September 19, 2008

Keeping your cattle disease free

The biggest threat to a country like New Zealand that relies on animal exports, and where tourism is a major income earner, is an outbreak of exotic animal disease brought into the country. So "biosecurity" to protect our borders from incoming pests and diseases is our lifeline.But farmers cannot just rely on protection at the border; they have to protect their own farms by having a robust animal health programme.

Aim: To have a farm with minimal disease that achieves high levels of production and profits.

Good signs

· No closure of the farm or the district because of disease outbreaks.

· Few local vet visits and no visits from government vets or local authorities.

· Rubbish bins free of old used health product packaging (especially antibiotics).

· Low animal health costs per animal.

· Calving with few problems and minimum deaths of offspring or dams.

· Production targets met.

· Cows that return to oestrus after calving and get back in calf quickly.

· High pregnancy rates.

· Cows always in satisfactory body condition for each stage of their production cycle.

· Happy staff who have signed on for next season.

Bad signs
  • Vet always on the farm.
  • Rubbish bin full of used health product packaging (especially antibiotics).
  • High animal health costs per cow.
  • Big bills for disposal of dead stock.
  • Production targets not met.
  • Poor pregnancy rates.
  • Empty cows and boners leaving the farm regularly.
  • Skinny animals – especially young stock in autumn and winter.
  • Neighbours considering reporting farmer to MAF or the NZSPCA.
  • High death rates.
  • Over-worked, tired and depressed staff who are looking for new jobs.
Prevention versus cures
Prevention is better than cures because it's cheaper, and if you get on to a problem early, the chances of a successful cure increases dramatically. It costs money to get the vet, so it's far better if you need to call your vet, to do it in good time and ensure a positive result. The vet's travel cost is the same per km to save the cow, as it is to shoot it!

Protect your property
With the constant risk of an exotic disease outbreak, farmers need to make very positive efforts to protect their own properties. Most farmers accept this concept, but find implementing it more difficult. So they never get around to it, and rely on the fact that the government "has systems in place" to protect them. There are too many examples in New Zealand in the last decade to prove that these systems still break down at regular intervals.

Have an Animal Health Plan
This is a concept constantly being pushed by veterinarians, but too many farmers see it as a cunning plan for their veterinarians to earn a fee for what appears to be doing very little. The farmer's traditional view of veterinarians is that you only call them when stock are sick and need to be cured.

To sort out an animal health plan, farmer and vet need to sit down and work out (and document) a complete disease prevention and treatment programme for all classes of stock on the farm. The plan needs to cover analysis of the common diseases on the farm and their treatment, and how to protect other diseases from arriving.

The animal health plan is especially important on large farms where managers and staff have big responsibilities and need to apply the principle of prevention being cheaper and more effective than cures.

Health costs/cow
This is a very handy guide to see how good or bad things are, and with computerised systems these days on dairy units, it's getting easier to keep track of drugs used and vet visits so they can be costed per cow.
Currently on New Zealand dairy farms costs around $40/cow are not too bad and you can consider things to be about average. Organic farmers who don't buy modern drugs and don't see their vet can get costs down to around $12/cow.
However, there are many farms where costs/cow are above $100/cow so you can see that at this level that there's a need for some intense investigation into what's going on, and what needs fixing - urgently.
Beware of two things. First is the possibility that costs/cow are low because stock are being neglected, but this would be very obvious from stock condition and death rates. The other argument is that high costs/cow can be justified if production/cow is high and will cover it. This is stupid logic!

Animal heath action plan
Here are some things to start working on:

All boundary fences in New Zealand must comply with the Fencing Act, which requires a seven-wire, post and batten fence. But it would be a wise move to double-fence the boundary with a substantial electric fence inside the boundary fence to prevent stock making any direct contact across the boundary. Trees for shade and shelter can be planted in between the fences. This would of course not stop viruses like foot and mouth disease spreading on the wind.

Isolate new arrivals
Make sure newly-arrived stock are kept separate for at least 3-4 days and preferably a week to see if any health problems show up. Long-term problems won't show but any rapid infections will. Veterinarians now advise "quarantine drenching" for internal parasites when stock arrive, but it would pay to consult your vet to get specific advice for your farm, as this depends on the parasites drench resistance present (if known).

Isolate young from old
This was an old gospel and still makes some sense on the principle that old mature stock have high levels of natural immunity to diseases which young stock have not yet developed. Worms are a good example where you don't want young stock to pick up larvae from their dams, so early weaning is the answer to put the young animals on "clean pasture". This idea has now changed and putting young stock on clean pasture is bad advice as their developing immune systems need to be "challenged" by infections.
Before the age of vaccines, farmers used to mix young and old to help development of immunity. Make decisions about running young and old stock together on ease of management and growth rate targets.

New Zealanders visiting farms in Europe are surprised when they are asked to wear protective clothing – to protect the farm from them! It's a concept that needs to be more widely applied on all NZ farms as new diseases (especially those caused by viruses) appear. So it's time for NZ farmers to at least provide a disinfectant bath and brush for visitors to clean their boots before walking on to the farm area. This would certainly be the case if a visitor had come from another calf rearing unit to visit your calf unit. Asking visitors to wear disposable clothing would be a next step.

