ANSC 460.3 Lecture Notes - Lecture 14: Pregnancy Rate, Obstructed Labour, Palpation
27 Jun 2018
School
Department
Course
Professor
Reproductive Management & Herd Fertility
Infertility and reproduction is the highest reason for culling
Inverse relationship between milk yield and fertility
milk production has gone up in dairy population and fertility has decreased
why?
- genetics, with higher milk production decrease in fertility is associated with negative
energy balance in early lactation
o this suppresses heat and delays recycling
- larger herd size so less time spent with each cow
o more dependent on heat detection
- inbreeding depression: every one using the high genet merit bulls
oinbreeding coefficient has increase and there is a negative relationship with
fertility
- cow comfort: lame cows
o they are reluctant to mount
ovisual heat detection depends on mounting cows
oto much time on concrete
- global warming could be factor
o when it gets super hot then cows can have silent heats
ohave heat stress which can reduce fertile
- proportion of fist calf heifers is higher now so this reduces fertility
ohigher culling rates so more first calf heifers
ofeeding them for milk production and growth so have more severe negative
energy balance
Extended calving intervals cost money
- have less calves so there are fewer replacements but this also means fewer calves to sell
- your health cost will increase because cows are likely going to have extended dry
periods when this happens there is a likely of cows getting over conditioned so then
have higher risk of metabolic diseases
Goals of reproductive management:
- milk production depends on reproduction
ocows should calve every 12-13 months
oextended lactation is delayed rebreeding so that you achieve calving intervals of
around 18 months
cows today are more persistent so with extending the calve interval the
cows can produce enough milk to make it worth it
- produce genetically superior heifer calves
oherd replacements
- minimize costs associated with non-lactating cows
- breed cows with desired phenotypic traits
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ohigh milk production, feet & legs ect.
- Minimize transmission of STDs
Reproductive Indices (R.I.)
- Indicators of reproductive performance of herd
- Gives an index of optimal values for different traits ( calving interval, average days open,
culling rate for reproductive problems)
- Shows values indicating serious problems
- Accurate record keeping critical
oFor calculation of R.I.
- Benefits of R.I.
oIdentify areas of improvement
oSet realistic goals
oMonitor progress
oIdentify problems early
oInvestigate history of problems
Calving interval
- Duration between successive calving
oIdeally 12-13 months
oGet cows rebred by 85-100 days in milk
- This R.I. value is questionable because it does not include cows that fail to conceive
Components of a calving interval
- Elective waiting period (EWP)
oAlso known as voluntary waiting period (VWP)
- Active-AI breeding period
- Gestation and dry period
Elective or voluntary waiting period
- 40-70 days
oduration is a management decision
- healing/ involution of reproductive tract
ohave to allow reproductive tract to recover from previous pregnancy
outerus needs time to contract back to normal size
oresumption of ovarian/ cycling activity
- longer EWP enhances conception rate
oif you wait to long you will lengthen calving interval which can have economic
issues
- uncomplicated calving’s and no metabolic disease when EWP is greater than 40 days
Active AI-Breeding period
- end of EWP, estrus detection, AI, conception
- duration depends one
find more resources at oneclass.com
find more resources at oneclass.com
oestrus detection efficiency
olevel of individual cow fertility
ofertility of service sire
ocorrect thawing and handling of semen
oAI technique
oTiming of AI
- 2 methods to breed cows
onatural service or use of bulls
oAI
Natural service
- Use of bulls declining
- Poor heat detection
oUse of bull increases conception rates
- Often used “to clean up”
- Long term genetic gain hampered
oMight not be superior bulls
Artificial insemination
- Semen introduced directly into uterus using insemination gun
- Advantages
oCan choose sires of high genetic merit
oRapid genetic gain
oEliminated cost and danger of keeping bull
oMinimizes risk of STDs
- Accurate heat detection also critical
o50% of heats undetected
What is heat?
- Period of acceptance for mating
oLasts 6-30 hours
oOccurs every 21 days
oCows must be bred when in heat to have successful fertilization
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Infertility and reproduction is the highest reason for culling. Minimize costs associated with non-lactating cows breed cows with desired phenotypic traits: high milk production, feet & legs ect. Gives an index of optimal values for different traits ( calving interval, average days open, culling rate for reproductive problems) Accurate record keeping critical: for calculation of r. i. Benefits of r. i: identify areas of improvement, set realistic goals, monitor progress, identify problems early, investigate history of problems. Duration between successive calving: ideally 12-13 months, get cows rebred by 85-100 days in milk. This r. i. value is questionable because it does not include cows that fail to conceive. Elective waiting period (ewp: also known as voluntary waiting period (vwp) Active ai-breeding period end of ewp, estrus detection, ai, conception duration depends one: estrus detection efficiency, level of individual cow fertility, fertility of service sire, correct thawing and handling of semen, ai technique, timing of ai.
