Therio - Bovine - Estrous Synchronization & AI

drraythe's version from 2017-09-10 03:47


Question Answer
What is F-TAI?Fixed-time AI
Do PGF2α –based programs affect the luteal or the follicular phases?LUTEAL bc prostaglandins rupture the CL (CL must be present for this to work, CL is in luteal phase)
Do Progestagen-based programs affect the luteal or the follicular phase?(Artificial progesterone!) LUTEAL bc inhibits LH & GnRH to keep diestrus going on suppress estrus so that when removed, whole heard starts at same time
Do GnRH-based programs affect the luteal or the follicular phases?FOLLICULAR (stim follicles to develop)
How long is the bovine gestation period?About 280 days (9mo...cows are people)
How long is the voluntary waiting period usually, & what purpose does it serve?Usually 45-70 days, allows the cow time to recover before becoming preg again
In beef systems, who breeds 1st- cow or heifer?Heifer- 1st time, needs more time to conceive
When will PGF2α- based programs not work?(These cz luteolysis of the CL, so..) If in luteal phase, WONT work if there is no CL or the CL isn't ready (after ovulation it will respond), also wont work if she's in the follicular phase (pro/es)
If cow is responsive to the PGF2α- based program she’ll come into estrus in 2-5 days after Injxn…. Why?Lysing CL signals end of diestrus, & destroying the thing that makes progesterone → rapid decline in progesterone → ceases inhibiting the GnRH/LH which allows the follicles which have matured during follicular waves to be stimulated by the LH & cz estrus/ovulation soon after → NOTE: there is a range (2-5 days) bc it depends on the follicular wave cycle if the follicle is immediately ready or needs a bit more time to mature
What are follicular waves? Why do they occur?Progesterone inhibits LH & GnRH, but does not inhibit SMALL amts of FSH from coming & allowing follicles to mature to a certain point (& produce low levels of estrogen). Therefore, during diestrus follicles are still maturing but then regressing w/ no stimulation, waiting for luteolysis so that they are not inhibited by the progesterone, so that they may get bigger & produce enough estrogen to trigger an LH surge
What percentage of cycling cows in a herd should respond to a single PGF2α Injxn?cycle is 21 days, & diestrus is about 12 days, so 12/21 days the cow will be responsive (since it works in diestrus), so 12/21 = 0.57 aka 57% of herd is likely to be in diestrus.
What is the benefit of having a PGF2α program where there are 2 Injxns, 11-14 days apart? Why that time gap?Then all cows that didn’t respond to the 1st Injxn will have a CL that’s btwn 6-17days old at the time of the 2nd Injxn. & all cows that responded to the 1st Injxn will have a CL that’s about 11-12 days old. Then you give the 2nd Injxn, & both groups get their CLs lysed, then going into heat all together around 48-72 hr
How would you go about AIing cows treated on a PGF2α- based program?Heat detection & AI using am-pm rule (F-TAI not recc)
(Not sure if important) what is the natural PGF2α you can use to synch? How does the synth differ from it?Dinoprost (Lutalyse). Synths are more potent, so need to use less than the natural
(Not sure if important) what are the synthetic PGF2α drugs?(More potent!) Cloprostenol (Estrumate®, Prostamate®) & Luprostenol (Prosolvin®)
What are the 2 different ways you can do the PGF2α program?(1) Option 1: After 1st Injxn, estrus detection & breeding. Any cows that are not bred, are given a 2nd Injxn 11-14 days later & bred
(2) Option 2: Only do estrus detection & breed after 2nd Injxn
Progestagen-based programs → how does this program work?Exogenous progestagen mimics the endogenous progesterone supplied by the CL (inhibits LH, which prevents the ovulation). Then, when exogenous source removed, cow ovulates & starts cycling again
How are progestagen based programs administered to the cows?Can be:
(1) Orally: Melengestrol acetate (MGA)
(2) Per vaginum: CIDR
(3) Subcutaneously: Crestar
What is the optimal period to supplement exogenous progestagen?>14 days: get aged oocyte w/ decreasing fertility
< 14 days: may not get regression of the endogenous CL, therefore, use w/ PGF (day 14 is near the end of diestrus)
What is ONLY approved by FDA for estrus suppression in heifers?Melengestrol acetate (MGA)
Explain how Melengestrol acetate (MGA) is used (what is it?)This is a exogenous progestagen (progesterone) which is supplemented orally, & can be given in a premix w/ food. Used for estrus SUPPRESSION IT can also Can be used in combo w/ PGF2α to synchronize estrus
How does PGF2α affect estrus? How does Progestagen affect estrus?PGF2α is a prostaglandin & works by lysing the CL & starting the estrus cycle. Progestagen is an exogenous progesterone, meaning that it suppresses estrus by maintaining diestrus. This 1 works by when you stop giving it to all the cattle, they all have dec progesterone → inc GnRH → inc LH → LH surge → ovulation at the same time
What is CIDR? How does it work?Controlled Internal Drug Release Is a progestagen, which is inserted intravaginally, & is left in place for 7 days. Then, PGF2α given the day before implant removal. This assures that the cows are in diestrus & then go into heat at the same time when the PGF2α is injected czs luteolysis (remove implant & watch for heat after Injxn)
What is Crestar? How does it work?(Progestagen program) Placed SQ behind the ear
How do GnRH-based programs work?GnRH czs release of LH from adenohyophysis → Czs ovulation or luteinization of the most dominant follicle (even in the presence of high progesterone) → Induces a new follicular wave → Therefore, 7 days later, there is luteal tissue present to respond to PGF2α (as well as old CL if present) (~so basically, makes sure there is a CL no matter what which you can then lyse w/ PGF2Α) → THEN, 2nd GnRH Injxn czs ovulation of the dominant follicle → Can use F-TAI 8-18h later
Which program can you use w/ F-TAI w/?GnRH based programs
What is ovsynch? How does it work?GnRH based program → no estrus monitoring required so can use F-TAI (8-18h after 2nd GnRH). Start w/ 1 Injxn of GnRH to induce ovulation OR luteinization, as well as induce a new follicular wave. 7 days later, give a shot of PGF2α to cz luteolysis. Then 2 days later, inject another GnRH, which induces ovulation. The next day you can go F-TAI
How does SelectSynch work?GnRH based program → GnRH Injxn, 7 days later PGF Injxn → Estrus detection starts 24-48h before PGF Injxn & continues for 5-7 days (go figure, "select" is less accurate w/ no F-TAI)
How does weaning affect the cattle's cycle?In beef cattle, temporarily removal of calves for 48h results in increased LH release & the cow comes into estrus w/in a few days


