Fillies are young female horses, typically under the age of four, that exhibit distinct physiological and behavioral characteristics compared to mature mares and stallions. As they transition from foals to adulthood, fillies undergo significant growth and developmental changes, which can influence their nutritional requirements, health management, and training protocols. Horses, in general, are large, herbivorous mammals known for their speed, strength, and versatility, playing important roles in various human activities, including sport, work, and companionship. This page compiles peer-reviewed research studies and scholarly articles that explore the development, health, behavior, and management of fillies and horses across different life stages and environments.
Murray DR, Ladds PW, Johnson RH, Pott BW.Extensive subcutaneous phycomycosis of the lower hindlimb developed over a period of 8 months in a Thoroughbred filly. There was no response to treatments such as trichlorphon, sodium iodide, or etisazole. Extension of the limb lesion over the following 3 months was associated with an enlarged inguinal lymph node, which was removed. Characteristic phycomycotic lesions were observed in the node, and a fungus having the morphologic features of Hyphomyces destruens was isolated from both the limb and nodal lesions.
Gilmour JS, Fraser JA.An 8-month old Welsh Cob filly had shown progressive ataxia of the hindquarters since about 3 months of age. Autopsy revealed a venous malformation resulting in malacia in the ninth thoracic segment of the spinal cord. It is proposed that the tissue destruction associated with this congenital lesion gave rise to the ataxia.
Critchley KL.A 6 month Welsh pony filly with an interventricular septal defect in conjunction with a pulmonary stenosis due to a bicuspid pulmonary valve is described. The animal had poor exercise tolerance, a loud pansystolic murmur and a precordial thrill. Blood pressure and oxygen tension values obtained during cardiac catheterization suggested the diagnosis which was confirmed at autopsy.
Green DA.One hundred and four animals aged 13-18 months were measured at monthly or two monthly intervals, as were comparable numbers of animals 19-36 months old. Height, girth and circumference of the cannon bone below the knee were recorded, measurements for colts and fillies are shown separately. The average height at 18 months was 148 cm (15.01/2 h.h.) and at 36 months 156 cm (15.31/2 h.h.).
Scott EA.A weanling Quarter Horse filly developed ventral swelling of the lower cervical area after difficult passage of a stomach tube for deworming. Intermittent bilateral nasal discharge developed. Radiography revealed fluid and gas density dorsal to the trachea and esophagus. Surgical incision with drainage and debridement of the abscess and fistulous tract, facilitated by use of drains, led to complete recovery. Contrast medium injected after surgery demonstrated a communication between the abscess and the pharyngeal region.
A 4-week old Quarter Horse filly was evaluated for abnormal gait and lateral deviation of the cervical spine. Physical examination findings prompted radiographs and computed tomography of the thoracic vertebral column which revealed hypoplasia of several thoracic vertebral bodies and resultant scoliosis of the thoracic vertebral column and deviation of the left and right hemithoraces and associated ribs. Collectively, radiography and computed tomography provided an accurate description of the vertebral malformations resulting in scoliosis in this foal.
Canisso IF, Ellerbrock RE, Wilkins PA.An 18-hour-old colt was presented for abdominal discomfort, preputial swelling, and frequent posturing to urinate. Examination of the scrotum confirmed 2 testes and no scrotal or inguinal hernia. Transabdominal ultrasound identified a distended bladder and no free fluid in the peritoneal cavity. Inspection of the preputial cavity revealed that the internal lamina of the prepuce was mostly attached to the glans penis. The preputial cavity was lubricated and manual traction was applied to detach the internal lamina of the prepuce from the glans penis. The colt urinated spontaneously 1 hour after...
Faccin M, Landsgaard KA, Milliron SM, Jennings AH, Keith Chaffin M, Giaretta PR, Rech RR.A 1.5-year-old American quarter horse gelding (case 1) and an 11-month-old American quarter horse filly (case 2) were presented for acute onset pelvic lameness and lethargy. Case 1 had nasal discharge, while case 2 developed rapid muscle atrophy. Both horses had elevated serum creatine kinase activity. The horses showed similar polyphasic histiocytic and lymphoplasmacytic myositis with necrosis, mineralization, and regeneration. Additionally, case 1 had Streptococcus equi subsp. equi-induced suppurative retropharyngeal lymphadenitis with renal purpura hemorrhagica and myoglobinuric nephropathy...
Whittaker CJ, Reynolds BD, McCarthy PM, Taylor SF, Major D, Caruso KA, Smith J.A 3-year-old Thoroughbred filly presented to a referral equine hospital for surgical correction of a severe cicatricial lateral lower eyelid ectropion OD, with secondary exposure keratitis. The severity of the ectropion deemed that conventional ectropion repairs would be unsuccessful. Therefore, a soft tissue expansion device was used to create sufficient local tissue for a rotational graft with tension-relieving horizontal incisions to be performed to facilitate closure and acceptable eyelid apposition. The keratitis had resolved by two months postoperatively. There were no long-term complica...
