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.
Held JP, Prater P, Stettler M.A 9-year-old Arabian stallion with a 3-year history of infertility was evaluated for breeding soundness. Both testes were small. Ultrasonography revealed a small amount of free fluid between the tunics of both testes. Results of cytologic examination of the fluid were unremarkable. On semen examination, progressive motility was 10%, and total number of spermatozoa in the ejaculate was 6.6 x 10(9), of which 92% were abnormal. Predominant abnormalities were head defects (75%): 57% of the heads had single or multiple vacuoles, and 60% also had midpiece swelling or bending.
Yamashita K, Fujinaga T, Okumura M, Takiguchi M, Tsunoda N, Mizuno S.The serum concentration of C-reactive protein (CRP) in horses was measured by single radial immunodiffusion (SRID) using rabbit anti-equine CRP serum to evaluate the significance of CRP as an acute-phase reactive protein. In serum samples of clinically normal newborn thoroughbred foals before being given colostrum, serum CRP was not detectable (less than or equal to 1 microgram/ml). The serum CRP concentration was found to increase quickly and reach a peak level of approximately 14.1 micrograms/ml in 12-month-old horses. Then, it decreased gradually to reach a low value of 5.4 micrograms/ml in...
Lowis TC, Hyland JH.The occurrence of fertile oestrus early in the breeding season is of paramount importance to the Thoroughbred industry to facilitate early conception. This paper compares 2 techniques for inducing fertile oestrus in anoestrous mares using either an extended photoperiod alone or together with gonadotrophin-releasing hormone (GnRH) infusions. Eleven mares were placed under conditions of 16 h light and 8 h darkness and 5 of these were implanted with osmotic minipumps delivering approximately 100 ng GnRH/kg/h for 28 days (treated mares). The treated mares ovulated 27.7 days earlier than and concei...
Putnam MR, Bransby DI, Schumacher J, Boosinger TR, Bush L, Shelby RA, Vaughan JT, Ball D, Brendemuehl JP.Effects of the endophyte Acremonium coenophialum in tall fescue on pregnant mares and foal viability were evaluated. Twenty-two mature pregnant mares were randomly chosen to graze either Kentucky-31 tall fescue that was free from A coenophialum (endophyte-free, EF) or tall fescue infected with A coenophialum (endophyte-present, EP) after the first 90 days of pregnancy through parturition. Concentrations of pyrrolizidine and ergopeptine alkaloids were significantly greater in EP grass, compared with EF pasture. Ten of 11 mares grazing EP pasture had obvious dystocia. Mean duration of gestation ...
Willis P, Caudle AB, Fayrer-Hosken RA.Objectives of the present research were to determine the influences of types of media, sera, time and hormones on equine oocyte in vitro maturation (IVM). The following types of media and sera were evaluated: Menezo's B2 medium (B2), modified Tissue Culture Medium 199 (TCM), Defined Medium (DM), fetal calf serum (FCS), mare serum collected on the first day of estrus (MS), and mare serum collected on the day of ovulation (MSO). Resultant oocyte maturation was compared with the control: DM with bovine serum albumin (BSA). Effect of culture time (0, 15, and 32 hr) and the following hormones on oo...
Enders AC, Liu IK.The structure of the equine chorionic girdle between days 28 and 42 of gestation was examined. Of particular interest were differentiation of trophoblastic cells within the girdle, adhesion between girdle and endometrium, invasion and displacement of the uterine epithelium, and the nature of the endometrium when girdle cells migrate into it to form endometrial cup cells. The chorionic girdle, identified initially as a band of tall columnar cells, becomes a stratified columnar epithelium indented by clefts and pits. Adhesion to and penetration through the endometrial luminal epithelium are rapi...
Curran S, Ginther OJ.Accuracy of transrectal ultrasonic diagnosis of fetal gender by identifying and locating the genital tubercle was assessed in 85 horses and 102 dairy heifers and cows. Examinations were made once (horses and cattle) under farm conditions (cattle) on approximately Days 50 to 100. Definite diagnosis was made by removal of fetuses (horses) or after calving or abortion (cattle). In both species and both parities, accuracy was 100% (109 109 totaled over both species) when the certainty level recorded at the time of examination was 95 or 99%. At the lower levels of certainty (65 to 80%, 85 to 90%), ...
