Wormer Resistance in sheep



In recent years worm resistance has become a big problem in our area. Some farms have resistance to one or two of the 3 wormer groups and others to all three wormer groups. The first signs of resistance usually noticed by farmers are poor weight gain, ill-thrift and scour, despite lambs having received worming treatments. Resistance can be detected long before it becomes a clinical problem so resistant worms have been established in the flock for some time before these signs are noticed. We can now check dung samples in our clinic in Rathdrum to verify resistance.

Most resistance is seen in farms that did the most to control worms.  This leads to too much use of wormers.  Sadly, the development of resistance has been an inevitable consequence of good short term worm control and not necessarily the result of bad farming practices. Unfortunately, most of the recommendations given to help slow down the development of resistance involve compromising the control of worms in the short term.

There are new wormers now which have no known resistance. It is important that these wormers are used sensibly and strategically to get best results.

To help prevent worm resistance take into account the following;

  • Dose when necessary. Use faecal egg counts . We can do these in our clinic in Rathdrum. Egg counts save money in the long run.
  • Administer wormers at the right dose. This means weighing the heaviest sheep and dosing for this weight, make sure guns are calibrated correctly and do not scrimp when getting to the end of the dosing container.
  • Use correct type of dose. Contact the clinic for further advice.
  • Test for resistance by using faecal egg counts
  • Reduce dependence on wormers . There are a number of ways of doing this . Seek veterinary advice as each farm is different.
  • Preserve susceptible worms for example after dosing don’t move to clean pasture for a week, dose 90% of animals in a group etc.
  • Adopt quarantine strategies. Ie use zolvix (no worm resistance) on bought in animals and don’t let out to pasture for 2 days.
  • Use zolvix strategically and sensibly before resistance occurs. This mainly means: dose lambs only once a year at or shortly before weaning with zolvix and leave 2 days before moving to new pasture. Please phone the clinic for advice on this


Coughing Cows – Making Assumptions Can be Costly

I received a call from a dairy farmer last July with cows and heifers coughing at grass. This had been going on for several weeks and his milk yield was now 30% below target. Milk solids had also taken a hammering. Several of his cows were noticeably thin.

I called out to him and examined the sick cows. Many were in poor body condition and most were coughing and had clear nasal discharges. A lot of them had high temperatures. I decided to question the farmer to get a history of the problem.

He told me he first noticed the replacement heifers coughing about one month earlier. He got talking to one of his farming neighbours who advised him to vaccinate with a live IBR vaccine as he had heard of other farmers who had been advised to do this by their vets.

He mentioned that he had given this vaccine subcutaneously. This did not stop the problem however and gradually more animals became ill. I asked if he had given any worm doses recently. He said he had dosed the heifers back in May but the cows don’t routinely get a dose. I asked what product he had used on the heifers but he couldn’t recall and said it was an old dose he had used before and thought they would all do the same job.

I decided I would have to take some samples from the sick animals to try and figure out what was causing these issues and to give a clear treatment plan going forward. I took blood samples, nasal swabs, dung samples and a bulk milk sample. When the results came back from the lab the main findings were high RSV levels in the blood and lungworm larvae in the dung samples. RSV (Respiratory Syncytial Virus) is a respiratory virus which was thought to only cause problems in calves but is increasingly seen as a cause of respiratory disease in adult cows.

Based on these findings, I advised the farmer to do his cows with eprinomectin pour-on and dose his heifers with levamisole. I also advised vaccination with an intranasal vaccine for RSV. I had advised him to switch to once a day milking to allow his cows to recover.

One month later there was a huge improvement on the farm. The cows were back milking normally, there was no coughing to be heard and no more runny noses.

The long-term plan is to continue to vaccinate against RSV and to develop a detailed worming plan. It is vital to have a plan for vaccination and worming on modern farms. If this farmer had been doing this he would have avoided this outbreak and all the lost revenue due to decreased milk yield and treatment costs.

