Mare Reproduction Physiology PDF

Lecture 1: Applied mare repro phys + mare breeding management ​ Be able to identify a mare in anestrus, transition, estrus, or diestrus based on behavioral, hormonal, or anatomical changes detected during reproductive exam -​ Equine estrus cycle: a)​ Estrus: 5-7...

Lecture 1: Applied mare repro phys + mare breeding management ​ Be able to identify a mare in anestrus, transition, estrus, or diestrus based on behavioral, hormonal, or anatomical changes detected during reproductive exam -​ Equine estrus cycle: a)​ Estrus: 5-7 days b)​ Diestrus 14-16 days c)​ Estrus + diestrus = 21 days long d)​ Ovulation = day 0 e)​ Estrus: -​ FSH high at the beginning of estrus (released from AP) -​ FSH induces follicular growth -​ Growing follicles produce estradiol and inhibin -​ Estradiol and inhibin inhibit FSH release -​ Large follicles grow on ovaries and produce estradiol, which induces sexual receptivity -​ Estradiol induces the peak of LH (AFTER ovulation in mare) -​ Ovulation occurs 1-2 days before the end of estrus (will still exhibit estrus behaviors for these 1-2 days) -​ LH reaches maximum concentration after ovulation f)​ Diestrus: -​ A corpus luteum forms after ovulation -​ The CL produces progesterone -​ Progesterone inhibits sexual receptivity -​ The endometrium releases PGF2a on day 14 -​ This lyses the CL and terminates diestrus → mare can go back into heat -​ Estrus detection: a)​ Teasing & vaginal exam -​ Method of estrus detection that evaluates the reaction of the mare to the stallion -​ Must use a physical barrier to ensure safety for humans and horse -​ Diestrus (not in heat) reactions: move away, hold ears back, switch tail, kick, bite, paw, vocalize  -​ Estrous behavior: approach stallion, remain calm, relaxed facial expression, raise tail, posture, urinate, wink, lean towards stallion -​ Requirements for mating: mare-stallion bond, peak of estrus, no distraction -​ Modern breeding practices: teased by unfamiliar stallion, no time or space for interaction, no intimacy, restraint associated with fear b)​ Ultrasound -​ Primary follicular wave: a)​ Emerges on day 9 (mid-diestrus) b)​ Results in ovulation c)​ All mares have primary waves d)​ Dominant follicles can exist during diestrus together with a CL e)​ Dominant follicle DOES NOT mean estrus !!! -​ Secondary follicular wave: a)​ Why we may see a follicle on US during diestrus b)​ Emerges around ovulation c)​ Dominant follicle usually regresses -​ A Mare’s Life: a)​ In between puberty and senescence, they have estrous cycles b)​ Cyclicity begins at puberty = 60-70% of adult body weight c)​ Ovarian activity ceases at 25 years old d)​ Estrous cycles are interrupted by 3 things: -​ Season: a)​ Goal: to give birth when weather conditions are optimal and food is abundant b)​ Horses are long-day breeders c)​ Birthing season = spring → d)​ 340 days gestation → e)​ Breeding season = spring f)​ Regulation of foaling season: -​ Longer gestation in early bred mares so foaling occurs in better weather conditions -​ Postpartum anestrus is longer in early bred mares g)​ How do they synchronize reproductive events with season: -​ Photoperiod *** (main cue) -​ Temperature a)​ High temperature induces the release of prolactin from the pituitary → b)​ Prolactin induces expression of LH and FSH receptors on the ovaries → c)​ The ovaries become more responsive to the increasing concentrations of LH and FSH -​ Nutrition h)​ Winter anestrus: -​ The pineal gland secretes melatonin during darkness -​ Melatonin inhibits GnRH secretion from the hypothalamus -​ Without GnRH, there