b Dominance vs. Recessiveness B Homozygous, Heterozygous Punnett - - PDF document

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1/ 26/ 2017 Know how. Know now. Know how. Know now. Breeding/Genetics Objectives Livestock Management CDE Beef: Breeding, Genetic, & Reproductive Mgmt Students should understand ... B. A. Reiling Dominance vs. Recessiveness

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1/ 26/ 2017 1

Know how. Know now.

Livestock Management CDE Beef: Breeding, Genetic, & Reproductive Mgmt

  • B. A. Reiling

January 19, 2017

University of Nebraska–Lincoln

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Breeding/Genetics – Objectives

 Students should understand ...

  • Dominance vs. Recessiveness
  • Phenotype = Genotype + Environment
  • Relative heritability of traits
  • Use of Performance Data & Genetic Evaluations
  • Actual Data & Ratios
  • EPDs
  • Selection Indexes
  • Benefits of Crossbreeding Programs

University of Nebraska–Lincoln

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Breeding/Genetics – What to Expect

 Dominance vs. Recessiveness

  • Homozygous, Heterozygous
  • Punnett Square: Black vs. Red, Polled vs. Horns
  • BB * bb =

Bb * bb =

  • Bb * Bb =

2 phenotypes 3 genotypes

University of Nebraska–Lincoln

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Punnet Square:

B b B b

BB Bb bB bb

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Codominance

 So how do we get a “ROAN” Shorthorn?  Example – Shorthorn Cattle

  • R = Red; W = White
  • RW = Roan

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Phenotype = Genotype + Environment

 Selection is based upon phenotype

  • Phenotype is not only the “looks”
  • But also, what we measure.
  • Birth Weights
  • Weaning Weights
  • Yearling Weights
  • Average Daily Gain
  • Pregnancy Rate
  • Etc.
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Phenotype = Genotype + Environment

 Environmental Effects

  • 1) Random
  • 2) Known  Adjusted Performance Records
  • 205-day Adjusted Weaning Weight
  • 1) ADG = (current weight – birth weight) / Days of Age.
  • 2) (ADG * 205 days) + birth weight
  • 3) Adjust for sex of calf & age of dam

2 3 4 5-10 11+ Male +60 +40 +20

  • +20

Female +54 +36 +18

  • +18

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Relative Heritability of Traits

General Traits Avg Heritability Reproduction LOW (<20%) Growth Performance Moderate (20-40%) Mature Size Carcass Traits HIGH (>40%)

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Use of Data & Genetic Evaluations

 Actual Data

  • Phenotype = Genotype + Environment
  • For growth traits, heritability = 30%
  • Minimal value for estimation of genetic merit

 Trait Ratios

  • = (Ind Perf / Avg Group Perf) * 100
  • Provides relative ranking among contemporaries

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Use of Data & Genetic Evaluations

 EPDs

  • Best tool for genetic improvement
  • Comparative Value
  • Expressed as + or – Values
  • Theoretical average = 0
  • Expressed in units of measure
  • For the trait

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Use of Data & Genetic Evaluations

 Comparing EPDs

  • Sire A = +90 Yearling Wt EPD
  • Sire B = +65 Yearling Wt EPD
  • Difference = 35 lbs
  • Calves of Sire A should weigh 35 lbs heavier (on

average) at one year of age than those of Sire B, when bred to the same cows and raised under the same environmental conditions.

University of Nebraska–Lincoln

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Use of Data & Genetic Evaluations

 EPDs are NOT additive

  • If the current average carcass weight = 800 lbs
  • Year 1: Sire CW EPD = +20
  • Year 2: Sire CW EPD = +30
  • Year 3: Sire CW EPD = +10
  • Year 4: Sire CW EPD = +15
  • After 4 years, how much more carcass weight?
  • Compare the differences = 15 lbs added CW

75 pounds! 875 lb CW!

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Use of Data & Genetic Evaluations

 True / False –

  • A bull with a negative marbling score EPD is

guaranteed to decrease the % of choice cattle in your herd.

 Selection Indexes

  • Profitability Indexes
  • Facilitate Multiple Trait Selection

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Benefits of Crossbreeding

 Breed Complementation

  • Matching the strengths & weaknesses of different breeds
  • Angus * Hereford = Black Baldy
  • Angus * Charolais

 Heterosis (hybrid vigor)

  •  in productivity of crossbred progeny

that is greater than expected based upon parent’s average performance University of Nebraska–Lincoln

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The Heterosis Advantage

Weaning weights

  • Dam (Breed A) =

460 lbs

  • Sire (Breed B) =

540 lbs

  • Average =

500 lbs expected

  • Crossbred AB =

530 lbs

  • Heterosis advantage

30 lbs

  • CRITICAL for REPRODUCTIVE Traits

University of Nebraska–Lincoln

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Use of Data & Genetic Evaluations

 What might your students have to do?

