Quiz 5 Flashcards
Why is milk seldom used in other food products
High Concentration of water and water is difficult and expensive to move
Grade A Milk
95% of milk is grade A
Grades determined by the Pasteruized Milk Ordinence
Nearly impossible to find producers who will take lower than Grade A
PMO Temperature Requirements for Grade A
Raw: 7 degrees C or less within 2 hours of milking
Pasteurized: 7 degrees C or less and maintained
PMO Bacterial Limits for Grade A
Raw: 100,000 or 300,000 CFU/mL Standard Plate Count
Coliforms 10 CFU/mL
Pasteurized: 20,000 CFU/mL
PMO SCC for Grade A
750,000 cells/mL
PMO Drug Test for Grade A
NONE
PMO Phosphatase Test for Grade A Milk
Pasteurized: Phosphatase Negative. Indicates proper time and temperature pasteurization
Titrateable Acidity
0.16% max
Measure of the Acidic Compound in Milk
High if bacteria make lactic acid
Freezing Point
-0.530 Degrees Celcius
Addition of water to milk raises the freezing point
Prevents artificial increases in volume
Total Solids
Whole: 12-13%
Skim: 8.9-9.3%
Which two microorganisms must raw milk be negative for?
Listeria
Salmonella
Standard Plate Count Limit for Psychrotrophic Bacteria
10 CFU/mL
Milk Processing Sequence
Heat Exchanger
Centrifugal Separater
Automatic Fat Standardization Device
Homogenizer
Return to Heat Exchanger
Standardization
Purpose: to provide a consistent fat content for processed products
–Nonfat (skim): <.5% milkfat
-Lowfat: 1-2% milkfat
-Full fat: 3.25% milkfat
-Half & Half: 11% milkfat
Primary and Secondary purposes of pasteurization
Primary: destroy all pathogenic bacteria to prevent milk-borne illness. Originally, tubercle bacillus, causative organism for tuberculosis (TB)
Secondary: reduce all vegetative (spoilage) bacteria and denature enzymes to extend shelf-life of milk
What is the organism on which the thermal process for pasteurization is based?
Coxiella burnetti – heat resistant pathogen; more resistant than TB organism
Mycobacterium paratuberculosis - concern
What is the relationship between time and temperature
in thermal processing?
Higher temperature, shorter time for same lethality
Time and Temperature for batch and HTST of milk
Batch = 30 min at 62.7 Degrees Celcius
HTST = 15 seconds at 71.6 Degrees Celcius
What are some detrimental effects of heat processing fluid milk?
Adverse effects on appearance, taste, nutritional value
Proteins denatured at high temps
– Affects cheese production and yield
- Cooked flavor
Why is the temperature for pasteurizing high fat products higher than for fluid milk?
Fat is a poor heat conductor so it takes longer to
heat the product thoroughly
Why isn’t the phosphatase test used for acidified products? What is used instead?
Peroxidase test used for acidified products because peroxidase takes a higher temperature for inactivation; heat cultured products higher in order to denature whey proteins
What is the primary purpose of ultra pasteurization processing?
UP: Extended shelf-life (ESL), allows for longer distribution periods
UHT (aseptic): Processing protects the product from re-introduction of bacteria from the air, filled into sterile package
Sterilization
In-package thermal process that kills all vegetative bacteria and destroys spores
Results of Homogenization
Milkfat globule size decreased
# globules increased
Surface area increased
surface material changed
Process of Homogenization
Milk fat globules are forced through a narrow gap so they break into smaller globules that are stable in the emulsion
Small droplets will still want to aggregate but they are easily separated
Two-stage process
Why does mastitis matter?
