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.
Moore GE, Leatherwood JL, Glass KG, Arnold CE, Paris BL, Carter MM, George JM, Fontenot AB, Martinez RE, Franklin MA, Norton SA, Bradbery AN....The objective was to evaluate dietary fermentation product (SCFP) on joint inflammation and cartilage metabolism in exercising yearlings challenged with intra-articular lipopolysaccharide (LPS), hypothesizing dietary SCFP (TruEquineC, Diamond V Mills, Inc.) would ameliorate joint inflammation and increase cartilage metabolism. Thirty Quarter Horse yearlings were stratified by bodyweight (BW), age, sex, and randomly assigned to dietary treatments (n = 10/treatment): control (0), 46, or 92 mg/kg BW/d SCFP. Treatments were top-dressed to 1% BW/d concentrate void of added microbials. Horses ...
Hardwick JL, Ahern BJ, Crawford KL, Allen KJ, Anderson BH, Rose KJ, Franklin SH.The relationship between Thoroughbred yearling laryngeal function (YLF) grade and race performance is unclear. Objective: To determine the effect of YLF on future race performance. Methods: Retrospective cohort study. Methods: Post-sale endoscopic recordings were reviewed from Australian yearling sales in 2018-2019. Race performance was evaluated for career and as 2-, 3- and ≥4-year-olds. Multivariable generalised linear modelling examined the association between YLF and performance, with risk estimates presented as coefficients (95% CI). Results: The YLF in 5175 examinations was graded I in...
Bertuglia A, Pallante M, Pagliara E, Valle D, Bergamini L, Bollo E, Bullone M, Riccio B.Tarsocrural osteochondrosis (OCD) is a developmental orthopedic disease commonly affecting young Standardbreds, with different fragment localization and size. Clinically, it is characterized by variable synovial effusion in the absence of lameness, whose determinants are ill-defined. We hypothesized that localization and physical characteristics of the osteochondral fragments like dimensions, multifragmentation, and instability influence joint effusion and correlate with synovial markers of cartilage degradation and inflammation. Clinical data, synovial fluid and intact osteochondral fragments...
Peat FJ, Kawcak CE, McIlwraith CW, Berk JT, Keenan DP.Changes in the proximal sesamoid bones (sesamoids) and the insertional region of the adjacent suspensory ligament branch (branch) are of particular importance in young Thoroughbreds sold at public auction. Little is known about the prevalence of concurrent ultrasonographical branch change, relative to the various grades of radiological sesamoid appearance. Objective: To examine the existence of concurrent radiological and ultrasonographical findings in individual sesamoid-branch units in sales horses; to determine whether there are any radiological findings that are consistently accompanied by...
Peat FJ, Kawcak CE, McIlwraith CW, Berk JT, Keenan DP, Selberg KT, Ojeda A.Equine suspensory ligament branch (branch) ultrasonography is becoming increasingly commonplace presale. No ultrasonographical branch reference data exists for Thoroughbred sales horses. Objective: To define the prevalence of ultrasonographical findings in the forelimb suspensory branches of yearling and 2-year-old sales Thoroughbreds and to analyse associations with racing performance. To track changes in branch findings between 1 and 2 years of age in horses that present for sale at both ages. Methods: Prospective cohort study using an enrolled sample. Methods: Horses were enrolled from a ...
Hardwick JL, Ahern BJ, Crawford KL, Allen KJ, Franklin SH.Yearling laryngeal function (YLF) is frequently assessed at the time of sale and the outcomes of these assessments can have significant economic implications. The YLF of horses that subsequently underwent a prosthetic laryngoplasty (PL) is unknown. Objective: We hypothesised horses with YLF ≥grade II.2 would be at increased risk of requiring PL, compared with YLF
Ishimaru M, Tsuchiya T, Endo Y, Matsui A, Ohmura H, Murase H, Korosue K, Sato F, Taya K.Effects of different winter paddock management of Thoroughbred weanlings and yearlings in Hokkaido, Japan, which is extremely cold in winter, on physiological function, endocrine function and growth were investigated. They were divided into two groups; those kept outdoors for 22 hr in the paddock (22hr group) and those kept outdoors for 7 hr in daytime with walking exercise for 1 hr using the horse-walker (7hr +W group), and the changes in daily distance travelled, body temperature (BT), heart rate (HR), HR variability (HRV), endocrine function and growth parameters were compared between the t...
