Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Topic:Reproduction
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.
Biological and immunological properties of zebra pituitary gonadotropins: comparison with horse and donkey gonadotropins. Previous studies from this laboratory have described the properties of purified luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from horse and donkey anterior pituitary glands. The present study afforded the opportunity to further characterize these previously purified hormone preparations and to compare them with enriched gonadotropin fractions from zebra pituitary glands. Although a single LH and FSH fraction was usually obtained for each pool of pituitaries, two separate zebra LH and two donkey FSH preparations were generated. Purified hormone preparations from the horse wer...
Gonadotropin-releasing hormone treatment induces follicular growth and ovulation in seasonally anestrous mares. A study was conducted to evaluate the effectiveness of gonadotropin-releasing hormone (GnRH) pulse infusion to stimulate follicular development and induce ovulation in seasonally anestrous standardbred mares. Seventeen mares were selected for use in this experiment, on the basis of a previous normal reproductive history, and were housed under a photoperiod of 8L:16D beginning one week prior to the start of the experiment (second week in January). Mares were infused with 20 micrograms (n = 7) or 2 micrograms (n = 6) GnRH/h, or were subjected to photoperiod treatment only (controls, n = 4). Seru...
Comparison of radioimmunoassay and enzyme-linked immunoassay for the measurement of progestogen in equine plasma and milk. Milk and plasma samples were obtained every 48 hours from eight pony mares for 40 days after foaling. Progestogen concentrations in milk and plasma were measured using an enzyme-linked immunoassay (ELISA) and compared with radioimmunoassay of the plasma. In general the three assays showed similar trends in progestogen concentration changes but absolute values varied considerably. Difficulty could occur in interpreting the results from single samples taken at times when progestogen concentrations were either rising (ie, after ovulation) or falling. ELISA could be used on plasma obtained by allo...
Surgical treatment of priapism in a stallion. Priapism occurred in a stallion after the administration of acetylpromazine. When conservative measures failed, the corpus cavernosum penis (CCP) was drained and irrigated, and a vascular shunt between the erectile bodies was created. Subsidence of erection resulted, but subsequently, the stallion was unable to retract or erect the penis. The stallion was castrated and the penis was surgically retracted into the sheath.
Hereditary multiple exostosis. A comparative human-equine-epidemiologic study. Hereditary multiple exostosis (HME), a bone tumor first described by Virchow, has been studied over a period of 15 years on a comparative basis. The horse, an excellent biomedical model for this physically deforming multiple bone tumor in man, has been utilized in this study. The etiology, hereditary pattern, potential for malignancy and other aspects of this strange affliction need additional clarification. This in-depth study of 261 individuals from 144 families was compared with that of 55 horses bearing the HME trait, selectively bred and studied over the same period. Important information...
Use of GnRH to induce oestrus in seasonally anoestrous mares. THE majority of non-pregnant mares pass through winter and
early spring in reproductive quiescence or anoestrus. True
anoestrus begins when day length decreases to less than 10.5 h
(Palmer, Driancourt and Ortavant 1982) and involves gradual
change in behaviour, hormone secretion patterns and follicular
dynamics. The length of anoestrus differs according to the
breed, latitude and management and may extend to seven or
eight months (Ginther 1974). It sometimes persists well into the
normal breeding season, especially in mares in poor physical
condition (Allen 1977).
In mares, as in oth...
Bactericidal activity of peripheral blood neutrophils during the oestrous cycle and early pregnancy in the mare. The oestrous cycles of 20 mixed-breed mares were synchronized with daily injections of 10 mg oestradiol-17 beta and 150 mg progesterone given i.m. for 10 days. On the 10th day, 10-15 mg prostaglandin F-2 alpha was administered i.m. to induce oestrus. Neutrophils were isolated from jugular blood on the 2nd or 3rd day of oestrus, Days 5 and 7 after ovulation or during early pregnancy (Days 18-34 of pregnancy). Neutrophils were challenged with Staphylococcus aureus and their bactericidal activity examined after 30 and 120 min of incubation for a reduction of colony forming units. Bactericidal act...
Imipramine-induced erection, masturbation, and ejaculation in male horses. Imipramine hydrochloride was administered to five male horses (400-500 kg b.wt.): one experienced young stallion, two mature normal breeding stallions, one 5-year-old stallion with erection and ejaculatory dysfunction, and one long-term castrated male horse. Oral imipramine treatment (100 to 600 mg, twice daily) led to frequent erection and masturbation while at rest in the stall in a nonsexual context. Intravenous imipramine treatment over a range of doses (50 to 1000 mg) similarly induced erection and masturbation in all animals. Erection typically occurred within 10 minutes after injection,...
