Premature luteal regression in a pregnant mare and subsequent pregnancy maintenance with the use of oral altrenogest

Abstract

Premature luteal demise or luteal insufficiency is not well characterised as a cause of pregnancy loss in domestic species, including horses. In this report, a mare inseminated with cooled-transported semen at our facility returned for a routine pregnancy diagnosis at 15 days post ovulation. Ultrasonography per rectum revealed endometrial oedema and the absence of visual indication of a corpus luteum on either ovary. Nonetheless, an embryonic vesicle small for the gestational age was identified. Daily oral altrenogest treatment was implemented immediately. Serum progesterone concentration was 0.67 ng/ml, which is below the threshold considered adequate for pregnancy maintenance in the mare. Examinations were repeated at 17, 25, 30, 39, 49, 72 and 120 days post ovulation. At 25 days post ovulation the embryonic vesicle presented normal development for the gestational age. In addition, sequential blood samples were collected to measure progesterone, equine chorionic gonadotrophin and oestrone sulphate concentrations. Although progesterone concentration did not exceed 2 ng/ml until 72 days post ovulation, all other results were unremarkable and a healthy filly was born uneventfully at 344 days post ovulation.

Do I give altrenogest to prevent pregnancy failure?

“…The literature search revealed 2 individual case reports of luteal insufficiency which resulted in the birth of a healthy foal: one case without adjunctive hormone therapy (Newcombe ) and one case with supplementation of altrenogest for the first 150 days of pregnancy (Canisso et al . ).…”

“…Only one out of 17 cases (6%) of early embryonic death could be attributed to low progesterone (<4 ng/ml) in a retrospective study on 179 Standardbred mares (Irvine et al 1990). The literature search revealed 2 individual case reports of luteal insufficiency which resulted in the birth of a healthy foal: one case without adjunctive hormone therapy (Newcombe 2000) and one case with supplementation of altrenogest for the first 150 days of pregnancy (Canisso et al 2013).…”

“…In daily stud practice mares are often supplemented with exogenous progestin (altrenogest, Regumate™) as a result of suspicions of inadequate progesterone production or a clinician's frustration when facing mares that repeatedly fail to conceive or carry a pregnancy to term (Canisso et al 2013). However, what is the clinical evidence for the use of altrenogest to prevent pregnancy failure?…”

Progress in broodmare practice as based on recent papers in Equine Veterinary Journal

“…Premature luteal regression and oral altrenogest [5] Many veterinarians, myself included, use considerable amounts of exogenous progestins in the belief that it reduces the incidence of early pregnancy failure. This is despite the fact that there is a lack of scientific evidence supporting any benefit [6].…”

Early Embryonic Development and Maternal Recognition of Pregnancy in Camelids: A Review

“…This process, which can be summarized as a mechanism of prevention of luteolysis, involves signaling between the embryo and the uterus leading to successful attachment/implantation. In-depth studies on MRP have been sparked by the impact of early pregnancy loss on productivity in various species such as cattle (Diskin and Morris, 2008), camelids (Fernandez-Baca et al, 1970;Tibary et al, 2007;, and horses (Allen et al, 2007;Ball and Woods, 1987;Canisso et al, 2013;Vanderwall, 2008). Additionally, early embryonic loss (during the pre-implantation period) is a common problem with many advanced reproductive biotechnologies involving embryo/gamete manipulations.…”