  • Answer some basic “test” questions
  • Keep/Cull with data & questions
  • Sire Summary Quiz

 Resources

  • NebGuide: EPD Basics & Definitions
  • NebGuide: Economic Indexes for Beef Sire Selection
  • Beef EPD Definitions (Reiling)
  • Sample Sire Summary Quizzes with Keys (Reiling)

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Objectives – Reproduction

 Students should ...

  • Identify basic reproductive organs/structures
  • of the cow (female reproductive tract)
  • Describe the importance of scrotal circumference
  • Discuss/outline/demonstrate reproductive mgmt practices
  • Estrous Synchronization & Artificial Insemination
  • Breeding Soundness Examinations
  • Process of Calving & Providing Calving Assistance
  • Identify & describe purpose of basic reproductive equipment
  • Know Beef reproductive numbers

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Bovine Female Reproductive Anatomy

Cervix Uterine Body Uterine Horns

(calf will develop in one of the horns)

Ovary

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Bovine Female Reproductive Anatomy Ovary

Oviduct (Fallopian Tube)

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Bovine Female Reproductive Anatomy Corpus Luteum

Oviduct (Fallopian Tube)

Follicle

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Bovine Female Reproductive Anatomy

 Ovarian Structures

  • Follicles
  • Grows in response to FSH
  • Secretes Estrogen
  • Corpus Luteum
  • Secretes progesterone
  • Maintain pregnancy

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Basic Reproductive Hormones

 Follicle Stimulating Hormone (FSH)

  • Causes the follicles to grow
  • Application – superovulation & embryo transfer

 Estrogen

  • Secreted by the follicles
  • Estrous behavior

 Luteinizing Hormone (LH)

  • Causes ovulation of egg from the follicle

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Basic Reproductive Hormones

 Progesterone

  • Secreted by corpus luteum (CL)
  • Maintains the pregnancy
  • Keeps “heat” from recurring
  • Application = Estrous synchronization

 Prostaglandin

  • Secreted by uterus, due to atrophy of egg
  • Regresses CL; restarts the cycle
  • Application = Estrous synchronization

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Male Reproductive Management

 Breeding Soundness Examination

  • 4 components
  • 1) External Body Evaluation
  • 2) External Reproductive Organ Evaluation
  • Scrotal Circumference
  • 3) Internal Reproductive Tract Evaluation
  • 4) Semen Evaluation
  • Motility, Morphology
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Possible Skill Activities (Hands-on)

 Artificial Insemination

  • Demonstrate proper loading of an AI pipette.
  • https://www.youtube.com/watch?v=KKlM0YZ_83A
  • Demonstrate proper AI technique (on tracts)

 Scrotal Circumference

  • Demonstrate proper measurement of SC
  • https://www.youtube.com/watch?v=U8PhqLZtrZk

University of Nebraska–Lincoln

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Possible Skill Activities (Hands-on)

 Calving Assistance

  • Demonstrate proper obstetrical chain application
  • https://www.youtube.com/watch?v=9aIcnLBXdL0

University of Nebraska–Lincoln

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Reproductive Equipment (20)

 AI gun/pipette  AI sheath  Artificial Vagina  Bulb Syringe  Cane  CIDR  CIDR applicator  Cito cutter  Electroejaculation Probe  Goblet  Heat Detection Patch  Hemacytometer  Obstetrical Chains  Pelvimeter, Rice  Pelvimeter, Krautman  Scrotal Tape  Semen Collection Device  Semen Straw  Warm Water Thaw

 Ultrasound Endocavity Probe University of Nebraska–Lincoln

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Beef Reproduction By the Numbers ...

 Age of Puberty: 8-15 months  Estrous cycle length: 21 days  Duration of Estrus: 18 hours  Time of Ovulation: 12-14 hrs AFTER estrus  Gestation Length: 285 days  1st estrus post-calving (PPI): 30-60 days

University of Nebraska–Lincoln

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Reproductive Management Resources

 Ext Circular: Synchronizing Estrus in Beef Cattle  NebGuide: Assisting the Beef Cow at Calving Time  Bull Management & Nutrition

  • From the Range Beef Cow Symposium, 2009

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Questions & Discussion

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Thank You

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Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture. The Youth Development program abides with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department

  • f Agriculture.