Farm Ireland

Friday 23 March 2018

Strive to eradicate diseases

Know your herd health status to keep your dairy stock clean

John Donworth

Should you be concerned if your neighbour is walking his greyhounds across the cow paddocks or on the farm roadway? Does the practice pose a threat to your dairy herd? The short answer is yes. And, while I have absolutely no problem sharing the countryside with my neighbours, it appears that any kind of dog is a threat to the dairy herd.

The problem is all to do with Neospora (Neospora Caninum). Neospora is a parasite and it causes abortions in dairy cows.

The problems begin when a dog eats material infected with the parasite. This material can either be an aborted foetus, afterbirth (placenta) or raw infected carcasses. The parasite grows in the intestine of the dog and the parasite is excreted with the faeces.

Cows grazing on pasture or eating a food contaminated by infected dog faeces ingest the parasite. The parasite ends up in the intestine of the cow but it doesn't stay there for long. It breaks through the wall of the small intestine and enters different tissues.

Further development of the parasite takes place and it eventually finds its way into the foetus of pregnant animals, via the placenta. Once the parasite finds its way into the placenta, two events can occur. One, the pregnancy can abort, or two, the calf is born healthy and 80-95pc are healthy. But if any calves are kept as replacement stock, they will maintain the infection within the herd. The cow or heifer is infected for life.

So, two events stand out. Dairy cows or heifers, infected with Neospora are much more likely to abort and replacement stock should not be kept from cows identified as being infected with Neospora.

Obviously, you should only buy cows or heifers that have been identified as being free of the parasite. Hygiene around the yard should be high on the agenda and dogs should be kept away from feed and water supplies. All afterbirths should be collected and buried, not thrown on the dung heap.

Many of you may not be familiar with Neospora but a number of you would have tested for the presence of parasites in the bulk milk samples.

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While Neospora may not hit the headlines in the same way as BVD, there are other organisms out there in the cow population that caused economic losses last year.

Buying cows

I know of several dairy farmers that have expanded rapidly in dairy cow numbers. While the advice would be to grow organically -- ie rearing your own replacements -- this is not always possible. For instance, depopulated herds cannot do this and have no choice but to go out into the market place.

Once in the market place, the ideal situation is to buy off one or two herds. Certainly, at most three. The last place you want to go is to the local mart, and it still amazes me that dairy farmers will go to the local mart to buy a few cows just to keep dairy cow numbers up. God only knows what threat you could be bringing into your own herd.

Over the past few years, there have been serious advances in herd health diagnosis in this country. That's about time and no farmer buying stock today can say that "if only I had known then what I know now, I would have made a different choice".

Any farmer going out to buy stock today should ask the seller for the status of the following six infectious diseases within the herd:

  • BVD -- Bovine Virus Diarrhoea virus.
  • IBR/IPA -- Bovine Herpes viruses.
  • Johne's -- Mycobacterium avium subspecies paratuberculosis.
  • Leptospirosis -- Leptospira hardjo.
  • Neosporosis -- Neospora caninum.
  • Salmonellosis -- Salmonella Dublin.

Recent Teagasc and Department of Agriculture surveys of dairy herds nationally show that BVD, IBR and Leptospirosis antibodies are present in more than 80pc of our herds. Antibodies for Salmonellosis have been found in 65pc of our dairy herds and Johne's Disease has been found in 30pc of our dairy cows.

Some of these diseases can affect breeding performance in our dairy herds. A pregnant cow exposed to the BVD virus between the second and fourth month of pregnancy may produce a persistently infected BVD calf. This occurs where the cow has not been vaccinated one month before breeding.

So, knowing as much as you can about what diseases are currently operating in the herd is a wise move.

Bulk milk test

Bulk milk sampling has revolutionised the area of herd health. For instance, bulk milk testing can now be carried out for the presence of BVD, fluke, IBR, Leptospirosis, Salmonellosis, Neosporosis, lung works and round worms.

The bulk milk sample should be carried out four times during the year to get good reliable results over the entire lactation. Carrying out one bulk milk sample is simply not good enough as infected animals often only yield positive results in late gestation. This service is provided by Progressive Genetics, Munster AI and Riverview Veterinary clinic in Bandon. I would regard it as an invaluable tool in the fight against animal diseases.

Of course, blood sampling also plays a key role and the fact that one can now pool blood samples reduces the costs considerably.

Anytime a vet takes a blood sample from a cow, that sample should be used for the identification of several diseases. It's a wasted opportunity otherwise.

Last year, Animal Health Ireland (AHI) spent a great deal of time dealing with BVD. At this stage, there is no excuse for any professional dealing with dairy farmers not to know all there is to know about BVD. The information is out there. This spring, a growing number of farmers carried out an ear notch test on their newborn calves to detect if any PI calves were born. Such calves should be immediately slaughtered.

I would have preferred to have seen targets set out by AHI for the elimination of BVD. We could certainly eliminate it. Look at what the Scandinavian countries have done.

So, I suppose the first stage of any animal health programme would be to know your herd health status, and using the diagnostic tests out there does help you achieve that goal.

The herd health plan

My next goal in any herd health plan would be to operate a closed herd policy (ie, no cattle movement, including bulls, onto the farm). If you have to buy in stock, then diseases such as BVD, IBR and Johne's can all be tested for. Also, the calf of any pregnant animal that is bought in should be tested for PI status when born.

What about footbaths at farm level? A definite yes. Personally, I am careless about footbaths and rarely look for them when I go onto a farm. This is a mistake on my part and I know a culture has crept in over the years which places animal diseases at too low a rung of the ladder. This must change.

What about vaccination? Sales of cattle-specific vaccines have increased by 78pc over the past four years. Have they a place? Yes. But they should be viewed as a component of a herd health plan, and not as the sole means of disease prevention within a herd. Over reliance on vaccination without the back up of proper compliance can lead to vaccine breakdown.

The last stage of any herd health plan is to monitor it, ie, make sure it is working year after year. This can be done by:

  • Routine herding of stock to pick up early signs of disease.
  • Monitoring records to detect changes in performance
  • Testing and treating bought-in stock.
  • Using screening methods (ie, bulk milk) to detect changes in herd health status.

Should you have a herd health statement for each disease that I have mentioned in this piece? Yes.

Will the market return a premium for that level of achievement? In an ideal world, yes. As herd size increases on farms, controlling infectious animal diseases will be a big challenge. But this time will be well spent.

Irish Independent