1. Animal Breeding Systems
Animal Science II
Chapter 12

2. Objectives
Name and explain common breeding systems used in livestock production
Explain the effects, advantages and disadvantages of using various breeding systems
Indentify the factors involved in selecting a breeding system
Calculate the percentage of parental stock in offspring using various breeding systems

3. Systems of Breeding 2 basic Straight breeding Cross breeding
Mating animals of the same breed
Variations-purebred, inbreeding, outcrossing, grading up
Cross breeding
Mating animals of different breeds
Variations-two-breed cross, three-breed cross, rotation

4. Purebred Breeding An animal of a particular breed
Both parents are purebred
Characteristics of the breed
Eligible for registry in breed association
Tend to be genetically homozygous
Specialized business

5. Inbreeding Mating related animals
Linebreeding and Closebreeding refer to how closely related the animals are
Requires a careful program of selection and culling
Expensive
Used most often by Universities for experimental work and Seedstock producers that provide animals for crossbreeding herds

6. Closebreeding Most intensive
Animals are very closely related and can be traced back to more than 1 common ancestor
Examples:
Sire to daughter
Son to dam
Brother to sister

7. Example 1st Mating A (Male) B (Female) 1st Generation ½ A ½ B
2nd Mating A
1/2A 1/2B
2nd Generation
3/4A 1/4B
The offspring of the 2nd generation have received 75% of their genetic make-up from the sire A because he appears closer in the pedigree to the offspring than he does in linebreeding. They have received only 25% of their genetic inheritance from the female B.

8. Linebreeding Mating animals that are more distantly related
Can be traced back to 1 common ancestor
Examples
Cousins
Grandparents to grand offspring
Half-brother to half-sister
Increases genetic purity
Several generations results in desirable and undesirable genes to become grouped together with greater frequency—making culling easier

9. Example 1st Mating A x B A x C 1st Generation ½ A ½ B ½ A ½ C
2nd Mating
1/2A1/2 B x 1/2A/2C
2nd Generation
½ A ¼ B ¼ C
The offspring in the second generation have received 50% of their genetic inheritance from the sire A because he appears twice in their pedigree. They have received only 25% of their genetic inheritance from each of the females B and C.

10. Outcrossing
Mating of animals of different families within the same breed
Animals are not closely related
Purpose is to bring into the breeding program traits that are desirable but not present in the original animals
Used most by purebred breeders
Popular because it reduces the chances of undeniable traits are still present
Sometimes used in inbreeding programs to bring in needed traits

11. Linecrossing
Mating animals from two different lines of breeding within a breed
Purpose is to bring together desirable traits from different lines
Experience is the best guide to use when line crossing

12. Grading Up Mating purebred males to grade females
Good way to improve quality
Less expensive
Use of purebred sires long enough will eventually lead to the amount of grade breeding left in the offspring being less than 1%

13. Example A1 x G A2 x ½ A1 ½ G 1st Mating 1st Generation 2nd Mating
50% Pure 50% Grade
2nd Mating
A2 x ½ A1 ½ G
2nd Generation
½ A2 ¼ A1 ¼ G
75% Purebred, 25% Grade
3rd Mating
A3 x ½ A2 ¼ A1 ¼ G
3rd Generation
½A3 ¼A2 1/8A1 1/8G
87.5% Purebred, 12.5% Grade

14. Crossbreeding (X) Mating two animals of different breeds
Offspring is a Hybrid
Usually results in improved traits because dominant genes mask undesirable recessive genes
Superior traits that result from crossbreeding are called hybrid vigor or heterosis

15. General Considerations Regarding Beef Crossbreeding Systems
Good record keeping is essential
Calving difficulties may increase when crossing large breed sires with small breed dams
Fewer calving problems if large breed dams are used
Large breed dams have higher maintenance costs
Artificial insemination allows access to better bulls
To avoid inbreeding more than 1 breeding pasture may be required

16. Beef Crossbreeding Systems
Terminal Sire Crossed with F1 Females
Rotate Herd Bull every 3-4 years
Two Breed Rotation
Three Breed Rotation
Four and Five Breed Rotation
Static Terminal Sire
Rotational Terminal Sire
Composite Systems

17. Terminal Sire Crossed with F1 Females
Replacement crossbred (F1) females in the herd are purchased and crossed with a terminal bull.
All offspring are sold.

