Yearlings refer to young horses that are between one and two years old. This developmental stage is significant in the growth and training of horses, as yearlings undergo physical and behavioral changes that prepare them for future performance or breeding roles. The term "yearling" is commonly used in the context of horse breeding, sales, and early training. Horses, as a broader category, encompass a wide range of breeds and ages, each with specific characteristics and needs. This page compiles peer-reviewed research studies and scholarly articles that explore the development, management, and health considerations of yearlings, as well as the broader aspects of equine physiology and care across different life stages.
Kornaś S, Cabaret J, Skalska M, Nowosad B.A 11-year survey on helminth intestinal infection of horses was done in seven provinces of southern Poland. 21,641 faecal samples were collected from horses of different age, sex, breed and management system originating from 84 farms. Age was the major factor influencing the cyathostome egg excretion, the maximum being observed in yearlings and second year horses. Parascaris was found mostly in foals and yearlings. The main factor for Anoplocephala was the access to pasture. The level of cyathostome egg shedding (EPG) could be related to sex (geldings had higher values of EPG), breed (Thorough...
Rossano MG, Smith AR, Lyons ET.Deworming horses with anthelmintics that have activity against encysted small strongyle larvae (L(3) and L(4)) is a common practice in parasite control programs. The two drugs currently available for this use are moxidectin (MOX) administered in a single dose of 0.4 mg/kg and fenbendazole (FBZ) given at the larvicidal dose (10mg/kg for 5 days). Here, we report the efficacy of MOX and the larvicidal dose of FBZ for reducing counts of strongyle-type eggs per gram of feces in naturally infected horses. Fecal egg counts (FECs) of 15 yearlings were observed following deworming. On day 0, 6 of the 1...
Kamm JL, Bramlage LR, Schnabel LV, Ruggles AJ, Embertson RM, Hopper SA.Analysis was performed to examine a method for refining the preoperative prognosis for horses that had surgery to remove apical fractures of the proximal sesamoid bones (PSBs). Objective: To determine if: 1) there was a difference in size or configuration of apical fractures between the different anatomical locations of the PSBs, which have been shown to affect the prognosis; and 2) the size or configuration could predict the prognosis for racehorses with these fractures. Methods: The study included 110 weanlings and yearlings and 56 training racehorses that underwent surgery to remove apical ...
Garrett KS, Pierce SW, Embertson RM, Stromberg AJ.OBJECTIVE-To determine the association between results of endoscopic evaluation of arytenoid function (AF) and epiglottic structure (ES) in Thoroughbred yearlings and racing performance at 2 to 4 years of age. DESIGN-Retrospective case series. ANIMALS-2,954 Thoroughbred yearlings. Procedures-Records of yearlings that had endoscopic evaluation of the larynx between 1998 and 2001 were obtained, and results were graded by use of standardized scales. A modified Havemeyer scale (grade I, II.1, II.2, III, or IV) was used to evaluate AF; ES was graded on a scale of 0 to IV. Records were annotated if ...
Southwood LL, Cohen J, Busschers E, Habecker P.To report a case of multiple acquired jejunal pseudodiverticula managed successfully by resection and jejunojejunostomy. Methods: Clinical report. Methods: Arabian filly. Methods: The filly was referred for signs of acute colic of several hours duration and had a 2-week history of inappetence and weight loss. Three meters of thickened, edematous, and dilated jejunum removed during exploratory celiotomy had an intussusception and numerous diverticula; jejunojejunostomy performed. The pathoanatomic diagnosis was proliferative enteropathy with pseudodiverticula formation and jejunal muscular hype...
Preston SA, Zimmel DN, Chmielewski TL, Trumble TN, Brown MP, Boneau JC, Hernandez JA.To estimate prevalences of various presale radiographic findings and of presale arthroscopy in horses offered for sale at the 2006 Keeneland September yearling sale and to compare sales prices between yearlings with and without various presale radiographic findings or a history of arthroscopy. Methods: 397 Thoroughbred yearlings. Methods: Cross-sectional study. Methods: Presale radiographs and health records were examined to estimate prevalences of various radiographic findings and presale arthroscopy. Sales price records were used to compare sales prices between yearlings with and without var...
