the shearer post

Sheep Internal Parasites. Worms, the Silent Killers

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Family Feud, Moving Sheep

Getting Sheep in to drench them is always a palava. The dogs are going in the wrong direction, everybody is yelling, giving orders, somebody or two are staring off into the middle distance and the sheep get past them and we all have to run around them and gather them in again. Time is running short because everybody has something else to do other than drench sheep. Emails to send, farmers to book in for livestock contracting, homework to be done (usually music to listen to, whilst pretending to do homework). Rugby or soccer training to get to. Or somebody’s feelings are hurt because dad has roused on a kid again. Well this is the start of the day for drenching our sheep. Or should I say the start of the late afternoon. It happens less now than it used to. Only because we drench less. More about that later.

Then & Now

My childhood memories of drenching come flooding back to me. Growing up on a small farm, with 100 licorice allsort ewes and their lambs is a lot like our modern small farm experiences, with some differences.

Dad & His Theories

Dad used the same drench for as long as I can remember. Thibenzole. Dad said you could trust Thibenzole. You could take it yourself and it would never hurt you. We didn’t use thibenzole on ourselves but we made sure all the dogs had a good dose along with the sheep. Poor dogs!!! Trying to shove the drench gun down the throat of our poorly trained, once in a blue moon, sheep dogs was fraught with danger. They obviously didn’t like the taste and wriggled and jiggled to get away from me and my 4 siblings to avoid the taste. So we thought.. (Maybe they didn’t like the drench gun thrust down their throats in the name of ridding them of sheep internal parasites) Whatever were we thinking? 

Hard Work Entrusted To Us Kids

Our process for drenching when I was a kid was screaming and shouting. We had to push 15 or 20 sheep up into the old sheep shearing shed, where we had a square yard 4m x 4m to hold and drench the sheep. I’m sure some sheep got drenched 3 times while others were never drenched at all. It was just too big for children to keep an eye on the sheep we had already drenched. This being said once the sheep were drenched, it felt like we had achieved a great milestone not only because we could get back to our cricket or footy game depending on the season but because our sheep were safe from the enemy, WORMS!!!!

Two Jobs at Once

We continued this style of drenching on our beloved mob of sheep, using the same Thibenzole drench until I was about 17. Then I learned to shear and crutch the sheep myself, so we drenched the sheep at shearing and crutching time. They were given Thibenzole just before I started the wool removal process. They also got a good drench at lamb marking time, the old fashioned way. I am sure that mob of sheep had the strongest natural resistance to worms in Australia. The same Thibenzole drench for at least 2 decades. It was survival of the fittest as the drench surely never killed a worm for many years as the worms built up their natural resistance to Thibenzole drench. They were bloody tough sheep.

Our Sheeps Job

Our sheep were a by-product of a busy family market garden. My parents used the sheep to clean up vegetable patches that were finished. We’d bring the sheep in on our picked paddocks of peas, beans, zucchini, squash, cucumbers, pumpkin and potatoes. They did a great job of devouring the weeds and the last of the vegetable plants and leaving their fertiliser mark on the paddock for next year’s crop. Dad was a great believer in putting back what you take out. In a way he was rotational grazing when rotational grazing didn’t have a name or was never even thought of. This helps lessen the worm burden, that Thibenzole couldn’t get rid of.

Light Bulb Moment to Kill the Worms

After I learned how to shear and went to TAFE to do a Certificate lll in Agriculture, we started to use a different family of drenches to Thibenzole. Ivermectin. The sheep were less daggy, bigger and heavier. After a family discussion we all realised the sheep worms were resistant to Thibenzole and we had to permanently change the way we drenched. We adopted a plan to rotate the drenches the sheep got to avoid resistance. This seemed to work for many years until we finally got rid of the old flock of sheep and started to trade a few lambs.

Farmer in Charge not the Worms

It wasn’t until 2016 when I leased a small farm of my own that I realised the importance of sheep management and a good drench plan, implementing a strategy of Worm Test Kits. Once I kept a good record of the drenches used and the Faecal Egg Counts coming back from the test labs, I could manage the flock much easier. Knowing the worm burden in our sheep was so important. It prevented unnecessary drenching, and made me think about my pasture and grazing plans to minimise worms on my pastures and in my sheep. It also helped me to recognise resistant drenches and effective drenches.