Most economically impactful disease in dairy production due to its prevalence and impact
Causes of mastitis
Physical Force (Trauma)
Infectious Agents (Bacteria)
Pathogenesis of Mastitis
Colonization by pathogen
- adhesion to mammary epithelium
- expression of virulence factors
- production of toxins
Inflammatory Response of Cow
- increased vascular permeability
- leukocyte migration
- phagocytosis
Spontaneous Cure, Clinical Case, Subclinical Case
Costs of Mastitis
18.6 Million Dollars in Virginia
2 Billion Dollars in US (OLD NUMBERS)
23% Replacement Cost
6% Discarded
5% Treatment
66% Reduced Milk Production
Milk Loss by SCS
Milk loss begins at SCS of 3 or SCC 72,000-141,999 at 1.5 pounds less per day
For every one increase in SCC there is a 1.5 pound increase in milk loss
Inflamation
- Inflammatio = set on fire
- Response to injury
○ Inflammation is part of the healing response
○ Deliver defensive materials (cells and plasma proteins) to a site of injury
- Role in repair and remodeling of tissue
Heat, Redness, Swelling, Pain, Loss of Function
Signs of Mastitis at Milking
Clots in milk after stripping
Susceptibility to Mastitis
Incidence of mastitis increases when defense mechanisms of the mammary gland are impaired.
○ The Transition Period - Reduces Immune function and increases susceptibility
Factors Affecting New Infection Rates?
Management and Environment - 90%
Genetics - 10%
Periods of Increased Susceptibility to Mastitis
Calving
Dry-Off
○ If there are pathogens in the mammary system, when we stop milking we are no longer flushing those out and they have the ability to grow in the mammary system
Transition Period
Factors that Affect the Rate of Infection
Environment
Bacteria
Cow
Environment x Cow = Stress
Environment X Bacteria = Spread
Bacteria x Cow = Exposure
Colonization of Mammary Gland by Pathogens
Once a pathogen enters the mammary gland it can grow faster than it can be controlled and the bacteria adhere to the mammary epithelial and colonize the mammary gland
Virulence factors improve the survivability of the pathogen in the mammary gland
Inflammatory Response of the Cow
Increased vascular permeability to move more immune cells into the interstitial fluid and mammary gland
White blood cells engulf pathogens
5 Point Plan of Mastitis Control
Proper maintenance/use of milking equipment
Teat Dips/Proper Milking Procedure
Treat Clinical Cases
Dry Cow Therapy
Cull
Categories of Pathogens
Contagious
○ Spreads from animal to animal
○ Sometimes bacteria varieties are those which use the mammary system as a host
Opportunistic
○ Cause infection if they have the opportunity but live other places
Environmental
○ Found in the environment but may cause infection
Contagious Pathogens
Spread from cow to cow during milking
§ Preventing cross contamination between infected and healthy cows
primary source is infected udders
transmission at milking
usually establish chronic subclinical mastitis
Streptococcus agalactiae
CONTAGIOUS PATHOGEN
Gram positive cocci
Beta hemolytic
Capsule
Obligate pathogen of the udder
Problematic in the past but not seen often anymore
Staphylococcus aureus
CONTAGIOUS PATHOGEN
Gram positive cocci
Sphere Shaped (cocci)
Grow in Clusters (Staphylo)
Colonize skin, nasal cavity, mucous membranes
Thrives on unhealthy skin
Multiple virulence factors
§ Help the organism be infective
§ Adhesin - ability to couple with the epithelial surface
§ Capsules, slime - factors that prevent access of IgG and Complement
§ Protein A - Bind antibodies in the wrong way
§ Coagulase - breaks fibrinogen
S. aureus is very difficult to control within the dairy industry
Can cause abscess and clot formation in the mammary system
If the clot blocks the mammary ducts there is regression of the lobe or lobule
Corynebacterium bovis
Contagious Pathogen
Opportunistic Pathogens
Coagulase Negative staphylococcus
Primary Source is on healthy teat skin and milker’s hands
Transmission is related ti bacterial load on teat ends
Common in heifers, often right after calving
Detected in ~25% of lactating cows
§ Rate changes with stage and number of lactation