Vineyard KR, Warren LK, Kivipelto J.To determine the effect of different sources of dietary n-3 fatty acids (FA) on plasma and red blood cell (RBC) FA composition and immune response, 18 Quarter Horse yearlings were randomly and equally assigned to 1 of 3 treatments: encapsulated fish oil (n = 6), milled flaxseed (n = 6), or no supplementation (control, n = 6). Fish oil contained 15 g of eicosapentaenoic acid (C20:5n-3) and 12.5 g of docosahexaenoic acid (C22:6n-3), and flaxseed contained 61 g of alpha-linolenic acid (C18:3n-3) per 100 g of FA. Horses had free access to bahiagrass pasture during the active growing season and wer...
Elsener J, Villeneuve A.The impact of a late fall treatment on the spring rise of fecal egg counts was evaluated in a controlled study with Canadian horses treated with 2 different dewormers immediately after removal from pasture for winter housing. The horses were stabled until the end of the trial period. Seventeen weanlings, 20 yearlings, and 15 2-year-old horses located in Ontario, which were presumed to be naturally infected with cyathostomins after pasture grazing, were randomly allocated to either a group treated with 0.4 mg/kg of moxidectin and 2.5 mg/kg of praziquantel or a group treated with 0.2 mg/kg of iv...
Van Grevenhof EM, Ducro BJ, Van Weeren PR, Van Tartwijk JM, Van den Belt AJ, Bijma P.Osteochondrosis (OC) is the most important orthopaedic developmental disorder in horses and may manifest in several different forms. No detailed study on the prevalence and/or interrelation of these forms is available, even though these data are a prerequisite for conclusive genetic studies. Objective: To assess the prevalence of the various manifestations of OC as detected radiographically and to evaluate possible relationships between their occurrence within the same joint and between different joints. Methods: The FP (femoropatellar), TC (tarsocrural) and MCP/MTP (metacarpophalangeal/metata...
van Grevenhof EM, Schurink A, Ducro BJ, van Weeren PR, van Tartwijk JM, Bijma P, van Arendonk JA.Osteochondrosis (OC) is an important orthopedic developmental disorder in many horse populations. A review of the literature revealed widely variable heritability estimates for the disorder. We estimated the genetic variables (heritabilities and genetic correlations) of various manifestations of OC. Femoropatellar, tarsocrural, and metacarpophalangeal and metatarsophalangeal joints of 811 randomly selected yearlings from the Royal Warmblood Studbook of The Netherlands, descending from 32 representative stallions, were scored for OC at 28 predilection sites. At each site, OC was scored in 5 cat...
Verwilghen D, Van Galen G, Vanderheyden L, Busoni V, Salciccia A, Balligand M, Serteyn D, Grulke S.To describe a technique for, and outcome after, mandibular osteodistraction in the horse. Methods: Clinical report. Methods: Warmblood horse. Methods: A half ring external fixator was applied on both sides of an osteotomy site performed on the mandible of a colt. A bite plate was placed on the upper incisors creating occlusion between lower and upper jaw. After a 5-day latency period, distraction was applied (1 mm/day) until the overjet was judged normal. Results: Mandibular elongation and correction of brachygnathia was obtained without major complications. Six months after the procedure the ...
Oliver LJ, Baird DK, Baird AN, Moore GE.To characterise the prevalence and distribution of radiographic changes in the hocks and stifles of Thoroughbred yearling colts and fillies in New Zealand and compare them with other populations of young horses. Methods: Repository radiographs taken in New Zealand for the 2003-2006 Thoroughbred national yearling sales were evaluated by two individual readers. The distribution of radiographic changes was classified as left side only, right side only, or bilateral. Lesions were categorised by type, location, and sex of the yearling. Complete sets of hock and stifle radiographs of 1,505 yearlings...
