10/8/25

Homozygous Animals:
- Have two identical alleles for a gene.
- Examples: $BB$ or $bb$ .
Heterozygous Animals:
- Possess non-alike alleles for a gene.
- Example: $Bb$ .
Genotype:
- Definition: The actual genetic makeup of the animal.
Phenotype:
- Definition: The physical presentation of that genetic makeup.
- Example: A heterozygote may appear phenotypically similar to a homozygous genotype.

Simple Inherited Traits:
- Influenced by one gene.
- Examples: Color, horned vs. polled.
Polygenic Traits:
- Influenced by multiple genes.
- Examples: Height, weight, fertility, age at puberty.
- Discussion on the influence of genetics and environmental conditions (e.g., diet).

Inbreeding:
- Definition: Mating of individuals more closely related than the average of the population.
Advantages of Inbreeding:
- Increased homozygosity.
- Prepotency: Ability to produce uniform progeny, leading to herds with similar traits (e.g., black Angus cattle).
Disadvantages of Inbreeding:
- Inbreeding depression affects polygenic traits negatively, particularly lowly heritable traits like fertility.
- Example: Increased health issues in purebred animals due to genetic fixing of bad mutations.

Outbreeding Definition:
- Mating of individuals more distantly related than the average of the population.
Types of Outbreeding:
- Line Breeding: Breeding within a related but distinct group (e.g., cross breeding a US breed with one from Germany).
- Crossbreeding: Involves two completely different breeds.
Advantages of Outbreeding:
- Increased heterozygosity which reduces the expression of recessive traits.
- Hybrid vigor: Increased performance in polygenic traits, more fertility, longevity, and fewer health issues.
Disadvantages of Outbreeding:
- Inconsistent traits due to diverse genetic backgrounds.
- Crossbred offspring cannot be retained as breeding stock without diluting the hybrid effects.

Definition: Planned mating of two or more breeds to capitalize on complementary traits.
Examples:
- Breeding A females x Breeding B males yields AB males (50% of each).
- Breeding C females x Breeding D males gives CD females (also 50% of each).
- Resulting composite offspring may yield a genetic mix from the parent breeds.

Main Goal of Breeding:
- To produce healthy, live offspring that are profitable and enhance overall performance.
Steps for Successful Breeding:
- Selecting superior animals based on genetic potential and health.
- Conducting reproductive exams to confirm readiness for breeding.
- Fertilization via natural mating or assisted reproductive techniques (e.g., artificial insemination).
- Pregnancy checks to confirm successful gestation.
- Ensuring a successful delivery and health of the offspring.

Superior Animal Selection:
- Focus on animals with desirable traits and health status for reproduction.
Breeding Methodologies:
- Emphasis is often placed on male contributions in large animal breeding scenarios due to harem breeding practices.
Evaluation Metrics:
- EPDs (Expected Progeny Differences), EBVs (Estimated Breeding Values), and confirmations of physical traits.
Expected Progeny Difference (EPD):
- Evaluates an animal's genetic potential for traits based on offspring data (e.g., carcass traits, birth weight).
- Low birth weight bulls for heifers vs. higher yearling weight bulls for mature cows.
Accuracy of EPD: Important to ensure data reliability.

Classification of Cattle Breeds:
- Beef breeds for meat production.
- Dairy breeds for milk production.
- Dual-purpose breeds for both traits.

British Breeds:
- Angus, Hereford, Shorthorn, Belted Galloway, Scottish Highland.
Continental Breeds:
- Charolais, Limousin, Maine Anjou.
Continental Dual Purpose Breeds:
- Simmental, Salers, Gelbvieh, Chianina.
American Breeds:
- Beefmaster, Santa Gertrudis.
Specialty Breeds:
- Texas Longhorn, show cattle types.

Angus:
- Naturally polled, hardy, good marbling, dark-skinned, adapted for cold.
Hereford:
- Red with white underbelly, known for vigor, early maturity, prone to cancer eye.
Shorthorn:
- Originally dual-purpose, now beef or dairy separated, various colors.
Belted Galloway:
- Hardy, long-haired foragers, known for lean beef.
Scottish Highland:
- Long-horned, low cholesterol beef, excellent foragers.
Charolais:
- Large muscled, white cattle.
Limousin:
- Red with straw underbelly, high carcass yield.
Maine Anjou:
- Large, heavily muscled, dark red with white underline.
Simmental:
- Typical coloring of gold red with white; high carcass yield.
Gelbvieh:
- Known for tick resistance, heavy muscled.
Brahman:
- Heat tolerant, variable colors, disease resistant.
Brangus:
- Crossbreed of Brahman and Angus; registered breed with better meat quality.

Negative genetic correlation between milk pounds produced and milk fat content; selecting for one typically decreases the other.

Meat Breeds: Known for meat traits.
Reproductive Breeds: Known for prolificacy.
Specific examples include:
- Duroc: Red-brown, droopy ears, dished face.
- Hampshire: Black with a white belt.
- Berkshire: Black with white underbelly and erect ears.
- Yorkshire: Pink or white with erect ears.

Meat breeds and wool breeds differentiated.
Examples include:
- Columbia: White wool, white nose/toes.
- Corriedale: White wool, black nose/toes.
- Rambouillet: White wool, males may have curled horns.
- Southdown: Baby doll sheep with wooly face.

Dairy Breeds:
- Nubians: Large, long droopy ears, provides 0.5 - 1.5 gallons/day.
- Alpines: Varied colors, 1 - 2 gallons/day.
- Saanen: Largest dairy goat breed, 3 gallons/day.
- Nigerian Dwarf: Small, highly efficient, 0.5 - 2 gallons of milk.
Meat Breeds:
- Boer: Large, primarily for meat production.
- Myotonic: Fainting goats, muscular defect affects behavior.

Understanding various breeds and breeding practices is critical for effective livestock management and production. Different breeds are optimized for specific traits, necessitating careful selection based on the goals of the breeding operation.