Genetics and Phenotypes

Question 1

Structure of commercial poultry breeding

Answer 1

• Small number of multi-national companies
• In the UK 2 companies supply ~ 90% of broiler
breeding stock
• UK breeding companies for layers – franchisees of international companies
• Rapid rates of genetic progress in ‘pure-bred’ breeding nucleus populations
• Rapid transfer of improvements through ‘breeding pyramid’ to commercial production of crossbred stock

Pure lines ➡️
Great-grand parent
(selection)➡️
Grand parent stock (crossed)➡️
Parent Stock
(2 way cross males and females)➡️
Production stock (4 way cross)

Question 2

Poultry – Primary Breeding Sector

Answer 2

• Pure lines
• Relatively small number breeding stock • Produce large number of chicks
• High selection differentials
• Typically selecting 1% males and 10% females
• Low generation intervals
• High Biosecurity
• High investment in research
• Use of measurement technology • Use of genomics
• Multiplication

Question 3

Breeding objectives - Layers

Answer 3

To obtain maximum number of saleable eggs per hen housed at low feed cost per egg or per kg egg mass and the eggs should have optimal internal and external qualities
• Age at sexual maturity • Rate of lay
• Livability
• Egg weight
• Feed conversion ratio • Albumen height
• Temperament
• Skeletal integrity
• Adaptation to heat stress • Shell colour and strength
• Body weight
More than 30 traits recorded and monitored in
pure-bred populations

Question 4

Breeding objectives - Broilers

Answer 4

Selection on commercial weight in commercial conditions
• Breast muscle weight • Meat quality
• Food Conversion Ratio • Hatchability
• Skeletal integrity
• Metabolic disorders and immune response
• Welfare
1000’s of measurements made – inc electronic feed recording,
CT scanning, bone x rays etc

Selection based on objective criteria

• Individual EBVs calculated using 1000’s of records
• EBVs combined into overall Selection Index
• Each trait weighted in Index
• Weightings based on
• Economicimportance
• Heritability
• Genetic correlations
• Required change

Question 5

Small scale poultry breeding

Answer 5

• 280breedsofpoultrykeptintheUK • 33 duck
• 23 geese
• 24 fowls
• 63miniaturefowls
• 20truebantamfowls
• 8 turkeys
• No pedigree registration
• No individual identity recording
• Poultry Club regulates exhibition breeders
• National Poultry collection – individual pedigree recording

Question 6

Structure of commercial pig breeding

Answer 6

• Multi-national companies
• Rapid rates of genetic progress in ‘pure-bred’
breeding nucleus populations
• Rapid transfer of improvements through ‘breeding pyramid’ to commercial production of crossbred stock
• Biosecurity prioritised
• Integrated production
• Significant investment in research

Pure lines➡️
Grand parent stock➡️
Parent Stock➡️
(Specialist sire and dam lines)➡️
Production stock (Crossbred)
 Or 
Artificial insemination from pure lines to Production stock (Crossbred)

Question 7

Pigs - Genetic improvement

Answer 7

• Specialised sire and dam lines (proprietary) • Multiple populations of each
• Index Selection – Performance Testing
• Measure performance in commercial systems
• Detailed recording of weight and feed intake • Ultrasonicmeasurementoffatdepth
• Large nucleus populations – allows high selection differentials • Hyper-prolific selection
• Marker Assisted Selection
• Genomic selection

Question 8

Pigs – Breeding objectives

Answer 8

• Lifetime production
• Pigsweanedpersowlifetime
• Feed efficiency
• Lean %
• Growth
• Meat quality
• Vitality
• Piglet survival
• Legstrengthandlocomotion

Question 9

Small scale pig breeding

Answer 9

• 11 Native Breeds
• All considered rare and at risk
• British Pig Association
• Purebred registration and pedigree services
• Conservation of rare breeds
• Gene banking

Question 10

Dairy cattle breeding

Answer 10

• Bulls – International AI companies/Co-operatives • Cows – Individual herds
• Progeny testing
• National breeding programmes
• Shareinformation
• Interbull – international evaluations
• Independent milk recording
• Widely published genetic evaluations
• Public or levy funding of research

Elite herds Bulls➡️
Artificial Insemination Companies➡️
   Progeny test➡️
Artificial Insemination➡️
Production herds

Question 11

Dairy cow Progeny Testing

Answer 11

Occurs over 6 years

Top AI bulls and Top cows mated ➡️ Young bulls screened➡️ Test inseminations ➡️ Progeny born ➡️ Daughters mated➡️ Daughters Calve➡️ Daughters complete lactation➡️ Bulls evaluated➡️ Semen sold from best bulls
And then back to Top AI bulls and Top cows mated

Question 12

Dairy cows Genetic evaluation - PTAs

Answer 12

• Include information from all relatives • Performing in different herds/systems • Expressed relative to average
• Production traits
• Milk, Fat, Protein
• Health, welfare and fitness traits • SCC, Lifespan, Fertility, Locomotion
• Management traits
• Temperament,Easeofcalving,
• Type traits
• Conformation

