Lecture 4 Flashcards by Danika Boltz

What is most important to understand for dairy vs. beef cattle?

dairy: lactation curve
beef: breeding and calving seasons

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What does estrus/heat behavior depend on in cattle?

-reduction in progesterone/P4
-rise in estrogen/E2
*both must occur for a cow to come into heat

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What are the characteristics of heat detection?

-important because of missed heats
-most common source of reproductive failure using AI is missed heats
-only 50% of heats are actually detected
-20% of cows bred are not in heat
-each missed heat costs producers more money

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What are the characteristics of mounting behavior in cattle?

-primary sign of estrus is standing quietly and firmly to be mounted
-lasts 3 to 7 seconds and is repeated for 8 to 30 hours
-relates best to LH surge; ovulation occurs 30 hours later

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Which factors can affect mounting and standing behavior in cattle?

-footing surface
-feet and leg problems
-cyclicity of herd mates
-time of day
-environmental temp
-nutrition

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What are less reliable, secondary signs of estrus?

-mounting others
-mucous discharge from vulva
-bellowing and excitement
-restlessness
-decreased appetite
-swollen vulva
-licking others

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When do dairy cows begin estrous cycles post-calving?

-first ovulation around 18 days post calving
-first signs of heat around 34 days post calving

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When do beef cows begin estrous cycles post-calving?

first signs of heat between 40 and 90 days post calving

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What can lead to delayed heat in beef and dairy cattle?

dairy: large negative energy balance
beef: suckling anestrous

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What are the characteristics of visual estrus detection?

-most cost effective but most failure
-cows are observed at least twice a day for 30 minutes each time
-must have a dedicated observer
-anywhere from 0 to 90% effective; average is 50%

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What are the mechanical aids used in estrus detection?

-heat patches
-tail chalk/paint

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How do heat patches work?

-patch is applied to cow’s back where it can be hit by another cow mounting
-chamber in patch can break like a glowstick from mounting pressure; indicates estrus

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What is the AM/PM rule?

-if a cow is seen in estrus in the AM, she should be bred in the next PM
-if a cow is seen in estrus in the PM, she should be bred in the next AM

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What are the characteristics of electronic estrus detection aids?

-similar to heat patches
-mounting pressure on rump sends a signal to a computer with cow ID, duration of mounting, and frequency
-more than 90% effective but much more costly

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What are the characteristics of physically altered bulls?

-have epididymectomy and penile translocation
-unable to produce semen or achieve intromission
-used to mount females and allow for estrus detection

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What are the efficiency goals around estrus detection?

-detect 80% or more of heats
-have 85% of cows seen in heat by 60 days post-partum
-have 85% of cows pregnant at palpation 40 days post-breeding
-have 60% of cows in an 18 to 24 day interval between breeding

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Why is it important to watch for estrus behavior in cows that have already been bred?

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cows that display estrus behavior have not had a successful conception; they can be re-bred to increase the number of pregnancies by the post-breeding palpation check

What are the goals of estrus synchronization?

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-predetermine time of estrus
-predetermine time for breeding
-improve repro. efficiency
-improve production performance
-facilitate use of AI
-set up females in ET programs

What can disqualify a cow from estrogen synchronization?

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-static/inactive ovaries
-plasma progesterone so high that there is no cycling and/or signs of estrus

What are the two broad categories of estrogen synchronization protocols?

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-shorten the luteal phase with PGF2a
-extend luteal phase with P4

What are the characteristics of PGF protocols that shorten the luteal phase?

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-works in females with a mature CL
-estrus behavior occurs over a 2 to 5 day period
-timed AI will have poor conception rates
-AI + heat detection will have greater conception rates
-easy and cheap to administer
-main disadvantage is range of days of estrus

What causes the range in estrus days with a PGF protocol?

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the size of the follicle at the time of PGF administration

What is the injection schedule for PGF protocols?

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-1 or 2 injections
-2 injections creates greater synchrony
-if 2 injections, often given 2 weeks apart

What are the characteristics of P4 protocols that extend the luteal phase?

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-allow for follicular maturation, estrus, and ovulation to occur with fair synchrony once progesterone source is withdrawn
-mimics function of a CL
-natural luteolysis will occur
-can do CIDR intravaginally or MGA in the feed

What are the potential problems with progestins?

-poor fertility at post-withdrawal estrus, esp. with prolonged MGA treatment -oral progesterone must be consumed; can be difficult to track

What are the advantages of progestins?

-induce anestrus females to cycle -prevent early regression of first CL -better estrus synchrony -timed AI is more successful

How does the type of progestin determine length and invasiveness of protocol?

-MGA requires a longer protocol since first estrus has poor fertility; less handling of animals -CIDR has shorter protocol due no aged oocyte or need to skip an estrus; more handling of animals

What are the uses of GnRH?

-estrus synchronization -ovulation -treatment of cystic ovarian diseases

What is the ovsynch protocol?

-give GnRH on day 0 to start a new follicular wave -give PGF on day 7 to lyse the CL -give GnRH on day 9 to induce ovulation -breed about 16 hours after ovulation; +/- 4 hours

When is an ovsynch protocol started?

typically around 60 days post-partum

What are the characteristics of the ovsynch protocol?

-mainly used in dairy industry -all cows are bred (effectively 100% heat detection) -not all responding cows display estrus -not a total substitute to estrus detection -must handle animals multiple times -allows for timed AI

What are the advantages of artificial insemination?

-inexpensive access to male germ plasm -unlimited shipment, storage, and lifespan of sperm -better control of venereal dz -ability for reproduction in spite of physical problems or behavioral incompatibilities

What are the disadvantages of artificial insemination?

-lower per cycle pregnancy rates -need for accurate timing of insemination -decreased value of lesser males -special equipment and training required -problems surrounding timing of insemination, semen placement, nitrogen tank management, and semen handling

What is embryo transfer?

recovery of embryos from one female donor and transferring them directly into the uterus of surrogate recipients or preserving them through cryo-preservation for transfer at a later date

Why is embryo transfer important?

it allows for genetically superior females to have more calves per lifetime than she could naturally produce

What is the process for embryo transfer?

-identify superior donor cow -super-ovulate the donor cow -breed the donor cow -recover and evaluate embryos -transfer or freeze embryos

How are embryos frozen?

in glycerol or ethylene glycol

What are the characteristics of an appropriate embryo recipient cow?

-young -healthy -fertile -easy to handle

How are frozen embryos transferred into recipient cows?

direct thaw and transfer

What must be considered when transferring an embryo?

-must go on the same side as recipient cow's CL -must go much deeper than with AI

What are the characteristics of ultrasound-guided transvaginal aspiration of ova/in vitro fertilization?

-oocytes are aspirated from the ovaries and fertilized in the lab -resulting embryos are transferred into recipient cows

What are the characteristics of sexed semen?

-XX sperm has more DNA than XY sperm; allows for separation by sex -2 million sperm/straw -50-60% poorer conception rate -typically done in heifers; can now also do in cows -must be done with observed estrus

Lecture 4 Flashcards

(42 cards)