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Theriogenology > Equine Breeding Management > Flashcards

Equine Breeding Management Flashcards

1
Q

What is the goal birthdate of racehorses? How is this most commonly reached?

A

January 1st

advance transitional or ovulatory periods from April to February to have mares pregnancy by February or March (~340 days of gestation)

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2
Q

How is photoperiod manipulated to get mares to delivery around January 1st? In what 2 ways is this done?

A

put mares under lights by December 1st

  1. stall - 16 hours of light (in effect by 60-70 days) or skeletal light exposure for 1-2 hours beginning 8-9.5 hours after the onset of darkness
  2. light mask - blue light directed in one eye for horses on pasture (Equilume)
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3
Q

What are 4 options for medically managing seasonal anestrus in horses?

A
  1. GnRH - administer BID-TID (response related to follicle size)
  2. hCG - induces large follicles to ovulate by mimicking an LH surge
  3. progesterone/progestin - synchronization, decreases LH (controversial)
  4. dopamine antagonists (Domperidone, Supriride)- increases plasma prolactin, acting directly on the ovary
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4
Q

What pre-treatment can potentiate dopamine antagonists effects?

A

estradiol

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5
Q

What are the 3 hormone treatments used to manipulate cycling mares? When are they used?

A
  1. PGF2a - 5-14 days after ovulation; induces luteolysis with missed insemination (will cause abortion in pregnant mares)
  2. GnRH. hCG - 20 days after ovulation; stimulates natural LH surge to induce an early round of ovulation
  3. PGF2a/oxytocin - evacuates fluid from endometritis and causes smooth muscle contraction
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6
Q

How is short-cycling performed in mares? What are the 2 most common options used? What timing is required?

A

use of luteolytic PGF2a to terminate the luteal phase before the normal release of endometrial PGF2a

  1. Dinoprost
  2. Clopostenol

> 5 days after ovulation - mare will be insensitive to a single dose any earlier while in early diestrus, but can still affect luteal function

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7
Q

What are 3 potential side effects to short cycling mares? How are the medications given?

A
  1. transient sweating
  2. abdominal cramping - SM contraction, looks like colic but is transient
  3. diarrhea

IM ONLY - VERY sensitive to IV due to reliance of systemic circulation to get PGF2a to the ovaries

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8
Q

What is required for inducing ovulation in mares? What are 2 options? When do each induce ovulation?

A

estrual mare with a follicle >30 mm diameter (large enough to ovulate)

  1. GnRH agonists (Deslorelin) - 40-42 hours
  2. hCG (LH-like action) - 36 hours, but has a larger average range —> not preferred
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9
Q

What is a possible side effect of using hCG to induce ovulation in mares?

A

human product may cause antibody formation that decreases effectiveness/efficiency

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10
Q

What 2 embolics can be used to manipulate equine estrous cycles? Why are they used?

A
  1. PGF2a - facilitate uterine clearance by stimulating myometrial contractions (Cloprostenol preferred due to longer half-life and less side effects)
  2. oxytocin - stimulates uterine smooth muscle contractions to evacuate uterine fluid (shorter half-life, 10-20 IU given SID-TID)
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11
Q

What 3 diseases are tested for before breeding horses?

A
  1. EIA
  2. Contagious equine metritis (CEM)
  3. EVA

(all can cause abortion!)

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12
Q

What are 2 options for natural cover breeding? What equipment is commonly used?

A
  1. bred on 2nd or 3rd day of estrus
  2. mated every other day until the mare is no longer receptive to the stallion

twitch, protective capes, neck apron, leg strap, Hobbles, kick boots, tail wrap, ovulation induction agent

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13
Q

What breed of horse only has one allowed way of assisted breeding? What is done?

A

Thoroughbred

reinforcement breeding - natural cover + aspiration of semen left in cranial vagina and insemination into uterus

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14
Q

Why is AI commonly performed for equine breeding programs?

A
  • safety for stallions, mares, and personnel
  • allows in-depth stallion management
  • can pick from different mares
  • allows horses for different regions to be used easily
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15
Q

What is the goal of using shipped-cooled semen for equine AI? What dose is used? When will managed ovulation occur?

