A Guide to Angus Research Selection Indexes

A Guide to Angus Research Selection Indexes As part of the review and updating of the selection indexes that are published within the TransTasman Angus Cattle Evaluation (TACE), Angus Australia, in association with the Animal Genetics & Breeding Unit (AGBU) and Agricultural Business Research Institute (ABRI), have developed a series of research selection indexes for industry review and feedback.

What is a selection index?

Selection indexes are utilised by livestock breeders of many species around the world and are considered an essential part of any modern livestock breeding program.

Selection indexes aid in the selection of animals for use within a breeding program where there are several traits of economic or functional importance by providing an overall “score” of an animal’s genetic value. Selection indexes are calculated for a specific breeding purpose and are calculated based on weightings placed on individual traits that are deemed to be important for that purpose.

For the production system and market scenario relevant to the respective selection index, the BreedObject software firstly calculates the net economic value of changing each trait in the breeding objective by one unit, independent of any change in other traits. The BreedObject software then links the economic value of the traits in the breeding objective with the Estimated Breeding Value (EBV) traits published in the TransTasman Angus Cattle Evaluation, and places appropriate emphasis on each EBV based on its relative economic importance in the defined production system and market scenario.

Example Selection Index Calculation Selection Index = b1T1 + b2T2 + b3T3 + …….. + bnTn Where b = weighting placed on the trait

T = trait Selection indexes assist in making “balanced” selection decisions, taking into account the relevant attributes of each animal to identify animals with genetics that are most aligned with the breeding objective for the given selection scenario.

How are the selection indexes within the TransTasman Angus Cattle Evaluation calculated?

The selection indexes published within TransTasman Angus Cattle Evaluation are economic selection indexes and are derived using BreedObject software, as developed by the Animal Genetics & Breeding Unit (AGBU) in Armidale, NSW. A range of different selection indexes are published, with each individual selection index reflecting differences in profitability in a defined production system and market endpoint.

Importantly, the trait emphasis that is placed on each EBV is determined by science, not the breeding preferences of either individual breeders, researchers, or staff at Angus Australia.

Understanding economic selection indexes

The economic selection indexes published in the TransTasman Angus Cattle Evaluation are reported as genetic differences in units of net profit per cow joined ($) for the given selection scenario.

The selection indexes are developed to reflect the economics in commercial beef production systems, rather than in seedstock breeding enterprises, and consider both

www.angusaustralia.com.au

the short term profit generated by an animal through the sale of their progeny, and where applicable, the longer term profit generated through the retention of their daughters in a self replacing breeding herd.

The selection indexes are “whole-chain” selection indexes, and consider traits influencing profitability across the entire commercial supply chain from conception to slaughter.

Why use an economic selection index?

Economic selection indexes assist in making balanced selection decisions across the suite of traits that influence profitability in a commercial beef enterprise.

Economic selection indexes not only consider the influence of each individual trait on profitability in the scenario defined by the index, but also balance the genetic relationships that exist between traits, both antagonistic and favourable, to place the appropriate emphasis on each EBV. By comparison to selection based on consideration of individual EBVs alone where each trait is considered sequentially, economic selection indexes consider all traits simultaneously, resulting in a balanced selection outcome across all the available EBVs. Economic selection indexes form an important decision support tool to assist breeders in the selection of breeding animal.

Selection indexes do not take the selection decision out of the hands of the breeder, but rather should be used in association with consideration of individual EBVs and any other available information to identify animals that possess genetics that are most aligned with the breeding objective of the individual breeding program for which they are being selected.

The Maternal and Maternal Plus selection index categories are designed for use in a self replacing breeding program where a portion of female progeny are retained as replacements. The Maternal and Maternal Plus categories are similar, with the difference being that the Maternal Plus selection indexes have an additional objective aiming to maintain mature weight, whereas the Maternal selection indexes do not include this component.

