E.coli scours typically occur in the first 2-3 days of life. There is rapid fluid loss in affected calves and death can occur quickly. Veterinary assistance is required if scouring appears in the first few days of life.
Calves need immediate rehydration and supplementary heat if the body temperature drops below 38°C. Rotavirus and coronavirus occur usually at 7-21 days of age, cryptosporidium at 5-15 days and coccidiosis from three weeks of age onwards.
Prevention methods include:
• Colostrum feeding: Calves have no immunity against disease at birth. They rely on the antibodies of the cow for protection, delivered via the colostrum, until they are old enough to produce their own antibodies.
Therefore, the feeding of early and an adequate amount of good quality colostrum is the first and most vital disease protection measure in the calf's life. Furthermore, vaccination against calf scours can only be effective by the calf getting adequate colostrum in the first hours of life. The guideline is that a calf should consume about 10pc of its weight in the first 24 hours. Therefore a 45kg calf should consume 4.5 litres.
Ideally, the calf should suckle 2-2.5 litres in the first two hours and the same amount again by 24 hours. Studies indicate that up to one-third of calves when left with the cow, fail to suckle within six hours. In most cases, these problems are obvious and action can be taken.
The reasons include weak calves, cows with bottle teats and pendulous udders, and nervous cows. Some beef cows, and more particularly heifers, will have low milk yields so the calf may need the content of 2-4 quarters to get adequate colostrum. If the calf is too weak to suckle, restrain the cow and take milk from her and feed the calf by teat or stomach tube.
A word of caution here: be very careful around cows at calving. There is a growing number of farmers being seriously injured at this time.
Vaccines are available to combat E.coli, rotavirus, coronavirus and salmonella. Vaccination is just a way of enhancing the natural antibodies in colostrum. These will give best results when targeted against identified disease organisms and where husbandry practices, especially colostrum feeding and hygiene, are good.
Table 1 (left) lists some of the vaccines used to control calf scours. Vaccines need to be administered several weeks pre-calving depending on the product chosen. At this stage, it will be too late to do herd vaccination but it may still be useful for the later-calving cows where there is a build-up of disease being experienced (also see tables 2 and 3, left and top right).
• Hygiene: If the first prong in disease prevention is enhancing immunity, the second is working to reduce the infection challenge to which young calves are exposed.
• Treat the calf's navel with iodine after calving.
• Keep calving boxes and creep beds dry by using enough straw.
• Move cows from slatted pens to well-bedded loose housing/ calving boxes about a week before calving.
• Top up bedding regularly and clean out after every 3-4 occupancies -- more often where there are disease problems.
• Thoroughly clean calving boxes by power washing and disinfecting as soon as calving is finished. Cryptosporidia spores are not killed by most disinfectants at normal rates of application but are killed by desiccation if sheds are clean and are kept dry in the summer.
Scouring causes dehydration, so the first treatment is to give oral re-hydration fluids (electrolytes). It is common to leave scouring calves with their dams and so the calf will not take electrolyte voluntarily by teat while it is getting plenty of milk. Electrolyte can be fed by stomach tube, according to the manufacturers' recommendations.
Ideally, treatment should be directed against the main causal organisms. Since the most common infectious agents are viruses (rotavirus, coronavirus) or parasites (cryptosporidia, coccodia), the use of antibiotics will not result in control of these infections.
There are medications to control crytosporidia and coccidia which limit the spread of infection. Veterinary advice should be sought if scouring persists, the calf stops suckling or gets weak, or where the temperature goes above or below the normal (38.5-39.5°C).
Identifying infectious agents requires vet and laboratory involvement. Where there has been a serious outbreak, it is necessary to identify the culprits so that a comprehensive control plan can be put in place.
Faecal samples from both healthy and scouring calves can be sent to the Regional Veterinary Laboratory for identification of infective organisms.
To a large extent, regardless of the organisms involved, it is the standard of animal husbandry (feeding, housing, hygiene and bio-security) that determines the level of severity and duration of the disease.
Liam Fitzgerald is a cattle specialist with Teagasc Athenry