Cattle Flashcards
features of highly fertile beef herd - calving pattern, female calve in first cycle, calving rate, age of heifers, heifer dystocia
- Calving pattern 8 weeks in cows and 6 weeks in heifers
- 70% of females calve in first cycle
- calving rate > 95%
- use highly fertile high serving capacity bulls
- heifers calve down as 2 year old
- heifer dystocia rate < 5%
- high heifer retention rate enabling cows to be sold at 8 years old having reared their 6th calf
Heifer critical mating weight what is it and how old are heifers at joining
- Puberty is related to body weight as well as age
- CMW definition: 84% conceive in 6 weeks
- Will vary with breed and herd
- Most breeds start cycling at about 52% mature BW
- Typical benchmark is 60-65% of average mature BW for the herd
- Growth rate about 1kg per day
How old are heifers at joining - Aim to calve at 2 years so oldest will be 15-16 months old, later clavers 13-14months
- THEREFORE later calving heifers need to achieve CMW at an earlier age - WHY CALVING PATTERN IS SO IMPORTANT
Heifer weaning when to wean and how related to energy in the paddock and the mothers nutrition - BEEF
When to wean
- Minimum Age = 100 days from when the last calf born
- Maximum Age = 6 months, depending on season and available feed
○ Why 6 months? At 6 months some bulls will be reproductively available
- If Cow condition drops to 2.5
Energy
- Certain amount of energy in the paddock
- Feed in paddock
○ 1. turn feed into calf OR 2. turn feed into milk THEN turn milk into calf
- At some point it is more efficient to turn the energy directly into the calf -> WANT TO WEAN AS SOON AS POSSIBLE
- Also FOR THE MOTHER
○ Dam eat feeds
§ Some feed used for maintenance
§ Some feed turn into milk
§ Excess feed stored as fat -> when wean move to this
○ Therefore in droughts “early weaning can be a good strategy”
Selection of heifers for joining how much retain of heifers, which age group better and 5 reasons whyv
- Herds often retain 40-50% of heifers
- This is equivalent to 20 -25% of herd size
- Retaining more heifers will lead to a younger herd- BETTER
1. Cow value declines after 6-7 years
2. Bodyweight peaks at 7-8 years
3. Weaning weights of calves declines in older cows
4. Older cows are more likely to die
○ Grass Tetany
○ Cancers
5. More flexibility to cull for genetic gain
Spermatogenesis overview what does it consist of and the cycle of the seminiferous epithelium, how long does it take
• Spermatocytogenesis ( = Phases one and two, or Proliferation and Meiosis)• Spermiogenesis (= Phase three, or Differentiation)
• Note cellular bridges allowing cells to develop as cohorts
Cycle of the Seminiferous Epithelium
- This is a useful analogy to help understand the cycle of the seminiferous epithelium
- Each 12 month cycle has two stages (semesters)
- It takes 4 cycles (years) to complete the process
○ Cell division
○ DNA packaging
○ Add a motor and energy cells
○ Switch it on
Toxic sperm how occur and type of defect formed
- After fertilization, the DNA must be carefully unpacked
○ If the packing is done poorly, it will be unpacked poorly and the fertilized egg will die - Eggs can only be fertilized once
○ “Uncompensible defects”
§ Minor insults can be worse than major ones -> major cannot get to egg but minor can get to egg BUT NOT FERTILISE
§ Dead sperm can be compensated for by other sperm - compensible defect
§ Toxic Sperm waste eggs - cannot be changed with increasing sperm
List some things that can cause sperm abnormalities, how long do they last and how do we aviod toxic sperm
What can cause sperm abnormalities - Transport, Diet - Temperature, Lameness - disease, stress, toxins How long do they last - 30-40 days later it may then become apparent How do we avoid Toxic Sperm ? - Know the history - Own the bull for 70 days - Don’t use a sick or injured bull for at least 70 days
What are the 4 main things you should vaccinate bulls against
- 5 in 1 (Clostridialdiseases)
- Leptospirosis
- Vibriosis
- Pestivirus
Veterinary bull breeding soundness evaluation (VBBSE) what is it, what does it do and the 5 components it reports
- a protocol developed by the ACV to be a relatively quick and economic procedure for screening bulls prior to sale or use.
