Measuring Genetic Merit
Measuring and monitoring are key to our goal of constantly improving our sheep genetics. All stud animals are evaluated for genetic merit through nProve – Sheep Improvement Ltd (SIL). nProve – SIL is New Zealand’s genetic engine provided by Beef + Lamb New Zealand Genetics. It generates the estimated breeding values for different traits and the economic indexes.
NZ Maternal Worth (NZMW) – Dual Purpose Production Index (DPP)
The NZMW – Dual Purpose Production Index (DPP) is the sum of all the trait indexes added together.
Below is a simple explanation of how the NZMW- DPP index helps sheep breeders select the animals that will provide the greatest economic benefit to their flock.
Indexes below are expressed in cents of value above an average stud sheep in 1995.
Purchasing a ram with a DPP of 2000 means a sheep breeder has purchased a ram with genetics of $20 greater value than a ram with a DPP of 0. For example, if the genetic merit of a commercial sheep flock is on average DPP 500 (i.e. $5.00 greater than stud sheep in 1995) and the farmer buys a ram with a DPP of 2000: this ram will pass on half of his genetics to his progeny ($10.00). The other half of his progeny’s genetics will come from the dam ($5.00). Consequently the progeny will be have a DPP of 1250 or $12.50.
Assuming both rams are of equal health, eczema tolerance and soundness. A ram buyer can quickly assess the cost benefit of two different rams by looking at their DPP index.
An Example of Comparing Rams using the DPP Index
A ram with a DPP of 2500 compared with another ram with a DPP of 1500 has $10.00 greater value. While this doesn’t seem a lot, when that ram goes across 100 ewes lambing at 140% each year for 3 years minimum, then he sires 420 progeny. Because each of his progeny gain half of their sire’s genetics, they gain a genetic merit $5.00 greater than if sired by the poorer ram with a DPP of 1500.
So the extra return on this ram is $2,100 greater than the poorer ram with a DPP of 1500.
i.e. 420 progeny x $5 = $2,100
When considering the price of rams, paying even up to a $1000 more for the high index ram compared with the low index ram, will result in a net return of $1,100.
The real advantage is that the improved genetics, when included into a breeders ewe flock, are cumulative with each generation. This is why buying top genetics is one of the best investments a sheep farmer can make. Research into the most profitable farmers shows that they always pay more for rams and bulls than average performing farmers.
When looking at various ram breeders to purchase from, always ask for their NZMW – DPP indexes to benchmark them between other breeders.
Make Accurate Comparisons
Also be careful to compare apples with apples. Look at the NZMW – DPP index, not a Dual Purpose Production Overall Index (DPO). The DPO measures sub-traits such as worm tolerance and eczema resistance. While these are important, their inclusion and how they are weighted affects the index value, so ensure you are benchmarking like with like.