Effective breeding programs are the key to increase health and welfare of animals and efficiency of the production process. Pigs for meat production are generally crossbred animals, while selection takes place in purebred animals. To predict the effects of selection of purebred animals on crossbred performance, we need to know how the two are related to each other. This is why the genetic correlation between purebred and crossbred performance, known as the purebred-crossbred correlation, is very important.
In an STW – Breed4Food Partnership study, researchers of Wageningen University & Research discuss the theory, estimates and implications of this purebred-crossbred correlation.
The purebred-crossbred correlation (rpc) is the genetic correlation between purebred and crossbred performance. When rpc is 1, purebred and crossbred performance are effectively the same trait. When rpc is lower than 1, it means that the best purebred animals don’t necessarily produce the best crossbred offspring. When rpc is low, it is important to use crossbred information for selecting the best purebred animals to improve crossbred offspring.
Why rpc is low?
There are three different reasons for an rpc below 1, which can result in different expressions of a trait. The first reason is a difference in environment. Purebred animals are generally kept in a high hygiene environment, crossbreds in farms under commercial conditions. The second reason is a difference in genetic background, because crossbreds are genetically a mix of different purebred lines.
The third reason is a difference in measuring the traits. For example backfat. In crossbred animals it is measured at the carcass. Backfat in purebred animals is measured with ultrasound so that the best animals can be used for breeding.
Estimates of rpc
The review considered 201 rpc estimates in pigs from 27 studies. The studies estimated the rpc for different purebred-crossbred combinations and different trait categories. Average rpc was 0.63 which is considerably lower than 1, with 50% of the estimates between 0.45 and 0.87.
For all trait categories, e.g. Growth, Meat amount, Meat quality, Feed, and Fertility, the average rpc was around 0.6. This indicates that rpc is likely different from 1 and that for a lot of traits, and crossbred information is very important to improve crossbred performance.
Implications for breeding programs
It appeared that differences in genetic background of purebreds and crossbreds have a larger effect on rpc than differences in environment.
This is important information, because it suggests that the breeding programs can be improved by collecting data of crossbred animals in the high hygiene environment of the purebreds. Improving breeding programs can help to increase health and welfare of the animals and the efficiency of production.