is no FSH and LH -​ Without FSH and LH, there is no follicular growth or ovulation, which leads to no estrogen production and no estrous behavior -​ This lasts November to January i)​ Spring transition: -​ Light is detected by photoreceptors in the retina -​ Via sympathetic nerves, light inhibits melatonin synthesis -​ With more hours of light, there is less melatonin in spring -​ Decreased melatonin allows for reactivation of GnRH secretion  -​ With increase GnRH, FSH is released first -​ FSH induces initiation of follicular waves -​ Mares show estrous behavior and follicular growth, but no ovulation -​ After 3-4 waves, follicles produce enough estrogens to induce an LH peak -​ LH induces the first ovulation of the year -​ This occurs February to march (60 days) j)​ Breeding season: -​ From first to last ovulation of the year -​ April to october -​ First ovulation is usually on 1st week of April -​ Mare displays estrous cycles -​ Pregnancy -​ Lactation Lecture 2: Pharm control of reproduction (mare) | no doses or brand names required !!! ​ Design and discuss protocols to advance the onset of the breeding season, induce ovulation, and induce luteolysis -​ Natural breeding season: april to october-december -​ Artificial breeding season: a)​ February to june & fixed by a breed registry b)​ January 1st is the official birth date c)​ Early foals are more mature at sales or shows -​ Artificial lighting protocols: a)​ Earliest start is thanksgiving / december 1st → until spring b)​ 100 lux (light intensity) at the end of the day (9 hours after sunset is the photoreceptor period we aim for) c)​ 14.5 to 16 hours of light per day d)​ Average time to ovulation = 70 days -​ Regulating prolactin: a)​ Domperidone $$$, a Dopamine D2 antagonist b)​ Increased prolactin → increased LH/FSH follicular receptors c)​ Give medication daily (later in season) until ovulation -​ Progestagens: a)​ Suppress release of LH → huge surge of built up LH at ovulation b)​ Requirements: late transition & >20mm follicles c)​ Progesterone and altrenogest ONLY d)​ Give medication for 12-15 days → ovulations (12-15 days) -​ Advancing the breeding season summary: a)​ Response depends on time of year (December!) and ovarian activity b)​ Lighting programs are the most physiologic, consistent, and cost-effective  -​ Induction of ovulation: a)​ Synchronize ovulation with breeding b)​ Important with cooled or frozen semen c)​ Minimize matings/cycle (conserve stallion power and minimize endometritis) d)​ Induce via LH & GnRH !!! e)​ Exogenous LH: human chorionic gonadotropin (hCG) f)​ Endogenous LH: GnRH agonists (deslorelin) g)​ Give when follicle is at least 35mm or greater h)​ 80-90% of mares should begin ovulating in 24-48 hours (around 36) -​ Induction of luteolysis: a)​ Inducing luteolysis results in lysing of the corpus luteum via PGF2a b)​ “Short cycling” or shortening of diestrus c)​ Indications: -​ Save time after missed ovulations -​ Accommodate mares to the stallion’s book -​ Treat prolonged diestrus -​ Induce pregnancy loss (lyse CL within 30 days) d)​ Medications: -​ Dinoprost (natural PGF2a) & cloprostenol (analog/synthetic) -​ Conditions: presence of a CL for at least 5 days -​ Give med → estrus (2-5 days) → ovulation (7-10 days) ​ Diagnose and treat behavioral problems -​ Estrus-related complaints: a)​ Pain or sensitivity b)​ Performance or behavioral problems c)​ Stallion-like behavior -​ Truly estrus-related or… a)​ Submissive behavior b)​ Urogenital disease (pneumovagina, cystitis, sotones, urethritis) c)​ Ovarian pathology d)​ Some are truly estrus-related -​ Granulosa-theca