I suppose there are several important lessons to learn from this experience. Firstly, the power of good communication skills. I only learned by chance that the IBR vaccine had been given under the skin. This should have been given intramuscularly, so would have had no effect and was wasted money. Also it was obvious that the farmer hadn’t a great understanding of the various worming products on the market and I can’t blame him. Worming protocols should be simple to implement but the vast array of products on the market would confuse anyone.

Secondly, I learned the foolishness of making assumptions. We make assumptions to try to save time but in reality it can end up costing us time and money. The farmer (thanks to his well-intentioned neighbour) had assumed IBR was the cause of his coughing cows. There has been much talk about IBR and much marketing of the vaccines against it. Whilst it is a very serious disease if an outbreak does occur, I believe that a lot of respiratory disease is blamed on IBR when there are a multitude of other possible causes.

I would have assumed that hoose would have been very likely given the time of year. However, if I just relied on this educated guess I could have failed to diagnose the RSV issue. The value of proper and thorough diagnostics cannot be overstated in a pneumonia outbreak.

Colostrum Large Animal

Easy as 1, 2, 3!

If you've ever raised a calf, you've probably heard the 1-2-3 rule of colostrum management: feed from the 1st milk, within the first 2 hours of life, and at least 3 litres.

Why is this important?

Colostrum provides not only nutrition, but also essential immunity to the newborn calf. This immunity helps protect them against common infections such as scour and pneumonia, and can make the difference between a strong healthy calf that never sees a vet, and an ill-thrifty calf that requires numerous costly vet visits and antibiotics.

Following the 1-2-3 rule maximises the benefit of this immunity. Using the cow's first milk and giving at least 3 litres ensures that the calf's first feed is packed with strong immunity and nutrition. It is essential that they receive this as soon as possible, always within the first 2 hours of life, because their ability to absorb this immunity starts to decline almost immediately after birth.

But wait, there's more!

Following the 1-2-3 rule has lifelong benefits. Not only do calves with good colostrum management thrive better, they are proven to be healthier and more productive adult cows.

Not all colostrum is created equal.

What exactly makes colostrum 'high quality?'

* Immunity content - IgG is an immune protein which can be measured as an indication of the overall level of immunity contained within the colostrum. The higher the IgG, the stronger the immunity the calf receives. Good colostrum should contain at least 50g/L of IgG.

* Nutritional content - colostrum should contain a complete and balanced diet for the newborn calf, including vitamins and minerals.

* Free from contaminants and pathogens - Colostrum is of little use if it exposes the calf to potentially serious infection. Colostrum should contain as little bacterial contamination as possible. Colostrum from cows with diseases which are transmittable through milk (such as mastitis, Johne's disease, Mycoplasma, or Salmonella) should not be fed.

Colostrum quality varies significantly between cows for a variety of reasons

* Breed - Though the quality of the colostrum itself does not vary predictibly between breeds, the large volume of milk produced by dairy breeds means that if there is any delay between birth and the first feed of colostrum, the concentration and therefore the level of immunity the calf receives is rapidly reduced. For this reason dairy cows have a reputation (though perhaps an unfair one) of having poorer colostrum than beef cowsd, and dairy calves a weaker immune system.

* Age - Like a good wine, colostrum gets better with age. Older cows generally produced better quality colostrum than heifers.

* Overall health - Cows with better nutritional status and which are free from illness will produce better quality colostrum as they are able to devote more resources to it. Cows with nutritional deficiencies, particularly selenium or vitamin E deficiency which are often seen in the Wicklow area, will produce smaller quantities of lower quality colostrum. Colostrum from cows which are in any way ill should never be fed to calves as this can transmit disease.

* Vaccination - The value of the immunity provided by colostrum is maximised if it is tailored to the diseases the calf is likely to be exposed to - vaccinations are a great way to achieve this. Vaccines given around 3-6 weeks pre-calving, usually for causes of scour such as Rotavirus, Coronavirus, E. coli, and Salmonella, stimulates the cow to produce specific immunity against these diseases which is transfered in the form of IgG into colostrum and on to the calf.

