Microsoft PowerPoint - NCBA_Cattlemens_College_Darrh_B

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1 Introduction to Genetics Darrh Bullock University of Kentucky

2 The Model Trait = Genetics + Environment

3 Genetics Additive Predictable effects that get passed from generation to generation Non-Additive Primarily dominance and genetic interactions Influenced by how genes match up

4 Crossbreeding

5 Why Crossbreed? Heterosis Advantage a crossbred has over the average of the parent breeds Due to non-additive genetics Breed Complementarity Matching breeds to fit each other Matching breeds to fit the environment

6 Selection

7 Types of Traits Qualitative Quantitative

8 Qualitative Traits Usually controlled by one pair of genes Usually limited impact by environment Most that we deal with have simple inheritance

9 Dominance/Recessive/Carriers Black (B) is dominant to red (b) Homozygous dominant (BB = Black) Heterozygous (Bb = Black) These animals are often referred to as carriers Homozygous recessive (bb = Red)

10 Mating a Carrier to a Carrier Black B b Black B b BB Black Bb Black Bb Black bb Red

11 Mating a Homozygous Dominant to a Carrier Black B B Black B b BB Black Bb Black BB Black Bb Black

12 Quantitative Traits Usually controlled by many gene pairs Usually a large impact by environment Interactions between genes and between genes and the environment Heritability the proportion of a trait that is controlled by additive gene action. The resemblance between parents and offspring, for a particular trait, due to genetics

13 Heritability Trait h 2 Reproduction Low Production Moderate Product High

14 Appearance History of Selection

15 Appearance

18 History of Selection Appearance Pedigree Information

19 History of Selection Appearance Pedigree Information Data Collection

20 Body Composition

21 History of Selection Appearance Pedigree Information Data Collection Ratios

22 Ratios Individual Weight X Contemporary Group Average 100

23 Contemporary Group 1 Physics Test Score Ratio = 86

24 Contemporary Group 2 Physics Test Score Ratio = 116

25 History of Selection Appearance Pedigree Information Measurable Trait Ratios Breeding Value Pedigree and Phenotype

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

27 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.

28 Angus Genetic Trends

29 Genetic Evaluation Models Trait = Genetics + Environment Basic Statistical Model Phenotype = Genetic Merit + Environment Effects + Unexplained Variation

30 Genetic Evaluation Models Basic Model Phenotype Environment Effects Unexplained Variation = Genetic Merit

31 Genetic Evaluation Models Basic Model Phenotype Environment Effects = Genetic Merit + Unexplained Variation

32 Unexplained Variation Data Accuracy Zero

33 75 lbs 55 lbs 95 lbs Potential Genetic Merit of Gametes Produced by a Bull

34 Mendelian Sampling Cattle have 30 pairs of chromosome and a parent passes one from each pair to a progeny. How many genetically different gametes (sperm or eggs) can a parent produce given this sampling process? 1,073,741,824

35 55 lbs 75 lbs 35 lbs 95 lbs Comparing Gametes Produced by Bulls with Differing EPDs

36 Accuracy Yearling Weight Accuracy in Angus Bulls.10 relates to a possible change value of 15 lbs. 75 ± 15 = 60 to relates to a possible change value of 2 lbs. 75 ± 2 = 73 to 77

37 Unexplained Variation Data Accuracy Zero

38 Selection Index Weights traits according to economic importance Allows comparison on single value Selection index = a 1 EPD 1 + a 2 EPD a k EPD k

39 Selection Index Selection index = a 1 MPV 1 + a 2 MVP a k MVP k Combined Selection index = a 1 MPV 1 + a 2 EPD 2 + a 3 MPV a k EPD k

40 Conclusions Crossbreeding is an essential part of every commercial beef operation Selection should be made on traits that economically impact your herd

41 Conclusions There are multiple tools to assist in making selection decisions. Visual EPDs Genomics Selection Indices

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