Breeding Systems

AgriScience 2

Animal Reproduction

Why is improving organisms important to agriculture?

• Three main factors driving this goal:– Rising World Population– Urbanization– Fewer people in production agriculture

What methods are used in agriscience to improve organisms?

• Two major approaches are used: – Controlled breeding – Genetic manipulation.

Controlled breeding

• Breeding plants or animals to achieve certain characteristics in the offspring.

• Considered a natural method of improving plants and animals. – Scientists control the natural breeding process.

Kinds of controlled breeding:• Selection

– Choosing a few parents with the desired traits with the intent of increasing the amount of desired qualities in the offspring.

Genetic manipulation

• Artificial means of producing desirable traits.

• Genes can be moved from one species to another.

• Gene splicing is the moving of hereditary characteristics from one organism to another often unrelated organism.

Hybridization

• Crossing of two different plants or animals

• Combines the traits of different parent strains.

• Many hybrids are not able to reproduce.

Straight breeding

• Inbreeding-

• close breeding

• purebreeding

Inbreeding-mating closely related animals

• Parent to offspring and siblings

• 1/2 brother and sister

• Uncle x niece

• Nephew x aunt

• 1/2 uncle to niece

• Cousin to cousin

25% inbred25% inbred

12.5% inbred12.5% inbred

6.25% inbred6.25% inbred

3.125% inbred3.125% inbred

Closebreeding- mating animals that share some common

ancestors

Purebreeding- mating animals that are not related but of the

same breed.

Crossbreeding- mating animals of different breeds.

Crossbreeding Systems

Cross breeding- Criss-Cross

F1 - 1/2 B 1/2 L

Criss-cross

F1 1/2B 1/2L Brahman

F2 1/4L 3/4 B

F2 3/4B 1/4L Limousin

F2 5/8L 3/8 B

Criss-Cross

Rotational Breeding-1st Cross

F1 - 1/2 C 1/2 DColumbia Dorset

Rotational Breeding-2nd Gen

F2 - 1/4 C 1/4 D 1/2 H

F1- 1/2C 1/2 D Hampshire

Rotational- 3rd Generation

F3 - 1/8 C 1/4 H 5/8 D

F2 - 1/4 C 1/4 D 1/2 H Dorset

Rotational Breeding

Terminal Cross

Roto-Terminal Cross

Roto-Terminal Cross

3 breed roto crossHampshire Terminal boar

1/2 Hamp, 1/2 white blend

Review / Summary

• Discuss the importance of improved organisms to agriculture.

• Identify methods used in agriscience to improve organisms.

• Identify breeding systems used in animal science.