Effects of age and altrenogest treatment on conceptus development and secretion of LH, progesterone and eCG in early-pregnant mares.

The research examines the impact of altrenogest treatment and age variables on the development of embryos and the secretion of LH, progesterone, and eCG in early-pregnant horses. It reveals that while altrenogest treatment had no significant effect on the pregnancy rate, it positively influenced the embryo’s development in mares over 8 years old.

Introduction to the Research

• The objective of the research was to investigate the effects of altrenogest treatment on early-pregnant mares, particularly mares with a history of repeated early embryonic losses. The researchers focused on the development of the conceptus (embryo and its adnexa) and the secretion of LH, progesterone and eCG hormones. The study also sought to understand differences related to the age of the mares.

Treatment and Sample Collection

• The mares in the study were treated with a routine dosage of altrenogest (a type of progestin) or sunflower oil from day 6 to day 100 after ovulation. The dosage of altrenogest used is 0.044 mg/kg once daily, and for sunflower oil, it’s 10 ml once daily.
• Blood samples were collected from the mares to analyze the levels of LH, progesterone, and eCG hormones. The embryonic vesicle and embryo/fetus’s size were also determined via ultrasound.

Study Findings

• The results showed that the per cycle pregnancy rate between mares treated with altrenogest (75%) and those treated with sunflower oil (74%) was similar. This indicated that there was no significant difference in the efficiency of altrenogest in preventing pregnancy loss compared to the control group.
• The study found a significant impact of the mare’s age on the embryonic vesicle’s diameter during the early days (12-22) of the pregnancy, but not of the altrenogest treatment.
• The findings also revealed a significant age and treatment effect on the size of the proper embryo between days 30 and 45 of the pregnancy.
• The study found no effect of age or treatment on the plasma concentrations of LH and progesterone.
• However, significant effects of age and altrenogest treatment were found on eCG concentrations between days 40 and 130.

Conclusion

• The study concludes that an altrenogest treatment shows a positive influence on the development of embryos in older mares (>8 years), particularly around the beginning of placentation, despite not affecting the per cycle pregnancy rate.
• This is the first study to highlight a positive impact of altrenogest treatment on the retarded development of embryos in older mares, indicating the potential use of this treatment to improve the outcomes of early pregnancy in such animals.