Dairy chapter 11
Introduction to Animal Science
Focus on Dairy Cattle Production
Learning Objectives
Identify overall structure and trends in the dairy industry
Identify the main dairy products, trends in consumption, and key steps in production
List the main dairy breeds and their key characteristics
Describe how milk is graded and processed
Identify key parts of the mammary gland and their functions
Describe a lactation curve and key events throughout a lactation cycle
Describe the process of milk let down
Describe what mastitis is and a method to diagnose it
Discuss key aspects contributing to the success of the dairy industry
Outline of Topics
Cattle domestication
Dairy industry overview
Dairy breeds
Life cycle of dairy cows
Calf care
Average dairy cow statistics
Reasons for culling dairy cows
Lactation process
Milking process
Milk quality assessment
Milk processing and dairy products
Success factors in the dairy industry
Cattle Domestication
Timeline:
5,800 BC - Bos taurus taurus (domestic cattle) originated in the Near East.
2,500 BC - Bos taurus indicus (Zebu) originated in the Indus Valley.
Originated in Eurasia from the Auroch (gigantic wild ox), a large, ancient bovine species that roamed across Europe, Asia, and North Africa.
Impact of domestication:
Products: provided essential resources like milk, meat, and leather for sustenance and materials.
Key role in the agrarian revolution as a draft animal, significantly aiding in plowing fields and transportation, which allowed for increased agricultural output and human settlement.
Dairy Industry Overview
Average herd size = 115 cows, though this varies significantly by region.
Farming trend: fewer farms with larger herds – this trend reflects increased efficiency, economies of scale, and the adoption of advanced technologies to manage larger operations.
74% of dairies have less than 100 cows, often representing smaller, family-owned operations.
85% of milk produced comes from herds with more than 100 cows, indicating that a smaller number of large dairies account for the majority of national milk production.
Dairy Farm Distribution
80% of the nation’s dairy farms concentrated in 10 states, due to favorable climate, feed availability, and established processing infrastructure.
These states produce 74% of the nation's milk, showcasing regional specialization.
Graph representation of the number of licensed herds in 2024 - States:
Wisconsin, Pennsylvania, New York, Minnesota, Ohio, California, Michigan, Iowa, Indiana, Vermont
Milk Production Statistics
Graph displaying total milk production (in millions of lbs) in 2024 - States contributing to production: California, Wisconsin, Texas, Idaho, New York, Michigan, Minnesota, Pennsylvania, Washington, Iowa
Comparative Overview: Traditional vs. Modern Dairy States
Traditional States:
Great Lakes (Midwest, Northeast), often characterized by rolling pastures and mixed farming systems.
Smaller herd sizes (<500 cows), typically resulting in more intensive management per animal and often a greater emphasis on family labor.
More historical dairying practices, which may include seasonal calving, pasture-based systems, and less reliance on large-scale automation.
Modern States:
Mostly in the West (e.g., California, Idaho, Texas), often in arid or semi-arid regions requiring irrigation for feed production.
Larger herds (>500 cows), demonstrating a highly industrialized approach to dairy farming.
Adoption of advanced technologies such as robotic milking systems, computerized feeding, advanced genetic selection, and precise environmental control to maximize efficiency and production.
Dairy Breeds and Characteristics
Holstein
Weight: 1500 lbs for mature cows.
Origin: The Netherlands, specifically the provinces of North Holland and Friesland.
Characteristics:
Most common dairy breed globally, prized for its high milk volume.
Highest milk production, often with lower butterfat and protein content compared to other breeds.
Distinctive white with black spots, though red and white varieties also exist.
Jersey
Weight: 800 - 1200 lbs, making them the smallest of the major dairy breeds.
Origin: Isle of Jersey, one of the Channel Islands.
Characteristics:
Light to dark brown, with a distinct dished face and prominent eyes.
Known for a docile temperament, making them easy to manage.
Produces milk with a high milk fat percentage (often >5.0%) and high protein, making it excellent for cheese and butter production. They are also known for efficient feed conversion.
Highly adaptable to various climates and management systems.
