Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Kenney RM.Normal histologic changes that occurred in concert with the ovarian cycle were evaluated. When combined with behavioral and physical findings, this evaluation enabled determination when there was synchrony between ovarian steroids (estrogen and progesterone) and their target tissues of endometrium. A system for classification as well as definitions of patterns types and degrees of severity of inflammatory and fibrotic changes was developed to facilitate a uniform system for description and communication. An attempt was made to relate the pathologic changes to their effect on fertility when fer...
Johnson L, Amann RP, Pickett BW.Changes within the equine seminiferous tubules during the cycle of the seminiferous epithelium were studied light and scanning electron microscopy (SEM). Once observed with SEM, tubules were sectioned and staged using light microscopy. As viewed by SEM, the weblike, spongy cytoplasm of germ cells or Sertoli cells in stages I and II extended over the entire height of the germinal epithelium. The cytoplasm of the basal portion of the germinal epithelium in stages III to VIII was similar to that in stages I and II. However, the cytoplasm which occupied the luminal third of the epithelium in stage...
Sandberg K, Juneja RK.Evidence for close linkage between the structural loci for albumin and Gc protein in the horse was presented. A recombination frequency (c) of 0.009 +/- 0.006 (95% confidence limits: 0.001 less than c less than 0.032) was estimated. These results were based on a study of a large sire family comprising 223 offspring from informative matings. No evidence of linkage disequilibrium was observed in one horse population studied.
Shehata R.The anatomy and histology of the male uterus were studied in the donkey and the horse. In the former it was found complete and long, while in the latter it was incomplete or absent. Some variations met with are described. A new concept of "internal male hermaphroditism' is presented and two types are differentiated.
Webster WR.A controlled on-farm trial was conducted to evaluate the effectiveness of a commercial gonadotrophin hormone mixture at overcoming a seasonal decrease in fertility in pigs in a sub-tropical environment (summer infertility). The average weaning to oestrus interval of the untreated sows was more than double that of the treated sows and this difference was highly significant. However, fewer of the treated sows farrowed and they produced smaller litters. The improvement in fertility in the treated group achieved by reducing the weaning to oestrus interval was more than cancelled out by an overall ...
Foote RH.Several inherited conditions associated with testicular defects, abnormal spermatogenesis and morphologically abnormal sperm have been found. These usually are controlled by single gene pairs. A notable exception is testicular size, with heritability in young bulls ranging from .42 to .88. Testicular size directly affects sperm output potential. The major contributor to variation in semen quality is the environment. Environmental effects may be temporary or permanent. Permanent effects occurring during prenatal and prepubertal periods and temporary or permanent factors acting after spermatogen...
Allen WR.Fertilized eggs reach the uterus of the mare by the sixth day after ovulation whereas unfertilized eggs remain lodged in the fallopian tubes for many months. However, embryo removal studies indicate that the fetal message for luteal maintenance in the pregnant mare is not transmitted until Days 14-16. The equine endometrial cups comprise a series of small, ulcer-like endometrial outgrowths which are present in the pregnant horn of the uterus between 40 and 150 days of gestation. Each cup consists of a discrete colony of large, gonadotropin-secreting, trophoblast cells derived from a specialize...
Kaminski M.The detection of the recessive null allele of horse serum esterase (Es) is possible in heterozygotes Es+/EsO which by starch gel electrophoresis appear like homozygotes Es+/Es+. Two methods are proposed, the titration of enzymatic activity of esterase and the immunochemical titration of esterase as antigen. These methods can be applied to solve the cases of suspect parentage or in population studies.
Deanesly R.During the 340 day pregnancy of the horse, the germ cells in the fetal ovary showed a meiotic prophase which began in days 60-70 and might be prolonged after day 200. Three or four successive oogonial mitotic proliferations passed into the meiotic prophase but the great majority of the oocytes first involved degenerated, and no appreciable numbers of primordial follicles were left behind. At 150 days of pregnancy and again at 197 days, oocytes in early meiotic stages filled the ovarian cortex. Primordial follicles were present, but rare. As the prophase gradually came to an end, groups of oocy...
