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Understanding Genetics in Beef Cattle for Optimal Production

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tanek
35 diapositives · 488 Views · Sep 01, 2014

This overview by the West Virginia University Extension Service explores the essential role of genetics in shaping the phenotype of beef cattle and its implications for production. With a focus on both quantitative and qualitative traits, the document explains how environmental factors and genetic makeup influence cattle performance. It discusses the importance of Expected Progeny Differences (EPDs) for evaluating genetic value and emphasizes the significance of accurate record-keeping for effective cattle breeding. Insights into managing environmental influences to enhance genetic potential are also presented.

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  1. West Virginia UniversityExtension Service Genetics in Beef Cattle Wayne R. Wagner

  2. West Virginia UniversityExtension Service • A Beef Animal’s Phenotype is completely determined by: • It’s genetic makeup • Cattle have 30 pairs of chromosomes • Genes located on chromosomes transmitted from parent to offspring • Genes code for production of proteins/enzymes

  3. West Virginia UniversityExtension Service • Quantitative – traits influenced by very few gene pairs. There is a distinct difference in phenotypes. Example horned vs polled or red vs black.

  4. Let B = Black b = Red Heterozygous X Heterozygous Heterozygous X Red B b b b B B b b 25% Homozygous Black 50% Black w/Red gene 50% Black w/Red Gene 50% Red 25% Red

  5. West Virginia UniversityExtension Service • Qualitative – traits influenced by many pairs of genes. Show continuous variations or gradual variation from one extreme to the other. Expression of these traits is influenced by the environment.

  6. West Virginia UniversityExtension Service • A Beef Animal’s Phenotype is completely determined by: • The Environment in which the animal is raised • Unknown • Includes weather (temperature, humidity, precipitation) • Disease, internal & external parasites (vaccination program) • Feed/forage both quality and amount • Unique factors including injury/sickness • Known • Age of dam • Age of calf • Sex of calf

  7. West Virginia UniversityExtension Service The differences between two Hereford calves born in 2006 are due to differences in genetics and the environments in which they are raised.

  8. West Virginia UniversityExtension Service • Beef producers keep records on various traits (Calving Ease, Weaning Weight, Yearling Weight, Scrotal circumference, IMF, REA) • These records are adjusted for known sources of variation so differences are due to genetics and unknown Environment → improves accuracy

  9. West Virginia UniversityExtension Service Additive G Non-additive P Known E Unknown

  10. West Virginia UniversityExtension Service • The objective of a seedstock producer is to limit differences due to Environmental effects as much as possible to get the best estimate of true genetic differences!

  11. West Virginia UniversityExtension Service • Contemporaries – calves born in a similar time frame and then raised together and treated alike.

  12. West Virginia UniversityExtension Service • Contemporary information is important because it is used in the computation of EPD’s.

  13. West Virginia UniversityExtension Service • EPD’s – Expected Progeny Difference • Allows you to compare two bulls of the same breed but raised in different environments and under different health and nutritional programs.

  14. West Virginia UniversityExtension Service • EPD’s reported in actual units.

  15. West Virginia UniversityExtension Service • EPD’s are for within breed comparisons.

  16. West Virginia UniversityExtension Service • EPD’s are not static – change as new and more data is collected.

  17. West Virginia UniversityExtension Service • EPD is our best estimate of an animal’s genetic value for a particular trait at a specific time and given the information that is available at that time. • ie. In March 2006 you buy a yearling bull with a YW EPD of 70 lbs. • In 2006 his dam raises another calf & yearling data is collected in March 2007 • In 2006 his sire produces 3000 additional progeny with yearling data collected in 2007 • The data added in 2007 updates the estimate of genetic value for the dam to a small degree and to the estimate of genetic value of the sire to a somewhat larger degree.

  18. West Virginia UniversityExtension Service • EPD’s depend upon accurate contemporary information being reported.

  19. West Virginia UniversityExtension Service • EPD’s are estimates of how future progeny will perform when mated at random to the average of the breed.

  20. West Virginia UniversityExtension Service • Breed average EPD’s ≠ 0

  21. West Virginia UniversityExtension Service • Acc is a measure of risk associated with an EPD. Acc is an indication of how much an EPD might change as additional data is collected.

  22. West Virginia UniversityExtension Service • Acc ranges from 0 – 1 • Acc below .4 would be low • Acc between .4 and .8 are moderate • Acc above .8 are high

  23. West Virginia UniversityExtension Service • Acc is an indication of how much an EPD might change. (Possible Change)

  24. West Virginia UniversityExtension Service

  25. West Virginia UniversityExtension Service • If you produce your own replacement females, the last 3 bulls used in a calf’s pedigree accounts for 87 ½ of the genetic makeup and potential.

  26. West Virginia UniversityExtension Service • The value of a herd depends upon the bulls used.

  27. West Virginia UniversityExtension Service • Often times, when cattle are raised in an excellent environment, it is difficult to determine how much of an animals superiority is due to nutrition, vaccination programs, etc and how much is genetic.

  28. West Virginia UniversityExtension Service • Crossbreeding • Heterosis – advantage of crossbred animal compared to average of parental breeds. • Complementarity – combination of breed strengths.

  29. West Virginia UniversityExtension Service • Heterosis: • Traits with low levels of heritability usually show significant amounts of heterosis. • Improves an animal’s ability to withstand stress.

  30. West Virginia UniversityExtension Service Economically Important Traits • Reproduction/Fertility • Calving Ease • Gestation Length • Scrotal Circumference • Cycling before breeding season starts • Feed Efficiency • Difficult to measure • Indicators – ADG & YW (should be within a frame size) • Product Merit • REA • Marbling

  31. West Virginia UniversityExtension Service • Future • Feed Efficiency – RFI • Fleshing Ability • Marker Assisted Selection • Balance/Optimums

  32. West Virginia UniversityExtension Service • Why RFI? • Feed:gain determines variable costs and is influenced by environment, body condition, appetite, stage of growth and rate and composition of gain.

  33. West Virginia UniversityExtension Service • Genetic makeup is the foundation of a cow herd.

  34. West Virginia UniversityExtension Service • www.nbcec.org • www.beefimprovement.org • www.angus.org • www.hereford.org • www.simmental.org • www.charolaisusa.com