Weaning is one of the most stressful event a calf will go through, which is why it can be the period when we see many disease related issues as the associated stress leads to immune compromise. Young cattle at weaning may also be going from a situation of being regularly observed to a less intensive management system such as a run off block, where problems may not be as readily detected.
From the moment they start eating grass calves are picking up worm larvae off pasture. They will not develop a full and robust immunity to these parasites until they are 18 – 24 months old. Calves suffering GASTROINTESTINAL PARASITISM are listless, with profuse diarrhoea, poor weight gain and dull coats. This is the number one production limiting disease of young stock in New Zealand. Drenching for worms is required once the calves diet is predominantly grass based, which does typically coincide with weaning. Calves are significant contributors to pasture contamination with worm eggs as well, so it really pays to have a good control programme in place. Cross grazing with older cattle or different stock types can help reduce burdens on pasture.
COCCIDIOSIS is probably the next most common cause of post weaning scours in calves. Bloody diarrhoea is frequently accompanied by significant straining, with decreased appetite and rapid weight loss quickly following. The consumption of large numbers of the parasitic organisms in conjunction with stress, overcrowding and poor weather conditions leads to outbreaks of disease. Preventative measures such as feeding medicated meal containing a coccidiostat may reduce the incidence of disease, but if this isn’t done for long enough or the level of challenge is too high, outbreaks can still occur. Fortunately, diagnosis is easy through faecal testing and treatment is usually successful if started early enough. For pasture grazed calves, it is important to utilise rotational grazing with careful stocking rates to reduce exposure to infection year on year.
Another cause of scours and ill thrift seen frequently in young cattle is YERSINIA. The bacteria Yersinia pseudotuberculosis is found in the gut of healthy cattle, so again stressors such as inclement weather or transportation act as a trigger for clinical disease. The lining of the gut becomes inflamed and ulcerated with the potential for long term damage to the gut, resulting in poor growth rates from reduced nutrient absorption. Affected animals range from 4-12 months old, presenting with diarrhoea that can contain mucus or blood. Again diagnosis is by finding the bug in a faecal sample and treatment is effective so long as not too much gut damage has occurred.
Moving from gut issues to a neurological one, THIAMINE DEFICIENCY (Polioencephalomalacia) is more sporadically seen, though occasional outbreaks can occur. It seems to occur with sudden dietary changes, from stalky, feed with higher DM content, to lusher, low fibre intakes. High dietary sulphur, especially with brassica feeding, may contribute to the incidence. Initially calves stand separately and stop eating, but signs will worsen over time from being unsteady on their feet, tremoring and appearing blind to full out convulsions and death. Treatment is very effective when given early, but it is important to note that B12/cobalt injections will not help with this issue as it is a different B vitamin that needs to be supplemented.
RESPIRATORY DISEASE, while more of a problem in housed cattle, can still be seen in pasture based young stock. This is a complicated disease complex, where again stressors like damp weather play a role. Multiple pathogens can be involved including viruses, bacteria or parasites. Affected calves usually have a cough, but can range in demeanour from bright with minimal discharge from their nose/eyes to very sick. Early diagnosis, treatment and prevention is vital to avoid permanent lung damage that will leave calves susceptible to ongoing bouts of respiratory disease as they grow.
Concurrent infection with BOVINE VIRAL DIARRHOEA VIRUS (BVDV) can often be a huge contributor in some of the aforementioned issues due to its’ immune suppressive effects, but it can also be a cause of disease all by itself. Acute infection with BVDV in young stock may cause no obvious clinical disease, but if it does, it can look very like gastrointestinal parasitism with diarrhoea, reduced appetite and weight gain and rough coat condition. Persistently infected animals – the ones that became infected in the uterus of the dam – tend to fail to thrive and grow poorly, while having an increased susceptibility to other diseases. These are the ones that need to be identified and culled as they will always carry the virus and be a source of infection to other cattle. This is an insidious but costly disease with a high prevalence in NZ. Fortunately, with accurate testing and effective vaccinations available it is possible to put together a management plan in conjunction with your vet to reduce the impact of BVD on young stock production.
This is far from an exhaustive list of the diseases we see in weaned calves, but perhaps some of the ones most likely to be encountered. The common theme is that there are frequently a combination of factors that lead to disease outbreaks in young stock. This is why striving to maintain good nutrition, good parasite control, and good animal husbandry alongside carefully considered vaccination programmes will be the most reliable way to ensure the health and reliable growth of young stock.