A

one breeding per cycle

at least 500 million motile sperm cells (more if available!) - similar pregnancy rates compared to natural cover and fresh semen AI

within 24-48 hours after AI —> important for timing of semen delivery

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16
Q

How is shipped-cooled semen prepared before AI?

A
  • diluted with semen extender to 25-50 million sperm/mL
  • cooling rate of -0.3 C/min —> no need to warm before, used to minimize metabolic rate to keep sperm alive longer
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17
Q

What is the best timing for delivering shipped-cooled semen? What 2 options for inducing ovulation and their pros/cons?

A

inform stud farm when the mare is in estrus (>30 mm follicle) to shep extended semen overnight or counter-to-counter

  1. breed and then induce with hCG or Deslorelin - semen is confirmed, but mare may not ovulate within 40 hours and sperm will not last, requiring more sperm from stud far
  2. induce ovulation a day before AI - gives sperm more time, but sperm may not be able to be collected and the mare will have to be short cycled to start again

(expected 85-90% ovulation within 48 hours!)

18
Q

In what 2 ways does frozen semen differ compared to shipped-cooled semen?

A
  1. more variable pregnancy rates - mare tends to react more poorly to this type of semen and endometritis is more common
  2. lower minimum dose of 250 million motile sperm cells - more valuable stallions tend to have their sperm frozen, so there is a pressure to use the least amount possible
19
Q

What are 2 options of protocol for AI with frozen semen? What way of insemination is preferred?

A
  1. one AI within 4-6 hours post-ovulation
  2. two AIs 12-16 hours apart with ovulation occurring between

transrectal-guided deep horn insemination - ensures the smaller (more valuable) dose has less distance to reach oocytes

20
Q

What timing is preferred for AI with frozen semen? What should be done if ovulation is or isn’t detected?

A

mare in estrus (follicle >30 mm) —> induce ovulation at 4 PM and then perform first AI 24-30 hours after induction (4PM-10PM)

  • 8 AM ovulation detected = second AI 40 hours after induction (8AM)
  • 8 AM no ovulation = keep checking periodically and second AI after ovulation

(no risk of delayed shipment, already on site)

21
Q

What are 2 recommendations for managing frozen semen for AI?

A
  1. higher doses per insemination
  2. at least 2 inseminations per cycle - one before and one after ovulation
22
Q

What is considered a “problem” mare?

A
  • abnormal estrous cycles
  • fails to conceive for more than 3 cycles in one season
  • early pregnancy loss within 60 days

(don’t forget the stallion!)

23
Q

What is physiologic endometritis? Pathologic?

A

immune response to eliminate seminal plasma, excess sperm, microorganisms, and debris following breeding

becomes uncontrolled and reduces fertility

24
Q

What signs are associated with endometritis? What cases require treatment?

A

typically indistinguishable +/- microorganisms in samples

excessive accumulation of PMNs and intraluminal fluid in the uterus

25
Q

What are the 4 most common bacterial pathogens that cause endometritis? What are 2 other causes? What can cause resistance to treatment?

A
  1. E. coli
  2. Streptococcus equi zooepidemicus
  3. Klebsiella pneumoniae
  4. Pseudomonas aeruginosa

Enterobacter, Proteus

biofilm formation

26
Q

What are some fungal causes of endometritis?

A
  • Aspergillus
  • Candida albicans
  • Mucor

typically secondary infections or caused by repeated/prolonged antibiotics usage that disrupts normal flora

27
Q

What is persistent mating-induced endometritis (PMIE)? When are mares considered susceptible or resistant?

A

mare is unable to control inflammatory response in uterus following mating

  • SUSCEPTIBLE = neutrophilia and upregulation of proinflammatory cytokines 24 hours following mating
  • RESISTANT = mare expresses higher levels of anti-inflammatory cytokines (IL10, IL6) within 6 hours of breeding
28
Q

What are 2 options for clearing uterine fluids in cases of endometritis?

A
  1. ECBOLICS - oxytocin (can be used alone with <2cm of hypoechoic fluid), PGF2a —> 4 hours after insemination until 5 days post ovulation —> any later = luteolysis and pushing of embryo out of uterus
  2. LAVAGE - crystalloids (LRS, 0.9% saline) to dilute contamination
29
Q

What antibiotic and antifungal therapies are recommended for endometritis?