cell tumor (GTCT):  a)​ Diagnosis: -​ Behavior -​ Rectal palpation: a)​ Benign, unilateral b)​ Round, large, smooth, no ovulation fossa c)​ Small, inactive contralateral ovary -​ Rectal US: -​ Hormone assays: a)​ Inhibin + Testosterone + AMH = 100% sensitivity !! b)​ Sensitivity: inhibin (80%), testosterone (48%), AMH (98%) c)​ Anti-mullerian hormone is produced by granulosa cells and is the first thing that goes up with a tumor b)​ Treatment: -​ Unilateral ovariectomy (remove ovary) a)​ Cyclicity in 2-16 months b)​ Regain normal fertility c)​ Rarely metastasizes or local invasion -​ Teratoma and dysgerminoma: a)​ Germ cell origin, unilateral, hormonally inactive b)​ Mares cycle normally c)​ Contain hair, cartilage, teeth, bone d)​ Teratoma = benign (good prognosis) e)​ Dysgerminoma = malignant -​ True estrus-related problems: a)​ Muscles relax and are less supportive b)​ Minor lameness becomes more evident c)​ Less cooperative or attentive d)​ Sensitivity around the ovaries e)​ Medications: -​ Progestagens: estrus suppressed for as long as they are administered; 3 days to suppress estrus; not always allowed f)​ Long-term solutions: -​ Immunocontraception: GnRH vaccine, GonaCon, effective for 2-5 years, USDA-approved for wild horses only -​ Ovariectomy Lecture 5: mare breeding soundness exam ​ Be able to discuss a mare BSE (steps, indications, and interpretation) -​ Notes: a)​ 60% of mares should be pregnant in 1 cycle b)​ Most mares should be pregnant within 2 estrous cycles c)​ BSE: series of diagnostic procedures to identify cause for subfertility, elaborate treatment plan, and give prognosis for fertility d)​ When to perform a BSE: fall or spring, after pregnancy loss, pre-purchase exam, prognosis for fertility e)​ Indications when in estrus: increased uterine defenses f)​ Diestrus indications: cervical function and endometrial glands atrophied g)​ Routine BSE: -​ Reproductive history: a)​ Mare identification and reproductive status b)​ Maiden = never bred c)​ Wet or foaling = nursing a foal d)​ Barren = faulted to conceive or maintain pregnancy -​ Physical exam a)​ Assess for extreme body condition scores as it impacts fertility and estrous cycles b)​ Obese animals are prone to endometritis and metabolic issues c)​ Ensure that the mare has no medical conditions that would put her welfare at risk like laminitis or MSK abnormalities because adding more weight with a pregnancy would be problematic d)​ Anatomic barriers to ascending infection into the sterile uterus: vulva, vestibulo-vaginal fold, and cervix e)​ Normal vulva conformation: >⅔ below ischium with a less than 10 degree angle directed down f)​ Vulvar discharges are abnormal in mares !! g)​ Cows in heat make a mucous discharge = normal h)​ Dogs have a bloody vulvar discharge in heat = normal i)​ Horses = DO NOT HAVE NORMAL DISCHARGE -​ Rectal palpation and US a)​ Rule out pregnancy b)​ Determine stage of the estrous cycle c)​ Detect physical abnormalities (size, location, tone, symmetry, contents) d)​ Do this BEFORE a vaginal or uterine exam !! e)​ Corpus luteum is NOT PALPABLE f)​ Corpus hemorrhagicum IS PALPABLE g)​ Mares do not have an ovarian bursa -​ Vaginoscopy and palpation (vaginal exam) a)​ Evaluate the integrity of the mucosa and structures b)​ Evaluate exudate, urine, or air c)​ Determine stage of the estrous cycle d)​ Cervical lacerations: -​ Inability to close → repeated ascending infection -​ Inability to open → delayed clearing of infection -​ Uterine culture and cytology a)​ Collect during estrus b)​ Guarded swabs or low volume lavage c)​ Aerobic culture and sensitivity