Hardwick JL, Ahern BJ, Franklin SH.To identify thoroughbred industry stakeholders' views on the yearling sales endoscopy in Australia. Methods: Semi-structured qualitative group interviews with equine veterinarians, thoroughbred breeders and yearling purchasers. Methods: Twenty-nine experienced thoroughbred industry stakeholders participated in online focus groups: (1) equine veterinarians involved in yearling endoscopy; (2) thoroughbred breeders; and (3) yearling buyers. The focus groups were audio and video recorded and digital whiteboards were available. Data was transcribed, live-coded and analysed thematically. Results: Th...
Pérez-Nogués M, Manso-Díaz G, Spirito M, López-Sanromán J.Subchondral cystic lesions (SCL) in the medial femoral condyle are a usual finding in Thoroughbred survey and auction repository radiographs. Several treatments with different outcomes have been studied over the years to improve soundness and racing prognosis. Our objective was to report the racing prognosis in Thoroughbred yearlings intended for racing that were diagnosed with SCL in the medial femoral condyle and were treated using four current and different techniques: intralesional injection of corticosteroids, SCL debridement through the joint with a drill bit, translesional cortical scre...
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...
Merlin A, Larcher N, Vallé-Casuso JC.This study assessed the anthelmintic resistance in strongylid nematodes against commonly used anthelmintic (AH) drugs in a French galloping racehorse stud farm from March to December 2023. Faecal egg count reduction tests (FECRTs) were conducted in three different groups of Thoroughbred yearlings (a group of 6 males, a group of 13 females and a group of 8 females and 3 males) following the new World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines. The efficacy of fenbendazole was tested in two groups once during the monitoring period (in March), the efficacy of iv...
Peat FJ, Kawcak CE, McIlwraith CW, Keenan DP, Berk JT, Mork DS.Radiological findings in the proximal sesamoid bones (sesamoids) are a persistent source of controversy at Thoroughbred sales, due to inconsistent classification and conflicting assignment of potential clinical importance. Objective: To define the prevalence of sesamoid findings on sales repository radiographs in yearling and 2-year-old Thoroughbreds and to analyse associations with racing performance. To track the changes in sesamoid findings between 1 and 2 years of age in horses that present for sale at both ages. Methods: Prospective cohort study using an enrolled sample. Methods: Horses...
Abbas G, Bauquier J, Beasley A, Jacobson C, El-Hage C, Wilkes EJA, Carrigan P, Cudmore L, Hurley J, Beveridge I, Nielsen MK, Hughes KJ, Stevenson MA....This study assessed worm control practices used by Australian Thoroughbred farm managers with an online questionnaire survey. The questionnaire comprised 52 questions (close-ended: 44; open-ended: 8) about farm demography and general husbandry practices, farm managers' knowledge of gastrointestinal nematodes (GIN) and their importance, diagnosis, worm control strategies and anthelmintics, anthelmintic resistance (AR) and grazing management. Following the pilot survey, the link for the questionnaire survey was sent to all (n = 657) registered members of the Thoroughbred Breeders Australia on ...
Mouncey R, Arango-Sabogal JC, de Mestre A, Verheyen KKL.Early-life locomotor activity during turn out may alter susceptibility to musculoskeletal disease and injury via modulation of behaviours and tissue development during growth. Objective: Investigate associations between turn out practices and rates of musculoskeletal disease and injury in young Thoroughbreds on stud farms in the United Kingdom. Methods: Prospective cohort. Methods: Daily records were kept on location and duration of turn out for 134 Thoroughbred foals on six stud farms, from birth until leaving the farm or study exit. Data on veterinary-attended episodes of musculoskeletal dis...