Brown Swiss
Weight: 1300 lbs for mature cows, making them one of the larger dairy breeds.
Origin: Switzerland, from the Alps mountains.
Characteristics:
Considered one of the oldest dairy breeds, with records dating back centuries.
Very docile and robust, known for their longevity and strong feet and legs.
Brown, nearly gray color, with a characteristic light band around the muzzle.
Produces desirable fat/protein ratio in their milk, suitable for various dairy products.
Ayrshire
Weight: 1200 lbs for mature cows.
Origin: County of Ayr, Scotland.
Characteristics:
Distinctive red and white markings, which can vary widely.
Highly adaptable to different environments and management systems, including grazing.
Excels in udder conformation, known for strong, well-attached udders that resist mastitis. Produces milk with a moderate butterfat content.
Guernsey
Weight: 1200 lbs for mature cows.
Origin: Isle of Guernsey, another of the Channel Islands.
Characteristics:
White and fawn-deep red markings.
Produces carotene-rich 'Golden Goodness' milk, which has a naturally golden color due to high beta-carotene content, a precursor to Vitamin A.
Known for milk with a good fat-to-protein ratio, making it particularly good for cheese production.
Life Cycle of Dairy Cows
Events in the life cycle, typically occurring in a continuous cycle:
Parturition (calving): the act of giving birth, marking the beginning of a new lactation cycle. Dairy cows are typically bred to calve once a year.
Rebreeding: efforts to impregnate the cow again, usually starting around
post-calving, to maintain the annual calving interval.
Gestation: the period of pregnancy, which lasts approximately 280 days or about 9 months.
Dry period: a non-lactating period of typically 45-60 days before the next calving, allowing the mammary gland to regenerate and prepare for the next lactation.
Lifespan of a cow’s reproductive cycle outlined:
Average interval between calvings = 13.1 months, slightly longer than an ideal 12-month interval, indicating challenges in rebreeding efficiency.
Average lactation period = 305 days, referring to the standard measure of milk production for a cow after calving.
Lactation Process and Curve
Lactation overview: The physiological process of producing milk in the mammary glands, driven by hormonal changes and nutritional intake.
Lactation curve indicating key phases: A graphical representation of daily milk yield over the lactation period.
Early lactation (first 100 days): Milk production rapidly increases, peaking typically between 45-90 days post-calving. Cows are in a state of negative energy balance, drawing on body reserves.
Mid lactation (100-200 days): Milk production gradually declines, but cows typically reach maximum dry matter intake and begin to regain body condition.
Late lactation (200-305 days): Milk production continues to decline at a faster rate. Cows are usually pregnant and replenishing body reserves in preparation for the dry period and next lactation.
Peak lactation statistics (e.g. 90 lbs/day): The highest point of milk output during a lactation cycle, a critical indicator of a cow's productive potential.
Calf Care
Calves are separated from the cow immediately after birth to minimize disease transmission, allow for precise colostrum management, and prevent mother-calf bonding that could interfere with milking routines.
Importance of colostrum intake within the first 24 hours: Colostrum, the first milk produced, is rich in antibodies (immunoglobulins) that provide passive immunity to the calf, protecting it from diseases as its own immune system develops. Absorption efficiency decreases rapidly after 24 hours.
Calf housing: kept in individual hutches from birth to 6-8 weeks of age to minimize disease spread between calves, allow for individual feeding management, and provide a clean, dry environment.
Feeding: milk replacer (milk powder) post-birth, gradually introduced after colostrum feeding, as a substitute for whole milk. This allows for precise nutritional control and cost-effectiveness.
Rumen development: introduction to grains and roughages from birth to stimulate the development of the rumen, which is essential for digesting solid feed and transitioning off liquid diets.
Main calf care issues:
Diarrhea (scours): a common and often fatal condition in young calves, usually caused by bacterial (e.g., E. coli), viral, or protozoal infections, leading to dehydration.
Respiratory problems: such as pneumonia, often caused by poor ventilation, overcrowding, or viral/bacterial pathogens.
Average Cow Statistics
First calving at 25 months of age, an important economic benchmark as earlier calving reduces the non-productive period of a heifer.
