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.
Dewes HF, Lowe MD.Events leading to the deaths of two fillies at pasture are described. Pasture hay containing the flowering stages of Senecio jacobea (ragwort) had been fed three to four months earlier. Paddocks were subdivided with posts and rails treated with copper chrome arsenate. Six horses on the property chewed rails spasmodically. Both fillies presented with haemoglobinurea. Values in liver of 83 mg Cu kg and kidney 35 mg Cu kg wet weight and serum 1.4 mg Cu/l together with histophathology of seneciosis support a sequence of ragwort poisoning followed by copper accumulation in liver and kidney terminat...
Sweeney CR, Sweeney RW, Raker CW, Freeman DE.A 3-year-old Thoroughbred filly had a pharyngeal abscess causing obstruction of the upper respiratory tract. Diagnosis was made by a combination of endoscopy, biopsy, cytology, and radiography. Treatment with antimicrobials and analgesics resulted in successful resolution of the abscess.
Yovich JV, Aanes WA.A fracture of the caudal portion of the greater tubercle of the humerus was diagnosed in a 16-month-old Thoroughbred filly. Initially the fracture caused severe lameness. Radiography of the affected shoulder revealed the fracture fragment to be extra-articular, with a surrounding bony callus and no evidence of joint disease. After 5 weeks rest in a stall and 11 months at pasture, the filly was trained and raced without lameness.
Zamora CS, Vitums A, Foreman JH, Bayly WM, Weidner JP.On the basis of clinical and laboratory examinations, a ventricular septal defect or a variant of the tetralogy of Fallot was suspected in a 3-year-old filly with a history of poor growth rate and exercise intolerance. The filly was euthanatized and found to have a 3-chambered heart (cor triloculare biatriatum). The heart had 2 normally formed atria and a large common ventricle into which the right and left atrioventricular orifices opened and from which the aorta arose. There was a small separate chamber from which the pulmonary trunk originated. This chamber communicated with the common vent...
Naylor JM, Bell R.Orphan foals are best reared by fostering them onto a brood mare of appropriate size. If no foster mother is available, they can be reared on 2 per cent fat skimmed cow's milk fortified with dextrose at the rate of 20 gm per L. This should be slowly increased from 10 per cent of body weight at 1 day of age to 25 per cent of body weight at 10 days of age. The amount should then be held constant until weaning. Alternatively, foals can be reared on milk replacers. Manufacturers' feeding instructions rarely mimic the milk intake obtained by a foal nursing her dam, and problems have been observed i...
Crowell-Davis SL, Houpt KA.In colts and fillies observed from birth to 24 weeks old, coprophagy occurred from Weeks 1 to 19. Its frequency was greatest during the first two months. Coprophagy was rarely observed in mares and stallions. Foals usually ate the faeces of their mother but were observed to eat their own and those of a stallion and another unrelated mare. Urination by the foal occurred before, during or after 26 per cent of the coprophagy incidents. It is hypothesised that foals may consume faeces in response to a maternal pheromone which signals the presence of deoxycholic acid or other acids which the foal m...
Hamilton MJ, Hughes IM, Hegreberg GA.Serum testosterone levels were measured in normal young male horses (29 to 34 weeks old). No differences were found between gelded and intact males. The values for all the horses were low. On the basis of their testosterone levels, all the horses were prepubertal.
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 ...
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...
Heird JC, Lennon AM, Bell RW.Twenty-four yearling Quarter Horse fillies were divided into three groups (I) very limited handling, (II) intermediate handling and (III) extensive handling. At about 14 months of age, each horse was preconditioned for 2 weeks and then run in a simple place-learning T-maze test in which it had to locate its feed. Thirty trials were run daily for 20 days, with the location of the feed changed each day. To retire from the maze, a horse had to meet the criterion: 11 correct responses in 12 tries, with the last eight being consecutive. Horses in Group II required the fewest trials to reach criteri...
Irwin DH, Howell DW.The clinical and laboratory findings of illness in a 2-year-old Thoroughbred filly are described. The treatment employed, including unilateral nephrectomy, and the macro- and microscopic findings in the diseases kidney are presented and this rare case is discussed briefly.