Absorption of neomycin from the equine uterus: effect of stage of oestrous cycle and volume of vehicle. Plasma concentrations of neomycin were measured following intrauterine infusion of 3.3 mg/kg bodyweight neomycin sulphate. Mares in oestrus absorbed approximately 6 per cent of neomycin infused whereas mares in a luteal phase absorbed 56 per cent. The volume of infusate also affected absorption as increased volume resulted in decreased absorption. The decreased absorption both during oestrus and when large volumes were used was probably due to reflux of antibiotic through the cervix.
Hormone therapy for control of reproduction in mares and stallions. Because the reproductive performance of mares is lower than that of any other domesticated species, hormone therapy is important in ensuring fertility and proper management of pregnancy. Current techniques of hormone therapy are discussed.
Opsonins of Streptococcus in uterine flushings of mares susceptible and resistant to endometritis: control of secretion and partial characterization. The release of opsonins into the uterine lumen of mares susceptible or resistant to endometritis was examined after intrauterine inoculation of a filtrate of Streptococcus culture fluid or vehicle. Uterine flushings were collected at 0.5 hour before and 2, 4, 6, 8, and 24 hours after inoculation on day 2 or 3 of estrus and on day 7 or 8 after ovulation. Amounts of opsonins in flushings were quantified as the H2O2 produced by leukocytes incubated with flushings-opsonized bacteria, compared with H2O2 produced by leukocytes incubated with nonopsonized bacteria. Opsonin values in flushings increas...
[Endometrial cups in horses]. Endometrial cups in horses are outgrowths appearing in the uterine wall of the pregnant horn between approximately 38 days and 150 of gestation. The cups are structures which vary in shape from oval to irregular and have distinct raised edges, showing an ulcer-like form. The maximum measurements are approximately 5 X 2.5 X 2.5 cm. Microscopic examination shows that they consist of large epithelioid decidual-like cells having large nucleoli. Pregnant Mare Endometrium Gonadotrophin (PMEG) is produced in the endometrial cups. PMEG may be regarded as a precursor of Pregnant Mare Serum Gonadotrophi...
Role of progesterone in mobility, fixation, orientation, and survival of the equine embryonic vesicle. Luteal progesterone was removed by an injection of prostaglandin F2alpha or bilateral ovariectomy on Day 12 of pregnancy in pony mares. The embryonic vesicle remained mobile in the uterus until loss occurred on Days 13, 13, 15, or 19 in four prostaglandin-treated mares and Days 15, 17, 19, or 26 in four ovariectomized mares. Exogenous progesterone given daily, starting on Day 12, maintained pregnancy until Day 40 in five of five prostaglandin-treated and three of four ovariectomized mares. During two-hour mobility trials on Day 14, embryonic vesicles in mares without luteal or exogenous proges...
Juvenile granulosa cell tumour in an equine weanling. A juvenile granulosa cell tumour is described in a 3-month-old Arabian filly. The 32 X 27 X 27 cm tumour had replaced the right ovary. The neoplasm was composed of multiple nodules of neoplastic granulosa cells which formed microfollicles, macrofillicles and cysts, as well as solid nests and trabeculae. The supporting stroma contained theca cells. Mixing of the neoplastic granulosa cells and theca cells in disorderly fashion was noted. The diagnosis was based on age of occurrence and histological appearance.
Control of breeding in the mare. Six mares were studied over a period of two years under varying conditions of lighting from total darkness to normal ambient lighting. The mares continued to cycle during the winter under natural lighting and also when kept in total darkness. Circulating melatonin, progesterone and oestrogen concentrations were determined and related to clinical changes in the reproductive tract.
Influence of administration of ovarian steroids on the function of neutrophils isolated from the blood and uterus of ovariectomized mares. The function of blood and uterine luminal neutrophils from ovariectomized mares treated with ovarian steroids was investigated 18 h after intrauterine infusion of 1 X 10(9) Streptococcus zooepidemicus. Random migration of blood neutrophils under agarose was reduced by treatment with progesterone compared with that of neutrophils from oestradiol-treated and control mares. In-vitro addition of progesterone to blood neutrophils from acyclic ponies also reduced migration. Uterine neutrophils did not migrate under agarose which was probably an effect of bacterial phagocytosis. Hormone treatment had...
Passive immunization of cyclic mares against androgen: gonadotropin and progesterone concentrations and estrous characteristics. Antiserum generated in a horse against testosterone conjugated to bovine serum albumin (BSA) was administered to six lighthorse mares (androgen-immunized mares) 1 to 3 d before a prostaglandin-induced estrus and twice again at 2-d intervals. Six control mares were administered antiserum generated against BSA on the same schedule. Relative to testosterone, cross-reactivities of other steroids with the testosterone antiserum were (%): dihydrotestosterone, 52; 5 alpha-androstane-3 alpha,17 beta-diol, 8.6; androst-4-ene-3,17-dione, 1.2; and all others tested less than .1. Tritiated testosterone bi...
