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Causes and Treatment of Agalactia/Hypogalactia in Mares Etta Agan Bradecamp DVM, DACT, DABVP Rood & Riddle Equine Hospital Physiology of lactation The hypothalamic-pituitary axis, ovaries and placenta all play a role in udder development and initiation of lactation. Factors involved in lactogenesis include: estrogen, progesterone, prolactin, oxytocin, growth hormone, insulin and thyroid hormone. Estrogen – induces development of mammary ducts Progesterone – stimulates lobuloaveolar growth and inhibits lactogenesis Prolactin – rise in prolactin production by lactotrophs in the anterior pituitary stimulates lactogenesis, controlled by dopamine secretion from the hypothalamus Oxytocin – synthesized in the hypothalamus, causes contraction of myoepithelial cells around the alveoli and expulsion of milk Causes of agalactia 1. Idiopathic: most commonly in primiparous mares, however there is the rare mare that repeatedly fails to develop an udder for unknown reason 2. Ingestion of ergot alkaloid (fescue toxicosis) 3. Administration of a dopamine agonist such as pergolide or bromocryptine 4. Inadequate nutrition 5. Selenium deficiency 6. Stress 7. Systemic illness, surgery Treatment The primary focus of treatment in mares with agalactia is to increase prolactin production by blocking the inhibitory affect of dopamine. Ergot alkaloids suppress prolactin production through their action as dopamine receptor agonists and serotonin antagonists. Compounds that block the inhibitory action of dopamine are: Thyrotropin-releasing hormone (2.0 mg SC q 12 hrs) Reserpine (0.5-2.0 mg IM q 48 hrs) (0.01 mg/kg PO q 24 hrs): May cause sedation and diarrhea. Phenothiazine tranquilizers Butyrophenones Metaclopramide (25 mg IM q 12 hrs) Domperidone (1.1 mg/kg PO q 24 hrs) Sulpiride (50 mg/100kg IM q 12 hrs) Compounds that are serotonin receptor agonists include: Buspirone Dichlorophenyl piperazine Mares should be removed from endophyte infected fescue pasture a minimum of 30 and ideally 60-90 days prior to expected due date. If this is not possible, domperidone administration should be started approximately 30 days prior to the expected due date. In mares that are removed from infected pasture domperidone treatment should be initiated if no udder development has occurred by 2 weeks prior to the expected due date. In mares that exhibit idiopathic hypogalactia post foaling domperidone alone or in combination with reserpine can be effective in stimulating milk production. Mares with sick foals that are not nursing should be milked frequently (every two hours) to keep milk production stimulated. It is also imperative to maintain a positive energy balance in post-foaling mares. Mares that foal early in the year are more likely to lose weight in the first two months of lactation due to being in a negative energy balance. This results in reduced milk production and decreased weight gain in their foals when compared to foals from mares that remained in a positive energy balance. Special attention should also be paid to the nutrition of lactating mares that suffer from illness or undergo major surgery. Due to pergolide being a dopamine agonist, mares being treated for PPID (Cushings) should discontinue treatment for approximately 30 days prior to their expected due date to allow for normal udder development to occur. Treatment can resume after foaling and does not appear to have a negative affect on lactation at that time.