Abbas G, Ghafar A, Beasley A, Stevenson MA, Bauquier J, Koehler AV, Wilkes EJA, McConnell E, El-Hage C, Carrigan P, Cudmore L, Hurley J, Gauci CG....This study reports the spatial and temporal distribution of ascarid and strongylid nematodes in Thoroughbred horses by age category across different climatic zones in Australia over an 18-month period. Faecal samples (n = 2046) from individual horses were analysed using the modified McMaster technique for faecal egg counts (FECs). Strongylids were identified using PCR-directed next-generation sequencing of the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA. Yearlings had the highest prevalence (82%) of strongyle eggs followed by weanlings (79%), foals (58%), wet mares ...
Lim SI, Kim MJ, Kim MJ, Lee SK, Yang HS, Kwon M, Lim EH, Ouh IO, Kim EJ, Hyun BH, Lee YH.Equine influenza virus (EIV) causes acute respiratory disease in horses and belongs to the influenza A virus family , genus . This virus may have severe financial implications for the horse industry owing to its highly contagious nature and rapid transmission. In the Republic of Korea, vaccination against EIV has been practiced with the active involvement of the Korea Racing Authority since 1974. In this study, we monitored the viral RNA for EIV using PCR, as well as the antibody levels against 'A/equine/South Africa/4/03 (H3N8, clade 1)', from 2020 to 2022. EIV was not detected using RT-PCR. ...
Abbas G, Ghafar A, Bauquier J, Beasley A, Ling E, Gauci CG, El-Hage C, Wilkes EJA, McConnell E, Carrigan P, Cudmore L, Hurley J, Beveridge I....The study presents the results of a cross-sectional survey to describe the epidemiology of ascarid and strongylid nematodes in horses, the impact of diverse climatic conditions on parasite diversity and the levels of faecal egg shedding in different age groups of managed Thoroughbred horses. Individual faecal samples (n = 1377) collected from 62 Thoroughbred farms across four climatic zones in Australia were analysed using the modified McMaster technique for faecal egg counts (FECs) and strongylid nematodes were identified utilising PCR-directed next-generation sequencing (NGS) of the second...
Pérez-Nogués M, López-Sanromán J, Spirito M, Manso-Díaz G.Subchondral cystic lesions (SCLs) in equines and their treatments have been mainly studied in the medial femoral condyle of the femur. SCLs in the distal extremities affecting the fetlock or interphalangeal joints are frequent, but treatment or prognosis studies in horses are currently sparse. Our objective was to compare four treatments for SCLs in the distal extremities (intralesional injection of corticosteroids, transcortical drilling, cortical screw placement, and absorbable hydroxyapatite implant placement) and report the racing prognoses for affected thoroughbred yearlings. Data from 11...
McCoy AM, Scolman KN.The aim of this study was to identify the radiographic prevalence of periarticular osteophytes of the distal tarsus in nonlame yearling Standardbred horses, and to evaluate its potential impact on race performance. Methods: Cross-sectional cohort study. Methods: Client-owned yearling Standardbred horses (n = 416). Methods: Bilateral tarsal radiographs were available from all horses for review. Osteophytes were measured on radiographs using clinical visualization software and categorized by size. Racing records were obtained from the United States Trotting Association. Regression analysis w...
Peat FJ, Kawcak CE, McIlwraith CW, Keenan DP, Berk JT, Mork DS.Subchondral lucencies (SCLs) in the distal aspect of the medial femoral condyle (MFC) of young Thoroughbred horses are a source of controversy on presale radiographs. There is limited scientific evidence regarding the risk of progression and impact on future racing performance. Objective: To (1) identify the prevalence of MFC SCLs on sales repository radiographs in yearling and 2-year-old Thoroughbreds; (2) identify any association between grade of MFC SCL and future racing performance and (3) monitor changes in MFC SCL grades between yearling and 2-year-old sales. Methods: Prospective cohort ...
Mouncey R, Arango-Sabogal JC, de Mestre AM, Verheyen KL.Up-to-date estimates of early-life morbidity and mortality in Thoroughbreds are lacking. Methods: A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded. Multilevel Poisson regression models with farm and foal as random effects were fitted to estimate incidence rates. Results: Data were available for 3328 foal-months at risk for 275 foals on seven farms. The overall rates of disease and injury requiring veterinary intervention and mortality were...
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...