- not a guarantee - NEED TO IDENTIFY THE BULL
- Screen out “high risk” rather than screen out “Infertile”
- Uniform accepted standards
The 5 components are reported:
1. Scrotal circumference - score 1-5
2. General Physical Examination
3. Crush Side Semen Evaluation
4. Serving Ability Testing
5. Semen Morphology Testing
Physical examination for Veterinary bull breeding soundness evaluation (VBBSE) what are the 8 things involved and what looking for
- Identify the bull
- Condition score
- Check the eyes - squamous cell carcinomas, vision impairment
- Sheath structure
- Examine the hooves - scissor claw, curled tow, worn claw, sand cracks
- Examine leg structure and conformation - posty leg, sickly hock, degenerative joint disease
- Examine gait
- Reproductive Organs
Crush side semen evaluation for Veterinary bull breeding soundness evaluation (VBBSE) what are the standards for the semen to pass
- Density of 1 or more
○ 200 sperm per 100x field under a cover slip - Absence of blood or urine staining
- Absence of flocculant material and large numbers of pus cells
- Percent progressively motile -> actively moving forward
○ Tick – 60% +
○ Pass – 30% ‐ 59%
○ Fail ‐ < 30%
Sperm morphology testing for Veterinary bull breeding soundness evaluation (VBBSE) how occurs, what identify and what need for AI and natural mating
- 8 drops of semen into a vial of buffered formol saline and send to lab
- Easy
- Identifies some permanent conditions
- Identifies some transient conditions
- Compensable vs non‐compensable defects
- Should have 70% normal sperm for AI
- 50%‐70% normal sperm ok for paddock mating
- Provided that
○ Not more than 20% uncompensable
○ Nor more than 30% of other individual abnormalities
Contagious mastitis pathogens when spread and list 4 main ones, do they respond to treatment
- Spread at milking time
1. Staph aureus
§ Responds well to treatment
2. Strep agalactiae
strep doesn’t respond as well to treatment
3. Strep dysgalactiae
4. Mycoplasma
§ Not as common but if have an outbreak highly contagious throughout the herds and highly problematic
Environmental mastitis pathogens how spread and list 5 important ones
- Spread via environment
○ Paddocks, mud, faeces, calving pads, bedding, tracks
1. Strep uberis
2. E. coli
§ Generally highly clinical, gangrenous, toxic - depending on virulence factors
3. Strep Dysgalactiae
4. Pesudomonas
§ Very nasty cause again - highly toxic clinical signs
5. A. pyogenes, Nocardia
Name 4 management risk and pathogen risk factors for mastitis
management
1. Environment - mud and faecal contamination
2. Seasonal conditions - heat, humidity, wet and muddy conditions
3. Milking practices - hygiene, stress, machine issues - IMPORTANT - EXAM
4. Existing prevalence in herd
Pathogen
1. Viability in environment
2. Virulence factors - colonisation of duct, adhere to mammary gland
3. Toxins - E. coli and Staph aureus
4. Antibiotic resistance - large problem with herd level conditions especially with staph - why may need to cull cow
ICCC what cells normally present, normal count, when increase
- Somatic cells are present in normal milk
- Epithelial cells and mononuclear leukocytes
- Usually in the order of 100,000 cells per mL
INCREASE - after calving (fall below 300,000 within 5 days)
- end of lactation
- Infection - On average 3.8 times higher than non-infected cow - Over 250,000 cells per mL for a 4 quarter sample suggests infection in at least one quarter - Cow with one count over 250,000 cells/ml, consider infected for entire lactation
BMCC how used when should seek advice and production relation
Somatic cell count taken from bulk tank
- Used to form payment scales by milk factories
- Premium paid if milk produced under 200,000 or 250,000 cells/mL (depending on factory)
- Severe penalties if milk produced over 600,000 or 750,000 cells/mL depending on factor but considered poor if >400,000
- Should seek advice if:
○ Over 250,000 for 6 months
○ Receive penalty payment
Production
○ If BMCC increasing, production will be decreasing
○ 2.5% for every 100,000 above 200,000 cells/mL
Antimicrobials for mastitis, what gets higher cure rate, which pathogens respond to treatment when and if no response what can you do
- Combination of parenteral and intramammary may result in higher cure rate
- Cure rates are dependent on pathogen
○ Staph aureus poor during lactation
○ Strep agalactiae very good
○ Strep uberis variable - can be difficult to cure
If no response to treatment - Treat for longer
- Try different antibiotic regime - culture
- Dry off quarter
- Chemically dry off quarter - infusing copper sulphate
- Dry off cow - DCT
- Cull
Gangrenous mastits treatment options
- If lost sensation in that teat -> just remove the teat
- Systemic infection so need to treat systemically
○ IV - antibiotic and anti-inflammatory and possible IV fluids
Another infected quarter -> give oxytocin -> promotes cow to let down milk
Dry cow management how long, why done and the 2 types
- Minimum of 6 weeks required to allow udder tissue to regenerate
- With no dry period milk production will be reduced in following lactation (seeing contray evidence to this fact)
- A keratin teat plug seals teat canal at the start of dry period -> sturdier than other seal throughout lactating
○ Formation of keratin plug aided by DCT (dry cow therapy)
1) antibiotic
2) teat sealant- physical barrier
List the 7 ways to manage mastitis
1) monitoring for mastitis via milk cultures, ICCC, BMCC, rapid mastitis test, NAGase test
2) treating clinical and subclinical infection
3) Looking at milking machine for faults
4) looking at milking technique for faults
5) scoring teat condition to see if that an issue
6) dry cow therapy - how conducted does it need to change
7) CULL COWS - with 3 or more clinical cases in lactation - not a long term fix
Staph aureus causing mastitis reservoir, spread, presentation, treatment how easy and when
- Reservoir - infected udders and skin of teats (Teat end damage)
- Spread at milking by contaminated milk - all milking cows susceptible (esp. with teat sores/teat end damage)
- Found on liners 6 to 8 cows after an infected cow is milked
Presentation - Persistent sub-clinical infection generally but anything from that to sub-acute gangrenous
Treatment - Very difficult to cure with antimicrobials
- Very difficult to cure during lactation - dry cow therapy important - gives higher cure rates
- Resistant to many antibiotics
- Best results with young newly infected cattle
Strep agalactiae causing mastitis characteristics, presentation and treatment
Obligate parasite, however can survive on milking machines, milker’s hands and clothes
- VERY RAPID SPREAD
- Infected cows shed very large numbers of bacteria
Presentation
- Causes very high rate of clinical mastitis
- Causes sub-clinical infections as well
- Can cause plate count failure
Treatment
- usually very effective during lactation - Penicillin sensitive
- DCT will cure up to 100% of infections
Mycoplasma spread and main issues
- Spreads very rapidly from cow to cow
- Hard to culture -> need specialised culture
- Milking hygiene problems are risk factors
- Response to treatment very poor
- Often destroys milk production in cows
○ Often need to cull up to 75% of cows infected