Average yield: 23,000 pounds of milk per lactation, reflecting significant genetic improvements and management practices.
Average lactation period: 336 days, slightly longer than the standard 305-day measurement.
Dry period: 57 days, a crucial time for udder health and fetal development.
Reasons for Culling Dairy Cows
Major causes, representing economic decisions to remove unproductive or problematic animals from the herd:
Reproductive failure: inability to get pregnant within a desired timeframe, leading to extended calving intervals and reduced lifetime milk production.
Udder breakdown: severe mastitis, poor udder conformation, or injury that persistently affects milk quality or quantity.
Low milk yield: cows that consistently produce less milk than the herd average or are no longer economically viable to maintain.
Mastitis: chronic or recurrent udder infections that are difficult to cure, compromise milk quality, or pose a risk to other cows.
Foot and leg problems: lameness or injury that impairs mobility, affects feed intake, or causes discomfort, impacting overall productivity and welfare.
Percentages of culling by reason visualized in a chart
Milk Quality Assessment
Good-quality raw milk should be:
Free of debris, sediment, off-flavors, abnormal color, and odor, indicating proper handling and hygiene.
Exhibit low bacterial counts, which determines shelf life and suitability for processing into various dairy products. High counts suggest contamination or inadequate cooling.
Free of chemicals (e.g., antibiotics): essential for food safety and preventing antibiotic resistance in humans. Milk from treated cows must be withheld for a specified period.
Composition:
Average components by percentage: These percentages can vary slightly by breed, diet, and stage of lactation.
Water: 87.7%, providing hydration.
Fat: 3.6%, contributing to flavor, texture, and energy content. This is typically butterfat.
Protein: 3.2%, primarily casein (approximately 80%) and whey proteins (approximately 20%), vital for nutrition and cheese making.
Lactose: 4.8%, the main sugar in milk, providing energy.
Ash/minerals: 0.7%, including calcium, phosphorus, and other trace elements essential for health.
Milk Grading
Grade A Milk:
Used for fluid consumption, meaning it can be bottled and sold directly as drinking milk. Subject to stricter sanitary standards due to direct human consumption.
Must be cooled to 45°F or less within 2 hours after milking and maintained at that temperature to inhibit bacterial growth.
Sanitary guidelines include a Standard Plate Count (bacterial count) of less than cfu/mL (colony-forming units per milliliter) and less than somatic cells/mL, indicating a very low level of bacterial contamination and udder inflammation.
Grade B Milk:
Used for manufacturing only, typically processed into cheese, butter, yogurt, or powdered milk, where further processing steps like pasteurization and fermentation can mitigate higher bacterial loads.
Cooling requirement: 40°F or less within 2 hours, similar to Grade A, emphasizing the importance of rapid cooling.
Bacterial count: generally permitted up to cfu/mL, reflecting less stringent bacterial standards compared to fluid milk.
Mastitis in Dairy Cows
Definition: Inflammatory response of udder tissue, often characterized by swelling, pain, heat, and redness, due to trauma (physical injury) or microorganism infections (bacteria, fungi, yeast) entering through the teat canal.
Methods to diagnose mastitis: Early and accurate diagnosis is crucial for timely treatment and preventing spread.
Visual inspection: observing changes in milk (flakes, clots, watery appearance) or udder (swelling, heat, pain).
pH measurement: milk pH can increase during mastitis.
Electrical conductivity: mastitic milk often has higher electrical conductivity due to increased ion concentrations.
Bulk tank somatic cell count (SCC): a measure of overall udder health in the entire herd's milk, with high numbers indicating widespread infection.
Culture testing: involves growing bacteria from milk samples to identify the specific pathogen causing the infection, guiding targeted antibiotic treatment.
Electronic somatic cell counters: rapid, automated methods for determining SCC in individual cows or herd milk samples.
California Mastitis Test (CMT): a cow-side test for rapid detection of subclinical mastitis.
California Mastitis Test
Method: Reagent reacts with DNA in somatic cells (SCC), specifically the nucleus of white blood cells (leukocytes) that increase in number during an inflammatory response such as mastitis.
