Introduction to Dairy Science: Dairy Cattle, Production, and Management

Overview of Dairy Science

Importance of Dairy Production

Dairy production is a significant agricultural enterprise, providing essential nutrients through milk and dairy products. It involves the management of dairy cattle for optimal health, productivity, and sustainability.

• Economic Impact: Dairy is a top agricultural earner in many states, including Tennessee, contributing approximately $150 million annually.

• Labor and Commitment: Dairy farming requires year-round, daily attention to animal welfare and farm operations.

• National Scope: Over 37,400 U.S. dairy farms supply milk, cheese, yogurt, and other products domestically and internationally.

• Family Ownership: About 97% of U.S. dairy farms are family-owned and operated.

Geographic Distribution and Production

• Major Dairy States: California, Wisconsin, New York, Pennsylvania, and Idaho are the top five dairy-producing states.

• Herd Size: The average U.S. dairy herd consists of 187 cows, with most farms having fewer than 200 cows.

• Global Consumption: Milk consumption varies worldwide, reflecting dietary habits and agricultural practices.

Dairy Cattle Breeds

Major Dairy Breeds

Several breeds of dairy cattle are raised for their unique milk production characteristics, adaptability, and physical traits.

Breed	Origin	Size	Color	Milk Traits
Holstein	The Netherlands	Large (~1,500 lbs)	Black & White or Red & White	Highest milk yield
Jersey	Isle of Jersey	Small (800–1,200 lbs)	Light gray to dark brown	High fat/protein milk
Guernsey	Isle of Guernsey	Medium (~1,000 lbs)	Fawn or red & white	Golden milk, high beta-carotene
Brown Swiss	Switzerland	Large (1,300–1,400 lbs)	Light brown/gray	Docile, strong legs
Ayrshire	Scotland	Medium (900–1,300 lbs)	Red & white	Excellent udder conformation
Milking Shorthorn	England	Large (1,410–1,500 lbs)	Red, white, or roan	Dual-purpose (dairy/beef)
Red and White	US/Canada	Large (~1,400 lbs)	Red & white	Genetic diversity

Breed Characteristics and Applications

• Holstein: Dominates U.S. dairy herds due to high milk yield.

• Jersey: Preferred for high butterfat content, ideal for cheese and ice cream.

• Guernsey: Known for golden-colored milk rich in beta-carotene.

• Brown Swiss: Valued for strength and longevity.

• Ayrshire: Recognized for udder quality and adaptability.

• Milking Shorthorn: Versatile for both milk and beef production.

• Red and White: Newest breed, with genetic input from several breeds.

Dairy Farm Management and Housing

Focus of Dairy Farmers

Dairy farmers prioritize animal welfare, productivity, and environmental stewardship to ensure sustainable operations.

• Animal Comfort: Clean, comfortable housing and access to food and water are essential.

• Reproductive Management: Efficient breeding practices support herd productivity.

• Environmental Stewardship: Responsible waste management and resource use protect the environment.

Types of Dairy Housing

Housing systems are designed to optimize cow health, hygiene, and productivity. Common systems include:

• Freestall Barns: Cows can move freely and rest in individual stalls.

• Tiestall Barns: Cows are tethered in individual stalls, common in colder regions.

• Open Barns: Provide shelter with open sides for ventilation.

• Dry Lots and Pasture: Outdoor systems where cows graze or are kept in open areas.

Dairy Cow Anatomy and Physiology

The Udder and Mammary Gland

The udder is the primary organ for milk production in dairy cows. Its structure and health are critical for efficient milk yield.

• Key Structures: Lateral and median suspensory ligaments, teat sphincter, teat cistern, gland cistern, and alveoli.

• Milk Production: Alveoli produce milk, which is expelled by myoepithelial cells under the influence of oxytocin.

• Udder Health: Cleanliness and proper milking procedures prevent mastitis and ensure milk quality.

Digestive Physiology: Ruminant vs. Non-Ruminant

Classification of Farm Animals

Farm animals are classified based on their digestive systems, which influences their diet and management.

• Non-Ruminants: Possess a single-chambered stomach (monogastric). Examples: swine, poultry, and horses (hindgut fermenters).

• Ruminants: Have a four-compartment stomach: rumen, reticulum, omasum, and abomasum. Examples: cattle, sheep, goats.

Ruminant Digestive Compartments

• Rumen: Large fermentation vat hosting bacteria and protozoa that break down cellulose and hemicellulose.

• Reticulum: Honeycomb structure that traps foreign objects; risk of hardware disease.

• Omasum: Many folds for water absorption.

• Abomasum: True stomach where enzymatic digestion occurs.

Feeding Dairy Cows

• Total Mixed Ration (TMR): A balanced mixture of forages, grains, vitamins, and minerals.

• Water: Most critical nutrient; cows require 30–50 gallons per day.

Ruminal Fermentation and Nutrient Production

Ruminants rely on microbial fermentation to digest fibrous plant material and produce essential nutrients.

• Volatile Fatty Acids (VFAs): Main energy source for ruminants, including acetic, propionic, and butyric acids.

• Microbial Protein and B-Vitamins: Synthesized by rumen microbes and absorbed by the animal.

• Symbiosis: Cattle provide a stable environment for microbes, which in turn digest forages into usable nutrients.

Rumination (Chewing the Cud)

Rumination is the process by which cows regurgitate, rechew, and reswallow their food to aid in digestion and nutrient absorption.

• Purpose: Reduces particle size and increases surface area for microbial action.

Summary Table: Ruminant vs. Non-Ruminant Digestive Systems

Feature	Ruminant	Non-Ruminant
Stomach Structure	Four compartments (rumen, reticulum, omasum, abomasum)	Single-chambered (monogastric)
Diet	Forage-based	Grain-based (except horses: forage-based)
Examples	Cattle, sheep, goats	Swine, poultry, horses
Fermentation Site	Rumen (foregut)	Cecum (hindgut, in horses)

Additional Resources

• UT Dairy: utdairy.utk.edu

• UT Dairy Club and social media

• Contact: Dr. Liz Eckelkamp and Dr. Lew Strickland, University of Tennessee