* Dry period - The dry period should be at least 3-4 weeks, any less than this doesn't allow the mammary glands sufficient time to rest and recover before the demanding process of making colostrum, and does not allow enough time for response to vaccines and transfer of IgG. A dry period of at least 40 days will maximize the volume of colostrum produced.

What else do I need to know?

How to feed - Don't rely on the calf! Even if you see them stand to suck, you can never be sure what volume they have taken. Calves should always be stomach tubed or bottle fed so there is no doubt as to exactly how much they have recieved.

Colostrum storage and thawing - Colostrum from healthy cows (rather than heifers) should be frozen and stored in 1L containers which can be gently and evenly thawed in warm water (temp no greater than 50C). Colostrum should never be microwaved or placed in boiling water. It can be safely stored for up to 12 months at -18 to -25C, or up to 24 hours in a refridgerator. Colostrum from neighbouring farms should be avoided due to risk of introducing disease.

Artificial colostrum - There is absolutely no comparison to the real thing. Colostrum from the cow has richer nutrition, stronger immunity, and is absorbed much better. Replacement colostrum can be used in an emergency, but products are variable so make sure to ask your vet for advice.

How do I know I'm getting it right?

Measuring colostrum

* RID - The gold standard of measuring colostrum quality, but expensive and samples must be sent to a lab, so it's not a very practical test.

* Brix Refractometer (Optical or Digital) - A small sample of colostrum is applied and a digital reading is given. A brix reading of >22% correlates to >50g/L of IgG and therefore an adequate level of immunity.

* Colostrometer - A glass float which is placed in room temperature colostrum. The higher the IgG content the more dense the colostrum, and the higher the colostrometer floats above the surface. They are generally marked to indicate good, adequate, and poor colostrum quality.

Measuring calf immunity (Calves 1-3 days old)

* Total Protein Refractometer - A small blood sample can be taken and the serum separated out. A drop of serum is applied to the refractometer and reading taken of the total protein, which can be used as an indicator of the level of IgG in the calf's bloodstream. This value should be at least 5.5g/dL to indicate adequate transfer of immunity, <5.0g/dL indicates complete failure of immune transfer. This is not a reliable test in sick or dehydrated calves.

* Brix refractometer - Uses calf serumm very similarly to a total protein refractomer, however the measurement is taken on the Brix scale. The exact cutoff hasn't been firmly established, but a reading of at least at least 8-10% suggests adequate transfer of immunity.

* ZST - A lab test run on a small blood sample. Results of 16-20 are acceptable, but should be at least 24 to confirm successful transefer of immunity.

Dairy Calf Housing: Keeping Calves Healthy Indoors

A well-designed dairy calf house will significantly reduce the incidence of scour and pneumonia.

Dairy calves are most susceptible to scour and pneumonia in the first 6-8 weeks of life. Scour is the biggest killer of calves under one month old and pneumonia causes the most deaths in animals over one month of age. We could use all the vaccines in the world but unless we have the housing right we will face an uphill battle to keep calves healthy.

During these crucial early weeks calves will be housed and we must ensure this housing is fit for purpose. A lot of investment goes into cows’ cubicle sheds but how much attention is paid to the calf housing? It should provide sufficient space, ventilation and comfort to allow calves to thrive and also be designed to minimise disease challenge. Every farm has different styles of calf housing from individual pens/hutches to sheds with larger groups of calves. Any of these systems can be successful when a few basic rules are followed.


General Points |

  • A lot of calf houses are poorly designed. Older sheds especially often have too few air outlets resulting in inadequate ventilation. Some small modifications can make a big difference.
  • Calves shouldn’t share an airspace with cows. Unfortunately, a lot of calf housing is in the same shed as the calving pens. If sick cows are kept in the calving pens, this makes a bad situation worse.
  • Ideally, there should be a maximum of 40-50 calves in the same airspace.
  • Using outdoor plastic hutches can be an excellent solution on certain farms. Bear in mind that in cold weather calves may need extra feed to supply energy to keep warm.


