Introduction to Animal Science and Ruminant Biology

Course Overview, Logistics, and Academic Resources

  • Course Identification and Schedule

    • Course Code: ANS001 (Introduction to Animal Science).

    • Key Academic Deadlines & Milestones:

    • Assignment 1: Posted on Friday, October 2, 2026; due on Monday, October 12, 2026.

    • Midterm Exam 1: Scheduled for Monday, October 19, 2026. Locations include Rock Hall or 100 Hunt Hall (TBA). Covers all lecture, textbook, and laboratory background material up to and including Friday, October 16, 2026.

    • Departmental Event: Department of Animal Science Fall Welcome Barbecue on Tuesday, October 6, 2026, at 5:00\n\text{PM} (dinner served at 5:45\n\text{PM}) at the UC Davis Horse Barn (across from Meyer Hall).

  • Laboratory Logistics and Facilities

    • Laboratory Location: Animal Science Teaching Facility (ASTF), situated near the dairy and water tower, or Cole A. Students must verify whether they are assigned to section 500500 or 600600

    • Required Preparation & Attire: Lab manual, grungy/work clothes, closed-toe solid shoes, and hats. Up to 1.5\n\text{hours} of preparatory instructional videos must be reviewed on Canvas prior to attending lab.

    • Biosecurity Regulations: UC Davis animal facilities permit service animals only to maintain institutional biosecurity standards.

  • Grading Policy and Structure

    • Final letter grades are calculated based on total points accumulated out of the overall course total (800\n\text{points}).

    • Grade Scale Breakdown:

    • A Level: 90.0\n\text{--}100\%. (A−A-: 90.0\n\text{--}92.5\%, AA: 92.5\n\text{--}97.5\%, A+A+: 97.5\n\text{--}100\%

    • B Level: 80.0\n\text{--}89.9\%

    • C Level: 70.0\n\text{--}79.9\%

    • D Level: 60.0\n\text{--}69.9\%

    • F Level: Below 60.0%60.0\%

    • Assessment Components: Major point drivers comprise midterms, final examinations, and formal assignments. Quizzes contribute a smaller proportion to the aggregate score.

  • Student Organizations and Campus Support

    • Ed DePeters Student Advising Center: Located in Meyer Hall; issues weekly newsletters regarding advising, scholarships, and departmental updates.

    • Young Cattlemen's Association (YCA): The longest-established student-run livestock club at UC Davis. Key events include General Meeting (Oct 8), Little International Stock Show (Nov 7), Artificial Insemination Clinic (March 22--24, 2027), and End of the Year Benefit Dinner (May 22).

    • Collar Scholars at UC Davis: Partnered with Canine Companions to raise, socialize, and train service dogs for individuals with disabilities.

    • MyBalto UCD: Student organization dedicated to fundraising for pet owners facing prohibitive veterinary medical costs.

    • Additional Related Organizations: VetAide Club, Driving Club.

Principles of Animal Domestication and Evolution

  • Definition and Criteria of Domestication

    • Domestication is a multi-generational, mutualistic relationship in which human communities assume control over the care, feeding, breeding, and spatial movement of animal populations.

    • Core Characteristics:

    • Mutual benefit to both human managers and target animal populations.

    • Morphological, physiological, and behavioral adaptation to human-controlled environments.

    • Controlled reproduction, allowing directional selection for specific economic or functional traits.

    • Selection for key traits alters natural evolutionary trajectories, fixing genetic modifications within domesticated lines.

    • Improved performance traits, such as accelerated growth rates, increased fecundity, and altered deposition of fat or muscle.

    • Taming vs. Domestication: Taming refers to behavioral conditioning of an individual wild animal to reduce fear of humans. Domestication involves fixed genetic modifications across an entire population over generations.

  • Historical Timelines and Geographic Origins of Major Domesticates

    • Dog (Canis lupus familiaris): 15,000\n\text{--}36,000\n\text{years ago} in Eurasia. Primary driver was behavioral selection for reduced fear and enhanced cooperation.

    • Goat (Capra hircus): 10,500\n\text{years ago} in the Middle East (Fertile Crescent).

    • Sheep (Ovis aries): 11,000\n\text{years ago} in the Middle East, descending from wild Asiatic mouflon (Ovis gmelini).

    • Pig (Sus domesticus): 10,300\n\text{years ago} in the Middle East and East Asia.

    • Cattle (Bos taurus): 10,300\n\text{years ago} in the Middle East and Europe.

    • Humped Cattle / Zebu (Bos indicus): 8,000\n\text{years ago} in South Asia (Indian subcontinent).

    • Cat (Felis catus): 9,500\n\text{years ago} in the Middle East.

    • Horse (Equus caballus): 5,500\n\text{years ago} in Central Asia (Botai culture / Eurasian Steppes).