McCue PM, Freeman DE, Donawick WJ.From 1977 to 1986, guttural pouch tympany was diagnosed in 15 horses--11 fillies and 4 colts. Review of the medical records provided results of physical, microbiologic, radiographic, and endoscopic examinations, treatment protocols, complications, and recovery rate. All affected horses had visible swelling in the parotid gland region, 9 had abnormal respiratory noise, 5 had pneumonia, and 1 had dysphagia. Six horses were treated by median septum fenestration alone, and in 8 horses, this procedure was combined with resection of the mucosal flap at the pharyngeal orifice of the eustachian tube. ...
Abutarbush SM.This report describes 2 foals with esophageal laceration due to ingestion of foreign bodies. Endoscopic examination of the esophagus revealed full thickness esophageal laceration in 1 colt and partial thickness laceration of the esophagus in the other. The esophageal obstruction was relieved by repetitive esophageal lavages and flush under general anesthesia in both foals. Lacération et obstruction œsophagiennes causées par un corps étranger chez deux jeunes poulains âgés de moins de 1 an. Ce rapport décrit deux poulains âgés de moins de 1 an souffrant d’une lacération œsophagienn...
Eagle RC, Font RL, Swerczek TW.An 18-month-old Standardbred filly had a large intraocular tumor involving the optic nerve. The tumor was a malignant medulloepithelioma, a rare intraocular neoplasm derived from the primitive medullary epithelium. By light microscopy the tumor had cords and lobules of primitive neuroepithelial cells that formed clefts and true rosettes. Electron microscopy of the rosettes showed a girdle of zonulae adherentes joining the apices of the cells as well as several basal bodies. This is the sixth report of equine intraocular medulloepithelioma, and, to the best of our knowledge, the first intraocul...
Wesson JA, Ginther OJ.Thirteen 6-8 month-old fillies were assigned to 3 treatment groups: Group 1 had a 16-h fixed daily photoperiod (16L:8D, N = 4), Group 2 a daily photoperiod equivalent to ambient daylength (control, N = 5), and Group 3 a 9-h fixed daily photoperiod (9L:15D, N = 4). The light treatments extended from 17 December to 9 August. Hair shedding occurred first in Group 1 followed by Group 2, then Group 3. The proportions of fillies with 1 or more ovulations (puberty) by the end of the project were 2/4, 5/5, 2/4 in Groups 1, 2 and 3, respectively. The hypothesis that a fixed daily photoperiod which corr...
Naden J, Squires EL, Nett TM.Puberty was studied using 15 fillies of Quarter Horse phenotype. Fillies were from dams treated daily from Days 20 to 325 of gestation with: (1) 2 ml neobee oil per 50 kg body weight (controls); or (2) 2 ml altrenogest (2.2 mg/ml) per 50 kg body weight. The clitoris was measured at birth and approximately every 12 weeks until 84 weeks of age. Blood samples were collected from 9 fillies (5 treated, 4 controls) every 4 days over a 28-day period at 8-week intervals from 4 to 68 weeks of age; sampling continued every 4 days after 72 weeks of age until first oestrus. Blood samples were collected da...
Allen BV.Results of blood counts have been analysed in three-year-old racehorses in training comprising 77 colt stayers, 27 colt sprinters, 61 filly stayers and 35 filly sprinters. The distributions of haemoglobin, erythrocyte count and haematocrit were significantly higher in colt stayers compared to the other three groups. In fillies these values were also significantly higher in stayers compared to sprinters. The erythrocyte count was significantly higher in filly stayers compared to colt sprinters but there were no significant differences between haemoglobin or haematocrit values in these groups. N...
Duggan VE, MacAllister CG, Davis MS.An 18-month-old Quarter Horse filly was evaluated because of dorsal displacement of the soft palate associated with epiglottic dysfunction that caused exercise intolerance and an abnormal respiratory noise. The abnormality of the epiglottis was corrected by use of a sedative dose of xylazine hydrochloride. There was no familial predisposition to hyperkalemic periodic paralysis, which may cause similar laryngopharyngeal signs, and the horse did not respond to administration of acetazolamide. There was no known history of trauma that could have caused neuritis, which has also been suggested as a...
Honnas CM, Schumacher J, Kuesis BS.A 6-month-old 300-kg Quarter Horse filly was treated for septic arthritis of the distal interphalangeal joint and septic navicular bursitis that developed as a result of a deep puncture to the foot. Initial treatment consisted of establishing ventral drainage for the navicular bursa, lavage of the distal interphalangeal joint, and administration of broad-spectrum antimicrobial drugs and non-steroidal anti-inflammatory drugs. Because of continuing sepsis in the distal interphalangeal joint, subsequent treatment included packing the defect in the bottom of the foot with cancellous bone in an att...