The inclusion of the additional mature weight objective in the Maternal Plus selection index category is a result of this category being modelled on a production system where the available pasture is fully utilised for the majority of the year. In this scenario, any increase in the maintenance requirements of the female breeding herd results in additional costs being incurred, and consequently an increase in mature weight is considered undesirable.

By comparison, the Maternal selection index category is modelled on a production system where the available pasture is not fully utilised for the majority of the year. In this scenario, any increase in the maintenance requirements of the female breeding herd results in minimal additional costs being incurred, and consequently an increase in mature weight is not considered undesirable.

The Terminal selection index category is designed for use in situations where Angus bulls are being used as a terminal sire over mature breeding females and all progeny, both male and female, are slaughtered.

What research selection indexes have been developed?

The research selection indexes that have been developed for industry review and feedback are grouped into three main categories, being Maternal, Maternal Plus and Terminal, with each category reflecting a different breeding system and objective, as outlined in Table 1.

Table 1 - Angus Research Selection Index Categories Category

Maternal

Maternal Plus

Terminal

Breeding System

Self-replacing

Self-replacing

Terminal

Pasture utilisation

Pasture is not fully utilised for the majority of the year. An increase in the maintenance requirements of the mature female breeding herd results in minimal additional costs being incurred.

Pasture is fully utilised for the majority of the year. An increase in the maintenance requirements of the mature female breeding herd results in additional costs being incurred

Not applicable

Mature Weight Objective

Do not maintain mature weight

Maintain mature weight

Not applicable

Maternal Angus Breeder Plus Index (AMB+)

Angus Terminal Sire Index (ATS)

Maternal Angus Breeder Index (AMB) Index Names & Maternal Domestic Steer Index (MDS) Abbreviations Maternal Heavy Grain Steer Index (MGN) Maternal Heavy Grass Steer Index (MGS)

Maternal Domestic Steer Plus Index (MDS+) Maternal Heavy Grain Steer Plus Index (MGN+) Maternal Heavy Grass Steer Plus Index (MGS+) AngusPRO Index (PRO)

A description of each selection index, along with a decision support tree to assist with the identification of the selection index (or indexes) of relevance to a particular breeding program is included on the pages following.

Important things to consider when reviewing the research selection indexes

When reviewing the research selection indexes that have been developed, there are a number of important considerations to make.

1. Increase in the magnitude and range of index values A notable feature of the research selection indexes is an increase in the magnitude and range of the selection index values that are published for animals. There are several main reasons for this. · While it is more sophisticated in practice, for the purposes of explanation, an economic index is calculated by multiplying each EBV by an economic value, and adding all the components together. This is illustrated in the formula below: Index = (EBV1 x EV1) + (EBV2 x EV2) + …….. (EBVn x EVn) While the EBVs used when calculating the research selection indexes are the same, the considerable increase in beef prices, coupled with relatively stable costs, means the economic value of each trait is now considerably higher than what they were when the selection indexes published in the TransTasman Angus Cattle Evaluation were last updated in 2014.

The multiplication of the same EBVs by a higher economic value results in the selection index value having a higher value. Similarly, the same difference in EBVs between two animals now results in a larger difference in their selection index values. · The selection index values published in the TransTasman Angus Cattle Evaluation include an adjustment that sets the breed average for each individual index to a similar level. These adjustments have not been made to the research selection indexes, meaning that the breed average values will be higher than those published in the TransTasman Angus Cattle Evalaution, and differ more between each individual index.

2.

Animals with extremely favourable EBVs for traits of high economic importance will still rank highly, irrespective of their EBVs for other traits The nature of an economic selection index means that animals with extremely favourable EBVs for traits of high economic importance will still rank highly on the index, even if they have EBVs for several other traits that many breeders would consider unfavourable. For example, an animal with an extremely high 400 or 600 Day Weight EBV may still rank highly even if its Calving Ease EBVs is below average.

