A recent upgrade of SIL’s genetic engine means every ram sold by a SIL breeder now has a single “index”: one number that’s comparable across all rams, regardless of breed.
The higher the number, the better the ram.
Dual purpose rams have a New Zealand “Maternal Worth” figure (NZMW). The average NZMW is 1600.
Terminal rams have a New Zealand “Terminal Worth” figure (NZTW). The average NZTW is 1150. Terminal rams have lower scores than maternal rams, because their figure is calculated from a smaller number of traits. (See table.)
Maternal Worth (NZMW) or Terminal Worth (NZTW)?
If you’re breeding both replacement and finishing stock, then look at rams with a high NZMW figure.
If you’re only breeding terminal stock, then look for rams with a high NZTW figure.
Want to target specific traits, like FE tolerance of resistance against internal parasites? NZMW can do that.
If you’re looking for facial eczema tolerance, identify breeders who prioritise FE, then ask them for NZMW + X (X = FE trait).
If you’re looking for resistance to internal parasites, identify breeders who prioritise this trait, then ask them for: NZMW + FEC (FEC = internal parasite resistance trait).
Again, the higher the number, the better the ram.