Effect of maternal treatment with altrenogest on age at puberty, hormone concentrations, pituitary response to exogenous GnRH, oestrous cycle characteristics and fertility of fillies.
Abstract: Puberty was studied using 15 fillies of Quarter Horse phenotype. Fillies were from dams treated daily from Days 20 to 325 of gestation with: (1) 2 ml neobee oil per 50 kg body weight (controls); or (2) 2 ml altrenogest (2.2 mg/ml) per 50 kg body weight. The clitoris was measured at birth and approximately every 12 weeks until 84 weeks of age. Blood samples were collected from 9 fillies (5 treated, 4 controls) every 4 days over a 28-day period at 8-week intervals from 4 to 68 weeks of age; sampling continued every 4 days after 72 weeks of age until first oestrus. Blood samples were collected daily during oestrus (greater than or equal to 35 mm follicle) and on Days 4, 6, 10, and 14 after ovulation for the first 2 oestrous cycles. GnRH challenges (5 micrograms/kg) were administered every 8 weeks from 32 to 96 weeks of age. Puberty was defined as the first oestrus with ovulation. Beginning 1 February 1987, fillies were teased daily and their ovaries were examined by ultrasonography every 3 days (daily during oestrus). Fillies were inseminated with 500 x 10(6) motile spermatozoa from one stallion. Pregnancy was diagnosed by ultrasonography on Days 11, 12, 15 and every 5 days until Day 50 after ovulation. Prenatal altrenogest treatment caused clitoral enlargement (P less than 0.05) and increased serum concentrations of LH from 1 to 7 months of age. The amount of LH released in response to exogenous GnRH was greater (P less than 0.05) in treated fillies at 32, 64, and 72 weeks of age. Treated fillies had higher serum concentrations of FSH from 1 to 4 months (P less than 0.05), but FSH was lower (P less than 0.05) in treated fillies before and during first oestrus. Serum concentrations of LH and FSH peaked transiently at 10 months and LH was depressed from 64 to 88 weeks and began to rise 14 days before first oestrus. Concentrations of FSH began to decline 14 days before first oestrus. The median age at puberty was 90 weeks. Durations of oestrus, dioestrus, and the oestrous cycle were not different between groups and were similar to those for adult mares. First cycle pregnancy rates and overall rates were 100 and 82% and 100 and 91.7% for control and treated fillies, respectively (P greater than 0.05). Maternal treatment with altrenogest did alter gonadotrophin secretion before puberty, but had no effect on functional reproductive performance in fillies.
Publication Date: 1990-01-01 PubMed ID: 2107301DOI: 10.1530/jrf.0.0880185Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research study investigates the implications of the maternal administration of altrenogest, a type of progestin, on various aspects of reproductive development and function in female offspring, specifically fillies. They found that maternal treatment with altrenogest can impact gonadotropin secretion in the fillies prior to puberty, but doesn’t appear to affect their overall reproductive performance.
Methodology
- The researchers utilized 15 Quarter Horse phenotype fillies. Some of the dams of these fillies had daily treatments from Days 20 to 325 of gestation with neobee oil (control group), while others were treated with altrenogest.
- The clitoral size of each filly was measured at birth and subsequently every 12 weeks up to 84 weeks of age. Blood samples from the fillies were collected to study hormone levels over time. Four of these fillies were from the control group and five were from the treatment group.
- Presence of oestrus was checked by taking daily blood samples during oestrus and on specific days after ovulation. Gonadotropin-releasing hormone (GnRH) challenges were also administered to track the body’s hormonal response.
- A daily check using teasing and ovaries ultrasound was conducted and the fillies were also artificially inseminated. Pregnancy was confirmed through ultrasound.
Findings
- Treatment with altrenogest led to considerable clitoral enlargement compared to the control group. These treated fillies also showed increased serum concentrations of luteinizing hormone (LH) from 1 to 7 months of age.
- The volume of LH released in response to exogenous GnRH was greater in treated fillies during specific weeks (32, 64, and 72). The serum concentrations of follicle-stimulating hormone (FSH) were generally higher in treated fillies, but it was observed to be lower just before and during the first oestrus.
- The median age for reaching puberty among the fillies was found to be 90 weeks. The durations of oestrus, dioestrus, and the oestrus cycle were not observed to show any differences between the treated and control groups.
- Overall fertility rates for the first cycle and generally were similar between treated and control fillies with no statistically significant difference.
Conclusion
- While maternal treatment with altrenogest was found to impact the secretion of gonadotropins like LH and FSH before puberty, it appears to not affect the functional reproductive performance in fillies, including fertility rates and duration of the oestrus cycle.
Cite This Article
APA
Naden J, Squires EL, Nett TM.
(1990).
Effect of maternal treatment with altrenogest on age at puberty, hormone concentrations, pituitary response to exogenous GnRH, oestrous cycle characteristics and fertility of fillies.
J Reprod Fertil, 88(1), 185-195.
https://doi.org/10.1530/jrf.0.0880185 Publication
Researcher Affiliations
- Animal Reproduction Laboratory, Colorado State University, Fort Collins 80523.
MeSH Terms
- Animals
- Estrenes / pharmacology
- Estrus / physiology
- Female
- Fertility / drug effects
- Follicle Stimulating Hormone / blood
- Horses / physiology
- Luteinizing Hormone / blood
- Pituitary Gland / drug effects
- Pituitary Gland / metabolism
- Pituitary Hormone-Releasing Hormones / pharmacology
- Pregnancy
- Prenatal Exposure Delayed Effects
- Progesterone Congeners / pharmacology
- Sexual Maturation / physiology
- Trenbolone Acetate / analogs & derivatives
- Trenbolone Acetate / pharmacology
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