This scenario does not reduce the value of the index as a selection tool, but highlights the importance of considering the index value in association with the individual EBVs when making selection decisions.

3. Trait contributions do not indicate the response to selection that will occur A common misconception is that the relative emphasis given to each trait in the calculation of the selection index equates to the relative change that will occur in that trait if selection decisions are based on the selection index.

In practice, the relative change that will occur in traits is influenced by not only the trait contribution, but also factors such as the animals that are available for selection and the genetic correlation that exists between traits.

A better representation of the response to selection is the selection advantage. The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on the selection index.

Next steps – the process for industry review and feedback

The research selection indexes have been developed for industry review and feedback prior to potential implementation into the TransTasman Angus Cattle Evaluation.

Once Angus breeders have had time to familiarise themselves with the research selection indexes, an industry consultation process will be facilitated during September and October to gather feedback and fine tune the research selection indexes.

The consultation will include an online survey, focus group sessions, and review by Angus Australia’s Genetic Evaluation Consultative Committee. Further information about how Angus breeders can participate in the consultation process will be circulated in due course.

Subject to the feedback received during the consultation, the selection indexes that are published in the TransTasman Angus Cattle Evaluation will be updated in late November in association with the December 2021 analysis.

Additional changes – modifications to the display of selection indexes

In association with the development of the research selection indexes, a number of changes are also being progressed with regards to the manner in which selection indexes are published and displayed on Angus animals.

These changes include: · less prominent display of selection indexes via removal of the selection indexes from the default display of EBV information on the Angus Database Search and within the catalogues that are available within Angus SELECT. · implementation of decision support systems to guide breeders who wish to access selection indexes to the selection index/es most aligned with their breeding objective, rather than the default display of all selection indexes · implementation of functionality to enable seedstock breeders to select whether selection indexes are displayed in any Angus Australia generated marketing materials, and if so, which selection indexes, rather than the default display of all selection indexes.

Questions

To further discuss the research selection indexes, contact Andrew Byrne, Breed Development & Extension Manager, on (02) 6773 4618 or andrew@angusaustralia.com.au.

Choosing the research selection index (or indexes) of relevance to your breeding program

Angus Maternal Breeder Indexes (AMB & AMB+) The Angus Maternal Breeder (AMB) and Angus Maternal Breeder Plus (AMB+) indexes estimate the genetic differences between animals in net profitability per cow joined in a typical commercial self replacing herd using Angus bulls.

These selection indexes are not specific to a particular production system or market end-point, but identify animals that will improve overall profitability in the majority of commercial, self replacing, grass and grain finishing beef production systems. Daughters are retained for breeding and therefore female traits are of importance.

The AMB+ index is similar to the AMB index, but includes an additional objective of maintaining mature cow weight, whereas the AMB index does not aim to limit the increase in mature cow weight.

Trait Contributions

Figure 1 shows the traits that are considered in the AMB & AMB+ indexes, and how much they contribute to the overall balance of each selection index. The larger the segment, the greater the impact on the selection index.

In both the AMB & AMB+ indexes, there is a focus on improving growth, carcase, calving ease and fertility traits.

The main difference is the increased emphasis on mature cow weight in the AMB+ index, whereas this emphasis is given to calving ease and fertility in the AMB index.

Selection Advantage

Figures 2 & 3 show the selection advantage if animals are selected using the AMB & AMB+ indexes.

The selection advantage is calculated by ranking well used sires within the Angus breed on each respective selection index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the

Selection Index Summary · Self replacing herd · Daughters are retained for breeding · Identifies animals that will improve overall performance in the majority of commercial, self

replacing, grass and grain finishing beef production systems · AMB+ includes an additional objective of maintaining mature cow weight highest 10% based on the AMB index had 18 kg higher 400 Day Weight EBVs and 0.6 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on each respective selection index. The actual response that is observed will vary depending on the features of the individual breeding program.

