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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Agalactia—failure of the mammary gland to secrete colostrum or milk after foaling
  • Hypogalactia—also referred to as dysgalactia is subnormal milk production

Pathophysiology!!navigator!!

  • Estrogens (equilin, equilenin, and estradiol-17β from the fetoplacental unit) in late gestation induce mammary duct development
  • Progestagen (5β-pregnane) stimulates lobuloalveolar growth
  • Lactogenesis is triggered by a decrease of progestagen and increase of prolactin in the last few days of pregnancy
  • After initiation of lactation, prolactin is not required for maintenance
  • Colostrogenesis is initiated a few days prior to parturition. Lactation peaks 30–60 days postpartum
  • Milk production is 2.5–4% of body weight and requires nutritional demands of the dam are met
  • Agalactia/hypogalactia may be caused by alterations of hormonal events (low prolactin level), defects in the mammary tissue itself (mammary disease), poor nutritional status, or presence of systemic illness or disease

Systems Affected!!navigator!!

Genetics!!navigator!!

Milk production is likely determined by genetics.

Incidence/Prevalence!!navigator!!

Agalactia or dysgalactia is commonly seen in equine practice when predisposing factors are present.

Geographic Distribution!!navigator!!

  • Fescue toxicosis—tall fescue infected by the fungus Neotyphodium coenophialum in central and southeast USA
  • Black oat infected by Claviceps purpurea in Brazil
  • Rye grass infected by Neotyphodium lolii in Argentina

Signalment!!navigator!!

Mares of any breed or age may be affected.

Signs!!navigator!!

Historical Findings

  • Grazing endophyte-infected tall fescue or ergot-infected feeds prepartum
  • Prolonged gestation, history of placentitis, dystocia, thickened fetal membranes, retained fetal membranes, and red bag (premature placental separation)
  • Previous history—agalactia/hypogalactia or mammary gland disease
  • Clinical evidence of systemic disease; known exposure to infectious disease

Physical Examination Findings

  • Weak, septicemic foal—FTPI and/or inadequate nutrition
  • Flaccid udder and secretion of a clear or thick, yellow-tinged fluid from the teats
  • Mastitis—swollen, painful udder, warm to the touch, secretion of grossly or microscopically abnormal milk
  • Distinct, palpable masses with mammary abscessation or neoplasia

Causes!!navigator!!

Endocrinologic Disorders

  • Ergot alkaloids (fescue toxicosis) depress prolactin secretion (dopamine DA2 receptor agonists and serotonin antagonists)
  • Abortion/premature birth affects normal progesterone, estrogen, and prolactin fluctuations necessary for lactation onset

Mammary Gland Disease

  • Inflammation and/or infection
  • Abscessation or fibrosis
  • Neoplasia
  • Trauma

Systemic Disease

  • Any debilitating systemic disease or stress-producing disorder
  • Malnutrition/nutritional deficiency

Others

  • Poor nutrition
  • Obesity

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Differentiating Similar Signs

  • Differentiate agalactia/hypogalactia from behavioral nursing problems:
    • Mare anxiety, pain, udder edema
    • Direct examination of udder and secretions
    • Observe interaction between mare and foal as its attempts to nurse
  • Failure of milk letdown can occur in mares:
    • Oxytocin stimulates milk letdown, not milk secretion

Differentiating Causes!!navigator!!

  • Indicators of fescue syndrome:
    • History of fescue ingestion
    • Prolonged gestation
    • Dystocia
    • Retained fetal membranes, thickened fetal membranes
    • Weak, dysmature foal; mare with agalactia
  • Full physical examination to differentiate mastitis, mammary fibrosis, neoplasia, abscessation, traumatic injury, systemic illness

Other Laboratory Tests!!navigator!!

Serum prolactin levels are decreased in fescue-induced agalactia.

Other Diagnostic Procedures!!navigator!!

  • If mastitis is suspected
  • If neoplasia is suspected
    • Fine needle aspirate—cytology
    • Biopsy—histopathology

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • Promote lactation using selective D2 dopamine receptor antagonists
  • Mastitis
    • Local or systemic antibiotics based on culture/sensitivity
    • Frequent stripping of mammary gland
    • Heat packs or hydrotherapy
    • Correct nutritional deficiencies

Nursing Care!!navigator!!

  • Foals at risk of FTPI need oral administration of colostrum from another mare
  • Foals with FTPI need supportive treatment and IV administration of hyperimmune plasma

Activity!!navigator!!

