Below are brief explanations of the individual trait indexes that all add together to calculate the NZ Maternal Worth – Dual Purpose Production Index.
DPP - Dual Purpose Production now known as New Zealand Maternal Worth (NZMW)
Overall value expressed in cents for a ram formed by adding the indexes below (excluding Dual Purpose Meat). The term 'Dual Purpose' is used to describe maternal breeds such as Coopworths that are bred for meat and wool production. A ram with a 3000 NZMW or DPP index has $10 (1,000 cents) greater value than a ram with a 2000 index. 100 of his daughters will receive half of his genetics therefore 50% of the $10 advantage. As breeding ewes will generate $500 more value than the daughters of a 2000 index ram.
DPR - Dual Purpose Reproduction.
This index shows in cents the fertility that a ewe expresses or a ram passes onto female progeny.
DPS - Dual Purpose Survival.
This index expresses in cents the mothering ability and vigour of lambs at birth that lead to lamb survival.
DPG - Dual Purpose Lamb Growth.
This index calculates in cents the economic value associated with growth. The faster the rates of growth the higher the growth index. This index has a very high economic weighting as lamb weaning weights are a significant driver of profitability.
DPA - Dual Purpose Adult Size.
This index expresses the cost of having a large adult ewe which needs to be maintained, particularly through winter when feed is expensive. New Zealand's sheep flock has been improving it's growth genetics but this also results in ewes that mature into heavier sheep. Consequently most New Zealand flocks have negative indexes on DPA which detracts from their overall DPP economic index. High DPA sheep genetically have the potential to mature into big adult sheep if they are fed to their potential.
DPM - Dual Purpose Meat Yield.
This index expresses the value of meat yield. While many argue that meat yield is important it doesn't attract the same economic weighting as Growth because processors do not pay much of a premium on meat yield if at all.
DPW - Dual Purpose Wool.
This index expresses in cents the extra income derived from extra wool weight clipped off a sheep. While many have stopped selecting for wool it still makes a reasonable contribution to the overall DPP index, as a sheep that clips a heavier fleece still generates extra revenue than a low fleece weight sheep, particularly when the shearing cost is the same.