The main difference in the selection advantage between the AMB & AMB+ indexes is in the growth traits and mature cow weight. Animals ranking highly on the AMB index have higher growth EBVs relative to the AMB+ index, meaning selection on the AMB index will result in a higher increase in growth to 200, 400 and 600 days of age than selection on the AMB+ index, however this is also associated with higher mature cow weight EBVs, meaning an increase in mature weight will also be observed. By comparison, the selection advantage of the AMB+ index for mature cow weight is close to 0, meaning that selection on this index will maintain mature cow weight, while still increasing growth to 200, 400 & 600 days of age.

Figure 1: Trait Contribution to the Angus Maternal Breeder and Angus Maternal Breeder Plus Indexes Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase Y Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase Yield

Calving Ease 22%

Growth 27%

AMB

Carcase Quality 9%

Growth 27%

Mature Cow Weight 5%

Fertility 19%

Carcase Yield 18%

Calving Ease 12%

AMB+

Mature Cow Weight 17%

Fertility 15%

Carcase Yield 19% Carcase Quality 10%

Maternal Domestic Steer Indexes (MDS & MDS+) The Maternal Domestic Steer (MDS) and Maternal Domestic Steer Plus (MDS+) indexes estimate the genetic differences between animals in net profitability per cow joined in a commercial self replacing herd targeting the domestic supermarket trade.

Daughters are retained for breeding and therefore female traits are of importance.

Steers are either finished using pasture, pasture supplemented by grain or grain (eg. 50 – 70 days) with steers assumed to be slaughtered at 510 kg live weight (280 kg carcase weight with 12 mm P8 fat depth) at 16 months of age.

Emphasis has been placed on eating quality and tenderness to favour animals that are suited to MSA requirements.

The MDS+ index is similar to the MDS index, but includes an additional objective of maintaining mature cow weight, whereas the MDS index does not aim to limit the increase in mature cow weight.

Trait Contributions

Figure 1 shows the traits that are considered in the MDS & MDS+ indexes, and how much they contribute to the overall balance of each selection index. The larger the segment, the greater the impact on the selection index.

In both the MDS & MDS+ indexes, there is a focus on improving growth, carcase, calving ease and fertility traits.

The main difference is the increased emphasis on mature cow weight in the MDS+ index, whereas this emphasis is given to calving ease and fertility in the MDS index.

Selection Advantage

Figures 2 & 3 show the selection advantage if animals are selected using the MDS & MDS+ indexes.

The selection advantage is calculated by ranking well used sires within the Angus breed on the respective selection index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which

Selection Index Summary · Self replacing herd · Daughters are retained for breeding · Steer progeny are either finished using pasture, pasture supplemented by grain or grain (eg. 50 70 days) · Steer progeny slaughtered at a carcase weight of 280kg at 16 months of age · Eating quality traits important to suit MSA program · MDS+ includes an additional objective of maintaining mature cow weight they were selected. For example, the sires ranked in the highest 10% based on the MDS index had 19 kg higher 400 Day Weight EBVs and 0.5 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on each respective selection index. The actual response that is observed will vary depending on the features of the individual breeding program.

The main difference in the selection advantage between the MDS & MDS+ indexes is in the growth traits and mature cow weight. Animals ranking highly on the MDS index have higher growth EBVs relative to the MDS+ index, meaning selection on the MDS index will result in a higher increase in growth to 200, 400 and 600 days of age than selection on the MDS+ index, however this is also associated with higher mature cow weight EBVs, meaning an increase in mature weight will also be observed. By comparison, the selection advantage of the MDS+ index for mature cow weight is close to 0, meaning that selection on this index will maintain mature cow weight, while still increasing growth to 200, 400 & 600 days of age.

