of farmers had seen scour in calves during the previous 12 months and 50 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
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
Rather than having to treat a disease in an animal, it is preferable to prevent it occurring in the first place. Recommended management practices for preventing the onset of calf scours include the following:
- Ensure newborn calves receive at least 2 L of colostrum within 12 hours of birth. Heifers have lower antibody levels in their colostrum than do cows, so it may be worthwhile to collect and freeze excess first-milking colostrum from older cows (which are free of enzootic bovine leucosis (EBL) and Johne’s disease) for feeding to the calves of young cows. Ideally, calves should receive 2 L of good quality colostrum within 1 hour of birth, and a further 2 L 12 hours later. Colostrum from freshly calved cows can be stored in the freezer for up to 12 months, and thawed in a microwave oven when needed. Note that colostrum must not be heated to over 56°C.
- Clean feeding equipment thoroughly after each use.
- House calves in a warm, dry, well-ventilated, clean location. If calves are kept in paddocks, they require protection from the prevailing winds.
- Clean calf housing regularly — antiseptic treatment of pens may be required. Rotate calf paddocks, ideally spelling them for at least 4 months between batches of calves.
- Provide adequate nutrition — increased feed may be required in cold weather.
- Avoid an abrupt change of milk replacer types.
- Immediately quarantine all introduced calves for 7 days in pens not used by home calves.
- Quickly separate new cases of diarrhoea from the unaffected calves, and clean up any contamination.
- Individually identify scouring calves, and record changes in their condition and any treatments which are given.
Your territory manager can advise you as to which control measures should be targeted, and can prescribe the most appropriate treatment.
