Sexual behavior in horses encompasses a range of physiological and behavioral actions associated with reproduction and mating. This behavior is influenced by hormonal changes, environmental factors, and social interactions within equine groups. Key aspects include courtship, mating rituals, and the roles of both stallions and mares during the breeding process. Understanding sexual behavior in horses is essential for effective breeding management and welfare practices. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, influences, and implications of sexual behavior in equine species.
Thompson DL, Pickett BW, Squires EL, Nett TM.Sixteen stallions were castrated and 30 days later assigned to one of four treatments: (1) testosterone propionate (175 microgram/kg body weight), (2) 17 beta-estradiol-3-benzoate (44 micrograms/kg body weight), (3) a combination of both steroids or, (4) vehicle only. These dosage were administered every other day for 18 days. The dosages were then doubled and continued for 20 days. Concentrations of testosterone and estradiol in serum decreased rapidly after castration and stabilized within about 6 hours. Mean concentrations of testosterone and estradiol maintained by the steroids were 1.4 an...
Nyaga PN, Wiggins AD, Priester WA.Three hundred and sixty cases of diagnosed equine influenza reported to the Veterinary
Medical Data Program (VMDP) of the National Cancer Institute, U.S.A., were tested for the
independent effects of age, breed and sex, relative to a reference clinic-hospital population of 84,562
equine patients. Horses of age category 2-6 months showed a significant risk above unity for
infection with equine influenza virus whereas, horses in age category 7-10 yr showed a significant,
low and sparing risk. Horses under two months or over 10 years, as well as those in ages from 6
months to 7 yr had non-s...
Amann RP, Thompson DL, Squires EL, Pickett BW.Extragonadal reserves totalled 89 X 10(9) spermatozoa for 5--16-year-old sexually rested stallions and 60 X 10(9) for 2--4-year-olds. Regardless of age, the cauda epididymidis contained 62% of the total reserves and the vas deferens, including the ampulla, contained 7% of the total reserves of spermatozoa. The caput plus corpus epididymidis from 5--16-year-old stallions (N = 41) contained 14.9 X 10(9) spermatozoa per side as compared (P less than 0.01) to 8.5 X 10(9) for 2--4-year olds (N = 30). Frequency of ejaculation did not influence the number of spermatozoa found in caput plus corpus epi...
Thompson DL, Pickett BW, Berndtson WE, Voss JL, Mett TM.Stallions were subjected to a gradually increasing photoperiod beginning on October 15, 1973. The maximum artificial daylength (16 hr) was imposed on February 8, 1974, and maintained until October 6, 1974. Two ejaculates were collected from each of five treated and four control stallions weekly, with an interval of 24 hr between die paired ejaculates on the first and alternate weeks, and an interval of 1 hr on the second and alternate weeks. During summer, stallions subjected to the artificial photoperiod produced less (P<.05) gel-free semen and gel per ejaculate and had more (P<.05) spermatoz...
Nitschelm D, Van der Horst CJ.It has been shown that stimulation of the uterus of mares by the daily taking of biopsies can result in the occurrence of oestrous symptoms. This is accompanied by some follicular growth and a progesterone content in the blood often higher than 1 ng/ml. The following observations suggest that this progesterone originates in the uterus and not in the ovaries: (1) no active corpora lutea appeared to be present in the ovaries after ovariectomy, (2) ovariectomized mares showed the same oestrous symptoms in similar experiments and even mating took place, (3) in the uterine biopsies the concentratio...
Ganjam VK, Kenney RM.Total androgens, testosterone and total oestrogens were measured in twenty-one intact, nine unilaterally cryptorchid, three bilaterally cryptorchid stallions and four geldings. Total oestrogens were significantly higher (P less than 0-005) and total androgens significantly lower (P less than 0-05) in the bilateral cryptorchid compared to other groups. There was a significant (P less than 0-025) day and night variation in total androgen levels. Thyroidectomized and intact animals showed a marked decrease in total androgen as well as testosterone levels during the winter period thus showing an e...
A review of the literature is given concerning the anatomy and pathophysiology of the equine penis with regard to priapism: a prolonged erection of the penis not associated with sexual arousal. Several treatment options, such as flushing of the corpus cavernosum penis with heparinized saline and the creation of shunt between the corpus cavernosum penis and the corpus spongiosum penis are discussed. Subsequently, a case of priapism in a stallion following the injection of acepromazine, is discussed. The priapism resolved after the corpus cavernosum penis was flushed with the stallion under gene...
Irvine CH, Alexander SL.In an experiment conducted late in the physiological breeding season, 5 stallions were fitted with indwelling pituitary venous cannulae that permitted unobtrusive collection of blood coming from the pituitary and the hypothalamo-hypophyseal portal vessels. The next day, blood samples were collected at 5 min intervals for several hours while the stallions were resting. Pulses of gonadotrophin-releasing hormone (GnRH), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) occurred approximately once per hour. After this, an oestrous mare was brought into contact with each stallion for ...
Nitschelm D, Van der Horst CJ.It has been shown that stimulation of the uterus of mares by the daily taking of biopsies can result in the occurrence of oestrous symptoms. This is accompanied by some follicular growth and a progesterone content in the blood often higher than 1 ng/ml. The following observations suggest that this progesterone originates in the uterus and not in the ovaries: (1) no active corpora lutea appeared to be present in the ovaries after ovariectomy, (2) ovariectomized mares showed the same oestrous symptoms in similar experiments and even mating took place, (3) in the uterine biopsies the concentratio...