Howell PG, Nurton JP, Nel D, Lourens CW, Guthrie AJ.Cohorts of yearlings were sampled over a period of 6 years in a retrospective serological survey to establish the annual prevalence of serotype specific antibody to equine encephalosis virus on Thoroughbred stud farms distributed within defined geographical regions of South Africa. Seasonal seroprevalence varied between 3.6% and 34.7%, revealing both single and multiple serotype infections in an individual yearling. During the course of this study serotypes 1 and 6 were most frequently and extensively identified while the remaining serotypes 2, 3, 4, 5 and 7 were all identified as sporadic and...
Horohov DW, Breathnach CC, Sturgill TL, Rashid C, Stiltner JL, Strong D, Nieman N, Holland RE.While immune modulators are used routinely in equine medicine, their mechanism of action is not always known. Objective: To determine the effect of a commercial preparation of inactivated parapoxvirus ovis (Orf virus; PPVO) on cytokine gene expression by equine peripheral blood mononuclear cells (PBMC) both in vitro and in vivo. Methods: PBMC were prepared from 6 mixed-breed yearlings and cultured in vitro with PPVO with or without Concanavalin A (Con A) for 24 h. Effects on the expression of IFNalpha, IFNbeta IFNgamma, TNFalpha and IL-18 were analysed by real time quantitative PCR (RT-PCR). I...
Axon JE, Russell CM, Begg AP, Adkins AR.A 10-month-old Thoroughbred filly was presented with a 2-month history of recurrent fever and pleural effusion. Major clinical findings were pyrexia and congested mucous membranes. Clinical pathology tests revealed an erythrocytosis, hyperfibrinogenaemia and hyperglobulinaemia. Pleural fluid was seen on ultrasonographic examination of the thorax and analysis of a thoracocentesis sample indicated a lymphocytic, modified transudate. A transtracheal aspirate was normal. The erythrocytosis persisted despite IV fluid therapy. Arterial blood gas analysis and bone marrow aspirate were normal. These f...
Frazer ML.Lawsonia intracellularis is an emerging equine pathogen that is a cause of equine proliferative enteropathy (EPE). Objective: To describe the signalment, month of presentation, common clinical signs, clinicopathologic values, diagnostic tests used, antimicrobial use, and survival status in horses affected with EPE; to evaluate how affected horses sold at public auction as yearlings; and to determine results of fecal polymerase chain reaction (PCR) and serum immunoperoxidase monolayer assay (IPMA) results in age matched, clinically normal herdmates. Methods: The study group was 57 horses treate...
Diallo IS, Hewitson GR, de Jong A, Kelly MA, Wright DJ, Corney BG, Rodwell BJ.Twelve nasal swabs were collected from yearling horses with respiratory distress and tested for equid herpesvirus 1 (EHV-1) and equid herpesvirus 4 (EHV-4) by real-time PCR targeting the glycoprotein B gene. All samples were negative for EHV-1; however, 3 were positive for EHV-4. When these samples were tested for EHV-2 and EHV-5 by PCR, all samples were negative for EHV-2 and 11 were positive for EHV-5. All three samples that were positive for EHV-4 were also positive for EHV-5. These three samples gave a limited CPE in ED cells reminiscent of EHV-4 CPE. EHV-4 CPE was obvious after 3 days and...
Masuda T, Takakura A, Kobayashi S.Flight and avoidance reactions from human were examined using 168 postweaning Thoroughbred foals in 22 breeding farms. Further 114 yearlings of 168 foals were tested in the following summer. The foal handlings by the stabler were asked in questionnaire. The relationship between the behavioural reactions and the foal handling frequencies was analyzed. The flight reaction was estimated as the distance from the animal to a stranger when the animal began to flight away from his approach. The avoidance scores were set up from (1) (not resistant) to (5) (touch rejection) from human touching. In the ...
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...
Preston SA, Trumble TN, Zimmel DN, Chmielewski TL, Brown MP, Hernandez JA.To characterize lameness during training and compare exercise variables and financial returns among yearling Thoroughbreds that were bought for the purpose of resale for profit. Methods: 40 yearling Thoroughbreds. Methods: Prospective study. Methods: Horses purchased at yearling sales (summer 2004) were trained prior to resale at 2-year-olds in training sales (spring 2005). Horses were monitored daily for diagnosis and treatment of lameness during training. Selected variables, including sex, age, purchase price, lameness, distance (No. of furlongs) galloped during training, and financial retur...