Bull KE, Allen KJ, Hodgkinson JE, Peachey LE.In recent years, resistance to the benzimidazole (BZ) and tetrahydropyrimidine (PYR) anthelmintics in global cyathostomin populations, has led to reliance on the macrocyclic lactone drugs (ML-of which ivermectin and moxidectin are licensed in horses) to control these parasites. Recently, the first confirmed case of resistance to both ivermectin (IVM) and moxidectin (MOX) was reported in the USA in yearlings imported from Ireland. This suggests that ML resistance in cyathostomins has emerged, and raises the possibility that regular movement of horses may result in rapid spread of ML resistant c...
Bertuglia A, Pallante M, Pillon G, Valle D, Pagliara E, Riccio B.This case series describes an alternative surgical technique to obtain reattachment of osteochondritis dissecans (OCD) lesions in the lateral trochlear ridge of the femur (LTRF) as well as the clinical and radiological outcome of treated cases. Four Standardbred yearlings (6 lesions in total) underwent surgical fixation of large OCD defects in the LTRF under arthroscopic guidance. Reattachment of the OCD lesions was obtained using 3.0/3.7 mm headless bio-compression and absorbable poly-l-lactic acid (PLLA) screws, inserted perpendicularly to the cartilage surface through the lesion. All horse...
Faulkner J, Vanderperren K, Duchateau L, O'Sullivan C.Ascertain the radiographic prevalence and variation in characteristics of juvenile osteochondral conditions (JOC) in the proximal interphalangeal joint (PIPJ) of Australian Thoroughbred racehorse yearlings. Establish whether there are any significant associations with public auction sale results and racing performance. Unassigned: Retrospective evaluation of 1,098 yearling repository radiograph sets. Comparison of sales results and whole career racing performance of the case group with two control groups: maternal siblings ( = 397) and yearlings without PIP JOC ( = 391). Unassigned: 6.3% of ye...
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...
Kambayashi Y, Nemoto M, Tsujimura K, Ohta M, Bannai H.Equine coronavirus (ECoV) causes fever, lethargy, anorexia and gastrointestinal signs in horses. There has been limited information about the prevalence and seasonality of ECoV among Thoroughbreds in Japan. Objective: To understand the epidemiology and to evaluate the potential risk of ECoV infection to the horse industry in Japan. Methods: Longitudinal. Methods: The virus-neutralisation (VN) test was performed using sera collected three times a year at 4 months intervals from 161 yearlings and at 6-7 months intervals from 181 active racehorses in Japan in 2017-2018, 2018-2019 and 2019-2020....
Barton CK, Sandow CB, Rodgerson DH.To describe an arthroscopic technique for the removal of osteochondral fragments located within the condylar fossa of the third metacarpal/tarsal bone. Methods: Retrospective study. Methods: Thoroughbred yearlings (n = 11). Methods: Osteochondral fragments located within the condylar fossa of the third metacarpal/tarsal bone identified during presale radiographic examination were removed via arthroscopy, assisted with ultrasonography in select cases. Complete fragment removal was confirmed by intraoperative radiography. Results: Fragments were successfully removed using rongeurs following di...
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...
Nielsen MK, Littman BA, Orzech SW, Ripley NE.Equine cyathostomins are ubiquitous in grazing horses around the world and a main target in parasite control programs. Anthelmintic resistance has been reported with increasing frequency in these parasites over the past decades, and recent findings of fulminant resistance to the macrocyclic lactone class have raised severe concerns. This study aimed to evaluate ivermectin efficacy in cohorts of yearlings and mares present on four different farms in Central Kentucky. Strongylid egg counts were determined with an automated egg counting system, and the percent fecal egg count reduction (FECR) was...
Brama PA, Tekoppele JM, Bank RA, Barneveld A, van Weeren PR.Biochemical heterogeneity of cartilage within a joint is well known in mature individuals. It has recently been reported that heterogeneity for proteoglycan content and chondrocyte metabolism in sheep develops postnatally under the influence of loading. No data exist on the collagen network in general or on the specific situation in the horse. The objective of this study was to investigate the alterations in equine articular cartilage biochemistry that occur from birth up to age one year, testing the hypothesis that the molecular composition of equine cartilage matrix is uniform at birth and b...
