Lectures 1-2 Flashcards
The profitable operation of a dairy farm is influenced by what?
Reproductive efficiency of lactating cows
What is reproductive efficiency a result of?
- Days that a cow spends in the most efficient time of the lactation curve
- Cull rate due to reproductive failure
What should a breeding program integrate in order to optimize reproductive performance?
Theriogenology and herd health/preventative medicine
What four reproductive indices determine the reproductive efficiency of a dairy herd?
Voluntary waiting period
Estrus detection rate
Conception rate
Pregnancy loss
What is pregnancy rate?
Number of cows pregnant
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Why do you need a voluntary waiting period?
- To allow for uterine involution and
2. Early onset of ovarian cyclicity
When does lactation peak?
1-2 months post calving
What is so challenging to the cow during lactation?
She drastically decreases her dry matter intake around calving and has to rely on her body energy stores to produce milk
What is the main difference between beef and dairy cattle
Dairy cattle have been selected to produce mass amounts of milk while beef cattle have not
What must happen for the cow to get pregnant again after calving
Needs to have involution of uterus and return to cyclicity
What must happen for the cow to resume cyclicity
She must get past the lowest point in NEB
Who else experiences negative energy balance after giving birth
Elephant seals and baleen (blue) whales
What have dairy cows been aggressively selected for
Efficient milk production (~6.5% body weight)
After the negative energy balances passes, what must cow do?
What does this cause?
Eat a lot in order to continue producing milk
Causes increased steroid metabolism
What does increased steroid metabolism result in?
Decreased estradiol and progesterone results in:
- decreased estrus behavior
- increased size of ovulatory follicle
- increased double ovulation
- decreased embryonic development
- decreased pregnancy rate
- increased pregnancy loss
What are the jobs of the vet in regards to breeding management
- Proactively work with groups of cows that are likely to get pregnant
- reduce potential for “lost opportunity”
- speed up establishment of pregnancy
- increase AI submission rate and pregnancy rate
Why work with AI instead of bulls?
There is little genetic variability among the bulls used for breeding nowadays
What is AI submission rate
Number of cows inseminated/ number of cows eligible to receive AI
In a 21 day period (length of cow estrus cycle)
What cows are eligible to receive AI
Cows that are not pregnant and have involuted their uterus already and have resumed cyclicity
What is pregnancy per AI
Number of cows pregnant/ number of cows inseminated
What is pregnancy rate?
Number of cows pregnant/ number of cows eligible to become pregnant
In a 21 day period
What is the most important parameter used for evaluation of reproductive performance
Pregnancy rate!!
What is pregnancy loss
Number of cows not pregnant/ number of cows diagnosed pregnant
What is the objective for producers regardless of strategy type
Maximum profit
How does reproductive strategies affect culling policies and profitability
- Good repro strategies means less culling due to repro problems which means more culling slots available for genetic/disease problems
- Less culling means you don’t have to buy lots of replacement heifers
- will have more “veteran” heifers going into second lactation which is more profitable
What is IOFC
Income over feed cost
Amount of money made from selling milk produced by that cow/ cost of feeding that cow
When is IOFC the most?
Early lactation- first 100 days
As lactation continues, profit margin decreases
How does a lower calving interval increase profitability
It decreases the time that the cow hangs out in the low profitability range of lactation
I.e. if calving interval is 14 months, cow only spends 23% of entire interval being most profitable. BUT if the calving interval is 12 months, the cow will spend 26% of the interval in high profitability
What are the options if a beef cow is delayed in getting pregnant? (Either at the end of breeding season or even after)
- shorten the next resting period (VWP)
- reduce breeding season..which can result in extra culling of open cows and excessive retention of female calves for replacement
- prolong breeding season which results in reduced performance of calves and cows in future seasons
*beef cattle’s only profit is calves. Dairy cows can still be milked if they don’t get pregnant
What things affect reproductive efficiency in both beef and dairy cattle? What do these disorders do?
Dystocia Poor nutrition Retained placenta Uterine Metabolic disorders Ovarian cysts
These disorders make the uterus take longer to involute
What is the goal of beef cattle management?
High rate of first service conception rate
What benefits do a high rate of first service conception give? Beef cattle
Increased cows pregnant early in season —> decreases distribution of calving dates
Decreased replacement rate —> decreased number of younger cows
Decreased number of heifer calves you need to retain for replacement —> decrease feed costs
What are the keys to reproductive efficiency?