Stevenson KR, Parkinson TJ, Wathes DC.Jugular venous blood samples were collected throughout a complete oestrous cycle from 9 mares for measurement of progesterone and oxytocin by radioimmunoassay. Mean oxytocin concentrations remained at approximately 1 pg/ml throughout, with no evidence of cyclic variation in the release pattern. Extracts of corpus luteum and follicles obtained from a further 33 mares at different stages of the cycle all contained oxytocin concentrations of less than 10 pg/g wet weight of tissue. We conclude that the ovaries are not a source of circulating oxytocin during the oestrous cycle in this species. The ...
Meyers PJ, Bonnett BN, McKee SL.This prospective field study was designed to describe the incidence of early embryonic mortality (EEM) and factors associated with the cause of EEM on three equine breeding farms in Ontario during the 1989 breeding season. Early embryonic mortality was defined as the loss of a single embryo during the first 40 days of pregnancy (day 0 = day of ovulation or last breeding). Pregnancy diagnoses and subsequent embryonic losses were observed by serial trans-rectal ultrasonography between days 12-20 (PD1) and 21-30 (PD2), and by trans-rectal ultrasonography or palpation per rectum between days 31-40...
Hrudka F, Betsch JM, Kenney RM.Anomalies of centriolar derivatives were identified in ejaculates and testicular and tracheal biopsies of a sterile stallion, using light, scanning, and transmission electron microscopy. LM revealed that over half the sperm population had only a vestigial or no tail, while the rest had tails of variable length and shape. The vestigial tail was represented by its anlage, which was implanted on the nucleus and differentiated up to capitulum and collum stage. The stunted tail had an axoneme and its derivatives, but was short in all tail segments. Regardless of the tail length or shape, virtually ...
Waelchli RO, Winder NC.Endometrial sections from mares with varying degrees of mononuclear cell infiltration were examined for immunoglobulin (Ig)A-, IgM-, IgG(T)- and IgG(Fc)-containing cells, luminal and glandular epithelial cell Ig-staining and free interstitial Ig-staining, using a peroxidase anti-peroxidase technique. Mares with mild to moderate (Group 2) and mares with severe diffuse mononuclear cell infiltration, superimposed by acute endometritis (Group 3), had significantly higher numbers of Ig-containing cells than genitally-normal mares (Group 1). The differences between Groups 1 and 3 were significant fo...
Freeman DA, Weber JA, Geary RT, Woods GL.The objectives of this study were 1) to determine the time of embryo transport through the mare oviduct, 2) to determine whether equine embryos increase in diameter prior to the time of oviductal transport, and 3) to assess the stage of equine embryonic development at the time of oviductal transport. The time of oviductal transport (interval from ovulation to uterine entry) was estimated by collecting embryos from the mare oviduct or uterus at 2-hour intervals from 120 to 168 h postovulation. The time of oviductal transport was 130 to 142 h, since 9 9 embryos were located in the oviduct from 1...
Weber JA, Woods GL.A technique was developed in which the accessory sex glands of stallions were visualized with transrectal ultrasonography during ejaculation. The technique was judged to be effective, since 10 of 11 stallions were trained to tolerate transrectal ultrasonography during ejaculation; they ejaculated during 195 of 200 attempts, and acceptable visualization of their accessory sex glands and excurrent ducts occurred during 97 of 195 ejaculations. Sixty-five percent (89 136 ) of the recordings were successful for stallions that weighed more than 300 kg, whereas 14% (8 59 ) of the recordings were succ...
Rudman R, Keiper RR.The summer body condition of 47 adult feral ponies on Assateague Island (off the coast of Maryland, USA) was assessed in June 1988 using a visual body condition scoring system. Winter body condition for 36 of the ponies was assessed in February and March, 1989. The ponies were categorised by gender, reproductive status and location on the island, and body condition scores of the ponies in each category were then compared by statistical analyses. No significant seasonal differences were found in the body conditions of the ponies. However, body condition of stallions was better than that of mare...