N/A

Diet!!navigator!!

Supplementation of mare feed to meet lactation demand.

Client Education!!navigator!!

  • Management of mares at risk of agalactia (remove from infected pastures)
  • Close monitoring of periparturient mares for mammary gland development or overt edema
  • Test colostrum quality upon parturition
  • Observe foal nursing behavior

Surgical Considerations!!navigator!!

N/A

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice For Fescue Toxicity!!navigator!!

  • Domperidone (1.1 mg/kg PO daily)
    • Selective DA2 dopamine receptor antagonist; reverses effects of fescue ingestion
    • Treat for minimum of 15 days prepartum; discontinue when/if lactation is observed at foaling
    • If the mare is agalactic at foaling and has not been treated prior to parturition, initiate treatment at foaling and continue for 5 days or until lactation ensues
  • Thyrotropin-releasing hormone—2.0 mg, SC, BID, 5 days, begin day 1 postpartum
    • Increases serum prolactin, due to its action as a prolactin-releasing factor

Contraindications!!navigator!!

  • Perphenazine, dopamine receptor antagonist; published, but:
    • Severe side effects in horses preclude its use
    • Sweating, colic, hyperesthesia, ataxia, posterior paresis
  • Metoclopramide is used to treat agalactia of unknown origin
    • Significant risk for developing severe central nervous system side effects in horses
    • Its use is contraindicated

Precautions!!navigator!!

  • Remove pregnant mares from endophyte-infected fescue pastures/hay minimum 30 days, preferably 60–90 days, prepartum
  • If removal is not possible, treat with domperidone during last 2–4 weeks of gestation

Alternative Drugs!!navigator!!

  • Acepromazine maleate (20 mg IM TID)
    • Some dopamine antagonistic properties; tried as agalactia treatment
      • At least one report of it having no effect on lactation
    • Sedation is the primary side effect
  • Reserpine (0.5–2.0 mg IM every 48 h or 0.01 mg/kg PO every 24 h)
    • Depletes serotonin, dopamine, and norepinephrine in the brain and other tissues
    • Gastrointestinal motility is greatly increased and can cause profuse diarrhea
    • Sedation—a common side effect
    • Not FDA approved for agalactia
  • Sulpiride (3.3 mg/kg PO daily)
    • Dopamine antagonist to treat agalactia; less effective than domperidone
    • Not FDA approved for agalactia

Follow-up ⬆ ⬇

FOLLOW-UP

Patient Monitoring

  • If effective, most treatments stimulate milk production in 2–5 days
  • In absence of other systemic signs, agalactia is not life-threatening
  • Foals need intensive medical and nutritional management with prolonged agalactia

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Mare

Prolonged gestation, abortion, dystocia, uterine rupture, thickened placental membranes, red bag, retained fetal membranes, infertility, prolonged luteal function, early embryonic death, weak and dysmature foals.

Neonate

  • FTPI
  • Malnutrition
  • Starvation

Abbreviations!!navigator!!

  • FDA = United States Food and Drug Administration
  • FTPI = failure of transfer of passive immunity

Suggested Reading ⬆ ⬇

Cross DL, Reinmeyer CR, Prado JC, et al. Efficacy of domperidone gel in an induced model of fescue toxicosis in periparturient mares. Theriogenology2012;78:1361–1370.

Evans TJ, Youngquist RS, Loch WE, Cross DL. A comparison of the relative efficacies of domperidone and reserpine in treating equine “fescue toxicosis.”Proc AAEP 1999;45:207–209.

Morresey PR. Agalactia, dysgalactia and nutrition of the postpartum mare. Proc AAEP 2012;58:370–374.

Tibary A. Mammary gland, lactation. In: Carleton CL, ed. Blackwell's Five Minute Veterinary Consult. Clinical Companion Equine Theriogenology. Ames, IA: Wiley Blackwell, 2011:348–354.

Tibary A. Mammary gland, mastitis. In: Carleton CL, ed. Blackwell's Five Minute Veterinary Consult. Clinical Companion Equine Theriogenology. Ames, IA: Wiley Blackwell, 2011:336–347.

Author(s) ⬆

Author: Ahmed Tibary

Consulting Editor: Carla L. Carleton

Acknowledgment: The author and editor acknowledge the prior contribution of Carole C. Miller.