History of Selection From Phenotypes to Economic Indexes NBCEC Brown Bagger 2012 October 3, 2012 Darrh Bullock, University of Kentucky

Assumptions of Selection Measurable Qualitative Quantitative Heritable Is there a resemblance between parents and offspring for the trait of interest

History of Selection Appearance

Appearance People’s Sexiest Man Alive 2010

History of Selection Appearance Pedigree Information Shorthorn 1846 Hereford 1880 Angus 1886

History of Selection Appearance Pedigree Information Data Collection

Body Composition Drugs Sex Rock and Roll Sushi Rice Meat Potatoes

Heritability h2 Trait Low Reproduction Production Moderate Product Heritability is a measure of how a trait will respond to selection. In highly heritable traits rapid progress can be made by selecting sires that are superior in that trait, in lowly heritable traits it takes considerably more time. Another way to look at heritability is how well the offspring will perform similar to their parents. In highly heritable traits, high performing parents will tend to produce high performing offspring for that trait. When looking at the chart reproduction is a lowly heritable trait. Therefore, we can make little progress in improving reproductive efficiency through our selection practices. That means we should focus on management (nutrition and health) and crossbreeding to ensure reproductive soundness and not selection. The production traits, growth and milk, are moderately heritable, which means we can make good progress in changing those traits through selection. Most traits associated with the end product are highly heritable, which means we can improve carcass characteristics rapidly through our selection practices. Product High 10

History of Selection Appearance Pedigree Information Data Collection Ratios

100 is average Ratios Individual Measurement X 100 Contemporary Group Average X 100 100 is average

Contemporary Group 1 Physics Test Score Ratio = 86

Contemporary Group 2 Physics Test Score Ratio = 116

History of Selection Appearance Pedigree Information Measurable Trait Ratios Breeding Values – C.R. Henderson Pedigree and Phenotype Development of EPDs

EPDs A prediction of the genetics a bull will pass on to his calves, when compared to other bulls within the breed Take into account the actual measurement on the bull, all ancestral measurements and environment Not a perfect science, so use as risk management tool EPDs – A prediction of the genetics a bull will pass on to his calves, when compared to other bulls within the breed. EPDs take into account the actual measurement on the bull, all ancestral measurements and the environment that the bull was raised in. By doing so, many of the errors associated with selection are eliminated. 16

Connectedness CG 1 CG 2 CG 2 CG 1

Expected Progeny Differences Physics Score EPDs 25 Points 15 Points -5 Points

Expected Progeny Differences 95 85 65

Expect the average difference in EPD +35 lbs +20 lbs Direct In this example we have a group of first calf heifers and want to select a bull that will give lighter calves at birth. In comparing the two bulls they are very similar in terms of their physical appearance and their genetics for growth and traits of importance. Which bull will give us lighter calves at birth? If we were to breed these bulls to a comparable set of females, in terms of their genetics and environment, we would expect calves by the bull on the right to weigh 2.9 lbs less at birth than calves by the bull on the left. The two key words are EXPECT and AVERAGE. We would expect the difference to be 2.9 lbs, however, the calculation of EPDs is not an exact science. If we were to do a study at UK with these bulls and bred them to 1000 cows each, the average difference in birth weight may not be 2.9 lbs, it may be 2 lbs or it may be 4 lbs. However, EPDs do a very good job in sorting bulls, so you can be fairly confident that the bull on the right will give you the lighter calves. Look at EPDs as risk management, you will make mistakes when using EPDs to select bulls, but you will make far fewer mistakes than if you were using actual measurements or ratios. Also, remember that we are dealing with averages. The bull on the right will have some calves that weigh more at birth than some of the calves by the bull on the left, however, on average the bull on the right will have lighter calves. Also, when using EPDs it is important to use EPDs alone for that trait, do use them in combination with actual measurements. This is a very hard concept for producers to accept, but is a must. Since the EPD calculations have already included the actual measurement including it again will only increase the risk of making an error in your selection. Expect the average difference in offspring to be 15 pounds. 20

Maternal EPD +25 lbs +15 lbs Expect the average difference in In this example we have a group of first calf heifers and want to select a bull that will give lighter calves at birth. In comparing the two bulls they are very similar in terms of their physical appearance and their genetics for growth and traits of importance. Which bull will give us lighter calves at birth? If we were to breed these bulls to a comparable set of females, in terms of their genetics and environment, we would expect calves by the bull on the right to weigh 2.9 lbs less at birth than calves by the bull on the left. The two key words are EXPECT and AVERAGE. We would expect the difference to be 2.9 lbs, however, the calculation of EPDs is not an exact science. If we were to do a study at UK with these bulls and bred them to 1000 cows each, the average difference in birth weight may not be 2.9 lbs, it may be 2 lbs or it may be 4 lbs. However, EPDs do a very good job in sorting bulls, so you can be fairly confident that the bull on the right will give you the lighter calves. Look at EPDs as risk management, you will make mistakes when using EPDs to select bulls, but you will make far fewer mistakes than if you were using actual measurements or ratios. Also, remember that we are dealing with averages. The bull on the right will have some calves that weigh more at birth than some of the calves by the bull on the left, however, on average the bull on the right will have lighter calves. Also, when using EPDs it is important to use EPDs alone for that trait, do use them in combination with actual measurements. This is a very hard concept for producers to accept, but is a must. Since the EPD calculations have already included the actual measurement including it again will only increase the risk of making an error in your selection. Expect the average difference in offspring of the sires daughters to be 10 pounds. 21

Has Selection Worked? Genetic Trends All breeds show drastic changes in genetic merit of most traits. Indicate that simultaneous selection for antagonistic traits is possible.

Angus Genetic Trends

Genomics (in the beginning) Physics Score MBV = 25 Points Physics Score EPD = 15 Points

Genomics (now) Physics Score EPD = 15 Points Phenotype Acc .15 Physics Score EPD = 20 Points Phenotype + Genomics Acc .30

Selection Index Allows comparison on single value Weights traits according to economic importance Selection index = a1EPD1 + a2EPD2 + . . . + akEPDk

Male Mate Selection Index $MM = 4(App EPD) -2(Comp EPD) + 1(Int EPD) + 3(Pers EPD) $MM = 4(App EPD) + 1(Int EPD) + 3(Pers EPD)

Selection Index Index Values 35 45 15

Summary I Win !