Rogers CW, Gee EK, Firth EC.To obtain initial baseline data on the management of Thoroughbred stud farms in the North Island of New Zealand. Methods: Data on the management of Thoroughbred stud farms were collected from a sample of 22 stud farms located in the south Auckland/Waikato region (n=15) and lower North Island (n=7) of New Zealand, using a face-to-face survey. The studmaster provided information on the size, scope and management of the farms during the 2004/2005 breeding season. Analysis was based on the location of the farm and size of the breeding operation (number of resident mares). Results: Effective farm s...
Huggons N.A Thoroughbred yearling was presented with neurological, radiographic, and myelographic abnormalities consistent with cervical vertebral stenotic myelopathy. Surgical correction was performed by using ventral cervical interbody fusion at 3 intervertebral spaces. The patient recovered uneventfully from surgery. The neurological status remained unchanged initially; however, significant improvement was noted 37 weeks postoperatively. Un Thoroughbred d’un an a été présenté avec des anomalies neurologiques, radiographiques et myélographiques compatibles avec une myélopathie sténosée des ...
Robert C, Valette JP, Denoix JM.The relationship between the presence of radiological abnormalities and subsequent racing performance is controversial. However, as training is expensive and time consuming, it would save time and money to identify subjects with osteo-articular lesions not compatible with a normal racing career on the basis of routine radiographic screenings at yearling age. Objective: To evaluate the impact of osteo-articular lesions on racing ability in French Trotters and identify radiographic changes associated with failure in 'qualification', in order to provide objective criteria for selection of horses ...
Cirak VY, Güleğen E, Yildirim F, Durmaz M.The aim of the present study was to determine the efficacy and the so-called "egg reappearance period" (ERP) of doramectin in horses naturally infected with strongyles during a period of 34 weeks. A group of yearlings of 10 animals was treated intramuscularly with doramectin at a dose rate of 0.2 mg/kg bodyweight (BW) at the begin of the grazing season. To obtain comparable data, another group of yearlings (n = 10) was treated orally with ivermectin at a dose rate of 0.2 mg/kg BW. Individual faecal samples were examined for strongyle egg counts per gram of faeces (EPG) in two-week intervals. T...
Love S, Wyse CA, Stirk AJ, Stear MJ, Calver P, Voute LC, Mellor DJ.The assessment of belief that equine conformation is associated with performance and durability is a fundamental concept of horsemanship. Surprisingly, there is almost no quantitative evidence to support these beliefs. Objective: To assess the prevalence and heritability of conformational traits in Thoroughbred yearlings, and investigate their significance for subsequent turf flat-racing performance and durability. Methods: Nine selected conformational traits were assessed in a consistent, qualitative manner by a single veterinary observer and entered into a database together with details of p...
Santschi EM, Leibsle SR, Morehead JP, Prichard MA, Clayton MK, Keuler NS.There is little information available about conformational changes in the forelimbs of growing foals. Objective: To describe the conformation of the carpus and fetlock of Thoroughbred foals from birth to yearling sale age. Methods: Subjective assessments of the fetlock and carpal conformation of 119 Thoroughbred foals were made within the first month of life and then at 30 day intervals until at least age 120 days. At least 70 subjects were examined further at 60 day intervals until September of their second year. Conformation grades are reported for 5 age groups: first 7 days and at a mean of...
Schnabel LV, Bramlage LR, Mohammed HO, Embertson RM, Ruggles AJ, Hopper SA.Studies on arthroscopic removal of apical proximal sesamoid fracture fragments in Thoroughbred (TB) horses age > or = 2 years have reported a high success rate. However, there are no reports documenting the racing prognosis of TB horses that undergo such surgery as weanlings or yearlings. Objective: To describe the incidence of apical proximal sesamoid fractures in immature TB horses, age < 2 years and determine probability and quality of racing performance after arthroscopic removal of such fractures in 151 TB weanlings and yearlings. Methods: The medical records of TB horses age < 2 years th...
