Marlow Genetics

22/09/2026

21/09/2026

NZ MATERNAL WORTH — BUT HOW IS IT ACTUALLY CALCULATED?

We’ve talked about what NZ Maternal Worth measures.

Now let’s look under the bonnet.

NZMW isn’t one breeding value.

It is an economic index made up of several different traits, each given an economic weighting based on its expected impact on a commercial maternal sheep system.

NZMW = Reproduction + Survival + Growth + Adult Size

🔹 REPRODUCTION — DPCR
How many lambs a ewe produces matters — but NZMW uses Capped Reproduction, meaning the economic value of continually increasing litter size reduces at very high reproduction levels.

🔹 SURVIVAL — DPS
Lamb survival is a major part of NZMW. It includes both the lamb's own genetic ability to survive and the maternal genetic effect from its dam.

🔹 GROWTH — DPG
Growth isn't simply weaning weight. NZMW combines:
• Direct weaning weight
• Maternal weaning weight
• Carcass weight

🔹 ADULT SIZE — DPA
Bigger isn't automatically better.

NZMW accounts for ewe liveweight because a larger ewe has greater maintenance requirements. That's why adult size has a negative economic weighting in the index.

So, rather than selecting for one trait in isolation, NZMW puts an economic value on the combination of traits that contribute to the performance of a maternal ewe flock.

That's the power of an index.

It turns multiple breeding values into one figure that represents the overall economic breeding objective.

Next time you look at an NZMW figure, remember — there's a lot happening behind that one number.

Source: Sheep Improvement Limited (SIL) — NZ Maternal Worth and 2022 Sheep Industry Breeding Objectives.



coopworthgenetics.co.nz

Photo credit Triple Farms Sheep Genetics

19/09/2026

A romworth hogget ewe and her romworth lambs. 4.7kg and 4.8kg birth weights - like always a fantastic mum, good condition with minimal drenches in her 12 months and plenty of milk.

09/09/2026

There goes lamb number 400 tagged from the stud. A nice set of lambs from a two tooth ewe. Only a handful more stud ewes left to tag then we move into the stud hogget tagging FE Gold

07/09/2026

06/09/2026

Useful insights on what these indexes mean B+LNZ Genetics

🐑 WHAT DOES DPG MEAN?

DPG = Dual Purpose Lamb Growth

DPG is a SIL index that helps farmers select sheep with better genetics for lamb growth.

It takes into account the lamb’s own growth, the ewe’s genetic contribution to lamb growth, and carcass weight.

So how can you use it?

When selecting rams, look for higher DPG values if improving growth is one of your breeding goals.

By consistently selecting rams with higher DPG, you can gradually increase the genetic potential for growth in your flock.

That means you're not just selecting the biggest-looking ram — you're selecting genetics that can improve growth across the flock over time.

📈 Higher DPG = greater genetic merit for lamb growth.