Changes in LH pulse frequency and amplitude in intact mares during the transition into the breeding season. Two groups of mares were exposed to an abrupt, artificial increase or a natural increase in daylength. In both groups, mean LH pulse frequency increased with time of year and was accompanied by a reciprocal decrease in LH pulse amplitude. A non-pulsatile pattern of LH secretion was observed in some mares sampled close to the day of ovulation. Maximum mean LH pulse frequency and the onset of the breeding season occurred earlier in those mares exposed to an abrupt artificial increase in daylength. In blood samples collected frequently, mean serum LH concentrations increased in relation to time o...
Motility and fertility of equine spermatozoa in a milk extender after 12 or 24 hours at 20 degrees C. The effects of extender and storage at 20 degrees C on equine spermatozoa were evaluated in two experiments using embryo recovery as the end point. In both experiments, inseminations were every other day, starting on Day 2 or 3 of estrus or after a 35-mm follicle was detected, with 250 x 10(6) progressively motile cells (based on initial evaluation). In Experiment 1, semen from two stallions was used to compare the motility and fertility of spermatozoa maintained in a) heated skim milk extender at 37 degrees C with insemination in <1 h; b) E-Z Mixin extender at 37 degrees C with inseminatio...
Effect of ovarian hormones on promotion of bactericidal activity by uterine secretions of ovariectomized mares. The bactericidal and phagocytic activities of blood neutrophils suspended in uterine washings and the mobilization of neutrophils into the uterine lumen were studied in ovariectomized mares receiving oestradiol benzoate (N = 4), progesterone (N = 4) or oily vehicle (N = 4). Uterine lavage was performed sequentially up to 144 h after induction of endometritis by intrauterine infusion of glycogen (1%). There was no significant difference between the 3 groups in speed of mobilization of neutrophils into the uterus in the first 6 h after infusion but there were significantly more uterine luminal n...
Pituitary responsiveness of mares challenged with GnRH at various stages of the transition into the breeding season. Four groups of mares, representing anestrus (AN; n = 8), early transition (ET; n = 7), late transition (LT; n = 8) and estrus (EST; n = 12) were used to examine release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) after a bolus injection of gonadotropin releasing hormone (GnRH) during the transition from anestrus into the breeding season. Estrous mares received GnRH on d 2 or 3 of estrus in the cycle immediately preceding slaughter. Anestrous, ET and LT mares received GnRH exactly 1 wk prior to slaughter. A single injection of GnRH (Sigma LHRH, L-0507, 2.0 micrograms/kg b...
Midline scrotal ablation technique for unilateral cryptorchid castration in horses. Thirty-nine unilateral cryptorchid horses were castrated, using a midline scrotal ablation technique. This approach was satisfactory to access both inguinal rings, to eliminate the need for 2 incisions, and to allow for completion of the surgery by primary closure. These horses recovered from surgery with few complications, returned to work promptly, and had excellent cosmetic results.
Influences of season and artificial photoperiod on stallions: testicular size, seminal characteristics and sexual behavior. To investigate the influence of daylength on the seasonal reproductive cycle of stallions, 21 stallions were assigned to one of three treatments: control, ambient (natural) photoperiod; S-L, 8 h light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984; S-S, 8:16 from July 16, 1982 until March 1984. Temperature was not controlled and was similar for all groups. Total scrotal width (TSW) was measured every 4 wk throughout the experiment. During 10 periods, semen was collected and evaluated every other day for 3 wk and sexual behavior was as...
Equine zona pellucida and capsule: some physicochemical and antigenic properties. The capsule which surrounds the pre-attachment equine embryo has been compared with the zona pellucida (zp) that it replaces, as well as with the rabbit blastocyst coverings, by means of physicochemical and immunological methods. Trypsin solution at pH varying between 7.5 and 9.0 completely solubilized the capsule, as did Na borohydride. However, solutions of pH 2.0 or 12.0, urea, high temperature (65 degrees C, 60 min or 80 degrees C, 30 min), mercaptoethanol and dithiothreitol were able to solubilize the zp but not the capsule at the concentrations used. Indirect immunofluorescence on cryost...
Effects of stallion seminal plasma on hydrogen peroxide release by leukocytes exposed to spermatozoa and bacteria. The ability of stallion seminal plasma to modify phagocytosis of spermatozoa and Streptococcus zooepidemicus was examined. Phagocytosis was monitored indirectly as the H2O2 produced by peripheral blood leukocytes after addition of spermatozoa or bacteria. Hydrogen peroxide production after addition of ejaculated spermatozoa was greater (P less than 0.01) than after addition of epididymal sperm. Furthermore, pre-incubation of epididymal sperm with 6.25-50% seminal plasma caused a dose-dependent increase in subsequent H2O2 production by leukocytes (P less than 0.05). In addition, equine serum wa...