Bidwell LA, Bowker RM.To evaluate morphologic changes of the stratum internum of hooves from near-term fetal, newborn, and yearling horses. Methods: Feet from 27 near-term equine fetuses, 19 newborn foals, and 8 yearlings. Methods: Primary epidermal laminae (PEL) of the stratum internum were examined for evidence of architectural changes. Results: In near-term fetuses, the PEL had a homogeneous appearance and symmetric distribution around the hoof wall with no significant differences in PEL density between the toe and quarters. However after birth, branched laminae at the toe formed within the first few weeks, whic...
Boros K, Dyson S, Kovács Á, Lang Z, Nagy A.Metacarpophalangeal joint region pain is a common cause of lameness in racehorses. Radiological abnormalities in the sagittal ridge (SR) of the third metacarpal bone have been associated with joint effusion, lameness and reduced sales prices. The aims were to describe computed tomographic (CT) appearance of the SR in racehorses, and to document the progression of these findings over three assessments. Forty yearlings were enrolled at the first examination (time 0). Re-examinations were performed twice, approximately six months apart on 31 (time 1) and 23 (time 2) horses, respectively. Computed...
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.).
Herd RP, Majewski GA.Studies on a Thoroughbred breeding farm in Ohio were done to: (1) compare the effects of daily administration of pyrantel tartrate feed pellets with monthly administration of a pyrantel pamoate paste to yearling horses (21 January-3 September); (2) assess the effects of daily pyrantel tartrate given strategically in spring/summer to foaling mares (1 April-16 August) and given for a prolonged period to barren mares (21 January-3 September); (3) determine if strategic medication of foaling mares with daily pyrantel tartrate protected their foals until weaning. There were no differences in cyatho...
Southwood LL, Cohen J, Busschers E, Habecker P.To report a case of multiple acquired jejunal pseudodiverticula managed successfully by resection and jejunojejunostomy. Methods: Clinical report. Methods: Arabian filly. Methods: The filly was referred for signs of acute colic of several hours duration and had a 2-week history of inappetence and weight loss. Three meters of thickened, edematous, and dilated jejunum removed during exploratory celiotomy had an intussusception and numerous diverticula; jejunojejunostomy performed. The pathoanatomic diagnosis was proliferative enteropathy with pseudodiverticula formation and jejunal muscular hype...
Ott EA, Asquith RL.Forty-six Thoroughbred and Quarter Horse yearlings were used in two experiments to evaluate the effect of mineral supplementation on growth and skeletal development. In the first experiment, concentrate and bermuda-grass hay diets providing 2.82 Mcal DE/kg (estimated), 13.0% CP, .62% Ca and .43% P on a DM basis were supplemented with trace minerals (TM) by adding 0, .5 or 1.0% TM premix to the concentrate. The TM content of the three diets (concentrate and hay) in mg/kg DM were: Fe 150, 162 and 176; Mn 56, 60 and 64; Zn 36, 53 and 69; and Cu 7, 8 and 11 for the low, medium and high TM levels, ...
Dowsett KF, Tshewang U, Knott LM, Jackson AE, Trigg TE.A series of experiments using an ovalbumin conjugated gonadotrophin releasing hormone was used to stimulate antibody production, suppress testosterone secretion and depress testicular function in yearling and 2 year old colts and fillies. In the preliminary experiment, an injectable oil-based formulation was administered to yearling colts. Testicular development and testosterone secretion were retarded for a period of approximately 28-32 weeks while antibody titres were greater than 1:1000. An implant and water-soluble vaccine (200 and 400 mg) is presently being tested in 2 year old colts. Tes...
