Autumn Ill-Thrift in Cattle.
Sara Sutherland, BVSc, MSc, BSc(Agr) Vet Services Wairarapa
Many farmers experience lower growth rates than expected in their R1 or R2 cattle in autumn. Typically these cattle have been growing well and then slow or even stop growing for three to eight weeks. They may or may not be scouring and have a poor body condition. You may be surprised to hear that autumn ill-thrift is a recognized condition in New Zealand.
There are several factors which may be involved, and not all of these will be present on each farm. The most common reason is that feed quality or quantity may be lower than you think. Other causes which are responsible on some farms are parasites, trace element deficiencies, diseases especially BVD, Yersiniosis, adenovirus, facial eczema, or toxic fungi in the grass. There are also some cases in which a cause cannot be found despite a comprehensive work-up, which means there may be something out there which has not yet been identified.
Nutrition is the most common reason for autumn ill-thrift. Steers weighing 500kg with a growth rate of 1kg per day require 127 MJME per day (range 109-135). This can be approximated to about half a bale of good quality Lucerne hay. Normally protein is not limiting in autumn pasture. Autumn pasture has a lower efficiency of energy use than spring pasture; even though it has high digestibility and high protein. This is because the pattern of volatile fatty acids (VFA’s) released from the rumen bacteria is different, and there is an increased energy demand to convert excess protein to urea.
Very low fibre, high soluble carbohydrate diets can lead to scouring and poor growth. Fast growing spring and autumn pasture in New Zealand is typically low in non-digestible fibre (NDF) and good growth rates are still achieved in many cases. If this is a component of the problem, adding fibre to the diet by supplying hay or straw will stop diarrhoea, and improve the efficiency of digestion.
Parasitism is the second most common factor contributing to autumn ill-thrift. Worm egg counts are less valuable in cattle than in lambs, and parasitism can be a factor even with low worm egg counts in R2 beef animals. However, high worm egg counts mean that a drench is needed. Cooperia is a common worm in young cattle in autumn. Often the most sensitive indirect measure of parasitism in cattle is lower than expected growth rates.
If your farm does not have a BVD control program or there has been a potential biosecurity breakdown, Bovine Viral Diarrhoea Virus may be the cause. Cattle infected at this age have a period of about one month of poor growth rate or weight loss and scouring. You may or may not also see lame animals, or sometimes animals that are drooling or have a discharge from the nose. Animals that are not born with BVD will recover in about four weeks and then usually regain full productivity after recovery. A blood test for antibody will tell us whether BVD is active in the herd. If BVD might be an issue in your herd, we strongly recommend that you book in a BVD consult with one of our vets. We will be able to help you make a BVD control program for your herd.
Yersiniosis is a bacterial disease that can affect weaner cattle in autumn after a period of cold, wet weather or after periods of stress including nutritional stress such as after an autumn drought. It causes fever, scouring, weight loss and occasionally some deaths. Diagnosis is by culture of the bacteria from faeces or from post mortem samples. Sick animals can be treated. Adenovirus can also cause scouring, weight loss and death in younger cattle. This disease also seems to occur more commonly after a period of poor nutrition.
Trace element deficiencies are common in cattle in the Wairarapa. The two most common deficiencies seen are copper and selenium. In young cattle either of these deficiencies will be displayed as poor growth rates. Trace elements are required as components of enzyme pathways. When they are absent or only available in low amounts, the pathways are slowed, causing poor growth rates. Blood samples or liver samples will tell us whether supplementation will improve growth rates in your animals. We can then advise which products will achieve this.
Research has implicated fungi and endophytes as part of the autumn ill-thrift syndrome, however we don’t know enough about these to make recommendations for their control. Facial eczema can cause reduced growth rate before you see visible lesions (reddened, crusty, peeling skin). Some years and some paddocks are more likely to grow the fungi that cause facial eczema. Grass can be tested for spore levels to determine whether facial eczema is likely to occur. Facial eczema is a problem in some years and not others in the Wairarapa. Other fungi or endophytes may cause problems but we do not yet have a way to test for these.
In summary, autumn ill-thrift is a common syndrome in beef cattle in New Zealand. There are a number of different factors that may be involved. This means it is always worth talking to us about a mob you are concerned about. The most common reason is poor nutrition. Remember that in autumn feed availability and quality may not be as good as it looks.
Published Friday 18th of May 2018