Barth AD, Barber SM, McKenzie NT.A two month old Thoroughbred filly was presented with signs of depression, grinding of the teeth, frothing of the mouth and abdominal pain. These signs had persisted for two weeks despite treatment with mineral oil, dioctyl sodium sulfosuccinate, meperidine and antibiotics. A variety of diagnostic tests were done, the only abnormal finding was a stress leukon. On exploratory laparotomy the stomach was dilated with fluid and gas and the pyloric canal was constricted. Pyloroplasty resulted in correction of the condition. The etiological possibilities are discussed. This is believed to be the fir...
Slone DE, Bergfeld WA, Walker TL.A filly with ataxia and splinting and crepitation in the neck was found to have atlantoaxial subluxation. Radiographic diagnosis was based on the same criteria as those used in other species, ie, increased distance between the atlas and spine of the axis and increased distance between the dens and floor of the atlas. Extensive hemilaminectomy was performed to decompress the spinal cord. Stabilization was not attempted. Immediate postoperative response was encouraging, but the untimely death of the filly prevented further evaluation of the procedure.
Ellis RN, Lawrence TL.In two separate experiments food intakes and heart rates were monitored in New Forest and Welsh filly foals maintained at constant weight (by energy restriction) or allowed to grow normally for 180 (New Forest) or 147 (Welsh) days. Subsequent to these periods voluntary food intakes from feeding the same diet for 107 days (New Forest ponies) and herbage dry matter intakes from allowing free access to pasture for 42 days (Welsh ponies) were recorded. In the ponies maintained at constant live-weight food intakes and heart rates declined to reach and remain at new low levels. Herbage dry matter co...
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...
Madison JB, Young D, Richardson D.Shoulder luxation in a 3-year-old Thoroughbred filly was treated by closed reduction, using a calf jack to provide traction on the limb. Arthroscopic examination of the shoulder allowed removal of soft tissue and bony debris. After surgery, the filly was confined to a box stall for 6 months. Eight months after surgery, the filly was doing light work and was not lame. Muscular atrophy present before surgery had resolved. Use of a calf jack may allow reduction of shoulder luxation under field conditions.
Cebulj-Kadunc N, Kosec M, Cestnik V.To determine seasonal changes in circulating leptin concentrations, as well as leptin fluctuations in various patterns of seasonal ovarian activity, blood samples were taken in 107 Lipizzan fillies aged 1-4 years over the whole year from January to December. Serum concentrations were measured in samples obtained once a month (leptin) or twice a month (progesterone), and evaluated with respect to the age of animals (yearlings, 2-, 3- and 4-year olds) and the pattern of ovarian activity (anoestrous, seasonal cycle, prolonged cyclicity, continuous cyclicity). The mean and monthly leptin concentra...
Carpenter RS, Goodrich LR, Baxter GM, Joyce J, Wallis TW.To report treatment of a comminuted ulnar carpal (UC) bone fracture associated with carpal instability by pancarpal arthrodesis using 2 locking compression plates (LCP). Methods: Case report. Methods: A 2-year-old Thoroughbred filly. Methods: An UC fracture and luxation of the proximal row of carpal bones was diagnosed radiographically. Pancarpal arthrodesis was performed with 2 LCP positioned dorsolaterally and dorsomedially and centered over the carpus through a single skin incision. The filly was maintained in a full limb cast for 15 days, followed by a tube cast for 14 days, and subsequent...
Breit S.Ten horses, younger than 1 year, were used to investigate the articulatio interphalangea distalis of the pelvic limb. The expansion of the dorsal recess was compared to those of adult horses. The recessus dorsalis always formed a shape like the letter 'm' or like a triangle with oblique angles. Consequently the great proximo-distal expansion on the medial side of the dorsal recess very probably has nothing to do with the age of horses.
Valentine BA, Ross CE, Bump JL, Eng VM.Intramuscular hemangiosarcoma resulting in severe anemia and thrombocytopenia was diagnosed in a 3-year-old Thoroughbred filly. Necropsy revealed multiple tumors within skeletal muscles and multiple pulmonary metastases.
Klugh DO.A 5-month-old quarter horse filly was presented for evaluation of a congenital overbite. The horse was diagnosed with a class 2 malocclusion. A non-removable, acrylic bite plane was constructed to provide a surface for the occlusal forces to be directed in a manner maintaining the normal anatomic position of the premaxilla. The preservation of normal anatomic relationships provided free range of motion of the mandible and maximized its growth potential, limiting the malocclusion. Although normal occlusion was not attained, partial incisor occlusion was present 20-months following initial treat...