Freeman DA, Butler JE, Weber JA, Geary RT, Woods GL.Oviductal and uterine embryos were collected from mares at 5 to 7 days following ovulation 1) to evaluate the effects of oviductal tissue explants on in vitro growth and development of equine embryos and 2) to study the morphologic development of equine embryos in culture. Embryos were incubated for 5 days in a medium (control group) or in medium supplemented with oviductal tissue explants (co-culture group). Embryos were evaluated and the media changed daily. Following 5 days in culture, 10 10 (100%) control embryos and 27 29 (93%) co-cultured embryos had doubled in diameter. All embryos that...
Heinrich B.This research article corrects a common misconception about the energy metabolism in horses during short sprinting and long-distance running events, emphasizing that short sprints are primarily powered by anaerobic activity, […]
Houpt KA.Some of the techniques that may be used to study social, reproductive, and ingestive behavior in horses are described in this paper. One of the aspects of equine social behavior is the dominance hierarchy or patterns of agonistic behavior. Paired or group feeding from a single food source may be used to determine dominance hierarchies quickly. Focal animal studies of undisturbed groups of horses may also be used; this method takes longer, but may reveal affiliative as well as agonistic relationships among the horses. Reproductive behavior includes flehmen, the functional significance of which ...
Weber JA, Freeman DA, Vanderwall DK, Woods GL.This study was conducted to identify embryonic products whose secretion was temporally associated with the oviductal transport period of the mare. Chemicals secreted by oviductal-transport-stage equine embryos were identified by incubating Day 6 or Day 7 early uterine embryos with 35S-methionine/cysteine, 3H-progesterone, or 3H-arachidonic acid for 24 h, and subsequently identifying radioactively labeled proteins (SDS-PAGE; n = 3 embryos), steroids (HPLC; n = 3 embryos), or prostaglandins (HPLC; n = 3 embryos) in the culture medium. Early uterine embryos secreted 116.1 +/- 45.5 pg of prostagla...
Liu DY, Lopata A, Pantke P, Baker HW.The present study demonstrates that horse and marmoset monkey sperm can bind to the human zona of salt-stored oocytes that failed to fertilize in vitro. Marmoset monkey sperm are also able to penetrate the salt-stored human zona. In contrast, human sperm do not bind to the zona of either horse or marmoset monkey oocytes. These results suggest that human sperm binding to the zona pellucida is more strictly species-specific than it is for horse and marmoset monkey sperm. In contrast, horse and marmoset monkey sperm contain receptors recognized by the human zona.
Whalley M, Robertson G, Bell C, Love D, Elphinstone M, Wiley L, Craven D.A homologue of the herpes simplex virus (HSV) glycoprotein D gene has been identified in the genome of equine herpesvirus-1 (EHV-1, equine abortion virus). An open reading frame in the middle of the short unique (US) region is capable of encoding a polypeptide of 402 amino acids that has 26% and 20% of its residues matching pseudorabies virus (PRV) gp50 and HSV-1 gD, respectively. Despite this low level of similarity, the positional identity of six cysteine residues and certain motifs, and the location of the EHV-1 gene, clearly define the EHV-1 polypeptide as one of a family of "gD-like" prot...
Martinuk SD, Manning AW, Black WD, Murphy BD.The sialylation of eCG was examined to determine its influence on the in vivo metabolism and biological activity of the molecule. Sialic acid was decrementally removed from eCG by incubation with agarose-linked neuraminidase for varying time periods. Pharmacokinetic parameters for the disappearance of 4,000 IU (267 micrograms) of three desialylated eCG preparations (20%, 53%, and 80% sialic acid removed) and control eCG were determined in sheep. The clearance rate of eCG increased (p less than 0.05) with each decrement of sialic acid. The removal of 53% sialic acid enhanced the distribution of...
Weber JA, Freeman DA, Vanderwall DK, Woods GL.The hypothesis that treatment of pregnant mares with prostaglandin E2 (PGE2) hastens the oviductal transport of equine embryos was tested by treating bred mares with PGE2 on Day 3 after ovulation and subsequently measuring the rate of hastened oviductal transport (estimated by the uterine embryo recovery rate on Day 4 after ovulation). In a preliminary, noncontrolled experiment, oviductal transport was apparently not hastened after intramuscular, intrauterine, or intraperitoneal PGE2 administration to bred mares (0/6, 0/3, and 0/3 mares, respectively). Oviductal transport appeared to be hasten...