Relf VE, Lester HE, Morgan ER, Hodgkinson JE, Matthews JB.Anthelmintic drugs have been applied indiscriminately to control horse nematodes for over 40 years. We undertook a comprehensive study to investigate efficacy of the four available broad-spectrum anthelmintic drugs on 16 Thoroughbred stud farms using the faecal egg count reduction test. Efficacy against strongyles was determined by calculating the percentage of reduction in faecal egg count between the group mean at Day 0 and Days 14-17 post-treatment and the 95% lower confidence intervals estimated by non-parametric bootstrapping. Individual strongyle faecal egg count reduction tests (n=429) ...
Newton JR, Townsend HG, Wood JL, Sinclair R, Hannant D, Mumford JA.Field outbreaks of influenza that occurred in vaccinated Thoroughbred racehorses in Newmarket in 1995 and 1996 were investigated by nucleoprotein ELISA and serology. Investigations showed that serum levels of vaccine-induced single radial haemolysis (SRH) antibody correlated closely with protective immunity against equine influenza and were consistent with observations made in previous experimental studies using nebulised aerosol challenge. In the second part of this study, antibody levels stimulated by vaccination were investigated to examine probable protection in high risk groups, such as y...
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...
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...
Burrows R, Goodridge D, Denyer MS.Vaccinated yearlings , two-year-old and in-foal pony mares with appropriate controls were exposed to aerosols of a subtype 1 virus one to two months after two or three vaccinations; all became infected. No obvious differences in the febrile responses, clinical signs and subsequent abortions were found between vaccinated and control mares. All vaccinated yearlings and two-year-old ponies developed a febrile respiratory disease but this was less severe than that suffered by the controls and the amounts and duration of virus shedding were reduced.
Cullinane A, Weld J, Osborne M, Nelly M, Mcbride C, Walsh C.The purpose of these studies was to examine the response of Thoroughbred foals and yearlings to different influenza vaccines and vaccination regimes. The horses' antibody levels against haemagglutinin, an established correlate of protection were measured by haemagglutination inhibition. The first study investigated the extent to which maternal antibodies interfered with the humoral response to a subunit vaccine. The findings suggest that repeat vaccination in the face of maternal antibodies may induce tolerance as defined by serological testing. The second study compared the immune response el...
Boersema JH, Eysker M, Maas J, van der Aar WM.The reappearance of strongyle eggs in faeces after treatment with ivermectin or pyrantel embonate was investigated in 22 foals, 36 yearlings, and 45 adult horses on five Dutch horse farms. The results confirmed earlier studies which showed an egg reappearance period of 9 and 6 weeks after ivermectin and pyrantel treatment, respectively. There were no differences between the egg reappearance periods of foals, yearlings, and adult horses. The mean egg counts of the yearlings were, however, consistently higher than the mean egg counts of the adult horses and foals in both ivermectin- and pyrantel...
Kane AJ, Park RD, McIlwraith CW, Rantanen NW, Morehead JP, Bramlage LR.Radiography in presale examinations of TB yearlings has become standard practice in recent years. Objective: To describe the prevalence and distribution of radiographic changes in the fetlocks, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings in central Kentucky when these joints were examined as part of routine pre- and post sale evaluations. Methods: Horses subjected to radiographs included the fore (n = 1127) and hind (n = 1102) fetlocks, carpi (n = 1130), tarsi (n = 1101), stifles (n = 660) and fore feet (n = 300). Radiographic changes were categorised by location and type of ...
Xiao L, Herd RP.Prevalence and infection patterns of Cryptosporidium and Giardia infections in horses were studied by a direct immunofluorescence staining method. Faecal examinations of 222 horses of different age groups revealed Cryptosporidium infection rates of 15-31% in 66 foals surveyed in central Ohio, southern Ohio and central Kentucky, USA. Only 1 of 39 weanlings, 0 of 46 yearlings, and 0 of 71 mares were positive. Giardia infection was found in all age groups, although the infection rates for foals were higher (17-35%). Chronological study of infection in 35 foals showed that foals started to excrete...
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...