Procedure:
Collect milk from first streams: foremilk (the first few squirts) is discarded, and milk is collected from each quarter into separate cups of a paddle.
Combine sample with reagent, swirl, and read results: equal parts milk and CMT reagent are mixed. The reagent causes the somatic cells to gel or thicken.
Results interpretation: Thick indicates mastitis positive. The degree of gel formation indicates the severity of the infection, from watery mixtures (trace) to thick gel (strong positive), correlating with SCC levels.
Success Factors in the Dairy Industry
Utilization of record systems (Dairy Herd Improvement Association - DHIA): DHIA provides standardized record-keeping for milk production, reproduction, health, and genetics, enabling dairy farmers to make informed management decisions to improve herd profitability and efficiency.
Selection of limited number of traits for breeding: Focusing on traits like milk yield, butterfat and protein content, udder health (low somatic cell count), and fertility improves genetic progress and overall herd productivity more effectively than trying to improve too many traits simultaneously.
Adaptation of technology including artificial insemination (AI) and precision farming:
AI allows for the widespread use of genetically superior bulls, significantly accelerating genetic improvement in herds.
Precision farming technologies (e.g., automated feeders, activity monitors, robotic milkers) help monitor individual animal health and performance, optimize feed delivery, manage breeding, and improve labor efficiency.
Environmental control and health programs: Implementing strategies to reduce heat stress, improve ventilation, ensure proper bedding, and vaccination protocols are crucial for maintaining cow comfort, health, productivity, and reducing disease incidence.
Milk Processing Techniques
Pasteurization:
Method to reduce microbial contamination by heating at 161°F for 15 seconds (High-Temperature, Short-Time or HTST pasteurization), then rapidly cooling to 39°F. The primary goal is to kill pathogenic bacteria (e.g., Salmonella, Listeria, E. coli) and other spoilage organisms, thereby increasing milk safety and extending its shelf life without significantly altering its nutritional value or flavor. Other methods include Ultra-High Temperature (UHT) for longer shelf life.
Homogenization:
Process to achieve uniform fat size by passing milk through a nozzle under high pressure and temperature, preventing cream separation. This breaks down large fat globules into much smaller, uniformly sized globules, so they remain suspended throughout the milk rather than rising to the top as a cream layer. This also contributes to a smoother, richer mouthfeel.
Dairy Products Categories
Fluid Milk:
Whole: 3.25% fat, typically the full fat content of milk.
Low Fat: 1% or 2% fat, with fat removed to a specified level.
Skim: 0.5% fat (or less), with virtually all fat removed.
Half and Half: 10.5%+ fat, a blend of milk and cream.
Whipping Cream: 30% fat, suitable for soft peaks when whipped.
Heavy Cream: 36% fat (or more), for firm peaks when whipped.
Cheese: Product from coagulation of caseins (milk proteins) using rennet or acid, and separation of whey (the liquid portion of milk).
Butter: Made by separating milkfat from other milk components, typically through churning cream.
Yogurt: Fermented milk, produced by bacterial cultures that convert lactose into lactic acid, giving it its characteristic tart flavor and thick texture.
Ice Cream: Produced by freezing cream/milk, sugar, and flavorings while churning, incorporating air to create a smooth consistency.
Statistics on Milk Sales
Graphs illustrating trends in fluid milk sales by product category from 1970-2025
Per capita fluid milk consumption statistics (in pounds) visualized from 1975-2017
Vocabulary Terms
Heifer
Cow
Bull
Bullock
Calf
Colostrum
Dry off
Early/mid/late lactation
Mammary involution
Epithelial cells/lactocyte
Lumen
Myoepithelial cells
Capillary system
Alveoli
Lobule
Duct system
Gland cistern
Teat cistern
Streak cannel
Oxytocin
Milk parlor systems (e.g., parallel, tandem, herringbone, robotic)
Casein
Whey proteins
Mastitis
California Mastitis Test
Pasteurization and Homogenization
Dairy product types (e.g., milk, cheese, butter, yogurt, ice cream)