Yovich JV, Aanes WA.A fracture of the caudal portion of the greater tubercle of the humerus was diagnosed in a 16-month-old Thoroughbred filly. Initially the fracture caused severe lameness. Radiography of the affected shoulder revealed the fracture fragment to be extra-articular, with a surrounding bony callus and no evidence of joint disease. After 5 weeks rest in a stall and 11 months at pasture, the filly was trained and raced without lameness.
McClintock SA, Collins AM.A 6-month-old Quarter Horse weanling filly was presented with lethargy, weight loss, inappetance, mild diarrhoea, marked ventral oedema and severe panhypoproteinaemia. Serum antibody titres for Lawsonia intracellularis were very high but PCR to detect faecal shedding of the organism was negative. Proliferative enteropathy due to L. intracellularis infection was diagnosed. After treatment for 4 weeks with oral erythromycin and rifampicin the filly made a complete recovery.
Geor RJ, Clark EG, Haines DM, Napier PG.Systemic lupus erythematosus (SLE) was diagnosed in a 2-year-old Standardbred filly. Clinical signs of SLE included weight loss, bilateral symmetric alopecia, seborrhea, oral ulceration, and lymphadenopathy. Abnormal laboratory findings included a Coombs test-positive hemolytic anemia and positive antinuclear antibody test result. Histologic evaluation of multiple skin biopsy specimens revealed interface dermatitis with linear deposition of IgG at the basement membrane zones of the epidermis and hair follicles. The filly did not respond to glucocorticoid treatment and was euthanatized. Necrops...
Clark ES, Morris DD, Allen D, Tyler DE.A yearling Hanoverian filly had intermittent colic for 6 weeks, chylous peritoneal effusion, and a firm mass palpable per rectum. Exploratory laparotomy revealed mesenteric lymphadenopathy, adhesion of the mesenteric root to the duodenum and jejunum, distention of the mesenteric veins and lymphatic vessels, and increased jejunal venous pressure. Lesions in the duodenum, jejunum, and colon included infiltration of lymphocytes and plasma cells in the lamina propria.
Page AE, Stills HF, Horohov DW.Multiple hypotheses into the age-based susceptibility of animals to Lawsonia intracellularis exist, including the decline of passively acquired antibodies. Objective: To determine whether the decline in passively acquired antibodies in horses is responsible for the age predilection of equine proliferative enteropathy (EPE). Additional objectives included examination of various risk factors for the development of EPE as well as the determination of naturally occurring attack rates for clinical and subclinical EPE. Methods: Prospective, multifarm field study. Methods: A total of 369 mare and f...
Millar H.A 6-month-old filly was presented with unilateral epistaxis. Based on clinical signs, endoscopic examination, and postmortem examination, guttural pouch mycosis was diagnosed. The young age of the filly and the fact that this was the 2nd diagnosis of guttural pouch mycosis on this farm was unusual. Mycose de la poche gutturale chez une pouliche de 6 mois. Une pouliche âgée de 6 mois a été présentée pour épistaxis unilatérale. En tenant compte des signes cliniques, de l’examen endoscopique et de l’examen post-mortem, un diagnostic de mycose de la poche gutturale a été posé. Le je...
Cebulj-Kadunc N, Cestnik V, Kosec M.The onset of puberty and duration of seasonal cyclicity in Lipizzan fillies and young mares have been determined mostly by empirical data, but very little is known about the hormonal changes at puberty and during the seasonal cyclicity in this breed. Objective: To determine the onset of puberty and the course of the cyclicity in young Lipizzan mares from age 1-4 years. Methods: Blood samples were collected twice a month for 2 years from 46 Lipizzan fillies age 1-4 years. Progesterone concentrations, indicating ovarian activity, were measured using an EIA kit. Values above 6.4 nmol/l were taken...
Dewes HF, Lowe MD.Events leading to the deaths of two fillies at pasture are described. Pasture hay containing the flowering stages of Senecio jacobea (ragwort) had been fed three to four months earlier. Paddocks were subdivided with posts and rails treated with copper chrome arsenate. Six horses on the property chewed rails spasmodically. Both fillies presented with haemoglobinurea. Values in liver of 83 mg Cu kg and kidney 35 mg Cu kg wet weight and serum 1.4 mg Cu/l together with histophathology of seneciosis support a sequence of ragwort poisoning followed by copper accumulation in liver and kidney terminat...
