h) w/c 4-Nov-13 Flashcards
What are the 4 genetic forces?
- Genetic drift (+ inbreeding)
- Selection
- Migration
- Mutation
Genetic drift is more likely in _____
smaller populations
what would be the imbreeding co-efficient of a parent/ offspring mating?
0.25
what would be the imbreeding co-efficient of a half sibling mating?
0.125
The rate of inbreeding is proportional to the ____. Ideally it would be no more than ____
effective population size. Ideally would be no more than 0.5% PER GENERATION with a population of >100
What are some potential solutions to prevent this inbreeding?
- Minimising coansestory matings
- Equal male/female populations
- Increased number of animals used for breeding
- Optimising genetic contributions
-Out-crossing (bring in new blood)
USE KENNEL CLUB MATE SELECT= Mating co-efficience
Define heritability
The proportion of observable variation made up of variation of genes
When looking at NFU ISCC what is the difference between new and first definitions?
New: Cows just become infected for first time in this lactation
First: Cows just calved. Could have calved with mastitis or got infected very early in lactation.
Also difference between REPEAT vs CHRONIC
What four things can happen to ISCC during the dry cow period?
Low to low = ideal
low to high = bad
high to low = good (effective dry cow therapy)
high to high= worst (cull???)
How is the predicted transmitting ability (PTA) related to EBV?
pta = 1/2 EBV
Define PIN vs PLI
pin= profit index pli = profitable lifetime index
What is included in the PLI index?
Milk PTA (Predicted transmitting ability). Fat, Protein, Lifespan, SCC, Locomotion, fertility (2006) Numbers = relative importance. + or - want to increase or decrease this statistic??
Why is environmental senstitivity important?
‘RobustCows’ Want cows to be profitable in any environment. Not just the environment where their traits are measured/ tested
Which two factors are incorporated into the fertility index?
Calving interval + Non-return rate
Which is the bacterium that infects the non-lactating (dry cow) gland and immature glands?
Arcanobacterium pyogenes
also (Streptococcus dysgalactiae)
What are the three entry points of bacterium to the mammary gland?
Galactogenic, Haematogenous (mycobacterium, brucella), Percutaneous (wounds)
What are the three primary roles in providing resistance to infection?
- Smooth muscle sphincter
- Chemicals from the epithelium containing proteins, fatty acids etc
- Furstenberg’s Rosette
What are the three parts of the Furstenberg’s Rosette?
a) Prevent physical entry of organisms to the canal
b) Fatty acids/ cationic proteins
c) Subepithelial plasma cells produce immunoglobulin
Three clinical presentations of mastitis
- Peracute (life-threatening) 2. Acute
When is peracute (gangrenous) mastitis most likely? What is the main causative agent?
Most common around parturition (Staphylococcus aureus).
Death can occur within hours.
Clinical presentation of a cow with peracute mastitis. Why might the animal become comatosed?
Swollen painful quarter, rapid progression to moist gangrene, dark-blue to to black in colour (due to ischemia) also becomes COLD to the touch (ischemic).
Animal may become comatosed due to the toxemia
What is the microscopic appearance of chronic mastitis? What does this result in…
In later stages, fibroplasia with obliteration of the acini. Ostruction of the ducts with polyps. Permanent loss of secretory tissue due to progressive destruction Becomes hard (due to fibrosis) and atrophic (due to blockage of acini)
Three main bacteria involved in lactating mastitis
- Staphylococcus aureus (skin commensal)
Can cause subclinical through to severly gangrenous). 70% beta lactamase positive - Esherichia coli
- Streptococcus uberis
Which is the only bacteria for which there is a vaccine (for mastitis)
Esherichia coli Vaccine = killed j5)
Acute mastitis. Becoming increasingly important in antimicrobial resistance.
According to the Lansfield groupings which is more pathogenic Streptococcus agalactiae or Streptococcus dysgalactiae?
Streptococcus dysgalactiae = group C = more pathogenic
S. agalactiae = group B
Is contagious or environmental mastitis more common in the dry period?
Environmental
E-coli is more of an _______ mastitis pathogen
environmental
Example of a contagious pathogen
Streptococcus agalactae, streptococcus dysaglactaie, steptococcus uberis
Different grades of clinical mastitis
Grade 1: Milk change only
Grad 2: Acute: Milk changes in udder, milk yield decreases
Grade 3: Systemic changes
Following trauma e.g. stepping on udder which pathogen is most likely to cause mastitis?
Streptococcus dysgalactiae (lesion, milkers hands etc). lansfield group C.
Steps when taking a Calofornia Milk Test (CMT)
- Wipe till clean!
- Strip (pathogens/ SCC gravitate)
- Sample
- Add detergent (opens up helix)
- Asses (pour and assess viscosity)
- POST-TEAT DIP!!!
MAKE SURE YOU KNOW WHICH SAMPLE FROM WHICH QUARTER
Mastitis clinical examination routine.
Systemic clinical exam.
Udder exam - inspect, palpate, check for prolapsed teat canal.
Check rear lymph nodes.
CMT milk test
What must be checked before treating dairy cows for mastitis. What is involved in this treatment?
MILK WITHDRAWEL PERIOD (also freeze a sample incase of treatment failure)
- Oxytocin (aids milk let down)
- NSAIDS e.g. meloxicam
- Corticosteriods
- Calcium
- Dextrose
What should you put when labelling a 2ml milk sample?
Cow’s number AND WHICH QUARTER IT WAS TAKEN FROM. When culturing 40% come back sterile. USE GLOVES.
How long is the dry period? Why is it bad if cows are infected in this time?
8 weeks = 60 days.
Infection in the dry period can cause problems in early lactation
Examples of environmental organisms that cause mastitis
E-coli, streptococcus uberis, klebsiella (wood chip)
Subclinical infections tend to be _______ organisms
contagious
What is the 5 point plan for mastitis
- Prompt detection and treatment
- Post milking teat dip
- Dry cow therapy
- Cull persistant offenders
- Regular serving and maintain of milking machines
Advantages of foremilking
Legal requirement.
Aids milk let down and speeds up milking time.
Avoid splash back
How long after milking does teat orifice remain open for? Examples of PMTD chemicals
30-40 minutes. Iodophores, Chlorine basd, Chlorhexidine, quarternary ammonium compounds. Skin is most overly worked!!
Two different types of DCT
DCT: Dry cow treatment
-Long acting antibiotics, treat any subacute infection and aims to prevent further infections (environmental)
Teat sealant; inert substance that is infused into teat canal to block bacteria entering e.g. bismuth.
Better to use LA antibiotic on the cows with ISCC >200,000/ml
How do the milking machines work? How often should the liners be replaced?
CONSTANT VACCUM APPLIED TO TEAT END.
Liner open and closes to massage teat otherwise it would get congested (pulsation)
Liners should be replaced every 2,500 milkings if rubber
What is the standard size of a cow stall?
8ft by 4ft. Should have a lunging bar at 5ft6 from front
What are the difference targets for mastitis INCIDENCE and PREVALENCE?
Incidence: 30cases/100cow/year
Prevalence: <200,000/ml
Three options of dealing with problem cows
- Cull
- Isolate into problem group
- Treat. Bacteriology of infected quarter
Explain the 5 point plan. Which one is commonly overlooked??
- Early detection and immediate treatment
- Post milking teat dipping
- Effective dry cow antibiotic therapy
- Culling cows with more than 3 cases/ 1 lactation
- GOOD MAINTENANCE OF MILKING MACHINE
What is the cow comfort index?
Proportion of cows standing one hour before milking