Verwilghen D, Van Galen G, Vanderheyden L, Busoni V, Salciccia A, Balligand M, Serteyn D, Grulke S.To describe a technique for, and outcome after, mandibular osteodistraction in the horse. Methods: Clinical report. Methods: Warmblood horse. Methods: A half ring external fixator was applied on both sides of an osteotomy site performed on the mandible of a colt. A bite plate was placed on the upper incisors creating occlusion between lower and upper jaw. After a 5-day latency period, distraction was applied (1 mm/day) until the overjet was judged normal. Results: Mandibular elongation and correction of brachygnathia was obtained without major complications. Six months after the procedure the ...
Stokes A, Wardley RC.Immunity to equine herpesvirus type 1 (EHV-1) was evaluated using sera collected from yearling horses involved in a trial of a commercial vaccine. Measurement of the ability of these sera to mediate antibody-dependent cellular cytotoxicity and complement-dependent lysis revealed that these mechanisms, although potentially important in recovery from EHV-1 infection, do not play a role in protection following vaccination.
Cymbaluk NF, Christensen DA.Five groups of horses were fed different diets of known trace mineral concentration for a minimum of six months. Copper (Cu), zinc (Zn) and manganese (Mn) concentrations were measured in livers of 125 yearling horses and kidneys of 81 yearling horses as an assessment of trace mineral status. Plasma Cu and Zn determinations were made for all horses.Mean hepatic Cu concentrations of horses fed diets containing 6.9 to 15.2 mg Cu/kg dry matter (DM) feed were 0.27 to 0.33 mumol/g DM tissue. Plasma Cu concentrations ranged between 22.8 to 28.3 mumol/L. There was no simple mathematical relationship b...
Jackson M, Vizard A, Anderson G, Clarke A, Whitton R.OBJECTIVES Describe the association between the purchase price of Thoroughbred yearlings sold in Australia and racing performance as 2- and 3-year-olds. METHODS Race performance data of 2773 Thoroughbred yearlings sold at auction during 2003 were collected. Associations between purchase price and the probability of starting, the number of race starts and the prize money earned were examined. RESULTS In total, 2206 (79.6%) horses started a race. The mean number of race starts was six and the mean prize money earned was A$24,420. A total of 1711 (61.5%) horses earned prize money, 402 (14.4%) ear...
Butt TD, MacDonald DG, Crawford WH, Dechant JE.A 14-month-old filly with chronic pharyngitis was diagnosed with incomplete esophageal constriction and megaesophagus due to a persistent right aortic arch. This report is unusual because clinical signs of respiratory dysfunction secondary to chronic regurgitation occurred prior to the recognition of dysphagia.
White-Springer SH, Vineyard KR, Kivipelto J, Warren LK.Omega-3 (n-3; ω-3) fatty acids (FA) are often included in the diet for their potential health benefits. However, because oxidative potential is increased with the degree of unsaturation in vitro, polyunsaturated FA such as eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) may be at increased risk of lipid peroxidation. We aimed to determine the effects of dietary n-3 FA supplementation on antioxidant status and lipid peroxidation in yearling horses. Quarter Horses (mean ± SEM; 14.6 ± 0.2 mo) were randomly assigned to receive no n-3 FA supplementation (CON; n = 6) ...
Singer ER, Livesey MA.To determine, in a population of young horses, whether a variation exists among neonates, sucklings, weanlings, and yearlings regarding recovery from anesthesia, short- and long-term survival rates, and postoperative adhesion formation following exploratory laparotomy. Methods: Retrospective study. Methods: 102 horses < 25 months old that underwent exploratory laparotomy. Methods: Pre-, intra-, and postoperative information was retrieved from medical records, conversations with referring veterinarians, owners, or trainers, and race records. Survival rates (recovery from anesthesia and short- a...
Ott EA, Kivipelto J.Thoroughbred and Quarter Horse yearlings (n = 24; 335+/-7 d of age) were used in a 112-d feeding trial to determine whether chromium (Cr) supplementation would alter growth, development, and energy metabolism of growing horses on high-concentrate diets. The horses were assigned at random within breed and gender subgroups to one of four treatment groups: A) basal concentrate; B) basal plus 175 microg of Cr/kg concentrate; C) basal plus 350 microg of Cr/kg concentrate; and D) basal plus 700 microg of Cr/kg concentrate. Chromium was provided via Cr tripicolinate (Prince Agri Products, Quincy, IL)...