Burlacu GH, Voicu D, Voicu I, Nicolae M, Petrache E, Georgescu GH, Balan S.The present study focused on energy and protein metabolism in pregnant and lactating mares, including the suckling and weaned growing horses, in order to determine feed availability, as also the energy and protein requirements. The authors found that the feeding diets, consisting of alfalfa hay, oats and compounds, had different availability values in terms of energy and protein, according to animal physiological conditions and age. Thus, the pregnant mares utilized the metabolizable energy (ME) and digestible crude protein (DCP) intake in average proportions of 64.5 +/- 3.2%, 54.6 +/- 3.0%, r...
Mack JK, Remler HP, Senckenberg E, Kienzle E.This study investigated the energy requirements of Warmblood foals with a change of the stud at weaning. Methods: Nine colts purchased at weaning participated in the study aged approximately 6 months to 1 year. They were transported to the stud by their breeders either having been separated from their dams in their home stable or upon arrival at the stud. The foals were offered a late first cut of haylage, oats and foal starter feed. To ensure individual feeding of concentrates, the foals were tethered twice daily. The total combined haylage intake of all foals per day was recorded. Individu...
Textor JA, Goodrich L, Wion L.An 8-hour-old Standardbred filly was evaluated because of an enlarging umbilical mass and stranguria. It was suspected that the mass was the urinary bladder; this was confirmed on surgical exploration of the abdomen. Despite a normal umbilical ring, the bladder had descended and partially everted through its urachal communication with the umbilical stalk. Partial cystectomy and umbilical resection were performed and resulted in an excellent clinical outcome. Evagination of the urinary bladder via the umbilicus has rarely been described in human infants, and, to our knowledge, it has not been r...
Tirosh-Levy S, Tatz A, Kelmer G.A 6-month-old Arabian filly escaped its handler while being led and slipped on pavement. The referring veterinarian recognized severe, soft tissue damage to the filly's lower jaw and referred the filly to the Veterinary Teaching Hospital for surgical management. Blessure de dégantage mandibulaire chez une pouliche arabe. Une pouliche arabe âgée de 6 ans s’est échappée de son préposé pendant qu’il la menait et a glissé sur la chaussée. Le vétérinaire traitant a reconnu des dommages graves aux tissus mous de la mâchoire inférieure de la pouliche et a recommandé la pouliche à l...
Shamis LD, Sanders-Shamis M, Bramlage LR.A 3-week-old Standardbred filly had a non-weightbearing forelimb lameness caused by scapular neck fracture. The fracture was repaired with 2 dynamic compression plates placed 90 degrees to each other. A 10-hole 4.5-mm narrow dynamic compression plate was placed on the cranial aspect of the scapular spine, and a 10-hole 3.5-mm dynamic compression plate was placed caudal to the scapular spine. One year after surgery, the filly was not lame when exercising in the pasture, and muscle atrophy was not evident on the affected limb. Eighteen months after surgery, the filly was in race training with no...
Mannaa M, Shamaa AA, Shawky A, Hassan IM, Refaey AM, Abu-Seida AM.Cervical vertebral stenotic myelopathy (CVSM), also known as equine wobbler syndrome or cervical ataxia, is a devastating neurological syndrome resulting from compression of the spinal cord at the cervical region. This report describes a novel surgical technique for treatment of 16-month-old Arabian filly with CVSM. The filly showed grade 4 ataxia, hypermetria, weakness of the hind limbs, stumbling during walking, and abnormal gait. Case history, clinical signs and myelography revealed spinal cord compression between the C3 and C4 and C4-C5. The filly underwent a novel surgical interference fo...
Broome TA, Allen D, Baxter GM, Pugh DG, Mahaffey E.A 2-year-old Arabian filly was referred for evaluation of a serosanguineous vaginal discharge. Palpation per rectum revealed a large, fluid-filled uterus and a uterine mass. The filly developed septic metritis and secondary laminitis as a result of torsion and necrosis of a pedunculated uterine mass. Ovariohysterectomy was performed. The entire cervix was removed with the uterus. Gross examination of the excised uterus revealed 3 intraluminal masses. Histologic evaluation identified the tumors as fibroleiomyoma. The filly recovered completely, and there was no recurrence of the tumor.
