B3: Breeding methods in cattle production: purebred breeding, crossbreeding Flashcards
Methods of natural and artificial breeding systems
Natural: Harem, stud or hand, used in Beef production, Sex ratio = 40-50 (60-79)
AI: Predominantly used in dairy industry, Sex ratio = 150-200 (single ejaculation. Deep-frozen semen).
what is a breed?
A breed population is characterized by common breeding history, reproduction unit & common breed characteristics.
The Population has common gene pool.
Inheritable characteristics passed on from parents to offspring.
Breeding systems: Advanatages of pure breeding?
- Increases allelic frequencies of favourable (desired) characteristics (inbreeding, linebreeding).
- Preservation of allelic frequencies as high as possible (maintenance breeding, gene preservation).
Breeding systems: Advantages of cross breeding?
- Introgression of specific single (major) genes ! polled, horns etc.
- Improvement of genetic level of a breed by additive gene effects of other breeds (breed improvement by introducing new genetic material -> grading up, crossbreds).
- New breed establishment (composites, synthetic breeds).
- Combination of different additive genetic traits (fertility of maternal lines & gain of paternal lines -> milk production & daily gain).
- Heterosis (hybrid vigour): In commercial beef production -> terminal crossings.
Name common crossbreeding systems
1) Terminal cross
2) Two breed cross
3) Back cross
4) Three breed cross
5) Rotational cross
6) Composite (synthetic) breed
What is terminal cross?
-> 2 or more breeds are crossed in an organized sequential system with the final cross going to slaughter (complexity increases as more breeds are
used).
-> Sire used must provide genes for good growth rate & carcass merit to suit the market demand.
What is two breed cross?
-> Requires a female herd of a particular breed -> One part is used for breed replacement, purebred females, the rest are used to produce crossbred
progeny which are sold for slaughter (or females are used by another, F1 breeder)
What is back cross?
-> One of the two parent breeds is mated back to the F1.
-> Lends itself to consistent product production.
What is three breed cross?
-> Requires min. 3 breeding paddocks
-> One purebred herd is used to breed purebred replacements.
-> One herd produces F1 cows.
-> F1 animals breed terminal slaughter animal
what is rotational cross?
-> Best uses & optimizes hybrid vigour & complimentary characteristics.
-> Purebred bulls of 2+ breeds are used in sequential rotation over crossbred females.
what are composite (synthetic) breed systems?
All crossbreeding systems require the continuous input of purebred animals.
shaver beef cattle are a 9 breed composite
what is the goal of breeding programmes?
Systematic production of breeding & commercial animals of defined pedigree & production traits.
Involves breeding associations & organizations
What are Corner points & requirements for successful breeding programs?
- Breeding population
- Marking of animals & Identification
- Safety of descent & origin of animals: Guaranteed by mating, parturition, bloodgroups, DNA analysis.
- Performance & progeny testing
- Reproduction techniques: AI, embryo transfer, MOET.
- Breeding value estimation
name 3 breeding programmes that can lead to gene improvement
- Embryo transfer
- MOET (Multiple Ovulation Embryo Transfer = conventional embryo flush; most common procedure used in advanced cattle breeding).
- Cloning
What does performance testing for breeding include?
- Milk performance
- Meat performance
- Reproductive performance
- Fertility
- Calving ease
- Health
- Milking ability
- Conformation
- Hereditary disorders