Nielsen K, Vibe-Petersen G.Heart scores increased with age and training. Yearlings had average heart scores of approximately 90 milliseconds (msecs). This increased to approximately 110 msecs in 5-year-old horses, after which there was only slight further increase. In horses 4 years or older, regression analysis revealed a highly significant correlation between heart score and kilometre time. In younger horses the level of significance was less. There was a positive correlation between heart scores and earnings in races. Thus, horses with heart scores above 115 msecs had won considerably more than horses with lower hear...
Cirak VY, Güleğen E, Yildirim F, Durmaz M.The aim of the present study was to determine the efficacy and the so-called "egg reappearance period" (ERP) of doramectin in horses naturally infected with strongyles during a period of 34 weeks. A group of yearlings of 10 animals was treated intramuscularly with doramectin at a dose rate of 0.2 mg/kg bodyweight (BW) at the begin of the grazing season. To obtain comparable data, another group of yearlings (n = 10) was treated orally with ivermectin at a dose rate of 0.2 mg/kg BW. Individual faecal samples were examined for strongyle egg counts per gram of faeces (EPG) in two-week intervals. T...
Elsener J, Villeneuve A.The impact of a late fall treatment on the spring rise of fecal egg counts was evaluated in a controlled study with Canadian horses treated with 2 different dewormers immediately after removal from pasture for winter housing. The horses were stabled until the end of the trial period. Seventeen weanlings, 20 yearlings, and 15 2-year-old horses located in Ontario, which were presumed to be naturally infected with cyathostomins after pasture grazing, were randomly allocated to either a group treated with 0.4 mg/kg of moxidectin and 2.5 mg/kg of praziquantel or a group treated with 0.2 mg/kg of iv...
Axon JE, Russell CM, Begg AP, Adkins AR.A 10-month-old Thoroughbred filly was presented with a 2-month history of recurrent fever and pleural effusion. Major clinical findings were pyrexia and congested mucous membranes. Clinical pathology tests revealed an erythrocytosis, hyperfibrinogenaemia and hyperglobulinaemia. Pleural fluid was seen on ultrasonographic examination of the thorax and analysis of a thoracocentesis sample indicated a lymphocytic, modified transudate. A transtracheal aspirate was normal. The erythrocytosis persisted despite IV fluid therapy. Arterial blood gas analysis and bone marrow aspirate were normal. These f...
Eysker M, Jansen J, Kooyman FN, Mirck MH, Wensing T.The small strongylid infections of two groups of three yearling female Shetland ponies and one yearling Shetland tracer pony were studied. One group was set stocked from April to November and was treated monthly with 5 mg kg-1 albendazole from two days before turnout until July. The other group grazed similar pasture until July, was treated with 5 mg kg-1 albendazole and subsequently removed to pasture grazed by sheep from April to July. The tracer ponies were added to both groups in September. The efficacy of both methods was not completely satisfactory probably because of low efficacy of ant...
Curtiss AL, Aceto H, Embertson RM.Epiglottic entrapment can occur in yearling Thoroughbreds (TB); however, race performance following surgical correction is unknown. Objective: To determine the race performance of horses treated surgically for epiglottic entrapment as yearlings as compared to an untreated cohort. A second objective was to identify risk factors for treated horses not racing post-operatively. Methods: Retrospective cohort and case-control studies. Methods: Medical (1989-2014) and race records of 66 treated TB racehorses were reviewed. Observed abnormalities on pre- and post-operative endoscopic images and surgic...
Arango-Sabogal JC, Mouncey R, de Mestre AM, Verheyen K.Thoroughbred breeders aim to have foals born early in the season, but scientific evidence on the advantages for race performance is scarce and contradictory. Unassigned: The association between date of birth and purchase price as foal/yearling, with race performance by the end of the second and third years of life of Thoroughbreds racing in flat races in the United Kingdom (UK) and Ireland (IRE) was assessed using negative binomial and zero-inflated negative binomial models on the entire 2014-2015 UK/IRE foal crops ( = 28,282). Unassigned: In total, 6666 and 9456 horses raced in UK/IRE flat r...