McDonnell SM, Pozor MA, Beech J, Sweeney RW.A 9-year-old atactic breeding stallion was trained to ejaculate, with only manual stimulation, while standing on the ground. Ejaculates obtained yielded fertile semen with morphologic and motility characteristics within the range for normal stallions. This method extended the breeding life of a stallion unable to mount a live or dummy mare or to ejaculate into an artificial vagina while standing on the ground.
Kot K, Tischner M.The aim of the experiment was to determine the effect of a year-to-year prolonged daylength on the patterns of equine reproductive activity and results of embryo recovery. Experiments using Konik Polski mares were conducted over four reproduction seasons. Five mares were exposed to a regimen of artificially prolonged daylength (APD) and another five mares in a control group were kept under conditions of natural daylight. Both the control and experimental groups were examined for appearance of estrus, ovulation and also for the state of their coats. A single stallion was used for breeding all o...
Lowis TC, Hyland JH.This project surveys the reproductive performance of 154 foaling Thoroughbred mares on a commercial stud in southern Victoria. Of these, 96 were served on foal heat (FHS) and 58 were served at a subsequent prostaglandin-induced oestrus (PGS). The PGS group of mares performed more favourably in all aspects except the foaling-to-conception interval where there was a 9.4 day advantage to the FHS group. The first service conception rate in the FHS group was 47.9% compared with 55.2% in PGS mares. Second heat period conception rates were 46% vs 57.7% for FHS and PGS mares, respectively. Overall con...
Heap RB, Hamon MH, Allen WR.Aromatase distribution in membranes of preimplantation horse and donkey conceptuses was compared by measuring the incorporation of [3H]androstenedione into oestrone and oestradiol-17 beta. In the donkey conceptus, aromatase activity was similar in all the tissues examined (yolk sac, chorionic girdle and allantochorion), whereas in the horse it was generally lower and showed the relationship chorionic girdle greater than yolk sac greater than allantochorion. A higher proportion of labelled precursor was incorporated into oestradiol-17 beta by extra-embryonic tissues of the donkey compared with ...
Watson ED, Sertich PL, Zanecosky HG.Ovulation has been likened to an inflammatory process. Inflammatory cells accumulate in the ovulating follicle, presumably because of chemotactic factors. Chemotactic activity was measured in fluid aspirated from follicles of estrous mares 0, 12, 24, and 36 hours after ultrasonographic detection of a 35-mm follicle and IV treatment with 2,500 IU of human chorionic gonadotropin. Chemotaxis was assessed by measuring directional migration of equine neutrophils under agarose. Follicular fluid acted as a chemoattractant for neutrophils, but there was no significant difference in chemotactic activit...
Johnson L, Varner DD, Tatum ME, Scrutchfield WL.To evaluate the effect of age and season on Sertoli cell number per paired testes, ratio of germ cells per Sertoli cell, and daily sperm production, testes were obtained from 184 adult (4-20 yr) stallions at slaughter throughout one year. Numbers of Sertoli cells or germ cells were derived from nuclear volume density, volume of individual nuclei, and parenchymal volume. Germ cell to Sertoli cell ratios were calculated from cell numbers. Regression analysis was used to detect age-related differences in the breeding season (May-Jul) or throughout the year. A two-way analysis of variance was used...
Zekas LJ, Ramirez S, Brown MP.Left dorsal displacement of the large colon was diagnosed in a 3-year-old Thoroughbred gelding. Conservative treatment that included lunging after administration of phenylephrine and rolling while under general anesthesia was not successful. The displaced segment of colon was reduced surgically through a ventral midline incision, but displacement recurred 4 days after surgery. Ablation of the nephrosplenic space by suturing the nephrosplenic ligament to the splenic capsule was performed through the left flank. At followup 1 year after surgery, the horse had not had further signs of colic and h...
Hyde KA, Aguiar FLN, Alves BG, Alves KA, Gastal GDA, Gastal MO, Gastal EL.Characterization of the ovarian preantral follicle population is a necessary step to improve understanding of folliculogenesis and ovarian physiology. Therefore, in the present study, the preantral follicle population in the equine ovary in young and old mares was investigated according to follicular morphology, follicular class, distance from the geometric center using ovarian maps, and follicular density within ovarian portions (lateral vs intermediary) and regions (dorsal vs ventral). Ovaries were collected from an abattoir and histologically processed for evaluation, and the follicle popul...
