With high numbers of dairy heifers moving to grazing units this month, it is worth pausing to consider the stress the girls are under, and the effect that can have on their health and productivity.
In young animals, any change in diet and environment will usually cause a 3-week check to growth rates. This is due to a week to 10 days of weight loss and a further week to 10 days to regain that weight. This can be seen even in healthy animals that appear to have little stress. It is a good idea to weigh young stock on arrival so that you have a clear idea of how much weight they need to gain and so you can monitor any weight loss, especially in the early weeks.
Transport is a key factor causing stress, and long journeys, especially in poor weather, will severely stress young cattle. They can get a pneumonia called ‘Transit fever’ which is associated with the stress and the air environment during trucking. The change in diet associated with moving farms can be considerable and even different grass species will require a change of gut flora to digest it properly which takes 7 to 10 days. Calves that have been fed meal should stay on the same feed for two to three weeks after moving to ease this transition. The sudden change in gut flora can lead to a lack of thiamine being made in the rumen which causes polioencephalomalacia (PEM) showing as blindness and incoordination.
The change in terrain that calves have to cope with can present surprising problems. Many dairy calves are reared on very flat paddocks and appear to have to learn how to run up and down hills. We can see leg injuries or animals getting stuck in gullies in the first few weeks after they arrive. If possible a gradual introduction to steep paddocks is advised.
Due to all the factors above, coccidiosis is an issue with these calves. Most calf meal supplements contain coccidiostats to prevent this disease, but often meal feed stops around this time precipitating an outbreak. The disease causes bloody diarrhoea with straining which can be severe enough to cause deaths. Coccidiosis is also a cause of ill thrift and poor weight gain. Diagnosis is by faecal sample, and treatment in the early stages of the disease is normally successful.
This disease can present in a very similar way to Coccidiosis, but the scour is often dark and very liquid. Animals are quite ill, and whilst treatment with antibiotics early on in the disease is usually successful, if the disease is too far on, then antibiotics do not seem to be effective. When Yersinia is severe, there is extensive damage to the gut lining and although antibiotics will kill the bacteria present, it is the gut damage that causes the diarrhoea and this will continue long after the infection has cleared. There is a vaccine available, but it is only licenced for deer. Use of the vaccine in calves is possible, but it requires veterinary surveillance and the use of antihistamines with the second shot as anaphylactic reactions are possible. Prompt treatment with Bivatop offers the best results.
When weather conditions are poor, and especially after long journeys, there is a risk of viral pneumonia with secondary bacterial infection. Calves will often look depressed, with their heads and ears down, and coughing is often present. Treatment with antibiotics and anti-inflammatories will cure the bacterial side of the infection which usually allows the calf to recover. However if the lung damage is severe then it can cause permanent damage to the lungs or even death.
As mentioned above, a lack of thiamine being produced daily in the rumen will lead to PEM which is due to brain swelling. The signs are sudden death, coma, blindness, circling and incoordination. Treatment with intravenous thiamine for affected individuals can be successful if caught in the early stages. Preventative treatment for the rest of the mob is by drenching with oral thiamine. Careful introduction of new diets is the main way to prevent this disease.
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