August 1, 2008

Getting rid of dags and worms - Part I

Part 1. Dagging and drenching have no future

Dagging has been the ruination of sheep farming and the solution in the past was always to drench. So after dagging sheep, you drenched to dry them up until they got daggy again. Then you drenched again and continued the whole daft exercise! It was part of sheep farming and we never complained.

Things have changed because the average sheep farmer is well over 50. His back has been painful for years and now his hips and knees are playing up. At $20,000 a replacement joint, the effects of dragging 60-80kg ewes over the board to cut dung from their bums is not on, and certainly not cost effective. The view even becomes boring!

What happened to the family members who used to come home to dag? They went to good boarding schools because of isolation, and are now lawyers and accountants or are overseas. Holidays back home don't feature dagging and crutching any more. It was maybe a mistake to educate them, as Dad and Mum are now in the shed on their own and it's lonely.

If you can find a young person willing to dag, they rightly should be paid 70c/sheep and soon will need $1. If you still have folk stupid enough to dag for 50-60c/sheep, then you're ripping them off, so don't let them read this.
Spending thousands of dollars on a sheep handler is an option, but still involves far too much waste of physical effort, time and money. On one New Zealand farm recently with 36,000 ewes to dag, the staff refused to dag unless the company purchased three sheep handling machines costing around $30,000.
Think about this. Why do we crutch sheep? A pre-lamb crutch makes sense to let the lamb find the udder, and maybe a pre-tup crutch helps the ram find the spot – but most rams could manage this unassisted. So when you think of it, all this bending and pain is for a questionable return in wool, and only prevents sheep getting daggy.
So if we get rid of dags, we prevent damage to the human body and brain, we save money, and staff stop looking for better jobs. Imagine an advert for shepherd's job which said "no dagging required".

It's maybe a good thing that it's too hard to calculate the true costs of dagging sheep; it would scare us to death. Dagging is a health and safety issue for shearers, and it should be for farmers and their staff too.

The solution
We can deal to dags and worms (note in that order) by genetics. This was done with Facial Eczema in New Zealand as drenching sheep once a week was never practical. The same principles can be applied again to dags and worms. The simple breeding principles involved have been around a while. Thomas Bakewell and the Colling brothers used them in the 1770s.
Some sheep facts;
  • Dags are inherited. They have a heritability of 25%, which means if you select dag-free parents, you will make genetic progress and this gain will not be lost. Fertility has low heritability at 10-15%, and look how that was improved by selection in New Zealand flocks before the Finn arrived.
  • The consistency of faeces is inherited. Faecal Consistency Score (FCS) has a heritability of about 35%, which means that if you mate rams that produce "marbles" (regardless of the kind of feed they are on) to ewes that product "marbles", you'll clean up the dags in very short time. There are about a dozen Kiwi farmers who are well on this "fast track' now and have seen big improvements in the first progeny.
  • Faecal marbles have other advantages apart from not sticking to wool and causing dags. Marbles have a greater surface area so dry out faster than "plops, slops or scour". Dehydration and radiation kills hatching larvae so the pasture contamination is reduced, and this is where over 90% of the worm problem is. Larvae are aquatic creatures so need moisture to move into the ground and up the plants.
  • A sheep that consistently produces marbles is also digesting its feed efficiently and is highly likely to have a good immune system which keeps it healthy, avoiding anything having to be poked into or on to it, costing money.
  • Immunity develops in the young lamb up to the hogget stage, and the fewer drugs (anthelmintics or pour-ons) it is given over this period the better. These drugs knock the developing immune system and it's no satisfaction to hear from pharmaceutical companies that "there is no evidence of ill effects". The long-term work has not been done.

So if we get rid of the "genetic daggers" in the flock, there's evidence building up from breeders' flocks that Faecal Egg Count (FEC) will drop and the proportion of genetically worm resistant sheep will increase.

  • Clearly the fastest path towards a genetically "Dag-Free and Worm-Free" (DFWF) flock is to select first for Faecal Consistency Score (FCS 1 - marbles), and then for low FEC (under 500 eggs/gram). See my book for details.
D.C.Dalton (2007). "Internal parasites of sheep and their control – now and in the future". 3rd Edition with cartoons by David Henshaw.
Book available from

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