Implementing a Sire-Dam pedigree structure in MACE

Abstract

The Interbull Community has decided to introduce a new MACE model including relationships on bull dams. The background for the change is to move genetic groups further away from animals with data in order for them to have less impact on the proofs. The consequences are changes in MACE breeding values (IEBV), especially for foreign bulls with no local progeny test, and an average increase in MACE reliabilities. The main reason for changes in IEBVs for this group of bulls is that the parent average of the bull is computed differently for sire-dam (SD)-MACE model compared to the sire-maternal-grandsire(S-MGS)-MACE model due to the change in the pedigree structure. The bull dam in the SD-MACE model gets a breeding value based on the relatives she has in the system. National breeding values (NEBV) of the bull dams are not included in the MACE model, and therefore the breeding value of the dam is only influenced by the performance of her relatives in the MACE system. A very positive performance of a dam, solely based on her relatives, will give a boost to a parent average of a bull compared to the parent average he had in the S-MGS system. A change in the parent average of a bull will therefore impact his converted IEBV to other country scales and is the main cause of changes between systems. The usage of the sire-dam pedigree in the MACE system contributes more information on the genetic background of a bull. In the case a dam has several sons tested in several countries; better links between countries are created.