d)​ Uterine isolates: NO NORMAL RESIDENT FLORA e)​ Goals of bacterial culture: -​ Screen for venereal endometritis a)​ Klebsiella pneumonia type 1, 2, or 5 b)​ Pseudomonas aeruginosa c)​ Taylorella equigenitalis (CEM) -​ Screen for ascending endometritis a)​ Streptococcus zooepidemicus b)​ Escherichia coli -​ Uterine biopsy a)​ Goals: -​ Determine presence and extent of endometrial degenerative changes and inflammatory changes -​ Endometrium superficial sample = mucosa + submucosa -​ Prognosis for fertility b)​ Endometrial function: -​ Prostaglandin production -​ Histotrophic nutrition (uterine milk from endometrial glands) -​ Hemotrophic nutrition (uterine and allantoic circulation) c)​ Kenney-Doig System: -​ Glandular degeneration: a)​ Periglandular fibrosis b)​ Cystic dilation c)​ Atrophy d)​ Nesting -​ Dilated lymphatics -​ Inflammation Lecture 8: mare infertility ​ Know causes, effects on fertility, diagnosis, treatment, and prognosis of endometritis, pneumovagina, urovagina, endometriosis, and endometrial cysts -​ Uterine defense mechanisms: a)​ Immune system: neutrophils, IgA, IgG b)​ Anatomical barriers: vulva, vestibulo-vaginal junction, cervix c)​ Physical clearance: myometrial contractions, cervical relaxation, uterine position, lymphatic drainage -​ Definitions: a)​ Endometritis: infection of the endometrium of the uterus (superficial) b)​ Metritis: uterine infection of endo and myometrium c)​ Perimetritis: uterine infection of the serosa d)​ Pyometra: purulent exudate in uterus -​ Endometritis: a)​ Main cause of infertility !!! b)​ 3rd most common medical problem after colic and respiratory disease c)​ Forms of endometritis: breeding-induced (BIE), chronic bacterial, venereal, and chronic degenerative -​ BIE: a)​ Sperm transport to oviduct complete in 4 hours → b)​ Residual sperm induce inflammatory response in all mares (peaks at 6 hours and resolves in 24 hours) → c)​ Failure to evacuate uterine contents leads to breeding-induced endometritis (BIE) d)​ Clinical diagnosis: -​ Multiparous, older mares -​ Failure to conceive or embryonic loss -​ Intrauterine fluid >24 hours after breeding e)​ Treatment: -​ Minimize inflammation (breed once / estrous cycle) -​ Evacuate uterine contents via uterine lavage and ecbolics a)​ Uterine lavage: -​ Sterile fluid to flush uterus until clear (for about 2-3 days, up to 5) -​ How soon after breeding would you start lavaging a mare’s uterus → 4 hours (earliest) !!! -​ Remove residual sperm and inflammatory products -​ Stimulate uterine contractions -​ Recruit fresh neutrophils and opsonins  b)​ Ecbolic drugs: -​ Oxytocin: a)​ Induce contractions for about 20-50 minutes b)​ Short action, so repeat every 2-6 hours -​ PGF2a: a)​ Induce contractions for 2-4 hours b)​ SID or BID c)​ Use before ovulation -​ Chronic bacterial endometritis: a)​ Contamination during mating or ascending infection from self-contamination b)​ Poor vulvar conformation: -​ Causes: conformation, age and parity, poor body condition, trauma -​ Consequences: pneumovagina, urovagina, fecal contamination, ascending endometritis, ascending placentitis c)​ Diagnosis: -​ May have mucopurulent discharge -​ May have uterine fluid -​ Culture → streptococcus zooepidemicus -​ Biopsy gives definitive diagnosis d)​ Treatment: -​ Physically remove uterine contents -​ Control bacterial growth -​ Restore homeostasis of immune system -​ Restore anatomical barriers -​ Can give intrauterine* or systemic antibiotics -​ DO NOT USE INTRAUTERINE ENROFLOXACIN because it has a very basic pH, so that will wipe off the endometrium (severe damage), but can give