A

ANTIBACTERIAL - systemic tx or intrauterine infusions based on C&S

ANTIFUNGAL - empirical intrauterine or systemic tx based on isolation and susceptibility and evidence on cytology

30
Q

What are 7 other options for endometritis treatment?

A
  1. antiseptics/disinfectants - diluted betadine, H2O2, vinegar
  2. chelators - Tris-EDTA
  3. mucolytics - N-acetylcysteine
  4. free radical scavenger - DMSO
  5. immunomodulation - NSAIDs, glucocorticoids, immunotimulats
  6. platelet-rich plasma
  7. stem cells
31
Q

What are the 2 major options for preventing endometritis in mares?

A
  1. good breeding management
  2. repair defects of external genitalia - Caslick’s valvuloplasty, perineal body repair, urethral extension (urine pooling)
32
Q

How is Caslick’s vulvoplasty performed? How must it be managed in breeding mares?

A
  • local anesthetic bottom to top - residual effect of Lidocaine as injections are given
  • remove 0.5 cm strips at the mucocutaneous junction at each labium with scissors
  • suture dorsal labia with a simple continuous (interlocking)

remove sutures before foaling + will likely need to be done yearly as too much tissue cannot be taken at once

33
Q

What is a persistent hymen in horses? How is it treated depending on thickness?

A

membranous fold at the vestibulovaginal junction allows for fluid accumulation cranially due to blocked outflow during estrus

  • THIN = disrupt it with a finger or blunt-tipped instrument
  • THICK = grasp hymen near its center and pull outward to evert it and incise
34
Q

What is old maiden mare syndrome?

A

Sport or Warmblood mares are typically not presented to be bred until their racing career is over (15-20 y/o), so it is common for their cervix to be abnormally tight, resulting in a higher susceptibility to post-breeding endometritis

cervix fails to relax during estrus = fluid accumulation aggravated after breeding, poor lymphatic drainage, and impaired myometrial contraction

35
Q

What is seen on endometrial biopsy in cases of old maiden mare syndrome? How is it treated?

A

glandular degenerative changes

lavage, antibiotics, etc.

36
Q

What are the 2 most common origins of uterine cysts? In what 3 ways can they have negative effects on fertility?

A

glandular (<10mm) or lymphatic (larger)

  1. prevention of embryo migration - interferes with maternal recognition
  2. interference with early embryonic histotroph absorption - cysts block gland outflow
  3. interference with placentation
37
Q

What can uterine cysts be mistaken for? How are they differentiated? What treatments are recommended?

A

embryonic vesicle - map location of cysts prior to breeding

  • snare
  • laser hysteroscpy
  • loop cautery
  • uterine biopsy removal
  • must remove stalk, if only ruptures it will return
38
Q

How does pyometra compare in horses? What is a common cause?

A

NOT just a diestral disease with an active CL —> some mares have normal, regular cyclic ovarian activity with no systemic illness

impaired ability to eliminate exudate due to cervical adhesions or an abnormally constricted, torturous, or irregular cervix

39
Q

How does pyometra affect equine fertility? How is it treated?

A

poor future fertility

  • repeated large-volume lavage
  • PGF2a, oxytocin
  • antibiotics
  • anti-inflammatories
  • hysterectomy if a cervical issue
40
Q

What is the most common ovarian tumor in mares? What are the 3 most common signs?

A

granulosa-theca cell tumor (GTCT)

  1. testosterone secretion = stallion-like behavior
  2. inhibit secretion = persistent anestrus
  3. heterogenous, honeycomb appearance of the affected ovary with a small, inactive contralateral ovary
41
Q

What 4 hormone analyses are used to diagnose GTCTs? What treatment is required?

A
  1. AMH - elevated (98%)
  2. inhibin - elevated (90%)
  3. testosterone - elevated (50%)
  4. progesterone - <0.25 ng/mL = absent luteal tissue

surgical removal + confirmation with histopath

42
Q

What is gonadal dysgenesis? What are 5 signs? How is it diagnosed?

A

Turner’s syndrome where mares are born with one X chromosome (63, XO - most common DSD in mares)

  1. infertile mare with irregular, or absent estrous cycles
  2. small stature
  3. bilaterally small ovaries
  4. small, flaccid uterus
  5. endometrial gland hypoplasia

kryotyping

Theriogenology (22 decks)

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