Robert C, Valette JP, Jacquet S, Lepeule J, Denoix JM.The possible aetiology of osteochondrosis and, to a lesser extent, other developmental orthopaedic diseases or juvenile osteochondral conditions (JOCC), has been intensively investigated. However, most studies have focused on single factors of this multi-factorial disorder, or have been conducted under experimental conditions. This paper aims to present and discuss the scientific background of the BOSAC (Breeding, Osteochondral Status and Athletic Career) research program, a multi-factorial investigation on JOCC risk factors in field conditions. The epidemiology of JOCC in horses born in Norma...
Fowler AL, Hansen TL, Strasinger LA, Harlow BE, Lawrence LM.Inorganic P is often added to growing horse diets because organic P, or phytate-P, is believed to have lower digestibility. If horses can efficiently digest organic P, then the need for inorganic P may be reduced. Much of the P in grain-based concentrates fed to growing horses is in the form of phytate-P. Little is known about the ability of growing horses to degrade phytate-P or whether horse age affects mineral digestion in horses. The objective of this study was to examine the effect of age on P, Ca, and Mg digestibility as well as phytate-P degradation. Four yearling geldings and 4 mature ...
Wagner AL, Urschel KL.To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age. Methods: 6 yearlings, six 2-year-old horses, and 6 mature horses. Methods: After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state). Blood samples were collected for the duration of the experimental ...
Hoey S, O'Sullivan J, Byrne J, Devine S, Toomey W, McAllister H, Skelly C.Osteochondrosis is a common condition of young horses where there is a failure of endochondral ossification, usually at predisposed sites. The estimated prevalence of osteochondrosis is 33-44%, with radiographic screening of yearlings being used to identify lesions. Radiography has two major limitations: poor sensitivity in detecting cartilaginous lesions and secondly, the exposure of the horse and personnel to ionising radiation. Ultrasonography allows imaging of the articular cartilage and subchondral bone margins and has been shown to be more sensitive in identifying osteochondrosis lesions...
Mienaltowski MJ, Belt A, Henderson JD, Boyd TN, Marter N, Maga EA, DePeters EJ.Prophylactic supplementation of psyllium husk is recommended to enhance passage of ingested sand from the gastrointestinal tracts of horses. We hypothesized that psyllium supplementation would increase fecal sand passage and favorably alter bacterial populations in the hindgut. Six yearlings and six mature mares were fed a psyllium supplement in the diet daily for seven days. Voluntarily-voided feces were collected over the course of 29 days, prior, during, and after treatment. Feces were analyzed for acid detergent fiber (ADF) and acid detergent insoluble ash analyses. Microbial DNA was also...
Schnabel LV, Bramlage LR, Mohammed HO, Embertson RM, Ruggles AJ, Hopper SA.Studies on arthroscopic removal of apical proximal sesamoid fracture fragments in Thoroughbred (TB) horses age > or = 2 years have reported a high success rate. However, there are no reports documenting the racing prognosis of TB horses that undergo such surgery as weanlings or yearlings. Objective: To describe the incidence of apical proximal sesamoid fractures in immature TB horses, age < 2 years and determine probability and quality of racing performance after arthroscopic removal of such fractures in 151 TB weanlings and yearlings. Methods: The medical records of TB horses age < 2 years th...
Pressanto MC, Pepe M, Coomer RPC, Pilati N, Beccati F.The purpose of this prospective study was to investigate the prevalence and severity of radiographic abnormalities of the interspinous spaces (ISSs) in the thoracolumbar vertebral column of unbroken yearlings and to compare these findings with a group of older trained Thoroughbred horses without perceived back pain. Yearlings (n = 47) and trained horses (55); 102 total. Each horse underwent a digital radiographic study of the thoracolumbar vertebral column (T7-L3) and each space graded for narrowing of the ISSs, increased opacity, radiolucency, and modeling of the cranial and caudal margins of...