Cox JE, Redhead PH.The long term effect of a single injection of 6,000 iu of human chorionic gonadotrophin (hCG) was studied in two pony stallions. Peripheral plasma samples were analysed for testosterone and oestrone sulphate. Testosterone concentrations were markedly elevated for five days after injection in both stallions. No adverse effects of these high concentrations were observed on concentrations later in the experiment. There was an initial increase in oestrone sulphate in one stallion, after which concentrations decreased to below pre-injection levels. The other stallion (whose initial oestrone sulphat...
Henneman K.Addressing poor performance issues in horses is a common yet challenging request to veterinarians. Often, there are limited field diagnostic or therapy choices. Growing lay popularity in integrative therapies, as well as increasing clinical incorporation, is creating more awareness of their clinical applications. Many modalities are showing increasing evidence of positive outcomes with minimal harm, but additional safety and efficacy evaluation is needed. Integrative modalities have unique ways of perceiving disease patterns that are different from more modern approaches, and these different p...
van der Velden MA, van der Harst MR.A literature review is given concerning the occurrence, clinical signs and possible treatment of the different types of inguinal herniation in foals. A six-week old filly with a reducible inguinal hernia is described in detail.
Brown AE, Hansen PJ, Asbury AC.Uterine flushings collected from mares before and after bacterial-induced inflammation were assayed for ability to opsonize Streptococcus zooepidemicus for phagocytosis by polymorphonuclear leukocytes. Opsonization was measured as the peak phagocytic rate of bacteria preincubated with uterine flushings relative to the peak phagocytic rate of unopsonized bacteria. Flushings from four mares with noninfected uteri were unable to opsonize bacteria regardless of whether uteri were flushed at estrus or on day 10 postovulation. In a second experiment, 7 X 10(9) live S. zooepidemicus were inoculated i...
Meliani S, Benallou B, Halbouche M, Haddouche Z.To enhance effectiveness of reproduction management in Arabian mares, factors influencing the time of foaling were investigated in this study. Methods: Data were collected at the National Haras of Tiaret in Algeria from 2003 to 2010. The foaling time of 255 Arabian pure bred mares, aged from 3 to 20 years were used for this study. Results: A total of 78.07% of foaling happens between 7 pm and 6 am. Conclusions: The influence of the month of foaling and the sex of the foal, on the time of foaling was statically significant.
Wilsher S, Ousey J, Allen WR.Abnormal cord attachment can be a manifestation of an inappropriate fixation position of the conceptus in the uterus, or it may result from disorientation of the conceptus post fixation. The potential for this resulting in fetal and neonatal compromise is reviewed in the light of previous reports and to which 3 cases within the authors' experience are added.
Seren E, Tamanini C, Gaiani R, Bono G.Plasma concentrations of progesterone and 17 alpha-hydroxyprogesterone were high in the 2nd and 3rd months of gestation, but 20 alpha-dihydroprogesterone increased from a level of 2 ng/ml, during the first 3 months, to 10-15 ng/ml during months 5-10, to reach 80-120 ng/ml during the last 30 days before foaling.
Lea RG, Bolton AE.Two-dimensional crossed immunoelectrophoresis of sera from pregnant and non-pregnant horses, using antisera developed against early pregnant mare serum, revealed the presence of two immunologically related proteins one of which appeared to be specific to the pregnant state. This pregnancy-specific protein had beta 2-electrophoretic mobility and was first detectable at Day 6 after successful mating with a stallion. The second protein had gamma 2-electrophoretic mobility and was present in sera from pregnant and non-pregnant horses. The proteins were termed beta 2-horse pregnancy protein and gam...
McKinnon AO, Belden JO.A surgical technique involving reconstruction of the caudal vaginal vault was used to correct vesicovaginal reflux in 32 of 34 mares. After surgery, 22 of 24 mares became pregnant, and embryos were harvested for transfer from 6 of the other 10 mares. It was concluded that the procedure was safe and efficacious.
Hooper RN, Taylor TS, Behrens EA, Varner DD.Ovariohysterectomy was performed in 20 mares at three stages of estrus. An ecraseur was used to severe the ovarian branch of the ovarian artery and vein and the ovarian suspensory ligament en masse. All other vessels supplying the ovaries and uterus were doubly ligated and transected. All mares survived. Complications were intraoperative hemorrhage in three mares, postoperative vaginal bleeding in two mares, and a hematoma in the remnant of the broad ligament in one mare. No adhesions between the uterine stump or remnants of the broad ligament and abdominal structures were detected by palpatio...
