Genetics and Phenotypes Flashcards
Structure of commercial poultry breeding
• 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)
Poultry – Primary Breeding Sector
- 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
Breeding objectives - Layers
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
Breeding objectives - Broilers
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
Small scale poultry breeding
- 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
Structure of commercial pig breeding
• 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)
Pigs - Genetic improvement
- 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
Pigs – Breeding objectives
- Lifetime production
- Pigsweanedpersowlifetime
- Feed efficiency
- Lean %
- Growth
- Meat quality
- Vitality
- Piglet survival
- Legstrengthandlocomotion
Small scale pig breeding
- 11 Native Breeds
- All considered rare and at risk
- British Pig Association
- Purebred registration and pedigree services
- Conservation of rare breeds
- Gene banking
Dairy cattle breeding
- 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
Dairy cow Progeny Testing
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
Dairy cows Genetic evaluation - PTAs
- 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
Dairy cows Genetic evaluation - PLI
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
Dairy cows Breeds and crossbreeding
- Dominated by Holstein-Friesian
- Majority ‘pure’
- Crossbreeding increasing in popularity
- Genetic evaluation – AHDB
- Individual breed societies • Pedigree registration
- Typeassessments
Beef cattle breeding
- 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
Beef cattle breeding – traits recorded
- 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
Beef cattle – data from commercial herds
- 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
Sheep breeding
- 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
Sheep breeding – hill breeds
- 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
Sheep breeding – maternal breeds
- 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
Sheep breeding – crossing breeds
• 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
Sheep breeding – terminal sires
- 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
EBVs in Dog Breeding
Complex (polygenic) inherited traits
- Inherited disorders
- Hip and elbow dysplasia
- Chiari Malformation Syringomyelia (CMSM)(?)
- Behavioural traits
- Guide Dogs
Recap of Poultry and Pigs breeding
- Breeding pyramid
- Integrated
- Objective measures
- High rates of genetic improvement
- High selection differentials
- Short generation intervals
- Measurement technology
Recap of Dairy Cattle breeding
• 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
Recap of Beef Cattle and Sheep breeding
• Limited AI • Small individual breeding herds and flocks • Independent genetic evaluations • Patchy genetic improvement • Low selection differentials • Long generation intervals • Limited use of EBVs