Figure 1: Trait Contribution to the Maternal Domestic Steer and Maternal Domestic Steer Plus Indexes Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase Yield Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase Yie

Calving Ease 23%

Growth 29%

MDS

Carcase Quality 5%

Growth 30%

Mature Cow Weight 3%

Fertility 21%

Carcase Yield 19%

Calving Ease 13%

MDS+

Carcase Yield 20%

Mature Cow Weight 15%

Fertility 18% Carcase Quality 5%

Maternal Heavy Grain Steer Indexes (MGN & MGN+) The Maternal Heavy Grain Steer (MGN) and Maternal Heavy Grain Steer Plus (MGN+) indexes estimate the genetic differences between animals in net profitability per cow joined in a commercial self replacing herd targeting pasture grown steers with a 250 day feedlot finishing period for the grain fed high quality, highly marbled markets.

Daughters are retained for breeding and therefore female traits are of importance.

Steers are assumed to be slaughtered at 800 kg live weight (455 kg carcase weight with 30 mm P8 fat depth) at 24 months of age, with a significant premium for steers that exhibit superior marbling.

The MGN+ index is similar to the MGN index, but includes an additional objective of maintaining mature cow weight, whereas the MGN index does not aim to limit the increase in mature cow weight.

Trait Contributions

Figure 1 shows the traits that are considered in the MGN & MGN+ indexes, and how much they contribute to the overall balance of each selection index. The larger the segment, the greater the impact on the selection index.

In both the MGN & MGN+ indexes, there is a focus on improving growth, carcase, calving ease and fertility traits.

The main difference is the increased emphasis on mature cow weight in the MGN+ index, whereas this emphasis is given to calving ease and fertility in the MGN index.

Selection Advantage

Figures 2 & 3 show the selection advantage if animals are selected using the MGN & MGN+ indexes.

The selection advantage is calculated by ranking well used sires within the Angus breed on the respective selection index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the highest 10% based on the MGN index had 16 kg higher

Selection Index Summary · Self replacing herd · Daughters are retained for breeding · Steer progeny are pasture grown with a 250 day feedlot finishing period · Steer progeny slaughtered at a carcase weight of 455kg at 24 months of age · Targeting high quality, highly marbled markets with a significant premium for superior marketing · MGN+ includes an additional objective of maintaining mature cow weight 400 Day Weight EBVs and 0.7 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on each respective selection index. The actual response that is observed will vary depending on the features of the individual breeding program.

The main difference in the selection advantage between the MGN & MGN+ indexes is in the growth traits and mature cow weight. Animals ranking highly on the MGN index have higher growth EBVs relative to the MGN+ index, meaning selection on the MGN index will result in a higher increase in growth to 200, 400 and 600 days of age than selection on the MGN+ index, however this is also associated with higher mature cow weight EBVs, meaning an increase in mature weight will also be observed. By comparison, the selection advantage of the MGN+ index for mature cow weight is close to 0, meaning that selection on this index will maintain mature cow weight, while still increasing growth to 200, 400 & 600 days of age.

Figure 1: Trait Contribution to the Maternal Heavy Grain Steer and Maternal Heavy Grain Steer Plus Indexes Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase Yield Calving Ease Mature Cow Weight Fertility Carcase Quality Carcase

Calving Ease 23%

Growth 27%

MGN Carcase Yield 18%

Growth 26%

Mature Cow Weight 5%

Fertility 17% Carcase Quality 11%

Calving Ease 12%

MGN+

Mature Cow Weight 16%

Fertility 14%

Carcase Yield 20% Carcase Quality 12%

e Yield

Maternal Heavy Grass Steer Indexes (MGS & MGS+) The Maternal Heavy Grass Steer (MGS) and Maternal Heavy Grass Steer Plus (MGS+) indexes estimate the genetic differences between animals in net profitability per cow joined in a commercial self replacing herd targeting pasture finished steers.

Daughters are retained for breeding and therefore female traits are of importance.

Steers are assumed to be slaughtered at 650 kg live weight (350 kg carcase weight with 12 mm P8 fat depth) at 22 months of age. Emphasis has been placed on eating quality and tenderness to favour animals that are suited to MSA requirements.

