Deep anestrous mares under natural photoperiod treated with recombinant equine FSH (reFSH) and LH (reLH) have fertile ovulations and become pregnant. 2017

Geraldine A Meyers-Brown, and Meaghan C Loud, and John C Hyland, and Janet F Roser
Department of Animal Science, One Shields Ave, University of California, Davis, CA 95616, USA.

The most common equine breeding practice to decrease the time to the first ovulation of the year is to use artificial lights starting December 1 in the Northern Hemisphere. It can take 60-90 d for this lighting regimen to induce a fertile ovulation. The success rate for pharmaceutical compounds to carry out the same process has been variable. One compound that did induce an early ovulation was recombinant equine follicle stimulating hormone (reFSH), but neither pregnancy nor cyclicity was established in that study. Starting on December 1, 20 deep-anestrous mares of light horse breeds (4-15 y old) with follicles ≤ 20 mm in diameter and progesterone < 1 ng/mL were maintained under natural photoperiod while 10 control mares were maintained under artificial photoperiod. Starting on February 6, treatment mares were randomly assigned to one of two groups: reFSH (n = 10) or reFSH/reLH (n = 10). Jugular blood samples were collected daily from all mares, and luteinizing hormone (LH), FSH, progesterone (P4), estradiol-17β (E2) and immunoreactive (ir)-inhibin were analyzed by radioimmunoassay (RIA). When the largest follicle reached ≥32 mm in diameter, reFSH treatment was discontinued in both groups while reLH treatment continued in the reFSH/reLH group until a cohort of follicles reached ≥35 mm in diameter. Human chorionic gonadotropin (hCG) was administered intravenously (iv) to induce ovulation, and mares were bred to a fertile stallion every other day until ovulation. Mares receiving either reFSH or reFSH/reLH developed follicles ≥35 mm within 5-6 d of treatment compared with 15.8 ± 3.4 d in the control group. Both reFSH and reFSH/reLH induced ovulation in 100% of the mares within 10 d after treatment resulting in an 80% conception rate and a 70% pregnancy rate for both groups. Conception and pregnancy were designated as either presence of a 14 d old embryo (n = 16) or a fetal heartbeat at 24 d (n = 14), respectively. Only three mares in the control group ovulated within the same treatment period. Later ovulations in the control group resulted in 100% conception and pregnancy rates. At 25 d post-conception, treated mares that were pregnant (n = 7 per group) were administered prostaglandin (PGF2α) to terminate the pregnancy and later returned to estrus. Treatment with reFSH or reFSH/reLH given to deep-anestrous mares under natural photoperiod induced fertile ovulations that resulted in pregnancy and cyclicity when pregnancies were terminated.

UI MeSH Term Description Entries
D007315 Insemination, Artificial Artificial introduction of SEMEN or SPERMATOZOA into the VAGINA to facilitate FERTILIZATION. Artificial Insemination,Eutelegenesis,Artificial Inseminations,Eutelegeneses,Inseminations, Artificial
D007986 Luteinizing Hormone A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Luteinizing hormone regulates steroid production by the interstitial cells of the TESTIS and the OVARY. The preovulatory LUTEINIZING HORMONE surge in females induces OVULATION, and subsequent LUTEINIZATION of the follicle. LUTEINIZING HORMONE consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH and FSH), but the beta subunit is unique and confers its biological specificity. ICSH (Interstitial Cell Stimulating Hormone),Interstitial Cell-Stimulating Hormone,LH (Luteinizing Hormone),Lutropin,Luteoziman,Luteozyman,Hormone, Interstitial Cell-Stimulating,Hormone, Luteinizing,Interstitial Cell Stimulating Hormone
D010060 Ovulation The discharge of an OVUM from a rupturing follicle in the OVARY. Ovulations
D011247 Pregnancy The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH. Gestation,Pregnancies
D011994 Recombinant Proteins Proteins prepared by recombinant DNA technology. Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D005260 Female Females
D005640 Follicle Stimulating Hormone A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Follicle-stimulating hormone stimulates GAMETOGENESIS and the supporting cells such as the ovarian GRANULOSA CELLS, the testicular SERTOLI CELLS, and LEYDIG CELLS. FSH consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity. FSH (Follicle Stimulating Hormone),Follicle-Stimulating Hormone,Follitropin
D006736 Horses Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest. Equus caballus,Equus przewalskii,Horse, Domestic,Domestic Horse,Domestic Horses,Horse,Horses, Domestic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D017440 Photoperiod The time period of daily exposure that an organism receives from daylight or artificial light. It is believed that photoperiodic responses may affect the control of energy balance and thermoregulation. Dark-Light Cycle,Daylight Cycle,Light Cycle,Light-Dark Cycle,Cycle, Dark-Light,Cycle, Daylight,Cycle, Light,Cycle, Light-Dark,Cycles, Dark-Light,Cycles, Daylight,Cycles, Light,Cycles, Light-Dark,Dark Light Cycle,Dark-Light Cycles,Daylight Cycles,Light Cycles,Light Dark Cycle,Light-Dark Cycles,Photoperiods

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