it IV or orally -​ Intrauterine infusions: 60 to 100 mL daily for 3-5 days during estrus -​ Modulation of the immune system: a)​ NSAIDs prevent release of PGF2a which is needed for ovulation so if you do give, do so prior to ovulation to risk not ovulating -​ Sexually transmitted endometritis (venereal): a)​ Asymptomatic in the stallion, so diagnosis usually comes from the mare  b)​ Transmitted from stallion to mare, stallion to stallion, mare to foal c)​ Can be transmitted from the phantom dummies, so make sure you clean them properly d)​ Taylorella equigenitalis (contagious equine metritis)= REPORTABLE -​ CEM testing: culture clitoris, endometrium, and cervix on days 1, 4, and 7; amies charcoal refrigerated; complement fixation; biological test, PCR e)​ Pseudomonas aeruginosa f)​ Klebsiella pneumoniae -​ Pneumovagina and Pneumometra: a)​ “Wind sucking” b)​ Aspiration of air into vagina and uterus c)​ Appears as white speckles on radiographs -​ Urovagina and Urometra: a)​ “Urine pooling” / accumulation of urine in vagina and uterus b)​ Predisposing factors: pneumovagina, pregnancy, post-partum, estrus, inadequate caslick’s suture, urinary tract disorders  c)​ Chemical and bacterial endometritis: decrease sperm and embryo viability d)​ Treatment: surgical correction, pre and post-breeding uterine lavage, and ecbolics -​ Endometriosis: a)​ Chronic degenerative condition b)​ Periglandular or subepithelial fibrosis** (hallmark) c)​ Common in older mares d)​ Irreversible and untreatable e)​ Pregnancy loss due to glandular and epithelial dysfunction f)​ Diagnosis: uterine biopsy -​ Endometrial cysts: a)​ Single or multiple b)​ Glandular (secondary to fibrosis, not visible grossly) c)​ Lymphatic (lymphangiectasia = dilated lymph channels) d)​ May look like an embryo e)​ Conception occurs → pregnancy loss < 90 days f)​ Treatment: laser ablation, hypertonic saline infusion, mechanical curettage, aspiration Lecture 12: equine obstetrics ​ Normal Foaling -​ Gestation length: 320-360 days (mean 340 days) -​ Pre-partum changes: a)​ Udder enlargement 4-6 weeks before b)​ Lactation 2-14 days before c)​ Colostrum in teats 24-48 hours before d)​ Waxing (dried colostrum in teats) 6-72 hours before -​ Milk electrolytes and pH: a)​ Calcium >200 ppm → 70% foaling within 24 hours and 98% within 72 hrs b)​ pH < 6.4 → 56% foaling within 24 hrs and 98% within 72 hours -​ Normal foaling stages: a)​ Stage 1: preparatory phase -​ Signs: sweating, restlessness, colic, spontaneous milking -​ Events: uterine contractions, pelvic and cervical relaxation, fetal repositioning -​ 50 minutes (30 minutes to 6 hours) b)​ Stage 2: fetal expulsion -​ Normal fetal disposition during expulsion: a)​ Anterior longitudinal presentation b)​ Dorso-sacral position c)​ Extended posture -​ Rupture of chorioallantoic membrane indicates stage 2 beginning  -​ Stage 2 lasts about 10-40 minutes (20 minute average) c)​ Stage 3: expulsion of fetal membranes -​ 15 minutes to 3 hours (60 minute average) ​ Dystocia -​ 4 to 10% of foalings resulting from abnormal posture -​ Premature placental separation or “red bag” -​ Identifying a dystocia: a)​ No fetal parts or amnion in the vulva 5 minutes after rupture of chorioallantois b)​ No progress 10 minutes after amnion or fetal parts in the vulva c)​ Soles of hooves up: caudal presentation & dorso-pubic position d)​ Abnormal combination of fetal parts in the vulva -​ Obstetrical exam: a)​ Assess: mare stability, dilated cervix, intact birth canal, fetus appearance, is the fetus alive, is the fetus too big b)​ Goals: deliver the foal & preserve the mare’s fertility -​ Management of dystocia: a)​ Assisted vaginal delivery: -​ Conscious mare, standing or lateral recumbency, for minor correction of posture b)​ Controlled vaginal delivery: -​ Under GA, dorsal recumbency, elevated hindquarters -​ Indications: minor corrections of posture, position, or presentation & decreased abdominal contractions c)​ Partial fetotomy: -​ 1 or 2 cuts with general anesthesia if straining -​ Indications: birth canal in good condition, dead fetus, flexions d)​ C-section -​ Prognosis: a)​ Foal survival: 2 hours → 30% & 7 hours → 5% b)​ Mare: -​ Survival: 80-90% -​ Complications: 30% -​ Foaling rate: 60-80% Lecture 14: postpartum mare ​ Postpartum mare -​ Goals of breeding operation: a)​ Produce one foal per mare per year b)​ Produce early foals c)​ 25 days to get the mare pregnant -​ Puerperium: a)​ Period from parturition to reinitiation of normal reproductive activity (postpartum) b)​ Uterine involution: -​Decrease in uterine size (uterus palpable in 3 days) -​Expulsion of loquia (vaginal discharge for 6 days, brownish bloody) c)​ Restoration of hypothalamic-pituitary function: -​ FSH peak at foaling → estrus 5-12 days post foaling (foal heat) -​ Breed in foal heat if normal parturition, normal puerperium, normal uterine involution d)​ Reinitiation of ovarian activity ​ Postpartum emergencies -​ List: colic, depression/inappetence, abnormal vulvar discharge, +/- endotoxemia, +/- cardiovascular shock -​ Retained fetal membranes: a)​ Failure to expel within 3 hours b)​ Risk factors: >15 years old, draft breed, dystocia, placentitis, fescue toxicosis c)​ Pathophysiology: adhesions, edema, hormones, weakness, inbreeding d)​ 2-10% e)​ Partial retention: usually breaks at tip of the horns f)​ Treatment goals: -​ Non-traumatic expulsion of the placenta: a)​ Oxytocin, distention of the allantoic cavity (Burns technique), uterine lavage, manual extraction, exercise b)​ Oxytocin: bolus, slow IV drip, every 2-6 hours until expulsion -​ Prevent complications -​ Tetanus prophylaxis -​ Toxic metritis: a)​ Bacterial contamination → metritis → septicemia/endotoxemia → laminitis b)​ Clinical signs: fever, depression, anorexia, tachycardia, tachypnea, injected mucous membranes, vulvar discharge (brown-yellow) c)​ Goals of treatment: control bacterial growth, evacuate uterine contents, prevent complications d)​ Treatment: -​ Postpartum hemorrhage: a)​ Arterial rupture: middle uterine, utero-ovarian, external iliac, vaginal, adrenal b)​ Bleeding into: broad ligament, uterine wall, uterine lumen, peritoneal cavity c)​ 40% of deaths in peri-partum mares (older multiparous) d)​ Diagnosis: pale, shock, painful, violent, active bleeding from vulva sometimes visible, palpate broad ligaments and feel hematoma -​ Hemoperitoneum: a)​ Treatment: -​ Restore cardiovascular volume via fluids or blood transfusion -​ Provide hemostasis via aminocaproic acid, 10% formalin, yunnan baiyao -​ Provide analgesia and sedation via flunixin, butorphanol, xylazine, detomidine, some people use acepromazine -​ Provide antimicrobial prophylaxis -​ Snowflake effect on ultrasound indicates active bleeding b)​ Complications: exsanguination (draining of blood in the body), death, abscessation, peritonitis, adhesions -​ Uterine prolapse: a)​ Secondary to abortion, dystocia, retained fetal membranes, lacerations b)​ Complications: uterine artery rupture, uterine rupture, metritis, rectal prolapse, incarceration of viscera c)​ Treatment: supportive therapy, repositioning***, oxytocin, caslick’s suture, fecal softeners for 3-5 days, treat metritis d)​ More common in cows than horses