Safety of altrenogest in pregnant mares and on health and development of offspring

https://doi.org/10.1016/S0737-0806(89)80030-9Get rights and content

Summary

Fifty-one light-horse mares were utilized to evaluate the safety of an oral progestin, altrenogest, administered throughout gestation on: gestation length, embryonic and fetal loss, periparturient events, health and development of offspring, and future reproductive capabilities of the mares. Pregnancies were established by inseminating mares with 250 × 106 progressively motile spermatozoa from the same stallion every other day throughout estrus or by non-surgical transfer of embryos. Mares were randomly assigned to 1 of 2 treatments upon confirmation of pregnancy on day 20: 1) controls, 2 ml of neobee oil orally per 44.5 kg of body weight; and 2) treated, 2 ml of altrenogest dissolved in neobee oil at a concentration of 2.2 mg/ml orally per 44.5 kg of body weight. Treatments were administered daily from day 20 to 320 of gestation.

There were no significant differences between treatment groups for duration of gestation, placental weight, time to placental expulsion and incidence of retained placental membranes. Number of female foals born from altrenogest treated mares (14 of 23) was greater (P<.05) than the number from untreated control mares (4 of 16). Female foals born from altrenogest treated mares had larger clitori (P<.05) than those from control mares. Times to sternal recumbency, standing and nursing were similar for the 2 groups (P>.05). Body weight and height at withers, heart girth circumference and length and width of cannon were measured at time of birth and at 2, 4, 6, 8, 12 and 16 weeks of age. Measurements did not differ (P>05) between treated and control foals for any development parameters.

Beginning on day 20 postpartum, mares were teased daily. During estrus, mares were inseminated every other day with 250 × 106 motile spermatozoa. Teasing and/or insemination was continued for 2 cycles or until mares were 35 days pregnant. The number of mares pregnant after 1 cycle and after 2 cycles of insemination was similar (P>.05) for treated and control mares. Nineteen of 21 treated mares and 15 of 16 control mares were pregnant after 2 cycles of insemination. Number of cycles per pregnancy was similar (P>.05) for treated and control mares (1.37 vs 1.13) as was number of days mares exhibited estrus (6.30 vs 6.13). Number of inseminations per cycle did not differ (P>.05) between treated and control mares (2.92 vs 3.00). In summary, there was no effect of treatment with altrenogest from day 20 to 320 of gestation on periparturient events, viability and growth of offspring and subsequent reproductive performance of mares.

References (18)

  • VillahozMD et al.

    Some observations on early embryonic death in mares

    Theriog

    (1985)
  • DouglasRH et al.

    Physiological and commercial parameters for producing progeny from subfertile mares by embryo transfer

    Eq Vet J

    (1985)
  • GanjamVK et al.

    Peripheral blood plasma levels and some unique metabolite aspects of progesterone in pregnant and non-pregnant mares

  • HinrichK et al.

    Pregnancy in ovariectomized mares achieved by embryo transfer: A preliminary study

    Eq Vet J

    (1985)
  • HinrichK et al.

    Use of altrenogest to prepare ovariectomized mares as embryo transfer recipients

    Theriog

    (1986)
  • HoltanDW et al.

    Effect of ovariectomy on pregnancy in mares

    J Reprod Fert

    (1979)
  • HughesJP et al.

    The use of hormones in reproductive management of the mare

    Aust Vet J

    (1977)
  • HuntsbergerDV et al.

    Elements of Statistical Inference

    (1981)
  • McKinnonAO et al.

    Pregnancy rates after surgical transfer into steroid-treated ovariectomized mares

    Therio

    (1988)
There are more references available in the full text version of this article.

Cited by (22)

  • Hormone supplementation protocol using estradiol benzoate and long-acting progesterone is efficient in maintaining pregnancy of anovulatory recipient mares during autumn transitional phase

    2015, Animal Reproduction Science
    Citation Excerpt :

    In addition, ovariectomized mare recipients are able to establish and maintain pregnancy when treated with progesterone until Day 100 of gestation (Hinrichs et al., 1987). For these reasons, hormonal protocols using progestins (Hinrichs et al., 1986; McKinnon et al., 1988; Shoemaker et al., 1989), progesterone (Hinrichs et al., 1987; Vanderwall et al., 2007), estradiol benzoate plus either progestins (Wiepz et al., 1988) or progesterone (Kaercher et al., 2013) have been used successfully to maintain pregnancy in anovulatory and ovariectomized embryo recipient mares. Thus, hormonal administration to anovulatory mares can make them suitable as embryo recipients, thereby reducing the problems associated to donor/recipient estrous synchronization and allowing the use of more recipients at the end of breeding season (Silva et al., 2014).

  • Laparoscopic Gonadectomy in Two Intersex Warmblood Horses

    2012, Journal of Equine Veterinary Science
    Citation Excerpt :

    Other reasons for stallion-like behavior are treatment with androgens or neoplasia of the ovaries such as granulosa cell tumor [35,36]. In case of foals of mares treated with altrenogest in late pregnancy, an enlarged clitoris has been described [37]. However, there was no history available concerning treatments of the two horses’ dams during pregnancy.

  • Concentrations of altrenogest in plasma of mares and foals and in allantoic and amniotic fluid at parturition

    2010, Theriogenology
    Citation Excerpt :

    This is similar to results from previous studies on cortisol metabolism in mature, healthy foals, showing high plasma cortisol concentrations within the first hour of life and a rapid decline within less than 8 h thereafter [28,29]. 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].

  • Progestins in Mid- to Late-Pregnant Mares

    1994, Journal of Equine Veterinary Science
  • Use of progestins in open and pregnant mares

    1993, Animal Reproduction Science
View all citing articles on Scopus

Authors' address: Animal Reproduction Laboratory, Colorado State University, Fort Collins, CO 80523.

View full text