Silberzahn P, Rashed F, Zwain I, Leymarie P.An homogenate from cortical tissue of mare adrenals was incubated in the presence of tritiated pregnenolone. The (3H) androstenedione and the (3H) testosterone synthesized during the incubation were extracted, purified, and co-crystallized to constant specific activity in the presence of unlabeled carriers. The rate of conversion of pregnenolone to androstenedione and testosterone was of the order of 5 and 0.15 per cent respectively. The high ratio of (3H) androstenedione to (3H) testosterone observed in this study suggests that androstenedione is the main androgen produced by mare adrenals. I...
Imai Y, Kurosawa H, Fujiwara T, Fukuchi S, Matsuo K, Kawada M, Ohtsuka G.Successful palliative repair of aortic atresia and hypoplastic aortic arch associated with tricuspid atresia in a neonate is described. The repair consisted of reconstruction of the hypoplastic aortic arch with an equine pericardial patch, division of the patient ductus arteriosus, connection of the pulmonary artery to the aorta, implantation of the proximal part of the ascending aorta into the main pulmonary artery, and anastomosis of a polytetrafluoroethylene graft 5 mm in diameter between the right ventricular outflow tract and the central pulmonary artery, which was transferred anteriorly ...
Merlo B, Mari G, Iacono E.The increase in demand for in vitro produced horse embryos is fostering the development of commercial laboratories for this purpose. Nevertheless, blastocyst production after intracytoplasmic sperm injection (ICSI) is still not as great as desired in most of these laboratories. In relation to horse oocyte classification, both expanded and compact cumulus-oocyte-complexes (COCs) are used for in vitro embryo production. The aim of this study was to compare in vitro embryo developmental capacity of COCs from horses including those with only the corona radiata, frequently collected after aspiratio...
Gomez-Cuetara C, Flores JM, Sanchez J, Rodriguez A, Sanchez MA.An histological study of the postpartum period in 29 mares was carried out. Uterine biopsies were taken daily during the first 10 days postpartum in a total of 87 samples. At day 0, equine endometrium was characterized in the surface by the presence of regularly ordered microcaruncles; the stratum spongiosum was oedematous and contained distended and scarce glands. Degenerative changes in microcaruncles and endometrial glands were present on day 1 postpartum. The epithelium of the microcaruncles from 2 to 5 days postpartum showed cytoplasmic vacuolization, karyorrhexis and an inflammatory reac...
Oberhaus EL, Thompson DL, Foster BA, Pinto CR.This experiment assessed the hormonal production, secretory aspects, and changes in luteinizing hormone (LH) receptor gene expression of early induced ovulatory-sized follicles relative to the first ovulatory-sized follicles occurring naturally in the spring. Anovulatory mares were treated on January 21 with (1) 50 mg of estradiol cypionate (ECP, n = 8) alone or (2) with ECP followed by two 3-g sulpiride injections (n = 8), 5 and 12 days later. Half of each group also received complete follicle ablation via transvaginal aspiration before ECP treatment. Ovaries were scanned regularly until ...
Gahne S, Gånheim A, Malmgren L.Different insemination doses have been used for artificial insemination(AI) in horses. Since the insemination dose can affect the pregnancy rate, it is important to ensure that an adequate dose be used regardless of the type of inseminationprotocol used. The aim of this study was to find out if it is possible to decrease the insemination dose from 500 x 10(6) progressively motile spermatozoa to 300 x 10(6) progressively motile spermatozoa and still maintain an acceptable pregnancy rate when using extended fresh semen. Thirteen stallions of known fertility and a well-defined group of 64 mares w...
Hodge SL, Kreider JL, Potter GD, Harms PG, Fleeger JL.Over a 2-year period, mares (n = 32) of predominantly Quarter Horse breeding and their foals were used to study the effects of photoperiod on reproduction during the periparturient period. Specific objectives of the study were (i) to evaluate the effects of an extended photoperiod regimen (16 hours' light) on gestation length, foal development, and postpartum reproductive performance, and (ii) to measure changes in plasma progesterone concentrations during the last trimester of gestation and plasma luteinizing hormone (LH) concentrations after foaling until ovulation. Mares in the extended day...