Robles M, Gautier C, Mendoza L, Peugnet P, Dubois C, Dahirel M, Lejeune JP, Caudron I, Guenon I, Camous S, Tarrade A, Wimel L, Serteyn D....Pregnant mares and post-weaning foals are often fed concentrates rich in soluble carbohydrates, together with forage. Recent studies suggest that the use of concentrates is linked to alterations of metabolism and the development of osteochondrosis in foals. The aim of this study was to determine if broodmare diet during gestation affects metabolism, osteoarticular status and growth of yearlings overfed from 20 to 24 months of age and/or sexual maturity in prepubertal colts. Methods: Twenty-four saddlebred mares were fed forage only (n = 12, group F) or cracked barley and forage (n = 12, group ...
Busse NI, Uberti B.A 12-year-old, multiparous, parturient show jumper embryo-recipient mare presented at a veterinary hospital, seven days past her due date and with a dilated cervix, for evaluation of mild colic. Gastrointestinal or metabolic abnormalities and fetal maldispositions were excluded as causes of dystocia, and a diagnosis of uterine inertia was made. There was no uterine response to oxytocin treatment. A live filly was delivered via C-section, and severe selenium deficiency was eventually confirmed in the mare, her offspring, and in the herd of origin. The filly was born with severe white muscle dis...
Claes A, Cuervo-Arango J, Colleoni S, Lazzari G, Galli C, Stout TA.The success of invitro embryo production (IVEP) in horses has increased considerably during recent years, but little is known about the effect of the speed of invitro embryo development. Blastocysts (n=390) were produced by intracytoplasmic sperm injection of IVM oocytes from warmblood mares, cryopreserved, thawed and transferred into recipient mares on Days 3, 4, 5 or 6 after ovulation. The time required for invitro-produced (IVP) embryos to reach the blastocyst stage was recorded (Day 7 vs Day 8). The likelihood of foaling was affected by the speed of invitro embryo development and recipient...
Tshewang U, Dowsett KF, Knott LM, Trigg TE.To investigate the effects of two doses (200 and 400 mg) of a water-soluble gonadotrophin-releasing hormone vaccine on the ovarian activity of 2-year-old fillies. Methods: A controlled vaccination dose rate experiment. Methods: Six 2-year-old Australian Stock Horse fillies were randomly allocated to three treatment groups; unvaccinated controls, those receiving 200 mg of the vaccine and those receiving 400 mg of the vaccine. Results: Ovarian activity of the treated fillies was suppressed at the peak of breeding season while that of untreated controls continued normally. The control fillies dis...
Abu-Seida AM, Shamaa AA.Congenital frontal osteoma has not been previously described in horses. This report records-for the first time-a congenital osteoma of the frontal bone in a 4-month-old Arabian filly. The filly had a frontal hard mass that was present at birth and then showed a slow and continuous growth. This mass appeared as a solitary, painless, oval dense tumor of compact bone, about 2 cm in diameter and 3 cm in length. The tumor was asymptomatic, and the skin over the mass was normal. Radiography revealed a well-defined oval, radio-dense mass projecting from the surface of the right frontal bone with no...
Mlodawska W, Okolski A.The effect of filly age on morphology of the ovaries, collected oocytes and their capacity for in vitro maturation (IVM) was examined. The ovaries of slaughtered fillies were classified into three groups, according to filly age: (I) <10 month old (<10MF); (II) approximately 1 year old (1YF); and (III) approximately 1.5 year old (1.5YF). The ovaries of mares were used as a control group. Ovarian morphology and collected oocytes were evaluated. Only oocytes with expanded (Ex) and compact (Cm) cumuli were used for IVM. In <10MF, 1YF, 1.5YF and mare groups, corpora lutea were found in the...
Davies Morel MC, Newcombe JR, Holland SJ.In order to assist in the accurate prediction of the timing of parturition in the mare true gestation length, along with the potential effect of a number of factors, was investigated. Data from 433 Thoroughbred foal pregnancies were used. Sequential ultrasonic scanning allowed the true gestation length (fertilisation-parturition) to be ascertained, as apposed to previous work, which used the mating-parturition interval. An average gestation length of 344.1 +/- 0.49 days was evident. Colt foal pregnancies were significantly (P < 0.001) longer (346.2 +/- 0.72) than fillies (342.4 +/- 0.65). Mont...
Timoney PJ, Powell DG.Between January 1978 and August 1982 the streptomycin resistant strain of the contagious equine metritis organism (CEMO) was isolated from 15 colts and two fillies in the United Kingdom and Ireland. A first season stallion was also suspected of having initiated an outbreak of contagious equine metritis (CEM) at the beginning of the 1982 breeding season. A detailed investigation of the breeding history of the dams and sires of each positive individual indicated that in a number of cases the CEMO was acquired either in utero or following transmission at the time of parturition. In several other ...
Neville E, Pigott J.To describe the clinical presentation of a Thoroughbred filly with acute hemoperitoneum from a splenic source immediately after racing. Methods: A 3-year-old Thoroughbred filly used for racing and that had raced shortly before presentation to the hospital. Unassigned: On presentation, the filly was quiet, alert, and responsive with a heart rate of 76 beats/min, pale mucous membranes, and absent borborygmi. All other physical examination parameters were within normal limits. Abdominal ultrasound was performed and revealed echogenic free abdominal fluid and a splenic hematoma. Abdominocentesis y...