Space  |

  • Calves require a minimum lying space of 1.7m2. A total floor area of 2.3m2 per calf is required if we include the feed passage. E.g. a pen for 6 calves should be roughly 12m2 (3m wide x 4m deep).
  • Calculate the size of your calf pens. Is there enough space for the number of calves you plan to put in each pen?
  • Have you enough pens to house the number of calves you expect on the ground?
  • Calves should be grouped according to age. Groups of 5-6 calves are generally preferred. It is easier to detect sick calves in small groups.
  • With automatic milk feeders calves would be in bigger groups. These should be observed frequently for any signs of illness.
  • DO NOT mix older calves back into pens with young calves, the older calves may be shedding infectious agents. Keep batches of calves together, the less mixing the better.
  • With compact calving where we might have 80% of cows calving within a 6-week window, there will be huge strain on calf housing in a short space of time.
  • Moving weaned calves to other sheds and selling bull calves early can ease some of this pressure.


Bedding  |

  • Straw bedding should be deep and dry. The bedding should be cleaned out between batches of calves.
  • If you kneel in the straw your knees should stay dry if the bedding is sufficient.
  • Some farms use calf slats in the feeding area, this is a huge help to hygiene.
  • Rubber mats can also be used to improve calf comfort. (Fig. 1)


Ventilation  |

  • Viruses and bacteria thrive in humid air. Having good ventilation without draughts will seriously reduce the risk of calf pneumonia and other diseases.
  • The air outlet area is the space provided at the apex of the roof for air to escape.
  • The air inlet area is usually at the eaves of the shed and must be at least twice the size of the outlet area. Ideally the air inlet would be at least 1.5m lower than the outlet.
  • The outlet should be at least 0.04m2 per calf.
  • A simple way to test ventilation is to crouch to calf level, if there is a smell of ammonia then the ventilation is inadequate.
  • Draughts must be avoided at all costs. Check there are no gaps under doors or holes in side sheeting near calf level. (Fig. 2) In large airy sheds down-draughts may be an issue. In this case plyboard can be used to create shelter for calves to lie under. These can be hinged up to allow a tractor in to clean the shed. (Fig. 3)


Sick Calves  |

  • Sick calves (scour/pneumonia) should be identified promptly and moved to an isolation pen (ideally in a separate shed).
  • Treat these sick calves as highly infectious unless proven otherwise. Feed them last. Use a designated feeder, stomach tube etc. Disinfect your boots when entering and leaving the sick calf pen.
  • If these calves are returned to the main calf shed put them back in with calves of their own age, never mix back in with younger calves.


Hygiene |

  • The easier it is to clean the calf house, the better. The walls should be smooth, with no cracks or crevices for dung to stick to.
  • Many farmers notice that most disease occurs in later born calves. This is due to the build-up of infectious agents over the housing period. Cleaning pens between batches of calves can help. You should never powerwash pens when calves are still in the shed.
  • When all the calves are turned out, clean and powerwash all surfaces of the calf house. Steam cleaning will improve hygiene. Disinfectant should be applied and allowed to soak in. Ideally leave the shed empty for 3-4 months. Talk to your vet about which disinfectant to use.


Some Tips to Keep Calves Healthy Indoors |

  • Don’t overcrowd calf pens
  • Keep groups together – avoid mixing batches
  • Dry deep bedding
  • Clean out straw bedding between batches of calves
  • No draughts – block any gaps
  • Isolate sick calves quickly

Figure 1.

This pen for 6 calves has slats at the feeding area and a rubber mat to improve calf comfort

Figure 2.

Gaps under doors will cause draughts.

Figure 3.

Plyboard shelters protect calves from down draughts.