Gildea S, Arkins S, Cullinane A.In Ireland, horses may be protected against equine influenza virus (EIV) as a result of natural exposure or vaccination. Current mandatory vaccination programmes are targeted at highly mobile horses. A correlation between antibody levels as measured by single radial haemolysis (SRH) and protective immunity against EIV has been established. Objective: The objective of this study was to determine the susceptibility of selected populations of horses by quantifying their antibodies to EIV. Methods: Blood samples were collected from Thoroughbred weanlings, yearlings, racehorses and broodmares, teas...
Berg EL, Fu CJ, Porter JH, Kerley MS.Short-chain fructooligosaccharides (FOS) were supplemented to the diets of nine quarter horses ranging in age from 489 to 539 d with initial BW averaging 400.6 +/- 21.2 kg. The objectives of this study were to determine the effects of dietary FOS on the fecal responses in terms of pH, the microbial population, and VFA concentrations. The horses were used in a 3 x 3 replicated Latin square design, fed according to NRC requirements, and their individual diets were supplemented with no FOS (CON), 8 g of FOS/d (LOW), or 24 g of FOS/d (HIGH) over three 10-d feeding periods. On the last 3 d of each ...
Kane AJ, McIlwraith CW, Park RD, Rantanen NW, Morehead JP, Bramlage LR.Although the radiographic examination of yearlings has become commonplace at some large Thoroughbred sales, there are few data to support the decisions facing veterinarians who are asked to evaluate future racing potential. Objective: To identify radiographic changes in the fetlocks, proximal sesamoid bones, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings associated with future racing performance during ages 2 and 3 years. Methods: Radiographs from routine pre- and post sale examinations of 1162 yearlings were used to identify individual radiographic changes in sale yearlings. St...
Cullinane A, Gildea S, Weldon E.Vaccination is crucial to the control of equine influenza (EI). The study was conducted in an effort to lay the groundwork for achieving international harmonisation of regulatory requirements based on scientific evidence of performance of different vaccination regimes. Objective: To evaluate the effectiveness of 3 different primary vaccination regimes: vaccination with the minimal intervals permitted by the racing authorities; vaccination in accordance with the manufacturer's instructions and vaccination with the longest intervals permitted by the racing authorities. Methods: Randomised, prosp...
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...
Matthee S, McGeoch MA.The current level of anthelmintic resistance in the horse-breeding industry is extremely high and therefore more emphasis is being placed on studies that focus on the judicious use of anthelmintic products. The aims of the study were to: 1) establish if there is variation in the egg excretion pattern of strongyles between the different age classes of Thoroughbred horses in the Western Cape Province (WCP), 2) test if a selective treatment approach successfully reduces the number of anthelmintic treatments and maintains acceptably low helminth burdens in adult Thoroughbred horses, and 3) evaluat...
Anderson TM, McIlwraith CW.There is little information available to define conformational changes with age using an objective but practical method of recording specific body measurements. Objective: To analyse conformation objectively in a population of racing Thoroughbreds and describe the changes from weanling to age 3 years. Methods: Annual photographs were taken over 4 years and conformation measurements made from photographs using specific reference points marked on the horses. Results: Correlation analysis revealed highly significant, moderate to strong relationships between long bone lengths and wither height for...
Robles M, Nouveau E, Gautier C, Mendoza L, Dubois C, Dahirel M, Lagofun B, Aubrière MC, Lejeune JP, Caudron I, Guenon I, Viguié C, Wimel L....Obesity is a growing concern in horses. The effects of maternal obesity on maternal metabolism and low-grade inflammation during pregnancy, as well as offspring growth, metabolism, low-grade inflammation, testicular maturation and osteochondrotic lesions until 18 months of age were investigated. Twenty-four mares were used and separated into two groups at insemination according to body condition score (BCS): Normal (N, n = 10, BCS ≤4) and Obese (O, n = 14, BCS ≥4.25). BCS and plasma glucose, insulin, triglyceride, urea, non-esterified fatty acid, serum amyloid A (SAA), leptin and adiponect...