The MGS+ index is similar to the MGS index, but includes an additional objective of maintaining mature cow weight, whereas the MGS index does not aim to limit the increase in mature cow weight

Trait Contributions

Figure 1 shows the traits that are considered in the MGS & MGS+ indexes, and how much they contribute to the overall balance of each selection index. The larger the segment, the greater the impact on the selection index.

In both the MGS & MGS+ indexes, there is a focus on improving growth, carcase, calving ease and fertility traits.

The main difference is the increased emphasis on mature cow weight in the MGS+ index, whereas this emphasis is given to calving ease and fertility in the MGS index.

Selection Advantage

Figures 2 & 3 show the selection advantage if animals are selected using the MGS & MGS+ indexes.

The selection advantage is calculated by ranking well used sires within the Angus breed on the respective selection index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the

Selection Index Summary · Self replacing herd · Daughters are retained for breeding · Steer progeny are finished on pasture · Steer progeny slaughtered at a carcase weight of 350kg at 22 months of age · Eating quality traits important to suit MSA program · MGS+ includes an additional objective of maintaining mature cow weight highest 10% based on the MGS index had 18 kg higher 400 Day Weight EBVs and 0.4 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on each respective selection index. The actual response that is observed will vary depending on the features of the individual breeding program.

The main difference in the selection advantage between the MGS & MGS+ indexes is in the growth traits and mature cow weight. Animals ranking highly on the MGS index have higher growth EBVs relative to the MGS+ index, meaning selection on the MGS index will result in a higher increase in growth to 200, 400 and 600 days of age than selection on the MGS+ index, however this is also associated with higher mature cow weight EBVs, meaning an increase in mature weight will also be observed. By comparison, the selection advantage of the MGS+ index for mature cow weight is close to 0, meaning that selection on this index will maintain mature cow weight, while still increasing growth to 200, 400 & 600 days of age.

Figure 1: Trait Contribution to the Maternal Heavy Grass Steer and Maternal Heavy Grass Steer Plus Indexes

Calving Ease Mature Cow Weight Fertility

Carcase Quality Carcase Yield Calving Ease Mature Cow Weight Fertility

Calving Ease 20%

Growth 28%

MGS

Carcase Quality 5%

Calving Ease 13%

Growth 27%

Mature Cow Weight 4%

Fertility 24%

Carcase Yield 18%

Carcase Quality Carcase

MGS+ Carcase Yield 21%

Mature Cow Weight 17%

Fertility 17% Carcase Quality 6%

e Yield

Angus Terminal Sire Index (ATS) The Angus Terminal Sire index (ATS) is designed for situations where Angus bulls are being used as a terminal sire over mature breeding females and all progeny, both male and female, are slaughtered.

The Angus Terminal Sire Index focusses on increasing growth, carcase yield and eating quality.

Daughters are not retained for breeding and therefore no emphasis is given to female fertility or maternal traits.

Trait Contributions

Figure 1 shows the traits that are considered in the ATS index, and how much they contribute to the overall balance of the selection index. The larger the segment, the greater the impact on the selection index.

Selection Advantage

Figure 2 shows the selection advantage if animals are selected using the ATS index.

The selection advantage is calculated by ranking well used sires within the Angus breed on the ATS index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the highest 10% based on the ATS index had 20 kg higher 400 Day Weight EBVs and 0.4 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the relativity of response that will occur in individual traits if selection is based on the ATS index. The actual response that is observed will vary depending on the features of the individual breeding program.