Predicted Transmitting Ability
PTA = 1⁄2 EBV

Question 13

Dairy cows Genetic evaluation - PLI

Answer 13

Genetic evaluation - PLI
  Profitable Lifetime Index
• Combines PTAs into one score
• Measures Overall genetic Merit
• Other indexes for specific systems
• Each country has it’s own Indexes 
• E.g. Ireland EBI

Question 14

Dairy cows Breeds and crossbreeding

Answer 14

• Dominated by Holstein-Friesian
• Majority ‘pure’
• Crossbreeding increasing in popularity
• Genetic evaluation – AHDB
• Individual breed societies • Pedigree registration
• Typeassessments

Question 15

Beef cattle breeding

Answer 15

• Individual pedigree herds
• Average>80cows
• Selling 5 breeding bulls per year on average
• Large number of breeds
• On farm performance recording
• Genetic evaluation services provided independently • Nationalevaluations–withinbreed
• EBVs
• Terminal sire Index + Self replacing Index
• Research limited – breed societies

Elite/pedigree herds ➡️ Bulls ➡️
Artificial Insemination Companies➡️ Dairy herds.
Or

Elite/pedigree herds ➡️ Bulls ➡️ Suckler herds
Or

Elite/pedigree herds ➡️ Bulls ➡️
Artificial Insemination Companies➡️ Suckler herds

Question 16

Beef cattle breeding – traits recorded

Answer 16

• Calving
• Birth weight
• Gestation Length
• Calving Ease
• Growth and Carcase
• 200daygrowth
• 400daygrowth
• Muscle depth/Eye muscle area
• Backfat depth
• Maternal traits
• 200daymilk
• Maternal calving ease
• Ageatfirstcalving
• Calving interval

Question 17

Beef cattle – data from commercial herds

Answer 17

• British Cattle Movement Service
• Sire notification on passport
• Abattoir data can be linked back to sire
• EBVs available for
• Agetoslaughter
• Carcaseweight
• Carcaseconformation
• Carcasefatclass
• Averagedailycarcasegain
• AHDB National Beef Evaluations

Question 18

Sheep breeding

Answer 18

• Industry – 56% crossbred ewes 44% purebred
• Individual pedigree flocks
• Selling breeding rams
• Very large number of breeds (>100)
• 62 breeds numerically small
• On farm performance recording
• Genetic evaluation services provided independently
• Nationalevaluations–withinbreed
• EBVs
• > 33%ramstradedhaveEBVs
• Terminalsires>maternalbreeds>hillbreeds
• Research limited – breed societies

Elite/pedigree flocks rams➡️. Commercial flock

Question 19

Sheep breeding – hill breeds

Answer 19

• Average flock size ~ 300 ewes • Mainly purebred
• Locallyadapted‘types’
• Very traditional selection
• On farm performance recording
• Difficult to achieve in hill conditions • DNA parentage used in Wales
• Traits
• Survival
• Maternal
• Growth and Carcase

Question 20

Sheep breeding – maternal breeds

Answer 20

• Commercial flocks – self replacing
• Greater use of EBVs when purchasing rams
• On farm performance recording
• Traits
• Survival
• Maternal
• Growth and Carcase
• Disease e.g nematode resistance

Question 21

Sheep breeding – crossing breeds

Answer 21

• Sires of crossbred ewes
• Purebred numbers small – but important genetic
contribution
• On farm performance recording
• Very limited in BFL and BL – very traditional
• Aberfield – all recorded and sold with EBVs 
• Innovis
• Traits
• Survival
• Maternal
• Growth and Carcase
• Diseasee.gnematoderesistance

Question 22

Sheep breeding – terminal sires

Answer 22

• Small purebred flocks
• On farm performance recording
• Extensive use of EBVs
• Traits
• Live weight Growth
• Muscle Depth and Fat Depth
• Most research has been focussed on Terminal sires

Question 23

EBVs in Dog Breeding

Complex (polygenic) inherited traits

Answer 23

• Inherited disorders
• Hip and elbow dysplasia
• Chiari Malformation Syringomyelia (CMSM)(?)
• Behavioural traits
• Guide Dogs

Question 24

Recap of Poultry and Pigs breeding

Answer 24

• Breeding pyramid
• Integrated
• Objective measures
• High rates of genetic improvement
• High selection differentials
• Short generation intervals
• Measurement technology

Question 25

Recap of Dairy Cattle breeding

Answer 25

``` • International AI companies • Bull breeding – highly organised • Cow breeding – farm level • Good rates of genetic improvement • High selection differentials • Long generation intervals • High accuracy of selection ```

Question 26

Recap of Beef Cattle and Sheep breeding

Answer 26

``` • Limited AI • Small individual breeding herds and flocks • Independent genetic evaluations • Patchy genetic improvement • Low selection differentials • Long generation intervals • Limited use of EBVs ```