Trotter GW.Surgical exploration of the horse that has presumably had a normal castration or a previously successful cryptorchid surgery remains a distinct challenge. No hard and fast rules dictate a proper course of action for each case. If a horse was anesthetized for routine castration, discovered to have only one scrotal testis, had a brief exploratory on the nondescended side and was recovered, trauma to the inguinal region would probably be sufficiently minimal that an inguinal approach could be used at subsequent exploratory surgery. If the inguinal canal was extensively manipulated and the tail of...
Desantis S, Ventriglia G, Zizza S, De Santis T, Di Summa A, De Metrio G, Dell'aquila ME.Equine cumulus-oocyte complexes (COCs) were analyzed by means of 13 lectins to evaluate their glycoconjugate patterns and to verify differences between COCs recovered with compact (Cp) and expanded (Exp) cumulus. Cumulus cells showed a similar staining pattern in both Cp and Exp COCs with all lectins used, except for a higher reactivity with SNA and GSA II in Cp COCs and SBA in Exp COCs. The zona pellucida (ZP) showed (1) uniform staining with MAL II, RCA(120), and SBA in both Cp and Exp COCs, (2) trilaminar binding pattern with WGA as well as higher Con A reactivity in the outer region of bot...
Ginther OJ, Douglas RH, Lawrence JR.Responses of 22 veterinarians to a questionnaire and the records of three brood-mare farms were examined to obtain information on twinning. The incidence rates of multiple ovulations on the three farms were 9%, 11%, and 22%. The multiple ovulation rate was reduced 42-67% in foaling mares compared to barren and maiden mares. Multiple ovulations were significantly more frequent in Thoroughbreds (19%) than in Quarter Horses (9%) and Appaloosas (8%). Both the questionnaire and the farm records indicated a high degree of repeatability of multiple ovulations and twin pregnancies within mares and wit...
Hannan MA, Haneda S, Murata K, Takeuchi S, Cheong SH, Nambo Y.Until now, there have been no reports of foals born through embryo transfer after artificial insemination using frozen semen in Japan. The aims of this study were to develop a riding crossbred horse and evaluate the prospects of embryo transfer technology in multiplying horse population. In both donor and recipient mares, luteolysis was induced by the administration of 0.1 mg Cloprostenol to synchronize the onset of estrus, and ovulation was induced by administering 2000 IU human chorionic gonadotropin (hCG) or 0.75 mg Deslorelin. Frozen semen from an Irish Connemara pony stallion was used to ...
Rua MAS, Quirino CR, Rodrigues ACC, Christo MM, Barreto MAP.The objective of this study was to evaluate the environmental effects on embryo recovery rate and pregnancy rate of Mangalarga Marchador mares. The reproductive characteristics of donor and recipient mares were evaluated during five years in Brazilian tropical environment. The mares were used throughout the year and seasons were classified as: October to April (breeding season - BS); May (autumn transition out of the breeding season - ATBS); June to August (non-breeding season - nBS); and September (vernal transition into the breeding season - VTBS). Daily temperature rainfall and hours of day...
Gonçalves AR, Telo da Gama L, Antunes L, Guimarães H, Bliebernicht M, Duarte JC, Cosinha C, Duarte Rego B, Ferro da Costa P, Guimarães T, Rocha A....The objectives of this study were to establish baseline information for seminal traits in Lusitano stallions, to assess the impact of inbreeding, interval between collections and age on semen quality during the breeding and non-breeding seasons, and to estimate the corresponding genetic parameters. A total of 2129 ejaculates by 146 Lusitano stallions used for artificial insemination, obtained from four equine reproduction centers distributed throughout Portugal, over a period of 14 years (2008-2021), were included in the study. The seminal traits analyzed, and the corresponding means and stand...
Alexander SL, Irvine CH, Evans MJ.We used our nonsurgical technique for collecting pituitary venous blood to relate the dynamics of thyrotrophin-releasing hormone (TRH) secretion to the secretion patterns of both prolactin and thyrotrophin in periovulatory mares, either euthyroid (n = 5) or made hypothyroid by treatment with propyl-thiouracil (n = 5). Pituitary venous blood was collected continuously and divided into 1-min aliquots for 4 h. To test the effect of dopamine on the relationship between secretion patterns, sulpiride, a selective D2 receptor antagonist, was given i.m. after 2 h of sampling. Thorough testing of the m...