Question Answer
Bulls that are selected to be AI sires are kept where?"Bull stations" (little individual cages)
What are some ways bull semen is collected?An artificial vagina (AV) w/ liner
What are some things needed for semen extender?Energy source (Glucose, lactose, fructose...)
Buffers aka TRIS, surfactants, ABx (like Ticarcillin, Tylosin, Gentamicin)
Cold shock protectants (like Lipoproteins, especially from egg yolk & skim milk)
Cryoprotectant for freezing (glycerol, DMSO)
After semen extender is added to the collected semen, what do you do w/ it?Put it in "straws"(Generally 0.25ml or 0.5ml French straws) w/ a Cotton plug on 1 end, colored plug/heat sealed at the other end, & then freeze it
(Not sure if important) How are the AI straws labeled?ID of bull, ID of AI center, CSS (Certified semen services), Breed registration #, Batch number, date
How many straws are needed for a cow?1 straw = 1 cow
How are the semen straws stored?Semen frozen & stored in liquid nitrogen!
Progeny Testing is what, & why do we do it?Wait for calf from that bulls semen to grow up & see how it performs in areas like milk production, milk composition, calving difficulty, as well as Structural soundness & conformation (Udder conformation, Udder attachment, feet & legs)
What are some pathogens which can be Xmitted in semen?Tritrichomona fetus
Campylobacter fetus subsp. Venerealis
FMD, etc..
Who uses AI more- beef or dairy cattle industry?Dairy
Liquid nitrogen safetyALWAYS wear cryoprotectant gloves & eye goggles! Liquid nitrogen can cz severe burns & damage to the cornea. Always insert objects into liquid nitrogen SLOWLY to prevent boiling & splashing. Can cz asphyxiation, so never transport in a closed vehicle.
If you are looking to ID the straw in the nitrogen tank, where should you NOT move the straw?DO NOT lift the semen above the FROST LINE (where the frost stops) (Any temperature fluctuation will result in thawing & then refreezing of semen, which will result in damage)
How do you thaw the straw if you wish to use it?Remove correct straw & thaw it in a water bath at 35-37°C (95-98.6°F) for 30 sec (can be a bit longer)
BEFORE you use the straw for anything, once is has been thawed, what MUST you do?WIPE IT DRY FROM ITS BATH - water is spermicidal (dont wipe too much or youll warm it up too much though)
How much you cut the semen straw?1 cm above end of insemination pipette, & MUST be at a 90* angle or the semen will come out
Why do we care about breeding sheaths? What can also help w/ the issue this addresses?Dz control, you can also add a sanitary sleeve over the breeding sheath to help prevent contamination. (Insemination gun is pushed through sleeve when it reaches the cervix, therefore preventing uterine contamination)
How should you transport a loaded AI gun?Keep safe & warm in your clothing
When’s the best time to inseminate?AM PM RULE If cow is seen standing in the morning, she is inseminated in the afternoon & vice versa
When does ovulation occur?12h after estrus
What conduct should you absolutely avoid w/ the semen?SEMEN IS SENSITIVE!! Avoid temp fluctuation (like pulling above frost line & then dropping back down), or excessive rubbing which can warm the straw, or letting it cool in the gun before AI. Thoroughly dry straw. DONT cut straw at an angle. Dont let too much time pass btwn thawing & AI
WHERE/how do you gun the semen into the female?In the uterine BODY (not horns) & do so slowly!

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