Bowman KF, Sweeney CL, Tate LP.A medial condylar fracture of the third metatarsal bone in a 2-year-old Thoroughbred filly was repaired successfully by use of compression bone plating. At discharge from the hospital, thickening of the metatarsus was evident, and proliferative changes were associated with the site of bone plate application. It was expected that these changes would limit the filly's use as a racehorse, and a return to training was not recommended. Especially in horses that may return to racing, use of compression bone plating initially should not replace stall rest or lag screw fixation treatment of this type ...
Foley JP, Legendre AM.Itraconazole, a tricyclic azole effective against a number of deep mycotic diseases, was used to treat a Quarter Horse filly with coccidioidomycosis. The horse was almost normal after 90 days of treatment. Five months after discontinuing itraconazole treatment, the filly had severe neck pain and neurologic signs from recurrence of coccidioidomycosis and was treated with itraconazole for an additional 6 months. Her clinical condition improved to almost normal and the filly has remained normal for 2 years. There was no evidence of drug toxicity.
Trump M, Kircher PR, Fürst A.Two fillies with hindlimb lameness and a tentative diagnosis of a pelvic fracture involving the acetabulum were examined using computed tomography (CT). The use of CT for these two cases revealed the exact course of the fractures and fissures, as well as the size and position of fragments, thus allowing for definitive diagnosis.
Naylor JM, Bell R.Orphan foals are best reared by fostering them onto a brood mare of appropriate size. If no foster mother is available, they can be reared on 2 per cent fat skimmed cow's milk fortified with dextrose at the rate of 20 gm per L. This should be slowly increased from 10 per cent of body weight at 1 day of age to 25 per cent of body weight at 10 days of age. The amount should then be held constant until weaning. Alternatively, foals can be reared on milk replacers. Manufacturers' feeding instructions rarely mimic the milk intake obtained by a foal nursing her dam, and problems have been observed i...
Smyth GB.A 3-year-old Thoroughbred filly examined because of poor performance after a fall was found to be ataxic. Radiography revealed a linear defect in the right dorsal cranial articular facet of the fifth cervical vertebra. The defect was thought to be a fracture or a developmental defect. Arthrodesis and stabilization were achieved by ventral implantation of a Bagby basket in the articulation between the fourth and fifth cervical vertebrae. The ataxia resolved within 4 months, and the filly was able to resume full race training.
Hahn K, Conze TM, Wollanke B, Distl O, Goehring LS, Witte TS.A 5-month-old draft horse filly was presented with incontinence and severe perivulvar dermatitis, which developed during the previous 2 months. Left-sided ectopic ureter entering in the caudal vaginal lumen, signs of cervix hypoplasia, and urine accumulation in the uterus were found during initial vaginal endoscopy. Therefore, a left ureter-nephrectomy was conducted under general anesthesia. Additionally, a cytogenetic examination was performed, which showed a XO monosomy with a 63,X/64,XX mosaic. This is the first case report presenting a chromosome abnormality in a draft horse filly combine...
Earing JE, Lawrence LM, Hayes SH, Brummer M, Vanzant E.The ability of young and mature horses to digest DM, OM, and NDF was compared using 6 weanling colts and 6 mature (13.2 ± 3.0 yr) geldings. Each colt was paired with a gelding, and the pair was adapted to a diet containing 67% alfalfa cubes and 33% concentrate for 21 d. During the adaptation period, horses were accustomed to housing and all handling procedures. The adaptation period was also used to adjust the amount of feed offered to minimize orts and to maintain similar rates of intake within a pair. After the adaptation period, a 5-d fecal collection period using fecal collection harnesse...
Vice JD, Shoemaker RS, Cho DY.A 2-year old Thoroughbred filly was examined for a 1-month history of persistent nasal discharge. Contrast radiography revealed a circumscribed mass within the right maxillary sinus which extended to the frontal sinus and ethmoid labyrinth. A discrete attachment of the mass to the ethmoid labyrinth was identified at surgery. Surgical removal of the mass eliminated the nasal discharge. On gross examination, the external structure of the mass was similar to a turbinate with a thin bony wall covered by a smooth mucosal membrane. The internal structure of the lesion had a lining membrane with mult...
Gunn AJ.This study involves the case of a young Thoroughbred filly who exhibited symptoms like reluctance to stand and vulva hemorrhagic discharge. The physical examination revealed normal physiological parameters, but an […]