Health, NOT hormones
- good transition period from gestation to lactation (comfort, proper nutrition, etc.)
What is the transition period?
Last 21 days of gestation up to first 21 days in milk
What do you want to do during the transition period to optimize repro efficiency
- reduce incidence of diseases
- minimize BCS loss (can’t eliminate it, but minimize it)
- expedite resumption to cyclicity
How do you reduce incidence of diseases, minimize BCS, and expedite resumption to cyclicity?
Comfort (avoid heat stress with shade, water, fans, etc; sufficient resting space)
Proper nutrition (availability of water, balanced and sufficient feed for all cows with minimal competition)
What does FSH spike cause
Recruitment of follicles
What keeps ovulation from happening
Progesterone
What causes drop in progesterone
Lyses of CL from prostaglandin
What happens when progesterone decreases?
LH peak occurs and then the follicle ovulates
When is the optimal time to inseminate a cow
About 8 hours after the cow goes into heat
What is one thing that can compromise fertility of cows
Improper detection of estrus and therefore bad timing of insemination
What are the high risks of infertility?
- Failure of fertilization (AI - 6 days)
- Early embryonic loss (defective embryo doesn’t signal to the cow to not secrete PGF2alpha) (6-17 days)
- late embryonic loss (24-42 days)
- fetal loss (42 days to term)
- abortions
What does the bovine embryo release to signal that it is there
Interferon tau
What will you see with fertilization failure and early embryonic loss?
Return to estrus
What will you see with late embryonic loss
Altered inter-estrus interval (not 21 day cycle)
What decreases pregnancy per AI
Fertilization failure
Early and late embryonic loss
What is anovular condition
Acyclicity
What is the most important hormone when the cow is pregnant?
Progesterone
What happens to hormones when the cow is about to calve
Progesterone goes down and estradiol goes up
Why won’t the cow begin cycling immediately after parturition since there is FSH, follicles, and low progesterone?
Because the cow is in negative energy balance, LH pulses are very small because there is very low IGF-1
What is the key hormone determining whether or not a cow will start cycling again? Why?
Insulin like growth factor 1
-without IGF1, the follicles will never reach the correct development needed to produce enough estradiol to induce LH peak (ovulation)
What is an issue encountered with Zebu cattle (brahman, nelore) returning to cyclicity?
Calves suckling on their teats release opioids, which blocks hypothalamic positive feedback of estradiol which prevents LH peak
What do they do with the zebu cows to avoid this problem?
Remove the calf to take away the opioids and induce cyclicity
What can peripartum health disorders affect in cows?
Delayed resumption of cyclicity
Lower number of quality embryos
Decreased chance to become pregnant next breeding season
Why do high producers have a lower estrus concentration, shorter estrus duration, and decreased number of standing events than heifers?
Because the increased DMI results in more steroid metabolism results in less estrus
Which cow is in estrus- the standing one or the one being mounted?
The one that is standing to be mounted!!
Who reaches the estradiol concentration necessary for estrus faster- heifers or cows?
Heifers because they have lower DMI and less estradiol is being metabolized (and therefore has a higher concentration)
Why do cows with high DMI have worse quality eggs than heifers?
Because the cows have a lower concentration of estradiol, it takes longer for the concentration to be high enough to induce ovulation, which means the embryo is aged (older than it would be if the cow had entered estrus and ovulated sooner)
Difference between lactating cows and non lactating heifers regarding fertility
Lactating cows:
Longer luteolysis- ovulation window
Bigger follicular diameter
Lower estradiol concentration
Heifers:
Shorter luteolysis- ovulation window
Smaller follicular diameter
Higher estradiol concentration
Who has higher progesterone concentration- cows or heifers?
Heifers
What does the embryo need to do to release interferon tau?
It needs to elongate
What does GnRH do? When would you use it?
Induces ovulation and increases progesterone concentration
Use only prior to breeding
How would you use progesterone?
Has vaginal inserts available…but would need to use more than 1 in order to increase the progesterone concentration sufficiently. This is off-label and therefore can get you in trouble with AMDUCA
What are viral infectious causes of infertility?
Infectious bovine rhinotracheitis (IBR)
Bovine viral diarrhea
What are bacterial infectious causes of infertility?
Clostridium
Lepto
Campylobacter
What is a protozal cause of infertility in the cow?
Neospora
What is a parasitic cause of infertility?
Tritrichomonas foetus- more related to the bull but the bull can contaminate the cow