18. Rotate Herd Bull Every 3-4 Years
Same breed of bull is used for several years and then replaced with a bull of a different breed.
Replacement females are selected from the herd.

19. Two-Breed Rotation
Bulls from Breed A are crossed with cows from Breed B.
Resulting heifers are bred to bulls from breed B for the duration of their productive life.
Replacement heifers from that cross are bred to bulls from breed A.
Each succeeding generation of replacement heifers is bred to a bull from the opposite breed used to sire the replacement heifer.

20. 3 Breed Rotation
Same pattern of breeding as the 2 breed rotation except that a bull from a 3rd breed is used in the sire rotation.

21. 4 and 5 Breed Rotations Larger herds
Bulls from a 4th or 5th breed may be used in the rotation of sires
This system requires a higher level of management and record keeping than 2 and 3 breed systems.

22. Static Terminal Sire System
4 breeding groups
Group 1 (25% of the herd) mates breed A bulls to breed A cows to produce replacement heifers for group 1 and group 2.
Group 2 (25% of the herd) breeds the AA heifers to a bull (breed B) to a different breed, producing crossbred heifers (breed AB)
Group 3 (50% of the herd) breeds the AB heifers to a terminal (T) bull selected for its ability to transmit a high rate of gain.
A subgroup (Group 4, 10% of the herd) of the 3rd group is composed of AB heifers being bred for the first time. These AB heifers are bred to a smaller breed (breed C) bull to reduce 1st time calving problems.
All the male offspring of groups 1 and 2 and all offspring of groups 3 and 4 are sold.
Any heifers from groups 1 and 2 that are not kept for breeding are also sold.

23. Rotational –Terminal Sire System
Two breeding groups needed
Bulls from breeds A and B are used on a rotating basis on 50% of the herd providing crossbred females for the entire herd
Mature cows in the herd are mated with a terminal bull to produce offspring, all of which are sold.
Replacement females come from mating of bulls A and B with younger cows in the herd.

24. Composite Breeds
Developing a new breed based on crossbreeding 4 or more existing breeds of cattle to avoid inbreeding problems
After development the composite breed is not crossbreed with other breeds

25. Composite Breeds
Noble Line Bull ¾ Gelbvieh, 1/3 Angus, 1/3 Brahman

26. Composite Breeds Leachman Stabalizer Cow
1/2 British: 1/2 Continental composite 1/4 Red Angus:1/4Hereford: 1/4 Gelbvieh: 1/4 Simmental

27. Composite Breeds Leachman Range Maker Bull
3/4 British: 1/4 Continental A blend of Red Angus and Black Angus,
South Devon, and Tarentaise (and/or Salers)

28. Crossbreeding Systems for Swine
Rotational Crossbreeding
Terminal Crossing System
Rotaterminal System

29. Crossbreeding Systems for Sheep
Rotational
Static
Rotostatic

30. Summary 2 basic breeding systems—straight and crossbreeding
The type of system used depends on: the size of the operation, the amount of money available and the goal of the producer
Purebred animal are eligible for registry and tend to be genetically homozygous
Inbreeding increases the genetic purity of livestock but generally reduces performance. It is not generally used by the average producer but rather by those that do experimental work to improve the breed.
Outcrossing brings genetic traits into the breeding program that tend to hide undesirable traits
Crossbreeding is the mating of animals from two different breeds, it is used by many commercial producers and usually results in hybrid vigor. This improves some traits but all little effect on feed efficiency and carcass traits.