Effect of altrenogest‐treatment of mares in late gestation on adrenocortical function, blood count and plasma electrolytes in their foals

Abstract

Altrenogest treatment of pregnant mares prolonged labour had no major effects on adrenocortical function in foals. A reduced neutrophil/lymphocyte ratio in these foals may suggest either immunomodulatory effects of altrenogest or dysmaturity of the foals.

Review of the reproductive endocrinology of the pregnant and parturient mare

“…Interestingly, gonadotropin release in response to gonadotropin-releasing hormone was also muted in colts from altrenogest-treated mares, though reproductive function was otherwise apparently normal [102]. More recently, foals from mares treated with altrenogest late in gestation were born with elevated cortisol [103], metabolic alkalosis, and depressed respiratory rates [104]. Three of six foals of treated mares had perinatal health issues, perhaps because labor was prolonged by several minutes [104].…”

Alteration of the mare's immune system by the synthetic progestin, altrenogest

“…These include shortened gestational length, an imbalanced lymphocyte/neutrophil ratio as well as decreased respiratory function in foals born to mares receiving ALT, and an increased number of neutrophils in the endometrium of mares postpartum, indicating that it may have negative effects in both the pregnant mare and fetus. 23,24 Altrenogest is a promiscuous activator of various steroid receptors, binding to the bovine PR with ten times the affinity of P4, and to the human androgen receptor (AR) at 75% the affinity of dihydrotestosterone (DHT). 25 In other species, various synthetic progestins have been found to bind to both the PR in addition to the GR, whereas others bind preferentially to just the PR, such as LNG.…”

Do I give altrenogest to prevent pregnancy failure?

“…In this study altrenogest treatment did not prevent parturition, and altrenogest treated mares had a tendency to foal earlier than the untreated controls (Neuhauser et al 2008). In a second study foals born to altrenogest-treated healthy mares showed a reduced neutrophil/lymphocyte ratio, which the authors attributed either to immunomodulatory effects of altrenogest or dysmaturity of the foals (Neuhauser et al 2009).…”

“…In a second study foals born to altrenogest‐treated healthy mares showed a reduced neutrophil/lymphocyte ratio, which the authors attributed either to immunomodulatory effects of altrenogest or dysmaturity of the foals (Neuhauser et al . ).…”