    • Llama (Lama glama): 6,000\n\text{years ago} in South America (Andean Highlands).

    • Alpaca (Vicugna pacos): 5,000\n\text{years ago} in South America.

    • Camel (Camelus dromedarius / Camelus bactrianus): 4,500\n\text{years ago} in Central Asia and the Arabian Peninsula.

    • Chicken (Gallus gallus domesticus): 4,000\n\text{years ago} in East Asia and Southeast Asia.

    • Goose (Anser anser domesticus): 3,000\n\text{years ago} in Egypt.

    • Turkey (Meleagris gallopavo): 2,000\n\text{years ago} in North America (Mesoamerica).

    • Duck (Anas platyrhynchos domesticus): 1,000\n\text{years ago} in East Asia.

Quantitative and Qualitative Genetics: Phenotype, Genotype, and Environment

  • Fundamental Genetic Equation   Phenotype (P)=Genotype (G)+Environment (E)\text{Phenotype } (P) = \text{Genotype } (G) + \text{Environment } (E)

  • Component Definitions

    • Phenotype (PP): The observable physical, physiological, biochemical, or behavioral characteristics of an organism. Phenotypes are species-specific, breed-specific, and context-specific.

    • Genotype (GG): The underlying genetic makeup of an individual, encompassing the specific sequence of DNA, gene combinations, and chromosomal structures inherited from parents.

    • Environment (EE): All non-genetic external factors that influence phenotypic expression. Examples include nutrition, management practices, housing, ambient temperature, health/pathogen exposures, social interactions, grooming, exercise, and time.

  • Quantitative vs. Qualitative Traits

    • Quantitative Traits:

    • Characteristics expressed along a continuous numerical scale.

    • Polygenic / Polymorphic: Controlled by many genetic loci acting additively alongside environmental influences.

    • Examples: Body weight, average daily gain (ADG), milk production yield, fleece fiber diameter (μm\mu\text{m}), staple length, and muscle depth.

    • Qualitative Traits:

    • Categorical traits described by discrete classes rather than continuous measurements.

    • Controlled by one or a few major genetic loci (monogenic or oligogenic).

    • Examples: Coat color (e.g., black vs. brown fur), eye color (e.g., red vs. white eyes), presence or absence of horns (polled condition), and specific blood types.

The Roles and Value of Animals to Human Society

  • Global Livestock Population Estimates

    • Cattle: ∼1.4×109\sim 1.4 \times 10^9 (1.4\n\text{billion}) head worldwide.

    • Sheep: \sim 1.1\n\text{--}1.2 \times 10^9 (1.1\n\text{--}1.2\n\text{billion}) head worldwide.

    • Goats: ∼9.6×108\sim 9.6 \times 10^8 (960\n\text{million}) head worldwide.

    • Pigs: ∼1.0×109\sim 1.0 \times 10^9 (1.0\n\text{billion}) head worldwide.

    • Chickens: ∼3.1×1010\sim 3.1 \times 10^{10} (31\n\text{billion}) birds worldwide.

  • Seventeen Primary Contributions of Animals to Humanity

    1. Biodiversity and Nutrient Cycling

    • Livestock utilize non-tillable land, native rangelands, and low-quality plant bio-residues that cannot be consumed directly by humans.

    • Ruminants recycle nitrogen, phosphorus, and organic matter back into the soil matrix via manure, supporting global soil health and insect biodiversity (e.g., dung beetle ecology).

    1. Human Nutrition

    • Energy: Animal-derived foods provide ∼18%\sim 18\% of total dietary energy globally and ∼27%\sim 27\% of total dietary energy in the United States.

    • Protein: Animal products provide ∼40%\sim 40\% of total dietary protein worldwide. Breakdown of global animal protein supply: Meat (∼50%\sim 50\%), Milk (∼25%\sim 25\%), Fish (∼17%\sim 17\%), Eggs (∼8%\sim 8\%).

    • In the United States, ∼66%\sim 66\% of total consumed protein is derived from animal sources.

    • Economic Correlation: Per capita income displays a strong positive correlation with per capita meat consumption.

  

Global meat supply quantity trends by region from 1961 to 2009

  1. Economics and Financial Value

    • Global livestock production market value is estimated at \sim \$1.4\n\text{trillion}.

    • In the United States, livestock, poultry, and product sales generate \sim \$180\n\text{billion} annually (e.g., \$182\n\text{billion} according to the USDA Census of Agriculture).

  2. Social Issues and Domestic Security

    • Pet ownership patterns intersect with human social dynamics. In domestic violence situations, abusers frequently exploit pet attachment to exercise control over victims.

    • Ascione (1998) Study Findings: 71%71\% of pet-owning women entering shelters reported that their abusive partner had threatened, harmed, or killed a family pet. 34%34\% of victims delayed leaving an abusive situation due to concern for their pets' safety.

  3. **Health, Disease, and