Antibiotics should only be used for calves that are depressed, are not eating and have a temperature.
The leading cause of calf scours in New Zealand is viral. This means that antibiotics will not treat the
cause of the scours.
So what is the problem with dosing scouring calves with antibiotics?
- Antibiotics promote antimicrobial resistance making the bugs harder to kill in the long term.
- Antibioitics may alter intestinal flora and induce diarrhoea
- It has been suggested that Coronavirus colonises the gut of calves treated with antibiotics. This opportunistic pathogen can upset the normal balance of the gut microbes.
- More ‘good’ bacteria than ‘bad’ may be harmed in the gut by antibiotics
- Antibiotics are not thought to be effective
- European legislation is concentrated on reducing antibiotic use in food producing animals in the near future and New Zealand relies heavily on international market access.
Oral administration of potentiated sulphonamides (Scourban and pink scour tablets) is not
recommended for treating calf diarrhoea because of the lack of efficacy studies (Constable 2004). This means that there has been no work done to show that these drugs work.
Injectable antibiotics can be recommended for use in calf diarrhoea and will need to be prescribed by your vet. Make sure you give the entire course of antibiotic since you may not fully clear up the problem and you may promote antibiotic resistance if you only give part of the course.
Calves with diarrhoea and no other signs of illness such as fever and depression should be monitored and not treated with antibiotics. Injectable antibiotics are preferable to oral and the injectable
antibiotic of choice should also be bactericidal and predominantly Gram negative in spectrum (Constable 2009). Often the bugs that have caused the calf to scour also damage the cells lining the gut. The gut has ‘finger-like’ projections called villi which increase the surface area for absorption of water and nutrients. Rotavirus infection in particular results in blunting and fusion of the villi, but villi will be damaged whatever the cause of the scour. Recovery depends on tissue repair and replacement of the cells lining the gut wall, so diarrhoea will often continue after the causative agent has been eliminated (Bazeley 2003; Lorenz et al. 2011). This means that antibiotics, while they may act on some of the causative agents of the diarrhoea, do not provide the entire therapeutic solution.
If we can’t use Scourban and pink scour tablets then how do we treat scouring calves?
Oral electrolyte therapy
Maintaining the water, electrolyte and energy balance is the most critical factor affecting survival of the diarrhoeic calf (Schouten 2004). By comparison, other therapeutic treatments have only a minor impact on calf losses (George 1987). Dehydration of 12 to 14% in diarrhoeic calves is considered fatal. Calves with diarrhoea urgently require water and electrolytes to correct fluid imbalances (Schouten, 2004) and it has become increasingly evident over the past 20 years that treatment of calves with diarrhoea should not include withholding milk (Heath et al. 1989; Garthwaite et al. 1994). To reduce body weight loss in scouring calves, farmers are now advised to use rehydrating electrolyte therapy in the treatment of diarrhoea (Garthwaite et al. 1994, McGuirk et al. 1998). However, prolonged electrolyte therapy as the sole treatment of diarrhoea (i.e. without supplementary milk) can cause death through starvation. An example treatment protocol would be to continue to feed milk at two litres twice daily, with supplementation of one to two litres of electrolyte, depending on the calf’s level of dehydration (Vermunt 2002). The electrolyte should not be mixed with milk and the two feeds should be separated by at least 1.5 hours. Feeding oral electrolytes and milk together may interfere with casein coagulation in the abomasum (McGuirk et al. 1998). Many New Zealand dairy farmers are still using the traditional treatment protocol of withholding milk from diarrhoeic calves for 24 hours, but this is not what is best for the calves.
Homeopathic therapy, probiotics and gut protectants
Although, homeopathic therapy for pre-weaning calf diarrhoea is increasing in popularity, particularly with the increasing number of organic dairy operations in Europe, none have been proven to be efficacious in peer-reviewed scientific literature (Constable, 2009). Similarly, intestinal ‘protectants’ and ‘absorbents’ have not been proven to be valuable (Constable, 2009).
Painkillers and anti-inflammatories for scouring calves
The addition of painkillers and anti-inflammatories to your treatment protocol is beneficial. These drugs have been shown to improve early consumption of starter rations and improve starter ration intakes in Europe and Canada. A single shot of painkiller (in conjunction with electrolyte and antibiotic therapy in very sick calves) increased feed intake, hydration score, improved faecal consistency and decreased signs of abdominal pain in scouring calves.