Henderson K, Stewart J.A dipstick, competitive immunoassay for rapidly measuring serum oestrone sulfate (OS) concentrations in horses was developed to distinguish mares 100 or more days pregnant from non-pregnant animals. 6-Ketoestrone 6-carboxymethyloxime conjugated to bovine serum albumin (oestrone CMO-BSA) was 'dotted' 25 mm from the bottom edge of 45 x 5 mm strips of polyester-film-supported cellulose nitrate membrane, pore size 3 microm. The strips were blocked, dried and a 15 x 5-mm cellulose absorbent sink attached 10 mm from the top of each strip. The manufactured dipsticks were stored with desiccant at room...
Snow DH.Anabolic steroids have been employed extensively in equine practice over the past 25 years. Their usefulness is largely dependent on subjective opinions, as only minimal studies have been carried out in horses. Therefore, their use will vary markedly between practitioners depending on their personal experiences and pressures by trainers to use them. They form part of rational therapy in a variety of conditions. In addition to use for increasing muscle mass, they are used to a varying extent in the raising of yearlings and in the training and racing of horses with the view of improving performa...
Pascoe RR.Within a group of 130 mares which, in the event, carried twin pregnancies, 29 (22.3 per cent) produced their twins following diagnosis of a single palpable follicle at service and a single pregnancy 42 days later. The whole group of 130 twin-pregnant mares gave birth to only 17 live foals (13 per cent). Breeding results for the following season were available for 102 of these mares, when 38 (37 per cent) produced live foals. Thus over the two seasons an average 23 per cent of this group produced live foals. In a second group, comprising 70 mares, twin pregnancy had been diagnosed in all of the...
Dippert KD, Jasko DJ, Seidel GE, Squires EL.Embryo recovery per ovulation has been shown to be lower in superovulated mares than in untreated controls. The objectives of this study were to 1) determine whether follicles stimulated with superovulatory treatment ovulate or luteinize without ovulation, 2) determine fertilization rates of oocytes in oviducts of superovulated and control mares, and 3) evaluate viability of early stage embryos from superovulated and control mares when cultured in equine oviductal cell-conditioned medium. Cyclic mares were randomly assigned to 1 of 2 groups (n=14 per group) on the day of ovulation (Day 0): Gro...
Scudamore CL, Pemberton AD, Miller HR, McDonnell AM, Thomson SR, Dawson A, Watson ED.An enzyme linked immunosorbent assay (ELISA) was developed and used to estimate the concentrations of the serine proteinase inhibitor, alpha-1 proteinase inhibitor (API), in uterine flushings recovered from mares at different stages of the oestrous cycle and before and after the induction of experimental endometritis. There was a significant increase in the concentrations of API and albumin relative to total protein in flushings recovered during oestrus compared with dioestrus but no difference was observed in the concentrations of these proteins relative to total protein before and after the ...
Jones LS, Berndtson WE.Testes from 47 stallions, 1-20 yr of age, were used to examine the influence of age on Sertoli and germ cell populations as well as on functional activity of Sertoli cells. For these stallions, the number of Sertoli cells per paired testes declined linearly with age, and was only 41.7% as great at age 20 as at age 2. However, development of reproductive organs proceeded until age 12-13, as evident from increases in paired testes weight and quantitative rates of spermatozoal production. Although the absolute number of Sertoli cells declined during this period of development, individual Sertoli ...
Pessoa GA, Martini AP, Trentin JM, Minela T, Fiorenza MF, Rubin MIB.The aim of this study was to compare the sperm separation technique using filtration through glass wool compared with just diluted cooled semen. Eighteen ejaculates were collected from 6 pony stallions of the Brazilian pony breed. Evaluations were done on pH, osmolarity, total motility, membrane functionality (HOST), membrane integrity (CFDA/PI), morphology and mitochondrial viability (MTT) in fresh, 24 and 48 h of cooled semen at 5°C. After dilution, the half of the extended semen was cooled (control group). The other half was cooled after filtration trough glass wool (filtered group). Reta...
