Thursday, March 28, 2024

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Over the past 20 years genetic gains in New Zealand sheep have accelerated as more accurate genetic information has become available and new traits added to breeding objectives. Mark Young explains why. The potential of genomics, where DNA tests can provide increased accuracy or bring new traits into the mix, will be realised over the next 20 years. Future gains will change as some traits approach optimums – for example, fatness in lambs and body condition score in ewes as well as the number of lambs each ewe has – and new traits such as ewe stayability and body condition score (BCS) are brought into the mix.
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Let’s consider the gains NZ ram breeding flocks have made using SIL genetic trend graphs for indices and key component traits. Each point on the graphs in this article is the average genetic merit (left-hand scale) of animals born in a year (bottom scale). Blue lines are for maternal (dual-purpose) sheep and red lines for meat (terminal) sheep. Data are from SIL-ACE, SIL’s largest genetic evaluation, for those flocks measuring the trait(s) and that have good genetic connections to each other.

New Zealand Standard Worth indices – Graph 1

SIL is introducing a standard definition of economic merit for maternal and meat sheep types (also known as dual purpose and terminal). The new definitions (and traits in them) are:

  • NZ Standard Maternal Worth (NZMW) – reproduction, lamb survival, lamb growth and adult size, carcase meat yield and wool production.
  • NZ Standard Terminal Worth (NZTW) – lamb survival, lamb growth and carcase meat yield. 

Graph 1 shows that the genetic gain in NZMW accelerated after 2003, about the time the Central Progeny Test (CPT) was established by Alliance Group (now the Beef + Lamb New Zealand Genetics CPT) and SIL-ACE (SIL’s largest across flock evaluation) was introduced. 

Gains since 1995 amount to $15 per ewe lambing for NZMW and $8 per lamb born for NZTW.

You can find out what traits a flock is recording on SIL using the FlockFinder smart app produced by B+LNZ Genetics. A link to this app is at www.sil.co.nz

  • Dr Mark Young is a senior geneticist with B+LNZ Genetics and SIL. If you have any questions relating to this article or give feedback please email: silhelp@sil.co.nz or call 0800-SILHELP (0800 745 435).
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