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Traditional (historical) Breeding

Gradual (but dramatic) genetic change over long time periods through observation and selective breeding (Instinctive Selection). Traditional (historical) Breeding. Economic pressures for rapid genetic change over short periods via optimal utilization of available breeding tools. Modern Breeding.

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Traditional (historical) Breeding

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  1. Gradual (but dramatic) genetic change over long time periods through observation and selective breeding (Instinctive Selection) Traditional (historical) Breeding

  2. Economic pressures for rapid genetic change over short periods via optimal utilization of available breeding tools Modern Breeding Co-improvement of technologies on nutrition, management crossbreeding and genetic improvement

  3. What Animal Breeding is? • Selection Theory • Genetic Evaluation • Crossing Theory • Reproductive Technology Where to go? Breeding Goal How to get there? Quantitative Genetics Tools Getting There Implementation

  4. What tools are available? • Visual assessment

  5. What tools are available? • Visual assessment • Pedigree Information

  6. What tools are available? • Visual assessment • Pedigree Information • Performance information - simple, traditional measures Ex: growth, fertility, calving easy

  7. What tools are available? • Visual assessment • Pedigree Information • Performance information - simple, traditional measures Ex: growth, fertility, calving easy -Advanced measures Ex: Ultrasound (IMF%, RE area, feed intake)

  8. Basic Genetics and Cytogenetics • Inheritance: May be defined as a tendency of parents to generate offspring with similar characteristics. • Variation: May be defined as every environmental or germinal differences between organisms related by ascendance. It can be due differences on the environment (nongenetic) or on the genotypes (genetic)

  9. Some Definitions • Gene: The basic unit of heredity consisting of a DNA sequence at a specific location on a chromosome • DNA: Deoxyribonucleic acid, the molecule that forms the genetic code • Chromosome: One of a number of long strands of DNA and associated proteins present in the nucleus of every cell • Homolog: One of a pair of chromosome having corresponding loci • Locus: The specific location of a gene on a chromosome • Allele: An alternative form of a gene • Multiple alleles: More than two possible alleles at a locus

  10. Some Definitions • Genotype: The combination of genes at a single locus or at a number of loci* • Homozygote: A one-locus genotype containing functionally identical genes • Heterozygote: A one-locus genotype containing functionally different genes • Segregation: The separation of the homolog chromosome during meiosis • Germ Cell or Gamete: A sex cell – a spermatozoid (sperm) or ovule (egg) • Meiosis: The process of germ cell formation • Mitosis: The process of cell multiplication: • Embryo: An organism I the early stages of development in the shell (birds) or uterus (mammal)

  11. 1. Gametes (sex cells) sperm cell ovum or egg 1n chromosome number at maturity 2. Somatic cells (non-sex cells) 2n chromosome number at maturity Cells are classified into two types

  12. Chromosomes • Located in nucleus of cell. • Each is a huge molecule, consisting of DNA and proteins called histones. • Occur in pairs in somatic cells, but as singles in gametes. E.g., in humans: • Somatic cells have 46 chromosomes (23 pairs). • Gametes have 23 chromosomes. • 2n = 46, 1n = 23 • The two chromosomes of a given pair are said to be homologous to one another.

  13. Chromosomes • X and Y are known as sex chromosomes; others as autosomes. • Female: • somatic cell contains X X • ovum contains X • Male: • somatic cell contains XY • sperm contains X or Y • Genes determining gender are located on the sex chromosomes

  14. Chromosome Number for Selected Species (2n)

  15. DNA – Genetic Code for Protein SynthesisDNA – Polymer of Nucleotide Bases Nucleotide Sequence –Amino acid Sequence of the Protein (Shape and function) Chromosomes- Chromatin and DNA

  16. I - DNA is the Genetic Code for Protein SynthesisProteins can be Enzymes, Hormones, Transcription Factors, Structural, etc.Nucleotide Sequence –Amino acid Sequence of the ProteinShape Determine the function/effect)

  17. Genetic Code for Protein Synthesis

  18. DNA Replication - Complementary Bases

  19. What are alleles? • Alternative gene forms that occupy the same locus on homologous chromosomes. • e.g., black (B) / red (b) coat color gene in cattle B ___._____________ ___._____________ b • Can have at most 2 alleles in an individual, but more than 2 in a population (A/B/O blood-type).