Beltman ME, Walsh SW, Canty MJ, Duffy P, Crowe MA.The objective was to characterise the hormonal composition of follicular fluid from mares with distinct anovulatory-cystic follicles. Follicular fluid was aspirated from six mares that presented with cystic follicles and from pre-ovulatory follicles of five normal mares (controls). Differences in progesterone, oestradiol, testosterone, IGF-I and IGF binding were analysed using Fisher's exact test. There were greater (P < 0.03) follicular fluid oestradiol concentrations in normal follicles and the testosterone concentration of the cystic fluid was greater (P < 0.05) than that of t...
Unilateral orchiectomy (UO) may interfere with thermoregulation of the remaining testis caused by inflammation surrounding the incision site, thus altering normal spermatogenesis and consequently sperm quality. Two measures of sperm DNA quality (neutral comet assay and the sperm chromatin structure assay [SCSA]) were compared before UO (0 days) and at 14, 30, and 60 days after UO to determine whether sperm DNA changed after a mild testis stress (i.e., UO). The percent DNA in the comet tail was higher at 14 and 60 days compared to 0 days (P < 0.05) after UO. All other comet tail measures (i....
Kaps M, Okada CTC, Gautier CM, Aurich J, Aurich C.There is an increasing interest in the manipulation of ovarian follicular populations in large domestic animals because this could prove beneficial for assisted reproductive techniques such as ovum pick-up (OPU). The aim of the present study was to evaluate the effects of deslorelin slow-release implants (SRI) on the interovulatory interval, antral follicle count (AFC), number of follicles of different size ranges and plasma anti-Muellerian hormone (AMH) concentration in mares. To synchronize their estrous cycles, Haflinger mares (n = 12) were treated twice with a PGF2α analogue. One day afte...
Silvia PJ, Meyer SL, Fitzgerald BP.Twelve horse mares were used in a repeated-measures design consisting of 3 replicates of 4 mares each. On Day 6 following ovulation, luteolysis was initiated with an i.m. injection of prostaglandin F2 alpha (PGF2 alpha; Lutalyse, 10 mg). Either 12 (-12) or 36 (-36) h before PGF2 alpha (PRE), blood samples were collected simultaneously from the intercavernous sinus (ICS) and jugular (JUG) vein at 10-min intervals for an 8-h period. Pituitary capacity to exogenous GnRH (2 micrograms/kg BW, i.v.) was evaluated at the alternate time point within this period. Frequent sampling and GnRH challenge we...
Pazinato FM, Curcio BDR, Varela Junior AS, Corcini CD, Wendt CG, Moreira F, Schmit RA, Nogueira CEW.Placental tissues from humans, rodents, and farm animal contain leptin and its receptor. Expression of leptin has already been described in horses, although there is no description about immunolocalization of leptin and its receptor. The aim of the present study was to investigate the presence and distribution of leptin and ObR-b in the equine placenta at term by immunofluorescence staining, and the changes on plasma leptin concentrations during late gestation. The present study involved eight Criollo-type mares carrying healthy pregnancies. Blood samples were collected during the third trimes...
Ferreira JC, Ignácio FS, Rocha NS, Thompson DL, Pinto CR, Meira C.The present experiment was divided into two studies to investigate the effect of age and endometrial degeneration on uterine blood flow of mares throughout the immediate post-breeding period. In study 1, uterine blood flow was characterized in mares (n = 7 mares/group) with minimal, moderate or severe endometrial degenerative changes (GI, GII and GIII, respectively). In study 2, the effect of age was investigated using young (≤ 6 years) and old (≥ 15 years) mares (n = 7 mares/group). Uterine vascular perfusion and mesometrial pulsatility index (PI) were evaluated every hour from H0 (moment...
Bertero A, Ritrovato F, Evangelista F, Stabile V, Fortina R, Ricci A, Revelli A, Vincenti L, Nervo T.The purpose of this study was to observe -matured equine oocytes with an objective computerized technique that involves the use of a polarized light microscope (PLM) in addition to the subjective morphological evaluation obtained using a classic light microscope (LM). Equine cumulus-oocyte complexes (COCs, = 922) were subjected to different maturation times (24, 36 or 45 h), however, only 36-h matured oocytes were analyzed using CLM. The 36-h matured oocytes that reached maturity were parthenogenetically activated to evaluate the quality and meiotic competence. Average maturation perce...
