March 5, 2010

Breeding sheep to eliminate dags and worms. 2.

By Dr Clive Dalton


Dag-Free & Worm-Free sheep – where to start?
Commercial sheep farmers have two options if they want to get rid or drastically reduce dags and worms:

Option1. Buy in the genetics (as rams) needed from established ‘stud breeders’.

Option 2.
Start a breeding programme in their own flock, which includes breeding their own rams.

Option1. Buy genetics from stud breeders.

Stud rams at public sale. FEC data are rare and Dag information non existent.
All rams are drenched frequently before sale.

  • Buying the genetics (as rams) from stud breeders seems the logical choice, as ‘stud breeders with registered flocks have been providing rams (and assumed genetic improvement) for commercial breeders since sheep farming began in New Zealand.
  • They record masses of data through Sheep Improvement Ltd (SIL) database via a number of bureaus.
  • But it’s often this mass of data that scares commercial buyers away. Stud breeders have all worked hard over many generations and none got rich from selling rams.
  • Few commercial buyers appreciate the costs, dedication and work involved in stud breeding.

Selection indexes

SIL Ram selection front page listing all the Indexes
There are 5 indexes and 11 Breeding Values provided.

  • The core of the SIL data provided to commercial farmers on the ‘ram selection list’ is in the ‘indexes’ and ‘sub indexes’, and there’s a range of them.
  • Breeding Values (BVs) are first calculated for each trait using all the information on the animal and its relatives.
  • They are then balanced up for varying genetic relationships between them and finally balanced for the relative economic value of each one. This is to achieve maximum overall gain expressed in cents.
  • See SIL website for details.
  • But geneticists never tell you how long it will take to see this overall and balanced improvement expressed in the index, in the bank account. Time is not built into the index – it cannot be.
  • The old genetic principle is well known – ‘that the more traits you select for, the slower is the rate of progress in any individual one’.
  • My concern is that today’s sheep farmers don’t have time to wait for these sophisticated indexes with all the various economic traits to bring about improved overall income, of which dags and worms are only a part.
  • If you want to fix dags and worms on ‘Fast Track’ because they are killing you and your profits, you need to hit them hard, and not let the rest of the index components slow you down.
Ram selection list showing extensive data on each animal.
This regularly scares ram buyers so they end up picking rams on their looks.

Special concern over dags and worms

The obvious conclusion: Farmers need to get rid of dags and worms on fast track as there’s nothing more important on a sheep farm right now.

Using ‘Independent Culling Levels’
  • We need to treat dags and worm resistance as ‘Independent Culling Levels’.
  • This is where you select for each trait independently (as they are unrelated), and if an animal fails to reach the pass mark for one trait (whatever level you set the pass mark at), then it fails the whole exam.
  • It’s like what the old School Certificate used to be – if you failed one critical subject like maths, no matter how good you were at the others – you failed the lot. It was tough.
  • Using the index approach, excellence in one trait can compensate for failure in another. This is not good enough to get rid of both dags and worms quickly – which is urgent right now.

The BIG problem:
Finding SIL breeders with Dag-Free and Worm-Free sheep
  • Very few SIL breeders have taken the option to select for host resistance to worms, and fewer still are selecting against dags to provide Breeding Values (BVs) for these traits.
  • This is understandable, as their clients are not asking for such rams. The new drench chemicals have now come along as the ultimate solution.
  • The BV for worm resistance (called WormFEC™) is based on a flexible protocol, (too flexible in my view) allowing great variation in FEC sampling times and methods, so accuracy for selection purposes has got to be a concern.
  • For those with WormFEC™ BVs, not all the lamb crop is always put up for testing, and this is often not made clear. So the choice of rams for sale within a flock can be very limited.
  • These BVs only apply within farms and not between them.
  • It would be hard to find a stud breeder who had not drenched the sale rams for at least two months before your visit. This is the minimal period needed to get an honest drug-free assessment of how genetically daggy individuals are.
  • Farmers are told by stud breeders, technical advisers and stock agents, that if they stop selecting rams for the main economic traits like fertility and growth (wool doesn’t worry them), then these traits will go backwards in their flock.
  • This is NOT true; they’ll just stay where they are, until selection moves things ahead again. You’d be hard put to select against these traits to start and lose them.
  • Ignoring the other main traits won’t drive you bankrupt for a couple of generations at least till you make a big dent in dags and worms.
Obvious conclusion: The choice of getting Dag-Free and Worm-Free rams from SIL breeders is very limited, so you need to look at starting a breeding programme in your own commercial flock.

Option 2. Start a breeding programme in your own flock.

What’s wrong with the idea?

Here’s some facts and fiction that you hear:
  • Fiction: Breeding is too much work and you’ll be buried in paper, stuck in the office when you should be outside – presumably dagging and drenching! Not true.
  • Fact: All you need to get started is some raddle and some tags (which may as well be numbered). Later on you may need to use your index finger!
  • Fiction: The genetics in your flock are not good enough as stud breeders have all the superior genes. Not true. This is biologically impossible.
  • Fact: If you’ve been buying rams from the same stud breeder for a number of years, you’ll have all the genes they have. Your flock will genetically be a couple of generations behind that stud.

The big positives

Sheep selected and bred on your farm will perform well on your farm.

  • You’ll be identifying top genetics in your own farming environment, and that’s a massive advantage. There’s no worry over whether a stud’s sheep will ‘shift well’ and adapt to your farm and management.
  • You don’t have to keep trying different studs in different areas to see which suits your environment. On your own farm – what you see is what you get, and you certainly can’t hide how much time and money has been spent on dagging and drench!
  • Also, because of the large numbers of animals in a commercial flock, there is a mass of scope for selection and culling, which many smaller studs don’t have. A high proportion of the ram lambs born in many small studs have to be sold as sires to make money.

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