Facts Not Fiction

We collected our first Worm Test Kit off our local farm store for free. We followed the easy instructions and collected the sheep poo and sent it away to be tested. Three days later we had our results which indicated a very light worm burden. All egg counts were under 100 eggs per gram of faeces and some were zero. No need to drench. Just saved myself $1,200 on drench. We tested periodically 4 or 5 times per year and found we only had to drench once a year. We were very conservatively stocked and rotated our sheep frequently onto new pastures.

When to Drench

When our faecal egg count rose to nearly 1,000 eggs per gram we drenched and followed the drench with a worm test to see if the drench we used was effective in killing >95% of all eggs. Great news. We had nearly a 100% kill, with very few eggs showing up in that test. We made sure we collected the faeces 10 to 14 days after the drench to ensure the drench killed all existing worms and no new worms were established from infected pastures.

Periodic Detention for New Arrivals

At the time we were buying merino wethers for wool production. Everytime we bought in a new mob of wethers we quarantined the wethers and gave them a broad spectrum drench to ensure a knock down of the intestinal worms, followed by a Worm Test to ensure no resistance in the new mob. Once we had established no resistance the sheep were added to the main farm flock. This usually took about 3 weeks, but gave us a huge peace of mind. 

The Enemies Are;

    1. Barbers Pole Worm. Blood Suckers. Active in wet summers and can lay 5,000 to 10,000 eggs per day. Can kill a sheep very quickly because of its prolific breeding in the right conditions. Symptoms include Anemia, white gums, lethargic and bottle jaw. And finally death.
    2. Brown Stomach Worm and Black Scour Worm. These worms can be found in sheep all year round. Laying about 100 eggs per day. Symptoms include Scouring or dags around the crutch and weight loss. Doesn’t usually kill.
    3. Liver Fluke. Found in the gallbladder and liver of the sheep. Sheep ingest the tiny snail on creeks and low lying wet areas in the summer. The liver fluke will kill a sheep very quickly.


SAVE $$$$$

It is important to note that the biggest cost of having worms in your sheep is not the drench or the Worm Test Kit, but the loss of production and the death of the sheep. 90% of the cost of worms on your farm comes from loss of production not the cost of the test or the drench. So it is vitally important to know the health of your sheep by regularly testing for Faecal eggs in your sheep and managing accordingly.

Brains Not Braun

Managing your sheep flock for worms is not hard. It just takes planning. If you have a small flock you can get each sheep independently tested for Faecal egg counts and manage accordingly. Bigger mobs you can gather random fresh samples and manage the mob holistically, drenching as required the whole mob.

Healthy Sheep

Drenching when needed after a high Faecal egg count and then managing that mob of sheep using NON CHEMICAL CONTROL can really slow up the resistant worms in your mob. Keeping your sheep in tip top condition for longer periods of time. Maximising their production and improving their well being.


Is a term used in your drenching plan to help minimise the use of drenching by managing your mob so they have less chance of picking up larvae from the pasture and finishing the lifecycle of the worms. These include.

  1. Genetics – Identifying the high risk to worm sheep. Easier to identify in small flocks when you individually test each sheep. Culling these sheep out.
  2. Nutrition – Have high quality feed in front of your sheep all the time. Using mineral supplements to maintain sheep health.
  3. Rotate with different species – Sheep, Goats and Alpacas carry the same sheep intestinal worms. If you want to clear up pastures with larvae on them cattle or horses can graze down that paddock and consume the larvae with no ill effects to the cattle or horses, leaving the pasture relatively free of larvae.
  4. Rotational Grazing – Move the sheep onto fresh pasture every few days, not allowing the sheep to graze the grass down to the last 4 or 5cm, which is where the larvae live. This will ensure a break in the life cycle of the larvae with fewer larvae consumed and less worm burden.
  5. Spelling paddocks – for up to 6 months in the cooler seasons to ensure the larvae die before putting sheep back on that paddock.
  6. WORM TEST – Test frequently to realise the worm burden in your sheep.
  7. Employ your local vet – Get them involved. They will know more on prevention and techniques that can really save you time, money and heartache and your sheeps well being will benefit from their advice as well.

Do all this in conjunction with a good drench and watch your sheep flourish.

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