  20. Law of random segregation • a random sample half of each gene pair of an individual is transmitted to a gamete (and offspring) parent B/b 1/2 1/2 gametes /b B/

  21. Law of Independent Assortment • Segregation of alleles at one locus is independent of segregation at other loci. Black, polled Bb Pp parent B P B p b P b p gametes

  22. Terminology • Dominant versus recessive black (B_) dominant to red (bb) • Homozygous versus heterozygous BB or bb versus Bb • Summary BB = homozygous dominant Bb = heterozygous bb = homozygous recessive

  23. Genetics = Heredity X Environment • Heredity: transmission of genetic or physical traits of parents to their offspring. • Environment: the sum total of all external conditions which effect the life of the animal

  24. Terminology • Heritability: describes what fraction of the differences in a trait is due to differences in genetic value rather than environmental factors. • Hereditary variation: variation caused by the heredity. • Environmental variation: variation caused by the environment.

  25. Heritability Estimate • Heritability estimate: hereditary variation due to additive gene action. • effects the rate of improvement • low heritability lends to slow rates of improvement • high heritability estimates yields faster rates of improvement

  26. Economic Important Traits • 205 day adjusted weaning weight • Yearling weight • Birth weight • Rib eye area • Intramuscular fat • Milk production • Average daily gain • Feed efficiency • Calf crop %

  27. Rate of Gain (feedlot cattle) 40-68% Ribeye Area 50-70% Calving Interval (Fertility) 10 % Weaning Weight 30 % Birth Weight 40 % Fat Thickness 45 % Pasture Gain 30 % Cancer-eye Suscept. 30 % Heritability Estimates foreconomical important traits

  28. Terminology • Prepotency: the amount that an offspring looks like the parent. • Nicking: when genes of the dam and sire complement each other. • Heterosis: the improvement that the offspring has over its parents.

  29. Production Testing and Selection • Performance testing- testing of the individual • Progeny testing- testing of the offspring • Pedigree selection- using the reputation or records of animals for breeding selection

  30. Multiple Trait Selection Systems • Tandem- looking at intensifying on one trait at a time • Independent Culling- using minimal criteria to select for two or more economic important traits • Selection Index- using the combination of two or more economic important traits by observing an index to make selections for breeding

  31. Selection Differential, Estimated Breeding Value and Expected Progeny Differences • Definition of S.D.= the difference between animals selected to be parents and the average of all animals in the herd for selection for a specific trait • EBV = ave. of animals selected minus the ave. of all animals X heritability • EPD = EBV X .5

  32. Expected Progeny Differences • Definition – the expected performance of an individual’s offspring relative to the average individual of the entire breed. • Examples – birth weight, weaning weight, yearling weight, scrotal circumference, ribeye area, etc. • Understanding a Sire Summary

  33. Types of Breeding • Purebreeding systems: • Outcrossing: the mating of relatively unrelated animals within the same breed. • Inbreeding: production of offspring from parents more closely related than the average of a population • Line breeding: a form of inbreeding in which an attempt is made to concentrate the inheritance of some ancestor in the pedigree.

  34. Crossbreeding Systems • Crossbreeding: the mating of animals of different breeds. • two-breed cross • two-breed backcross • three-breed rotational cross • three-breed terminal cross

  35. Frame size vs. production vs. type • Size - frame • grazing area vs frame • market size vs frame • nutrition vs frame

  36. Genetic/Repro Problems in Cattle • Freemartins-hormonal influence • Dwarfism – genetic influence • Dark cutters / more environment • muscular hypertrophy (double muscling) • increase in size of muscle fibers • Quality vs quantity vs performance

  37. Genetic Defects • Tibial hemimelia (TH) • Pulmonary Hypoplasia with Anasarca (PHA) • Bovine Arthrogyrposis Multiplex Congenita (AM) aka curly calf • Neuropathic Hydrocephalus (NH) • Dwarfism (Angus mutation, DW1) • Osteopetrosis (OS) aka marble bone • Contractual Arachnodactyly (CA)- aka Fawn Calf Syndrome

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