ARTIFICIAL PHOTOPERIOD

• The average date of the first ovulation of the year in mares maintained under ambient light conditions is MID-APRIL TO EARLY MAY in North America
• Provision of a stimulatory artificial photoperiod is used to advance the date of the FIRST OVULATION OF THE YEAR
• The artificial photoperiod should begin on or about DECEMBER 1
• Approximately 60 TO 70 DAYS of an artificial photoperiod is necessary to stimulate ovulation; if the artificial photoperiod is applied appropriately, mares should ovulate by early to mid-February
• A minimum of 10 FOOT-CANDLES OF LIGHT are recommended; this may be achieved by use of a 100 or 200 watt light bulb in a 12 x 12 foot box stall
• INCANDESCENT OR FLUORESCENT LIGHTS are both effective
• Automatic timers may be used to turn the lights ON AT DUSK AND OFF AT 11:00 PM
• Mares should be allowed an 8 HOUR PERIOD OF DARKNESS; providing 24 hours of light is less effective
• Maintain the artificial photoperiod until at least APRIL 1 or mares may revert back into anestrus
• Late-term pregnant mares due to foal in January, February or March may be housed ‘UNDER LIGHTS’ to help ensure that they cycle after foaling and not experience post-partum anestrus

STIMULATION OF FOLLICULAR DEVELOPMENT IN TRANSITIONAL MARES

• Mares in DEEP SEASONAL ANESTRUS have ovarian follicles less than 20 mm in diameter
• TRANSITIONAL MARES have one or more ovarian follicles greater than 20 mm in diameter
• Mares may remain in transition for SEVERAL WEEKS
• Administration of LOWLOSE DESLORELIN can stimulate follicular development in transitional mares
  • A dose of 50 μg of deslorelin is administered intramuscularly twice daily
  • Treatment is discontinued when one or more follicles is at least 35 mm in diameter
  • The follicle is allowed to mature without any hormone therapy for 24 hours (a ‘coast’ period)
  • The mare is subsequently administered hCG to induce ovulation; note that administration of a ‘high-dose’ of deslorelin (i.e. 1.8 mg) is less effective at inducing ovulation in low-dose deslorelin treated mares
• Low-dose deslorelin therapy is MORE EFFECTIVE IN TRANSITIONAL MARES than mares in deep anestrus
• The AVERAGE DURATION OF LOWDOSE DESLORELIN THERAPY is 5 days; treatment should be discontinued if no significant follicular development is evident after 10 days

INDUCTION OF A TIMED OVULATION

• It is common practice to administer either HCG (Chorulon^®) or DESLORELIN
• Hormone therapy is generally effective if the mare is in behavioral ESTRUS and/or has endometrial EDEMA visible on ultrasonography and has a dominant follicle at least 35 MM
  in diameter (i.e. in Quarter Horse, Arabian and Thoroughbred mares)
• Administration of HCG (2,500 IU, IV) will usually induce ovulation in approximately 36 HOURS, whereas DESLORELIN (1.8 mg, IM) treatment typically induces ovulation in approximately 40 HOURS
• Mares to be bred with frozen semen may be administered hCG or deslorelin to induce a TIMED OVULATION and make breeding management more efficient
  • If two (2) doses of frozen semen are available, one can administor deslorelin at 8:00 am or administer hCG at 12:00 pm (noon) and anticipate ovulation at 12:00 am (midnight), in 40 or 36 hours, respectively. The mare is inseminated the evening before the anticipated ovulation and the morning after ovulation is confirmed
  • If one (1) dose of frozen semen is available, one can administer deslorelin at 8:00 pm and anticipate ovulation at 12:00 pm (noon) 40 hours later and inseminate post-ovulation
  • In both scenarios, ultrasound examinations are performed at specified time intervals after hormone therapy in case of an early ovulation