Mizobe F, Takahashi Y, Kusano K.Jockey safety is an important subject from a welfare perspective and public perception. This is the first retrospective case-control study that aims to identify risk factors associated with jockey falls (JF) in Thoroughbred jump races held by the Japan Racing Association (JRA). JF in 17,459 maiden-class race starts at eight racecourses from 2003 to 2017 were retrospectively reviewed. Data were extracted from a database and official accident reports maintained by the JRA. Thirteen possible risk factors were evaluated using multivariable logistic regression to identify those that were significan...
Pluháček J, Tučková V, Šárová R, King SRB.Whereas most studies on overmarking in mammals analysed the rate of overmarking, that those investigate time between exploration of an olfactory stimulus and the response to it remain less common, with inconsistent results. We examined the latency in time between elimination by the sender and sniffing by the receiver, and from sniffing and overmarking, in four captive African equid species to explore differences among species, and among age and sex classes. We investigated these latency time periods in light of three potential hypotheses explaining overmarking behaviour in equids: social bonds...
Thompson DL, Pickett BW, Squires EL, Nett TM.Sixteen stallions were castrated and 30 days later assigned to one of four treatments: (1) testosterone propionate (175 microgram/kg body weight), (2) 17 beta-estradiol-3-benzoate (44 micrograms/kg body weight), (3) a combination of both steroids or, (4) vehicle only. These dosage were administered every other day for 18 days. The dosages were then doubled and continued for 20 days. Concentrations of testosterone and estradiol in serum decreased rapidly after castration and stabilized within about 6 hours. Mean concentrations of testosterone and estradiol maintained by the steroids were 1.4 an...
Withrow JM, Sargent GF, Scheffrahn NS, Kesler DJ.Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrou...
Braun J, Muto Y, Sato K, Schallenberger E.Semen from three stallions was collected weekly for six months (December through May) to determine semen parameters and hormones (testosterone and estradiol-17 beta) in seminal plasma. Once a month three ejaculates were collected at intervals of one hour and examined accordingly. Testosterone and estradiol-17 beta were also determined in peripheral blood plasma (V. jugularis) collected twice a week. Semen parameters (volume, gel-free volume and sperm concentration) were clearly influenced by season. The testosterone concentration in peripheral blood plasma was lowest during December whereas in...
Dinger JE, Noiles EE.Eight sexually inexperienced, 2-yr-old Morgan stallions were used in a consecutive two-phase design with two groups of four stallions each. Each phase lasted 16 wk, with semen collections every 14 d. Libido scores were assigned to stallions during each semen collection. Scores ranged from zero to four, with zero indicating minimum and four representing maximum libido. In Phase 1, four stallions received daily forced exercise for 16 wk, and the remaining four stallions were confined to box stalls. In Phase 2, the previously exercised stallions were confined to box stalls, and the non-exercised ...
Magalhaes HB, Canisso IF.This study aimed to establish normal ranges and determine variables affecting the duration of gestation, placental and fetal eyeball measurements in donkeys. Jennies (n = 121) were submitted to transrectal ultrasonography at 15-day-intervals from 120 days of gestation until parturition. During each examination, variables assessed included: the combined thickness of uterus and placenta (CTUP), fetal eyeball diameter, amniotic membrane thickness, allantoic and amniotic fluids echogenicity, and chorioallantois edema. Parametric data were analyzed with t-test, linear regression, mixed models, AN...
Stout TA.Situations in which suppression or stimulation of reproductive activity in stallions has been attempted, or is desired, include resolution of the equine arteritis virus 'shedding' state, induction of testicular descent in inguinal cryptorchids, and the improvement of sperm production capacity and/or semen quality in sub-fertile stallions. However, the most common reason for wanting to modulate reproductive activity in a stallion is to alter the expression of sexual behaviour. In the case of intact stallions used for competitive or recreational purposes, the overt expression of sexual or aggres...
Hagen J, Kojah K, Geiger M.The angulation of the equine fetlock determines the load of associated tendons and probably their predisposition for injuries. However, it is questionable how the individual toe conformation and tendon properties interact with the dorsal metacarpophalangeal joint angle (DMPJ). Data are needed for a tangible evaluation of the equine limb conformation for more specific orthopaedic treatment. The aim was to evaluate the correlation between the DMPJ, toe conformation and cross-sectional area (CSA) of both flexor tendons; the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (...
Grillaert K.Erection and masturbation in horses are considered unwanted behaviors in training contexts, despite recognition that these are naturally occurring behaviors that are integral to the welfare of male horses. Equestrians, especially those who use positive reinforcement in their training, expressed concern that the presence of such behaviors might be associated with aggressive or sexual behaviors aimed at humans participating in horse-human interactions. The implications of such attitudes could negatively affect male horses by excluding them from welfare-friendly training systems. In this study, f...
A review of the literature is given concerning the anatomy and pathophysiology of the equine penis with regard to priapism: a prolonged erection of the penis not associated with sexual arousal. Several treatment options, such as flushing of the corpus cavernosum penis with heparinized saline and the creation of shunt between the corpus cavernosum penis and the corpus spongiosum penis are discussed. Subsequently, a case of priapism in a stallion following the injection of acepromazine, is discussed. The priapism resolved after the corpus cavernosum penis was flushed with the stallion under gene...
Metz GE, Serena MS, Panei CJ, Nosetto EO, Echeverria MG.A semen sample from a stallion infected during the 2010 equine arteritis virus (EAV) outbreak was received for viral isolation prior to castration of the animal. The virus was identified using a polyclonal antibody immunofluorescence test. Reverse-transcription polymerase chain reaction (RT-PCR) was used to amplify a region of the GP5 gene with primers GL105F and GL673R. The PCR products were purified and sequences of both strands were determined in a MegaBACE™1000 with inner primers CR2 and EAV32. A phylogenetic dataset was built with the previously reported sequences of five strains isolat...
