Using a selection index in a breeding program A tool to genetic selection

Jake Phillips, Breed Development Officer

Across the world, animal breeding selection indexes have been a crucial tool utilised to make genetic gains in multiple traits of importance at one time.

Selection index usage has been well adopted in a multitude your minimum criteria and show them in ranking order to of plant and animal species across the world. Examples of the economic index you have decided to use. the successful implementation of using selection indexes 6. Consider additional selection criteria include in plant breeding for broad acre crops where Modify your search to include any additional selection multiple factors impact the economic benefit such as yield, criteria or other information not captured in the selection flowering time and disease resistance. In other animal index such as unique property management differences, industries such as the sheep industry, has used selection pedigree, docility, research EBVs and importantly a indexes for selecting on wool quality and a clear breach to robust structural and physical examination which may prevent fly strike and in the pork industry for the number of include fertility checks in crush side semen testing as well piglets successfully farrowed and the days it will then take as morphology . them to reach the market specification. It should come as no surprise that the tools available to Angus Australia members to make genetic selection and Why is it important to follow a step by step approach to genetic selection? breeding decisions also include selection indexes for The nature of how a selection index works means that it is consideration. The availability of these industry and market possible that the combination of traits can lead to animals relevant selection indexes for use by Angus cattle breeders having the same selection index value (Fig3). This means is part of Angus Australia’s continual quest to provide that without adding additional criteria to your selection the very best and latest tools to utilise when making such as nominating an acceptable range for some traits breeding decisions. A step-by-step guide to using a selection index when making breeding decisions

1. Define your breeding objective. Before considering decisions regarding bull selection, it is important to develop a clearly defined plan of what you are attempting to achieve from your breeding program. This may be described as setting a breeding objective or breeding goals, and should consider aspects such as the relative economic importance of different traits, future customer requirements, future herd production targets, current herd performance, and the environment in which your breeding enterprise is run. 3. Identify the selection index which is most aligned with your breeding objective. Background information regarding all the selection indexes published in the TransTasman Angus Cattle Evaluation can be found on the Angus Australia website under the TACE menu and then Understanding Angus Selection Indexes. 4. Rank animals on the selection index of relevance Use the ‘Database Search’ function of the Angus Australia website to rank the animals available for selection on the selection index of most relevance to your breeding objective. For example, animals available in a sale or semen catalogue. 5. Consider individual EBVs Modify your search by adding minimum or maximum acceptable EBV values for your four or five key traits of importance in the additional criteria EBV Tab. A suggestion could be placing these limits to avoid the extremes by using breed average to ensure you then only search animals with breed average or more desirable in those traits important to you. The revised list will now show animals that meet

Figure 4. An example of two sires with the same selection index value but significantly different Calving Ease Direct, Mature Cow Weight and Rib Fat EBV values .