Effect of prolonged use of altrenogest on behaviour in mares

doi:10.1016/j.tvjl.2004.04.020

The Veterinary Journal

Volume 169, Issue 1, January 2005, Pages 113-115

https://doi.org/10.1016/j.tvjl.2004.04.020 Get rights and content

Abstract

Oral administration of altrenogest for oestrus suppression in competition horses is believed to be widespread in some equestrian disciplines, and can be administered continuously for several months during a competition season. To examine whether altrenogest has any anabolic or other potential performance enhancing properties that may give a horse an unfair advantage, we examined the effect of oral altrenogest (0.044 mg/kg), given daily for a period of eight weeks, on social hierarchy, activity budget, body-mass and body condition score of 12 sedentary mares. We concluded that prolonged oral administration of altrenogest at recommended dose rates to sedentary mares resulted in no effect on dominance hierarchies, body mass or condition score.

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Concentrations of altrenogest in plasma of mares and foals and in allantoic and amniotic fluid at parturition
2010, Theriogenology
Citation Excerpt :
A lack of detrimental effects on foals from altrenogest-treated mares where administration was ceased at day 320, i.e., several days before parturition occurred [19] does not only show that the fetus is capable of clearing altrenogest from tissues but also suggests that effects are caused by acute action of altrenogest on respective tissue. In contrast to foals, negative effects have never been reported in mares treated with altrenogest [17–19,30,31]. However, the concentration of altrenogest in the plasma of the neonates more than doubled levels in their dams and may thus have reached a more critical concentration.
Treatment with the progestin altrenogest is widely used in pregnant mares. The fact that foals born from healthy mares treated with altrenogest until term suffered from neonatal problems raises the question of direct effects of altrenogest on vital functions in the neonate. We have therefore investigated altrenogest concentrations in maternal and neonatal blood plasma and in fetal fluids. Pregnant mares were treated with altrenogest orally once daily (0,088 mg/kg bodyweight, n = 7) or left untreated (n = 8) from 280 d of gestation until foaling. Altrenogest concentration was determined in plasma of the mares, their foals and in amniotic and allantoic fluid. The concentration of altrenogest in plasma from treated mares (2.6 ± 1.0 ng/mL) was significantly lower than in plasma from their foals immediately after birth (5.6 ± 1.9 ng/mL; p < 0.05), but was significantly higher than in their fetal fluids (amniotic fluid: 0.4 ± 0.1 ng/mL; p < 0.05; allantoic fluid: 3.0 ± 1.5 ng/mL). Altrenogest was undetectable in maternal and fetal plasma and fetal fluids of control pregnancies at all times. Altrenogest concentration in plasma of foals from treated mares was strongly correlated to the altrenogest concentration in plasma of their dams (r = 0.938, p < 0.001) and in amniotic (r = 0.886, p < 0.001) and allantoic fluid (r = 0.562, p < 0.05). A significant decrease in altrenogest concentration between the time periods 0–15 min, 30–120 min, and 180–360 min after parturition was seen in the plasma from foals born to altrenogest-treated mares. In conclusion, our data demonstrate that altrenogest reaches the equine fetus at high concentrations.
Structure-activity relationships of synthetic progestins in a yeast-based in vitro androgen bioassay
2008, Journal of Steroid Biochemistry and Molecular Biology
The recent identification of tetrahydrogestrinone (THG), a non-marketed designer androgen used for sports doping but previously undetectable by established mass spectrometry-based urine drug screens, and its production by a facile chemical modification of gestrinone has raised concerns about the risks of developing designer androgens from numerous marketed progestins. We therefore have used yeast-based in vitro androgen and progesterone bioassays to conduct a structure–activity study assessing the intrinsic androgenic potential of commercially available progestins and their derivatives, to identify those compounds or structures with the highest risk of forming a basis for such misapplication. Progestins had a wide range of androgenic bioactivity that was not reliably predicted for individual steroids by their progestin bioactivity. 17α-Hydroxyprogesterone and 19-norprogesterone derivatives with their bulky 17β-substituents were strong progestins but generally weak androgens. 17α-Ethynylated derivatives of testosterone, 19-nortestosterone and 18-methyl-19-nortestosterone such as gestrinone, ethisterone, norethisterone and norgestrel had the most significant intrinsic androgenicity of all the commercially marketed progestins. Facile chemical modification of the 17α-ethynyl group of each of these progestins produces 17α-methyl, ethyl and allyl derivatives, including THG and norbolethone, which further enhanced androgenic bioactivity. Thus by using the rapid and sensitive yeast bioassay we have screened a comprehensive set of progestins and associated structures and identified the ethynylated testosterone, 19-nortestosterone and 18-methyl-19-nortestosterone derivatives as possessing the highest risk for abuse and potential for conversion to still more potent androgens. By contrast, modern progestins such as progesterone, 17α-hydroxyprogesterone and 19-norprogesterone derivatives had minimal androgenic bioactivity and pose low risk.
Management of estrus in the performance mare
2005, Clinical Techniques in Equine Practice
The equine practitioner commonly receives requests to manage the estrous cycle in performance mares. These requests stem from complaints of less than desirable performance or problem behaviors related to the estrous cycle. Unwanted behaviors or poor performance may be truly related to the different phases of the estrous cycle or they may be behaviors that either resemble some sexually receptive behavior or problems that are ascribed to estrus but have no relationship to the estrous cycle. The approach to these cases involves working with owners, trainers, and caretakers to precisely define and then document daily changes in behavior or performance. The veterinarian should start with a complete history and physical examination and then document the reproductive events in the mare. Finally, working together, the owners/trainers and the veterinarian must establish parallelism between behavior and ovarian events, institute a treatment protocol, and then verify the efficacy of that treatment and management regime.
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A review of oestrus suppression techniques in mares
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Short CommunicationEffect of prolonged use of altrenogest on behaviour in mares

Abstract

Applied Animal Behaviour Science

Applied Animal Behaviour Science

Stability of equine hierarchies and the prevention of dominance related aggression

Equine Veterinary Journal

Short Communication
Effect of prolonged use of altrenogest on behaviour in mares