March 5, 2010

Breeding sheep to eliminate dags and worms. 6.

By Dr Clive Dalton


Selecting male replacements from the A team nucleus

Remember the aim:

  • To use the dams in the A team as mothers for future rams for use in the commercial flock, and also the best of them to be used as sires in the nucleus.
  • The major drive through the males is to fast-track ‘Dag-Free and Worm-Free’ genes into the commercial flock.

Docking ram lambs
  • Keep all the ram lambs entire from the A team ewes.
  • Do NOT drench any ram lambs at docking - and this means both the A team and commercials.
Drenching lambs at docking - the very worst thing you can do!
Avoid this like the plague!

  • At this stage, the lambs’ immunity is starting to develop and anthelmintic drenching will damage it. Vets will not agree but we don’t know enough about the complex immune system, and until we do, don’t drench.
  • The only exception (and it would be rare indeed) would be a major animal health crisis, confirmed by a veterinarian.
  • Mark all the ram lambs with ear-markers to cut a bit out of the ear or punch a hole. Use the opposite ear to the ewe lambs described earlier.
  • If you have enough helpers, put a small plastic tag in them.
Tag lambs at docking if you have enough helpers

  • Hopefully all the A team ram lambs will all be twins, but don’t worry about any singles in the mob.

Weaning ram lambs
  • Do NOT drench any of them.
  • Treat them as for the ewe lambs in Pathway 1.

Ram hoggets

  • Give these hoggets a permanent ID (number and year born) with a reliable plastic tag if you didn’t do it at docking. They are now very valuable stock.
  • Manage them the same as the ewe hoggets, except put a more selection pressure on them. A good starting target is to cull 80%, and end up with 20% for the final selection.
  • Be very strict on what you keep, and get rid of any that don’t meet your standards.
  • Every 2-3 weeks (a month is too long) after weaning, draft off any ‘tail-enders’ and if you think they need it, give these culls a conventional combination drench and mark them for sale.
  • Don’t mix these drenched culls with the replacement ram hoggets.

Dag and worm status of ram hoggets
Repeat the programme described for the ewe hoggets. There is one big difference though – in autumn do check ALL the hoggets (see below).

March/April (autumn)
  • As with the ewe hoggets, this is a good time to do an initial check of FEC/FCS to see how immunity is developing.
  • But because of their lower numbers and the importance of keeping selection pressure high, take a sample from every animal.

May/June (mid winter)
  • This is the ideal time to put even more selection pressure on these ram hoggets against dags and worms.
  • They will have come through the autumn rise, and worm burdens are always high in winter.
  • There are also more species of worms active at this time.

Key points again of the routine:
  • Do a FEC on every ram hogget through a reliable laboratory. If you want to check the lab’s accuracy, split a few samples and send them in as separate animals. There should only be a discrepancy of a few hundred epg between samples.
Use a reliable laboratory with good quality control systems.
There should be good agreement between duplicate samples.

  • Do a FCS at the same time as sampling for FEC, including the FCS score as part of the sample ID. See Part 8.
  • This makes it easy to do the correction before making final decisions.
  • Hoggets producing marbles need to be marked as the top group, followed by hand grenaders.
  • Then anything below this with sloppy dungs need to be given a separate mark as potential culls, regardless of how low their FEC is.
  • Keep the drench gun locked away unless there is a real worm blow-up (e.g. Barber’s pole) confirmed by your vet.
  • Keep culling any animals showing ill thrift or that get daggy and don’t dry up quickly. Look for animals consistently passing marbles and hand grenades. Be ruthless on sloppy dung!

Live weight & fleece weight:
  • If possible, record their live weight twice. First in May (winter) and then in August (spring).
  • Ignore fleece weight as it’s highly correlated to body weight, but certainly cull any sheep with off-type fleeces.

Picking the top team
  • Use this information to start sorting out a top team by adding the two live weights and put them in order from highest to lowest.
  • Then put the FEC corrected for FCS alongside each animal.
  • Now come down the list looking first for animals with Nil FEC then individuals with the highest combined weight.
  • If you can’t achieve nil FEC then go for the next lowest figures e.g. under 50epg.
  • See what the numbers look like, aiming to end up with around 20% of the original group to proceed to the two-tooth stage.
  • Be more severe in you selection if you like.

Agreement between autumn and winter FECs
  • It’s always interesting to see what agreement there is between the two FECs.
  • We have to realise that the accuracy of FECs is prone to many variables, but it’s the best we have, and if you get your samples done at a reliable laboratory using a ‘High Dilution’ technique, then things are as good as you can get.
  • If immunity is well developed, there should be good agreement (within a few hundred epgs) between each sampling time, but you have to be concerned if individual animals differ by thousands.
  • When deciding which rams to use, go for those with consistent FECs first, but certainly accept any rams that were high in autumn but were low in winter.
  • I’d be suspicious of any individuals that were the other way around.
  • Remember how important the FCS is as a ram with low FEC but with high FCS is no good to you. In fact, you could give more emphasis on FCS than FEC!
  • As well as these figures, use the visual health of the ram as an important guide too.

Tempting thought – use as ram hoggets
  • Having seen how good these ram hoggets look, it would be tempting to use the very best of them as sires in the flock, and even in the A team.
  • This would certainly speed up genetic gain by shortening the Generation Interval.
  • But let’s not get carried away at this stage, and don’t make any decisions until the two-tooth stage to be absolutely sure that they don’t have any late-developing problems.
  • Keep this in mind for the future when you have a lot more confidence in what you have achieved.
Two-tooth rams

Top two-tooth Romney rams selected for Facial Eczema tolerance and worm resistance

  • Now the hoggets are two-tooths, they should look a picture, and if they don’t, review what you have done.
  • Feeding is critical so make sure they are well fed and managed.
  • Keep studying the selection list described above, and if you still want to reduce numbers, do another FEC and FCS on the very top ones as a reassurance that they are consistently dag free and resistant to worms.
  • It’s probably not worth taking another live weight as there will be little variation between them by this stage.
  • Be ruthless on structural soundness as there is always a few last-minute cases of footrot, scald or injuries, or maybe teeth that go wrong.

Which ones to use?

  • The task is now to select a top two-tooth ram team to mate with the A team ewes. Make sure they all had nil (or near nil) FEC and FCS of 1 (marbles).
  • Keep a second team of rams to mate to the flock ewes – again if possible with nil (or near nil) FEC corrected for FCS.
  • At this stage, don’t get carried away about individual rams.
  • Think of using them as a ‘fast-track team’ on the commercial flock to get rid of dags and worms. They'll be a lot more effective than the handpiece!
  • If there was one outstanding individual among them, then single-sire mate him to 100 ewes in the main flock, but be careful as he may be a fluke!
  • Better to use the team approach at this stage when a rapid change is needed from a low starting point.

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