MANAGEMENT OF PERSISTENT MATING-INDUCED ENDOMETRITIS

• All mares experience UTERINE INFLAMMATION after either live cover or artificial insemination
• Inflammation PEAKS AT 8 TO 12 HOURS and is usually resolved by 24 hours in normal mares
• Endometritis may PERSIST for more than 24 hours in some mares
• THERAPY for persistent mating-induced endometritis (PMIE) includes:
  • Uterine lavage to remove excessive fluid, inflammatory cells, dead sperm and debris:
    • The uterus is lavaged with sequential one-liter volumes of either sterile saline or lactated Ringer’s solution until the effluent fluid is clear
  • Administration of oxytocin or prostaglandins
    • Oxytocin will stimulate uterine contractions for 30 to 45 minutes
    • Cloprostenol (Estrumate^®) will stimulate uterine contractions for 2 to 4 hours
• PREVENTIVE MANAGEMENT procedures on each subsequent cycle may include:
  • Administration of dexamethasone (30 to 50 mg, IV) once at the time of breeding
  • Only breeding the mare one time to limit re-inflammation
  • Performing a uterine lavage 4 to 6 hours after breeding
  • Prophylactic administration of ecbolic agents beginning 4 to 6 hours after breeding

DIAGNOSIS AND TREATMENT OF BACTERIAL ENDOMETRITIS

• DIAGNOSIS of bacterial endometritis is based on:
  • Culture of a pathogenic organism from a uterine swab or low-volume lavage:
    • The most common bacterial organisms are Streptococcus equi subsp. zooepidemicus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae
  • Presence of inflammatory cells (neutrophils) and possibly bacteria on uterine cytology
  • Detection of bacterial DNA using PCR analysis
• TREATMENT includes:
  • Uterine lavage to remove bacterial organisms and inflammatory debris
  • Infusion of an antimicrobial agent into the uterus for 3 to 5 consecutive days in estrus
    • Selection should be based on results of antimicrobial susceptibility testing
  • Empirical choice may include:
    • Naxcel^® or Timentin^® as the only agent
    • A combination of a beta-lactam antibiotic (i.e. penicillin)
      plus an aminoglycoside
• Systemic antibiotics may also be considered; common options include:
  • Ceftiofur crystalline free acid (Excede^®); enrofl oxacin (Baytril^®); trimethoprim-sulfamethoxasole

DIAGNOSIS AND TREATMENT OF FUNGAL ENDOMETRITIS

• Diagnosis of fungal endometritis is based on:
  • Culture of a pathogenic organism from a uterine swab
    or low-volume lavage
    • The most common fungal organisms are the yeast Candida albicans, and hyphate fungal organisms Aspergillus fumigatus and Mucor sp.
  • Presence of inflammatory cells (neutrophils) and possibly fungal organisms on cytology
  • Detection of fungal DNA using PCR analysis
• Treatment includes:
  • Uterine lavage to remove fungal organisms and inflammatory debris
  • Infusion of an antifungal agent into the uterus for 3 to 5 consecutive days in estrus
    • Our current choice for intrauterine infusion is nystatin
  • Systemic administration of an antifungal agent for 2 to 3 weeks
    • Fluconazole
• A COMBINATION of a systemic antifungal agent and an intrauterine antifungal agent may be more effective than either treatment alone in challenging cases
• It is common to subsequently culture the bacterium S. equi subsp. zooepidemicus after successful elimination of the fungal infection

PROGESTERONE SUPPLEMENTATION FOR PREGNANT MARES

• Progesterone is a steroid hormone required for MAINTENANCE OF PREGNANCY
• The vast majority of pregnant mares do not need progesterone supplementation
• In some clinical cases, progesterone supplementation should be considered in a pregnant mare:
  • Small corpus luteum and/or evidence of uterine edema on ultrasound
  • Progesterone level less than 4.0 ng/ml
  • History of repeated pregnancy loss
• Treatment protocols include:
  • Administration of altrenogest (0.044 mg/kg, PO, q 24 hr)
  • Administration of long-acting progesterone once per week
• Options for discontinuing supplementation include:
  • Endogenous progesterone greater than 4.0 ng/ml in a mare treated with altrenogest
  • Ultrasound evidence of secondary corpora lutea formation (by approximately day 50 to 60)
  • Treatment until at least 90 to 120 days, at which time the placenta is producing sufficient progestagens to maintain pregnancy
• ​​​​​​​NOTE: altrenogest is not detected in most traditional progesterone assays

