Autumn dairy herd health checklist

With changes in the weather and extra stress on animals at housing time, the autumn is usually a high-risk period for animal health issues. Like with everything, prevention is better than cure, but with margins on dairy and beef farms squeezed, there is a temptation to skimp on some routine preventative measures.

Animal health costs on farms can be broken down into three areas: Routine (eg dosing, testing and vaccinations), veterinary call-outs and treatment costs and, finally, costs associated with loss of production due to diseases and parasites.

An effective animal health programme will reduce the costs associated with treatments and losses by putting in place adequate preventative process involving routine dosing and vaccination. Skimping on this will lead to higher risks of disease outbreaks and resultant treatment costs.

Worms

Grazing weanlings and calves should have been treated for worms since midsummer as they have no immunity to stomach worms. It is only after exposure to worms that animals build up immunity. Without dosing, though, the worm burden becomes too high and animal performance drops significantly. Over and/or under-dosing in the first year will affect subsequent immunity and may lead to resistance so it is important to use the correct dose rate per kilo of liveweight. Most of the stomach wormers also treat for lungworms. Lungworm (hoose) was a big problem last year, especially in high rainfall areas and on heavy farms. The symptoms of hoose include a husky cough and difficulty in breathing. Immunity to lungworms only lasts for six months so adult cattle can get re-infected, especially if they are grazing high-risk pastures (fields previously grazed by infected youngstock).

Do adult cows need to be dosed for worms? The answer to this depends on their exposure and infection levels. An ELISA test on a bulk tank milk sample (when all the herd is going into the tank) will confirm what the herd’s exposure is to worms. Faecal samples from cows are the ultimate test for stomach worms. If there are over 500 eggs per gramme, you are recommended to dose. Many farmers now routinely dose their cows for worms during the dry period as they find that natural immunity is reducing in adult dairy cows.

Liver fluke

Most farmers will need to routinely treat their stock for liver fluke. Faecal samples will determine the presence and density of infection, but it is normally only very dry farms, with no wet areas that can get away without dosing.

For dairy stock, you can only treat in the dry period; otherwise you have to withhold milk. The most important thing when treating for liver fluke is to understand the product that you are using. Some products only treat adult fluke so a second dose, probably four weeks later, will be required to kill the immature fluke at the first dose. Because all flukicides have a milk withdrawal period, it is really important that a good treatment programme is in place during the dry period to reduce the burden.

Rumen fluke

Most doses for liver fluke do not kill rumen fluke. Rumen fluke was identified as a big problem after the wet summer of 2009 but shouldn’t be as much of an issue this year. The oxyclozanide range of flukicides have been proven to kill rumen fluke but dosing should really only be used to treat clinical cases. Most farmers shouldn’t have to routinely dose for rumen fluke. Doing so could cause resistance developing to the drug.

Salmonella

Every year I hear of cases of a salmonella outbreak in dairy herds resulting in multiple cases of abortions and sometimes sick cows. In some cases the herds are vaccinated but the vaccine wasn’t correctly administered or it was given too late. In some cases the strain of the outbreak can be different to that vaccinated against. The financial consequences can be traumatic.

In spring-calving herds, August and September are the best times to give the salmonella vaccine. However, vaccinating at this time will only protect the cow from abortions – it will not reduce the risk of salmonella scour in calves.

All pregnant animals and bulls in contact with the herd should be vaccinated. Heifers getting their first vaccine will need two shots two to three weeks apart. Pregnant cows can be vaccinated again three to four weeks before calving to help pass on immunity to their calves.

IBR

IBR is a respiratory disease that can affect all bovine animals. It is a virus that can develop into pneumonia and can cause severe ill thrift and death. Most vaccination programmes are either annual or twice a year. Some vaccines are live while others are inactive. Which vaccination programme to choose will depend on the veterinary advice for your farm, based on system of production and so on.

Because it is a viral infection, exposure to other animals will increase the risk of infection so biosecurity is a very important method of control. Make sure livestock don’t have access to other livestock, eg a neighbour’s cattle. Buying in stock is a big risk. Isolate and quarantine bought-in stock. Ideally animals should be blood-tested for IBR before they come into the herd and blood tested again before they leave quarantine to make sure they are not carriers.

Routinely sampling milk from the bulk tank will help to identify your herd’s exposure to the IBR virus and can help to decide if vaccination is necessary. In spring-calving herds, IBR vaccinations are usually given in winter and again in midsummer if on the twice yearly programme. However, depending on risk and previous experience, some farmers will vaccinate youngstock for IBR and other respiratory diseases such as RSV and Pi-3 when housing to help prevent pneumonia.

Autumn tetany

The autumn is a high-risk period for grass tetany. Where concentrate is being fed, make sure magnesium is included in the ration. Where no meal is fed your options are to paddock dust with cal-mag or include magnesium in the water. Both methods are effective. Including magnesium in the water works well but it needs management, especially on very wet days when cows’ water intake declines to about 5l per cow per day, so either up the inclusion rate or use an alternative method.

Minerals

Sticking with minerals, many farmers will be purchasing dry cow minerals over the next few months. There are lots of products on the market, each with their own unique selling point. The most important ingredients are magnesium (should be around 20% magnesium) and phosphorus (4%). There should be no calcium in a dry cow mineral but sodium should be included at a rate of about 12%. On the trace element side, iodine and selenium are the most important as deficiencies in these nutrients can cause issues with calves. Compare the specs of dry cow minerals before purchasing and don’t just buy the cheapest one.

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Focus: Winter animal health