About half of infections are persistent
§ Dependent on pathogen
§ Not easy to control
Readily eliminated with efficacious post milking teat dipping
Dry cow therapy eliminated most existing infections
New infections at calving respond to lactation therapy
Environmental Pathogens
Primary source is the cow’s environment
Transmission of bacteria occurs between milkings
Incidence is higher in herds that control the contagious pathogens
§ Eliminating one pathogen creates the opportunity for other pathogens to infect the mammary system due to decreased competition
Coliforms
§ Present in the environment of all dairy cows
□ Gram Negative Rods
□ Differentiation
® MacConkey Agar
◊ Selective for gram negative and Lactose Fermentation = pink colonies
Examples of Opportunistic Pathogens
Staphylococcus chromogenes
Staphylococcus hyicus
Staphylococcus warneri
Staphylococcus epidermidis
Staphylococcus simulans
Staphylococcus xylosus
Staphylococcus sciuri
Examples of Environmental Pahogens
Escherichia coli
Klebsiella species
Enterobacter species
Streptococcus uberis
Streptococcus dysgalactiae
Pathogenesis of E. Coli
The immune system is responding to the toxins, not necessarily the bacteria
In severe coliform infections, the infection can take over the whole body
Lipopolysaccharide
Part of the cell wall of most gram negative bacteria
Consists of three components
- O Side Chain
- Inner Core
- Lipid A
Therapy of Coliform Mastitis
Typically controlled by the cow herself
Treatment Considerations
○ “Stripping out” mild clinical cases of coliform mastitis is preferred
○ Most coliform infections are cleared by natural defenses of the host
○ Supportive therapy is important
§ For when the infection is systemic
§ IV Fluids
§ Fever = Systemic Response
○ Vaccine
§ Does not prevent the infection but reduces the effect of the toxin
Trueperella pyogenes
Opportunistic (soil pathogen)
Bad infusion practices
Nocardia species
◦ Opportunistic (soil pathogen)
◦ Bad infusion practices
Prototheca species
Colorless algae (water/soil pathogen)
◦ Bad infusion practices
Yeast and molds
Bad infusion practices
Bacillus spp.
Bad infusion practices
Psuedomonas aeruginosa
Environmental
Water
Drop hoses
Proteus spp.
Environmental
On blood agar, it will swarm across the plate
Mycoplasma species
Contagious
Outbreak preceded by respiratory disease
California Mastitis Test
Used for Detection and Diagnosis of Mastitis
Measures nuclear DNA
Equal volume milk and CMT solution
Mix by rotating in circular motion
Determine gelling by rocking back and forth
Degree of thickness will determine degree of inflammation
Somatic Cell Counts - Why?
Increases in milk to combat bacteria
Why should you culture individual cow’s milk
Identifies specific pathogens
Therapy recommendations
Culling decisions
When should milk cultures be done?
Before drying off
At calving
Clinical symptoms
High SCC
Bacteriostatic
Inhibit Growth
Bactericidal
Kill
Discovery of Penicillin
Alexander Flemming
- Penicillium notatum mold inhibited the S. aureus growth on his culture
Howard Florey and Ernest Chain
- Mass production of penicillin for human use
Mode of Action of Antibiotics
Inhibition of Cell Wall Synthesis
Inhibition of Protein Synthesis
Inhibition of Synthesis of Essential Metabolites
Injury to Plasma Membrane
Inhibition of Neucleic Acid Replication and Transcription
Sources of Resistance
Nosocomical Infections
Animal Treatments and Feed Additives
Inappropriate Treatment Regimes
Premature use of Last Resort Drug
Failure to confirm culture and susceptibility
Why are antibiotic residues in milk a bad thing?
Many consumers have allergies to antibiotics
National Mastitis Council Mastitis Prevention
Pre and Post Milking Teat Disinfection
Blanket Dry Cow Therapy
Proper Treatment of Clinical Cases
Regular Milking System Analysis and Maintenance
Cull Chronically Infected Cows
Monitor High SCC
Common Contagious Pathogens
Staphylococcus aureus
Streptococcus agalactiae
Prototheca
C. bovis
Common Environmental Pathogens
Coliforms
Streptococcus dysgalactiae
Streptocuccus uberis
Environmental Strepts
