1. Cross-breeding

• Definition: Mating animals from different breeds to combine desirable traits.
• Commonly used: In the commercial livestock industry.
• Benefit: Produces hybrid vigor, also known as heterosis, which leads to superior offspring.

Examples:

• Fresian x Malawi Zebu.
• Hereford Bull x Aberdeen Angus Cow.

Advantages:

• Better adaptation to harsh environments.
• Combines genetic traits from both parents.
• Increases genetic diversity (heterozygosity).

Disadvantages:

• Determining when and how to cross-breed can be difficult.
• Expensive for small-scale farmers.

2. In-breeding

• Definition: Mating animals that are closely related (e.g., brother to sister or daughter to father).
• Commonly used: By breeders to enhance desirable traits.
• Effect: Increases genetic similarity (gene pairing).

Advantages:

• Retains known desirable genes.
• Promotes uniformity within the population.
• Helps identify carriers of hereditary defects.

Disadvantages:

• Increases the chances of undesirable recessive traits.
• May lead to reduced vitality and performance.

3. Out-breeding

• Definition: Mating animals of the same breed but without close genetic relationships (4–6 generations apart).
• Commonly used: By purebred breeders (e.g., sheep).

Advantages:

• Enhances genetic improvement.
• Ideal for beginners in livestock breeding.
• Introduces desirable traits without close inbreeding.

Disadvantages:

• Expensive to source semen for individual farmers.
• Availability of semen may be affected by importation timing.

ARTIFICIAL INSEMINATION (AI)

• Definition: The process of introducing semen into a female’s reproductive system without using a male (bull).
• Semen collection: From superior bulls, using an artificial vagina.
• Semen storage: Stored in liquid nitrogen after dilution with diluents like egg yolk, milk, and glucose.

Advantages:

• One bull’s semen can be used to inseminate many females (one ejaculation = 300 ml for 200 cows).
• Semen can be stored for extended periods.
• Reduces the cost of keeping and feeding a bull.
• Allows the spread of superior traits across a wide area.
• Reduces the spread of sexually transmitted diseases.
• Easy to plan and manage.

Disadvantages:

• Requires specialized skills.
• Managing heat signs for insemination can be challenging.
• Expensive to maintain an artificial insemination program.

SELECTION

• Definition: The process of choosing the best animals based on performance and strength.
• Aim: To improve livestock traits through selected breeding.

Types of Selection

1. Artificial Selection:
   • Controlled by breeders.
   • Selection based on phenotypic traits like body size and egg size.
   • Individual Selection: Based on the performance of a single animal.
   • Sib Selection: When a bull is selected based on the performance of its relatives (e.g., high-yielding mother).
2. Natural Selection:
   • Occurs without human intervention.
   • Animals adapt to survive in their environment.
   • Weaker animals may die off due to environmental pressures, ensuring only the strongest reproduce.