INDUCTION OF LACTATION IN A NURSE MARE

• In the event that a young foal is orphaned by the unexpected death of its dam, LACTATION CAN BE INDUCED in another mare that may serve as a nurse mare
• The potential nurse mare must have GIVEN BIRTH AND LACTATED PREVIOUSLY, have good maternal instincts and have a gentle disposition
• Lactation can be stimulated by a combination of ESTRADIOL 17ß and a DOPAMINE ANTAGONIST such as domperidone or sulpiride; lactation can also be stimulated by administration of a dopamine antagonist alone
• Therapy for induction of lactation:
  • Pre-treatment with estradiol-17ß(3 to 5 mg) for 2 to 3 days
    • The goal is to enhance the prolactin response to domperidone therapy
  • Administration of domperidone (Equidone^®); 1.1 mg/kg
    (approximately 5 mls of Equidone^® gel) once daily for
    5 to 10 days
  • Begin hand-milking once lactation begins
  • Carefully introduce the foal to the nurse mare
• ​​​​​​​NOTE: mares induced to lactate do not produce colostrum; an orphaned neonatal foal will need to be provided with an alternative supply of colostrum, a colostrum substitute or hyperimmune plasma

Diagnosis and treatment of placentitis

• Ascending bacterial PLACENTITIS is one of the most common infectious causes of abortion
• External CLINICAL SIGNS may include premature lactation, vaginal discharge or abortion
• Diagnostic techniques include:
  • Ultrasonographic evaluation of the placenta per rectum to evaluate placental thickness (i.e. combined thickness of the uterus and placenta, CTUP)
  • Detection of placental separation from the uterus
• Therapy for placentitis includes:
  • Systemic antibiotics
    • Trimethoprim-sulfamethoxasole (30 mg/kg, PO q 12h), twice daily for the duration of pregnancy
  • Progestin supplementation
    • Altrenogest (i.e. Regu-Mate^®), 0.088 mg/kg (double-dose), for the duration of pregnancy
  • Non-steroidal anti-inflammatory medications (options):
    • Pentoxifylline (8.4 mg/kg, PO, q 6h to q 8h, for the duration of pregnancy
    • Flunixin meglumine (1.1 mg/kg, IV) - as needed
    • Firocoxib (Equioxx^® Paste); loading dose: 0.3 mg/kg; daily dose: 0.1 mg/kg, PO, q 24 hrs, for the duration of pregnancy

Prediction of foaling

• The gestation length of mares is approximately 340 days in duration
• CLINICAL SIGNS OF IMPENDING FOALING include:
  • Mammary gland development
    • Begins about 7 to 14 days prior to foaling
  • Waxing of teat ends
    • Approximately 70 % of mares ‘wax-up’; mares that wax usually foal in 24 to 72 hrs
  • Increase in calcium levels in mammary secretions
    • A majority of mares have milk calcium levels greater than 200 ppm prior to foaling
      • However, not all mares will reach 200 ppm; some mares will foal with a milk calcium level less than 100 ppm
    • Most mares will foal within 24 to 48 hours after milk calcium reaches 200 ppm
  • Decrease in pH in mammary secretions
    • Mammary secretion pH is 7.0 to 7.4 in the days prior to foaling
    • pH of equine mammary fluid decrease to approximately 6.4 within 12 to 24 hrs prior to foaling
• NOTE: changes in mammary pH are less diagnostic than changes in milk calcium