Selection Index Summary · Terminal breeding program where Angus bulls are being used as a terminal sire over mature females · All progeny, both male and female, are slaughtered · Focus on increasing growth, carcase yield and eating quality · No emphasis is given to female fertility or maternal traits

Mature Cow Weight Fertility Carcase Carcase Y FigureCalving 1: Trait Ease Contribution to the Angus Terminal SireQuality Index

Calving Ease 22% Growth 34%

ATS Carcase Quality 21% Carcase Yield 23%

AngusPRO Index (PRO) The AngusPRO index (PRO) estimates the genetic differences between animals in net profitability per cow joined in a commercial self replacing herd based in New Zealand that targets the production of grass finished steers for the AngusPure programme.

Daughters are retained for breeding and therefore female traits are of importance.

Steers are assumed marketed at approximately 530 kg live weight (290 kg carcase weight with 10 mm P8 fat depth) at 20 months of age, with a significant premium for steers that exhibit superior marbling.

Trait Contributions

Figure 1 shows the traits that are considered in the PRO index, and how much they contribute to the overall balance of the selection index. The larger the segment, the greater the impact on the selection index.

Selection Advantage

Figure 2 shows the selection advantage if animals are selected using the PRO index.

The selection advantage is calculated by ranking well used sires within the Angus breed on the PRO index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the highest 10% based on the PRO index had 9 kg higher 400 Day Weight EBVs and 1.2 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.

The selection advantage is indicative of the long term direction and relativity of response that will occur in individual traits if selection is based on the PRO index. The actual response that is observed will vary depending on the features of the individual breeding program.

Selection Index Summary · New Zealand production system · Self replacing herd · Daughters are retained for breeding · Steer progeny are finished on pasture for the AngusPure programme. · Steer progeny slaughtered at a carcase weight of 290 kg at 20 months of age · Significant premium for steers that exhibit superior marbling Figure 1:Calving Trait Ease Contribution to the AngusPRO Index Mature Cow Weight Fertility Carcase Quality Carcase Yield Calving Ease 14%

Growth 28%

PRO Carcase Yield 21%

Mature Cow Weight 11%

Fertility 18% Carcase Quality 8%

A feature of the PRO index is a selection advantage of close to 0 for mature cow weight, meaning that selection on this index will maintain mature cow weight, while still increasing growth to 200, 400 & 600 days of age.

MDS & MDS+

· Self replacing herd · Daughters are retained for breeding · Steer progeny are either finished using pasture, pasture supplemented by grain or grain (eg. 50 – 70 days) · Steer progeny slaughtered at a carcase weight of 280 kg at 16 months of age · Eating quality traits important to suit MSA program · MDS+ includes an additional objective of maintaining mature cow weight

AMB & AMB+

· Self replacing herd · Daughters are retained for breeding · Identifies animals that will improve overall profitability in the majority of commercial, self replacing, grass and grain finishing beef production systems. · AMB+ includes an additional objective of maintaining mature cow weight

ATS · Terminal breeding program where Angus bulls are being used as a terminal sire over mature females · All progeny, both male and female, are slaughtered · Focus on increasing growth, carcase yield and eating quality. · No emphasis is given to female fertility or maternal traits

MGS & MGS+ · Self replacing herd · Daughters are retained for breeding · Steer progeny are finished on pasture · Steer progeny slaughtered at a carcase weight of 350 kg at 22 months of age · Eating quality traits important to suit MSA program · MGS+ includes an additional objective of maintaining mature cow weight

· Self replacing herd · Daughters are retained for breeding · Steer progeny are pasture grown with a 250 day feedlot finishing period · Steer progeny slaughtered at a carcase weight of 455 kg at 24 months of age · Targeting high quality, highly marbled markets with a significant premium for superior marbling · MGN+ includes an additional objective of maintaining mature cow weight

Selection Index Description MGN & MGN+

Angus Research Selection Index Comparison · New Zealand production system · Self replacing herd · Daughters are retained for breeding · Steer progeny are finished on pasture for the AngusPure programme. · Steer progeny slaughtered at a carcase weight of 290 kg at 20 months of age · Significant premium for steers that exhibit superior marbling

