.  Editorial Commentary   .

Composite rams push performance to higher level
by Not Specified

Categories: Case Study;Production;
Publication: Country-Wide Northern; Date: 2004-07-01

My Comments:

1. If you are considering using composites, I believe you need to consider where you will be in 10 years time.   What will you put over the progeny.  Once the hybrid vigour is gone the performance will tail off dramatically.

2.  High scanning figures are only a benefit, if it translates into high weaning figures, there are composite flocks out there that scan in excess of 200%, but only wean 120%. Surely it is better to scan 175-180 and wean 150, this is what we generally achieve at waidale.  Survivability is an issue.

3. It is inevitable that you will get a lift in the  first cross WHY? Because of Hybrid Vigour, the problem is what happens when the hybrid vigour disappears.  Scientific Studies have shown that Hybrid Vigour in itself can be responsible for:

Trait Heterosis (percentage response)
Barenness (hybrids less barren)18
Lambs born per ewe lambing19-20
Lambs weaned per ewe joined60
Lamb survival10-15
Lamb birth weight6

( Dalton, 1980)

The above figures come from a book put out by Meat NZ "A guide to improved lambing percentage"  These figures will of course vary for differing crosses.  The point I am trying to make is that your composite in many cases will result in an increase, solely because of  HYBRID VIGOUR alone.  If you have perendales and put romneys across them you will get the same result.  If you have romneys and put perendales across, again the same results.  Note with the right purebreds, you may still get the same results without the short term burst of hybrid vigour, ie genuine genetic gains. 

If you do not ensure that you buy rams that have the performance and track record, ie pedigree and history of performance, then you will be in serious trouble when you are putting composites back over composite progeny, there will no hybrid vigour to keep performance up then.  If you go to the right breeder you will get the same or close to the same results from a purebred, the difference being you will continue to get those results 10 years down the track, I doubt you will with composites.   If you are a sheep farmer for the long haul, then you need to seriously consider where you are going.

This is not new, look at coopworths, the first cross was an amazing animal (on the right country), 2nd cross not so good, the further in you got the worse it would be.  It got so bad that the coopworth society allowed breeders to cross other breeds (such as the romney) back over their coopworths. 

What I am saying above is the same old problems, which have been disguised by the word "composite"

4.  There is a growing problem with black fibre in composite wool.  This is going to be a significant issue in New Zealand.  It is true that wool does not make up as much of our incomes as it used to, but it is still a significant cheque, it is still perhaps 25% of most sheep farmers income.  You talk to your wool buyer, and they will tell you that NZ gets paid a premium because of the quality and colour of our wool and that black fibre arising from Composite use is now a major issue.

5.  Longevity of composites is also an issue, ie the ewes are not producing for as long as your traditional ewe flock, some flocks are shot before they reach full mouth.  What does this mean as a cost?: it means you have to keep significantly more replacement hoggets to allow for this, which means you have less lambs to sell and more young stock to carry through and feed. 

All the above are things that any farmer must consider before deciding to follow the trendy change to composites, it is easy to stuff your flock with one cross.

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Genetics Breeding Success

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Note my comments pertaining to the previous article are also relevant to this article.  Hybrid Vigour can only prop you up for a short time, eventually you need quality and peformance to come from more than Hybrid Vigour.   Composites crossed over composites are simply a pure bred like the perendale, south suffolk etc, and unless that animal has quality, has the basics, which means uniformity as a line, production and performance will eventually decline.   The following are my comments that specifically pertain to the use of DNA to trace parentage and not the use of DNA to find fertility, footrot tolerance etc type genes:

  1. DNA testing will only be the be all and end all for tracing parentage when it is close to 100%.  It is nowhere near that at present, it is closer to 80%.   There are some corporate ram breeders who uses this as a marketing gimmick and to date that is all it is, as the reality is that on our flock of romney ewes it could tell me who the sire is (most likely), but unlikely to be able to tell me the dam as the bloodlines are too close to distinguish between families.  Therefore a breeder who pushes DNA testing, will be able to tell you the sire, but pretty unreliable as to its dam and accordingly that breeders SIL figures will be at best be of little use and at worst incorrect and totally Misleading.
  2. We still shepherd, tag and record at birth for the principal purpose of recording as accurate as we possibly can the lambs parents.   This accuracy then translates through to SIL figures that may be of some use to the client and ourselves.  Those who claim to rely on DNA for parentage, dont tell you how unreliable it is when it comes to the dam. 
  3. I would love to simply tail the lambs and take a sample then to record the parentage of the lambs as I believe my going around the ewes creates more problems than it solves, but until such time as DNA testing is virtually 100% accurate, we will continue to Shepherd, tag and record at lambing time.
  4. Similarly those breeders who claim "I dont shepherd at lambing time" then record and tag at tailing time, have considerably less reliable records than those breeders who are still tagging at birth.  I say beware of these breeders as they are using such a line as a marketing gimmick.  I shepherd and record any problems (I lambed around 6 ewes last year, which were culled) that may occur at the time on my pocket PC. 

 

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