Induction of labor

• It may be indicated to induce labor in a mare for medical or management reasons
• Situations may include a previous history of giving birth to a stillborn foal, dystocia or injury during foaling, potential for neonatal isoerythrolysis or diagnosis of a potentially life-threating condition such as hydrops
• Ideally, QUALIFICATIONS FOR INDUCTION OF LABOR should include:
  • Gestation length of at least 330 days
  • Mammary gland development
  • Waxing of the teat ends
  • Milk calcium levels of at least 200 ppm
  • Some clinicians also include relaxation of the cervix as a qualification for induction
• The TECHNIQUE used at CSU for induction of labor is:
  • Administration of 5 units (0.25 mls) of oxytocin
  • A second dose of oxytocin (10 units) is administered 15 minutes later
  • Most mares ‘break their water’ 8 to 10 minutes after the second dose of oxytocin
• Mares induced to foal have a higher incidence of RETAINED PLACENTA than mares with a spontaneous delivery

Treatment of retained placenta

• RETAINED PLACENTA is common after dystocia, obstetrical intervention, induction of labor and abortion
• Mares that experience one retained placenta are likely to retain their placenta in SUBSEQUENT births
• A placenta is considered to be retained in the mare after 3 HOURS; considered a medical emergency
• TREATMENT for retained placenta may include some or all of the following, depending on clinical circumstances, duration placenta has been retained, medical condition of the mare, etc.:
  • Administration of oxytocin (10 to 20 units, IV or IM)
  • Infusion of ~ 3 gallons warm water containing povidone-iodine into the allantoic cavity (‘Burns Technique’); fluid is held within the allantoic cavity for 3 to 5 minutes before being evacuated
  • Uterine lavage (i.e. fluid is infused outside of the retained membranes)
  • Careful manual manipulation to disconnect retained chorioallantoic membrane from endometrium
  • Systemic antibiotics
  • Local infusion of antibiotics into the uterine lumen
  • Administration of a non-steroidal anti-inflammatory drug (i.e. flunixin meglumine)
  • Tetanus toxoid
  • Frog support pads or deep bedding
  • Administration of 100 to 150 mls of 23 % calcium gluconate added to 1 liter of lactated Ringer’s solution (if mare is hypocalcemic)
• NOTE: cannulation of a placental blood vessel followed by infusion of water may also be effective in resolution of a retained placenta

hCG response test for detection of cryptorchid testes

• Aggressive or stallion-like behavior in a gelding may indicate the presence of CRYPTORCHID TESTES
• Endocrine options for detection of the presence of cryptorchid testes include:

Category	Testosterone Level (pg/ml)
Gelding	< 100 pg/ml
Cryptorchid	200 to 1,000 pg/ml
Intact Stallion	?1,000 pg/ml

• Initial blood sample is collected
• HCG is administered (10,000 international units, IV)
• Second blood sample is collected 1 to 2 hours later
• Both samples are analyzed for TESTOSTERONE concentration and levels compared
• An increase in testosterone level in the second sample suggests the presence of testicular tissue

Category	Testosterone Level (pg/ml)
Gelding	No change
Cryptorchid	Increased
Intact Stallion	Increased

• Other diagnostic tests for the presence of cryptorchid testes include
  • Anti-Müllerian Hormone (AMH) concentration
  • Ultrasound examination – inguinal, flank and transrectal

Chemical ejaculation of a stallion

• Pharmacologically induced ex copula ejaculation, or chemical ejaculation, may be used to COLLECT SEMEN from stallions with physical disabilities, penile abnormalities, behavioral issues or ejaculatory dysfunction
• Semen collected by chemical ejaculation is typically LOW IN VOLUME and HIGH IN SPERM CONCENTRATION
• The procedure should be performed in a quiet place with minimal distractions (i.e. the stallion’s regular stall)
• Clinical procedure:
  • Administration of IMIPRAMINE HYDROCHLORIDE (2.2 mg/kg, PO)
  • Administration of XYLAZINE HYDROCHLORIDE 0.3 to 0.4 mg/kg intravenously one to two hours later
• Passive emission of semen usually occurs within 3 TO 5 MINUTES after administration of xylazine as the horse is becoming sedated
• Ejaculation may also occur 10 TO 15 MINUTES after administration as the sedation is wearing off
• Semen can be collected using a hand-held cup attached to a long pole or into a collection device placed over the prepuce and tied over the back of the horse
• Chemical ejaculation is effective in 30 TO 75% of horses treated