PRO

www.angusaustralia.com.au

+0.0 %

+0.9 %

Retail Beef Yield

Intramuscular Fat

Docility

+1.0 %

+0.1 %

-0.2 mm

-0.2 mm

+2.3 cm2

+9 kg

+0.2 cm

-1.9 days

+5 kg

-1 kg

+14 kg

+13 kg

+8 kg

-0.9 kg

-0.5 days

+2.9 %

+3.9 %

AMB+

+0.6 %

+0.3 %

-0.5 mm

-0.2 mm

+1.4 cm2

+14 kg

+0.4 cm

-1.8 days

+3 kg

+17 kg

+23 kg

+19 kg

+11 kg

-0.5 kg

-1.2 days

+3.9 %

+4.2 %

MDS

+0.5 %

+0.5 %

-0.3 mm

-0.2 mm

+2.3 cm2

+8 kg

+0.2 cm

-1.6 days

+5 kg

-2 kg

+13 kg

+14 kg

+8 kg

-1.0 kg

-0.6 days

+3.3 %

+4.1 %

MDS+

+1.2 %

-0.1 %

-0.4 mm

-0.3 mm

+1.5 cm2

+13 kg

+0.2 cm

-2.0 days

+4 kg

+11 kg

+19 kg

+16 kg

+9 kg

-0.7 kg

-1.0 days

+3.9 %

+4.4 %

MGN

Selection Advantage

+1.3 %

-0.1 %

-0.2 mm

-0.2 mm

+1.9 cm2

+9 kg

+0.0 cm

-1.5 days

+5 kg

-1 kg

+13 kg

+13 kg

+8 kg

-0.9 kg

-0.2 days

+2.6 %

+3.7 %

MGN+

+0.9 %

-0.0 %

-0.3 mm

-0.2 mm

+1.3 cm2

+14 kg

+0.5 cm

-2.3 days

+3 kg

+18 kg

+23 kg

+18 kg

+10 kg

-0.4 kg

-1.5 days

+3.9 %

+4.1 %

MGS

+1.0 %

+0.1 %

-0.2 mm

-0.1 mm

+2.4 cm2

+9 kg

+0.3 cm

-1.9 days

+5 kg

-2 kg

+13 kg

+12 kg

+8 kg

-0.9 kg

-0.4 days

+3.0 %

+3.9 %

MGS+

+1.0 %

+0.2 %

-1.0 mm

-0.6 mm

+1.6 cm2

+15 kg

+0.3 cm

-0.9 days

+4 kg

+19 kg

+25 kg

+20 kg

+11 kg

-0.4 kg

-0.8 days

+2.6 %

+3.0 %

ATS

+1.2 %

-0.2 %

+0.1 mm

+0.3 mm

+1.6 cm2

+8 kg

+0.2 cm

-2.6 days

+1 kg

-0 kg

+9 kg

+9 kg

+6 kg

-1.2 kg

-1.2 days

+4.5 %

+5.8 %

PRO

-1 %

-1 %

-0 %

-1 %

-0 %

-1 %

-1 %

-1 %

-0 %

-2 %

+0.16 kg/day +0.21 kg/day +0.12 kg/day +0.18 kg/day +0.18 kg/day +0.24 kg/day +0.17 kg/day +0.22 kg/day +0.11 kg/day +0.27 kg/day

-0.4 mm

Rump Fat

NFI (Feedlot)

-0.2 mm

Rib Fat

+3 kg

Milk

+1.3 cm2

+17 kg

Mature Cow Weight

Eye Muscle Area

+22 kg

600 Day Weight

+14 kg

+18 kg

400 Day Weight

Carcase Weight

+10 kg

200 Day Growth

+0.4 cm

-0.5 kg

Birth Weight

Scrotal Size

-1.2 days

Gestation Length

-2.1 days

+3.8 %

Calving Ease Dtrs

Days to Calving

+4.3 %

Calving Ease Direct

AMB

Angus Research Selection Index Comparison