Poultry Genetics. AgScience Poultry Science Curriculum Section 2

Transcription

1 Poultry Genetics AgScience Poultry Science Curriculum Section 2

2 Historical Overview Bird used prior to 1950s were dual purpose 1950s saw introduction of breeding for a specific purpose Dual Purpose Dual purpose birds were used primarily for egg production, and occasionally used for meat Watt Publishing, 122 S. Wesley Ave., Mt. Morris, IL USA Chickens used for meat production are called broilers. Broilers are a genetic cross of the Cornish breed and the White Plymouth Rock Breed Meat Production Egg Production Chickens used for egg production are the Leghorn breed

3 Performance Performance Historical Overview Decision to move to breeds specifically for meat and eggs was very important These two factors are negatively correlated If a hen produces eggs well she will not grow well Broiler Leghorn Meat Eggs Meat Eggs 1960s, 70s, 80s saw more improvement in genetics and increased breeding for and production of white meat 1990s, 2000s development of specialized genetics to meet market demands Small bird Fast food market, Big bird debone market

4 Historical Overview Companies also began selecting for specialized traits for males and females Traits emphasized in males: Meat yield Weight for age Days to market Feed efficiency Body conformation Fat content Traits emphasized in females: Fertility Hatchability Age at sexual onset Rate of egg production Growth performance is still monitored **In recent years males have also been selected for reproductive performance

5 Historical Overview Geneticists use heritability for making genetic selection Heritability the ability of measurable traits to be transmitted from parents to offspring Traits with high heritability as passed well from parent to offspring High heritability = rapid genetic progress between generation Low heritability = more generations to improve upon selected trait Geneticists have focused on improving broiler breast meat yield Domestic preference for white meat Highly heritable trait

6 Distribution Distribution Selection Pressure Level of selection pressure applied and the amount genetic progress are closely related Selection pressure Amount of pressure applied to a selection criteria Increased selection pressure = fewer birds selected Fewer birds selected = increased genetic progress with each generation Flock A Flock B Selected Population Selected Population Body weights Body weights Flock B will have increased body weight compared to Flock A because of the greater selection pressure applied

7 Genetic Improvement: Natural Attributes Two natural attributes have attributed to the genetic improvement of poultry: Hens produce a large number of eggs More offspring = more opportunity for genetic progress within one generation Short generation interval weeks a hen will come into production One hen will produce dozens of offspring Lots of options available and can choose the best for breeding Reproduce few offspring over a long period of time 2 years Choose the best to reproduce; options are limited 2 years Because of short generation interval risks have been low and opportunity for improvement high Finally, genetic progress but has taken several years; high risk, low opportunity for improvement within one generation

8 Genetic Improvement: Important Inventions Two innovations have been critical to the success of poultry breeding programs: Trap-nests Nest used to keep hens on the nest until a caretaker releases them Monitor egg production for each hen Maintain accurate records for each bird Hens which produce best kept for continued breeding Artificial incubator Allowed for the hatching of large numbers of offspring at the same time Precise control incubator environment Maximizes the number of eggs hatched

9 Primary Breeder Programs Primary breeder companies are organized to promote genetic improvement and multiplication to meet market demands Pedigree level Genetic selection occurs at this level, geneticists keep only the birds that meet specific criteria for continuation of the Great-Grand Parent pedigree level line Mated to produce Grandparent birds. Still owned by primary breeder company Selected pedigree Unselected pedigree Grandparent level, mated to produce parent birds. Still owned by primary breeder company Parent birds, mated to produce commercial broilers. Breeder company product, birds sold to integrators Broiler Level, birds owned by the integrator, birds that are raised and sold for meat

10 Primary Breeder Programs Primary breeder companies are organized to promote genetic improvement and multiplication to meet market demands $1,500/chick $150/chick $15/chick 1 male, 10 female 150 chicks 6,000 chicks Ped. GGP GP $1.50/chick 240,000 chicks Parent $0.15/chick 28,800,000 chicks Commercial Broiler

11 Primary Breeder Programs Pedigree lines are crossed at the grandparent level** Resulting bird is a mixture of the male and female line Crossing the pedigree lines results in hybrid vigor Hybrid vigor Crossing of lines producing heterosis specific traits in the offspring (GPs) are improved relative to the sire and dam (GGPs). **This also provides protection of the pedigree line; by purchasing parent birds someone would not be able to re-create pedigree line Pedigree

12 Learning Evaluation What was the primary reason for moving away from dual purpose birds toward birds bred specifically for egg or meat production? Meat and egg production are negatively correlated attributes. Therefore a bird that produces meat more efficiently will produce fewer eggs and vice versa.

13 Learning Evaluation How does heritability affect genetic progress? Traits with high heritability are passed very well from parents to offspring, allowing for large genetic advances to be made with each generation. Therefore, rapid genetic progress can be made when breeding for traits with high heritability, whereas traits with low heritability require more generations to improve

14 Learning Evaluation Increased selection pressure results in greater or lesser genetic improvements with each generation? Greater

15 Learning Evaluation Critical Thinking Several traits can be selected for genetic improvement of commercial poultry. Some of these could include: Increase of 28 hatching eggs per breeder hen 2.2% increase in livability of broilers Extra 0.4 pounds of broiler body weight without increasing grow-out time All of these would provide the same financial benefit as selecting for improved breast meat yield. Why then was breast meat yield selected to improve upon by poultry geneticist? Breast meat yield improvement is a highly heritable trait, more so than the other traits mentioned