These are a great potential source of disease spread. Since the NZ policy of not leaving dead stock by the roadside for pickup, trucks soiled from other farms and animals must enter the farm. It's a similar risk of stock trucks picking up animals from different farms and taking them to a saleyard. In future planning it would be wise for farmers to plan their stock loading facility was restricted to an area so that trucks did not have to come on to the farm property.

Colostrum at birth
Making sure all new-born animals get more than an adequate amount of colostrum must be the basis of all animal health plans.

Before you buy vaccines, check with your vet what is needed on your particular farm, as hopefully the vet clinic will have recorded this – in your previous animal health plan. There may be some diseases that you don't have, but these days more vaccines are being included in the one shot, eg five-in-one and ten-in-one so you have little choice.
The key thing is to vaccinate in good time because it takes a few weeks for immunity to develop fully. Too many people vaccinate the day after they lose an animal.

Parasites – internal (worms)
We now know that in New Zealand we have major problems with worms which have become resistant to the three drugs used in anthelmintics (worm drenches). The widespread use of pourons in cattle have made the situation worse, as it has confined most of the treatments to one chemical family.

Drench resistance is spreading in cattle as it starts off on dairy farms where mature cows are treated, and resistant worms are carried by calves to graziers farms where stock mix (and resistant and tolerant worms interbreed) before returning to their home farm carrying even more resistant worms.

Farmers and managers need to seriously question the need to drench adult stock that should have developed sufficient immunity to worms not to need drenching. They should consult their vet and use Faecal Egg Counting (FEC) to confirm that young stock need a drench and which product to use to avoid resistance getting worse.

Making stock graze hard and "clean up" before they move on forces them to graze the pasture hard around previous dung pats which is rich in worm larvae. This has been shown to increase the chances of reinfection. Forcing stock to seek green feed in swamps which are infected with the snails that carry liver fluke.

Testing for drench resistance
Contact your vet clinic for advice and materials needed (eg pottles for faeces).
  • Select around 50-60 well-grown calves or rising yearlings of similar weight that have not been drenched with an anthelmintic for at least 6 weeks.
  • Run them as one mob and move them to a fresh paddock so can see their fresh faeces.
  • Collect 10 fresh faecal samples off the ground from separate droppings.
  • Get a FEC done by sending them to your vet who will either do them at the clinic or send them to a vet pathology lab. You can do FECs yourself with a commercially available kit.
  • The average FEC must reach at least 250 eggs/gm of faeces (epg), before the test can proceed. So if the first test is not high enough, sample again a week later.
  • Once above 250 epg, start the test.
  • Tag 10 individual animals and weigh them.
  • Then and do a FEC as a "start of test" value.
  • Drench the test animals orally with the chemical families (called actives) to be tested. You need the liveweight taken earlier to get the dose rate right for each test individual.
  • Run the stock together for another 7-10 days. Don't put them on a clean paddock as you want them to get infected with larvae.
  • Do another FEC on the tagged animals and compare the start and end FEC.
  • If the drench families have worked, there should have been a kill rate of at least 95%. Anything less than this will confirm that drench resistance is present to that particular family.
Parasites – external (lice)

Lice are the main problem and they can have a big impact on young stock – even killing calves that are in poor condition. Lice too are developing resistance to the chemicals used to kill them, so again discuss treatment and products to use with your vet. As well as lice there are mange mites, ticks in some hot areas, biting flies and blowflies.

Pests and vermin

The farm needs a policy to deal with all vermin. Possums, wild pigs and mustelids (ferrets, stoats and weasels) are vectors for bovine Tb, rats can carry leptospirosis, and dogs and cats can spread neospora abortions. Mice can get into the back of fridges and freezers and cause electrical short circuits.
These are diseases that can be transferred from animals to humans. The main concern is leptospirosis which can be very debilitating. If you get it more than once you will have to leave farming as a third bout could be fatal. So the key is to make sure that every animal in the herd has been vaccinated and that all booster shots are given.
Other zoonoses are tuberculosis, ringworm, campylobacter and salmonella.
Venereal diseases
These diseases were a major problem before Artificial Insemination came along and eliminated the use of bulls spreading the diseases.
They are still around and with the use in large herds of bulls being brought in on contract from specialist bull suppliers, there is always the chance of problems appearing again. The main concerns are trichomoniasis and vibrio foetus.
Using young virgin bulls is the best guarantee of health but you will have to check their fertility and libido as the two are not related. Also make sure bulls coming on to the farm have been tested for Tb and BVD which they can spread by close contact.
Animals on farms are regularly poisoned by a range of things. Here are some examples:
  • Calves licking old paint off old doors and the walls of sheds.
  • Bloat oil drums used for calf feeders before they have been washed out properly.
  • Arsenic from treated shavings in calf pens.
  • Pasture covered with superphosphate or basic slag before it has been washed in.
  • Nitrate from crops or pasture where fertiliser has been spread or the Nitrogen has naturally accumulated over a dry weather period before rain.
  • A wide range of plants can be toxic to varying degrees, and especially when wilted when they are more palatable. Common examples are yew, tutu, rhododendron, oleander, macrocarpa.
  • Acorns from oak trees in autumn.
  • Overdosing with animal remedies.
Genetics (breeding)
Certain diseases are inherited so it's important to report any defects that you find among a new crop of calves. Artificial breeding companies need to know this. Examples seen in New Zealand are BLAD, flexed pasterns, undershot jaw, overshot jaw, udder defects, extra teats, extra legs, two heads, no anus and dwarfism.

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