animal breeding system

Breeding systems

These are various ways of evaluation and selection of desired genetic traits in a breed or species.

Mating systems

These are various ways in which members of a given species arrange themselves to copulate (monogamy, polygamy).

Straightbreeding

Mating animals of the same breed

Crossbreeding

Mating animals of different breeds

Systems in straightbreeding

• Purebred breeding

• Inbreeding

• Outcrossing

• Grading up

Purebred

an animal of a particular breed that has the characteristics of the breed to which it belongs.

Parents of the animal is also purebred

They are usually registered in purebred association

Purebred

Ancestors can be traced back from the herd book of purebred animal association registry

have the tendency to be genetically homozygous

Purebred breeding advantages

Specialized business/ Purebred shows

Provides the foundation stock for crossbreeding and commercial production systems

Purebred breeding disadvantages

Appearance of undesirable recessive characteristics due to homozygosity of the genes of the parent animals

Requires a higher investment than raising market animals

Inbreeding

Mating of related animals

The mating of animals more closely related than the average of the breed or population.  

Increases genetic purity and homozygosity

Desirable and undesirable genes grouped together and therefore the undesirable and desirable traits are more visible.

Inbreeding

Breeders can easily identify animals with undesirable traits and could eliminate them from the breeding program.

It is expensive because all animals with undesirable traits must be removed from the breeding program.

Average of animal breeders does not find this system desirable

2 types of inbreeding

Closebreeding

Linebreeding

Closebreeding

Most intensive form

The animals being mated are very closely related and can be traced back to more than one common ancestor.

sire to daughter, son to dam, or brother to sister

Linebreeding

It refers to mating of animals that are more distantly related and can be traced back to one common ancestor

cousins, grandparent to grandoffspring, or half-brother to half-sister

Closebreeding

Linebreeding

Outcrossing

Mating of animals of different families within the same breed.

It aims to bring traits that are desirable but not present in the original animal breeding program.

Outcrossing

It  is popular with purebred breeders because it reduces the chances of undesirable traits appearing in the offspring.

Used in combination with inbreeding programs to bring in traits that are needed.

Line crossing

Mating animals from two different lines of breeding within a breed.

The purpose is to bring together desirable traits from different lines of breeding.

Some lines cross better than other lines because of different gene combinations.

Grade animal

Any animal not eligible for registry

Grading up

Mating of purebred sires to grade females

Aims to improve the quality of animals in farm

Not very expensive

It only requires purchase of Purebred sires, or their semen.

Percent improvement per generation

First generation

50% purebred

2nd generation

75% purebred

3rd generation

87.5% purebred

Grading up

Crossbreeding

Mating of two animals from different breeds

offspring usually have improved traits and referred to as “Hybrid”.

In this system the dominant genes tend to mask undesirable recessive genes.

Production of superior traits, “Hybrid Vigor or heterosis”

Breed complementary

using benefits from breeds while hiding the flaws

Heterosis

measured by the average superiority of the hybrid offspring over the average of the parents.

Traits with a high degree of heritability…

…little improvement from crossbreeding

Traits with low heritability…

…greatest improvement as a result of crossbreeding

Forms of heterosis

• individual heterosis

• Maternal heterosis

• Paternal heterosis

Individual heterosis

Advantages of crossbred offspring

Focuses on terminal offspring

Maternal heterosis

Advantages provided by mother

Focuses on maternal traits

maternal ability, reproduction, longevity etc.

Paternal heterosis

Advantages provided by sire

bull fertility

Systems in crossbreeding

• Two-breed crosses

• Three-breed crosses

• Rotation breeding

3rd group

breeds the AB heifers to a terminal (T) bull selected for ability to transmit a high rate of gain.

50% of the herd

Subgroup

It 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 first-time calving problems.

(group four, 10 percent of the herd) of the third group

Crossbreeding systems for swine

1. Rotational crossbreeding

2. Terminal crossing systems

3. Rotaterminal systems

Rotational crossbreeding

In this system, A boar from breed A is mated with sows from breed B, producing offspring AB.

Selected gilts (AB) are bred to a boar from breed B.

Selected gilts from this mating are bred to a boar from breed A

Rotational crossbreeding

The pattern is repeated, switching back and forth to the breed of the most distantly related boar.

It may have two-, three-, four or five- breeding system

Reduction in heterosis if possible pattern is not followed

Rotational crossbreeding

Terminal crossing system

Crossbred (F1 ) females, with superior maternal traits, are bred to boars selected for desirable back fat and rate of gain.

All of the offspring go to market.

The costs are generally higher than in rotational breeding systems.

Terminal crossing system

Risk of introducing health issues from new breeding stock brought into the herd.

Maintain the maximum advantage of heterosis and breed differences in the breeding system.

Terminal crossing system

Rotaterminal system

The combination of the rotational breeding system and the terminal breeding system

Crossbred females are produced by breeding boars of different breeds in a rotating pattern to crossbred females produced by previous matings in the system.

Rotaterminal system

All the offspring produced in the terminal breeding go to market.

This system of crossbreeding maintains a high level of heterosis and allows the producer to select breeds with desirable traits.

It does require the use of more boars of different breeds.

Rotaterminal system