Kunii H, Nambo Y, Okano A, Matsui A, Ishimaru M, Asai Y, Sato F, Fujii K, Nagaoka K, Watanabe G, Taya K.The effects of an extended photoperiod (EP) in Thoroughbreds colts and fillies from winter at one year old to spring at two years old on the gonadal functions, coat condition, and endocrine changes were investigated. Sixty-two Thoroughbreds (31 colts and 31 fillies) reared in the Hidaka Training and Research Center (Hidaka), Japan Racing Association were used. Thirty of them (15 colts and 15 fillies) were reared under EP conditions from December 20 to April 10, and the remaining 32 horses were reared under natural light alone as a control group. For EP, a 100-watt white bulb was set near the c...
Lyons ET, Tolliver SC, Collins SS, Ionita M, Kuzmina TA, Rossano M.Efficacy of ivermectin (IVM) and moxidectin (MOX) against small strongyles was evaluated in horses (n=363) in field tests on 14 farms in Central Kentucky between 2007 and 2009. Most of the horses were yearlings but a few were weanlings and mares. The number of horses treated with IVM was 255 and those treated with MOX was 108. Horses on six farms were allotted into two groups. One group was treated with each of the two drugs, whereas horses on the other eight farms were treated with only one of the two drugs--IVM on six farms and MOX on two farms. Strongyle eggs per gram of feces (EPGs) compar...
Stick JA, Peloso JG, Morehead JP, Lloyd J, Eberhart S, Padungtod P, Derksen FJ.To compare endoscopic findings of the upper portion of the respiratory tract in Thoroughbred yearlings with their subsequent race records to determine whether subjective assessment of airway function may be used as a predictor of future racing performance. Methods: Retrospective study. Methods: 427 Thoroughbred yearlings. Methods: Endoscopic examination findings were obtained from the medical records and the videoendoscopic repository of the Keeneland 1996 September yearling sales. Racing records were requested for the yearlings through the end of their 4-year-old racing season (1997-2000). Tw...
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...
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...
LaCasha PA, Brady HA, Allen VG, Richardson CR, Pond KR.Matua bromegrass (Bromus willdenowii Kunth. cv. Grasslands Matua) was introduced in 1973, but little information exists concerning its potential as a hay for horses. Thus, voluntary intake and apparent digestibility of OM, CP, and fiber components of Matua by 18 Quarter Horse yearlings (mean initial BW 354 kg; SE 5.8) were compared with alfalfa (Medicago sativa L.) and coastal bermudagrass (Cynodon dactylon L.) as hays in a randomized block design. A 15-d adjustment period was followed by a 5-d collection period during which the hays were consumed ad libitum. Voluntary intake of DM was greater...
Lyons ET, Tolliver SC, Drudge JH, Swerczek TW, Crowe MW.A total of 278 Thoroughbreds (less than 1 to 31 years old) were examined at necropsy (July 9, 1985, to Feb 2, 1986) in Kentucky for various internal parasites. Examination was not made of all the horses for each of the parasites. Specific parasites recovered from the stomach of foals (n = 30) and yearlings and older horses (n = 96) and percentage (in parentheses) of each age category infected, respectively, were as follows: Gasterophilus intestinalis 2nd instar (53% and 32%) and 3rd instar (37% and 24%); G nasalis 2nd instar (7% and 8%) and 3rd instar (7% and 10%); Habronema spp immature (7% a...
Ziebell KL, Steinmann H, Kretzdorn D, Schlapp T, Failing K, Schmeer N.The efficacy of an immunomodulator, Baypamun N, was tested in 4-10-month-old horses which were exposed to stress by weaning, transport and commingling with yearlings from different breeders (crowding). Verum (n = 26) and placebo animals (n = 27) received three intramuscular injections of the investigational preparations (days 0, 2, 9) starting at the day of commingling in one stable. The incidence of acute respiratory disease was high during the first 4 weeks after commingling. Approximately 50% of all horses showed seroconversion due to field infection by EHV1 and EHV4 during the observation ...
Russell J, Matika O, Russell T, Reardon RJ.Osteochondrosis is considered multifactorial in origin, with factors such as nutrition, conformation, body size, trauma and genetics thought to contribute to its pathogenesis. Few studies have investigated the effects of genetic variability of osteochondrosis in Thoroughbreds. Objective: To describe the prevalence and genetic variability of a subset of osteochondrosis lesions in a group of Thoroughbred yearlings. Methods: Retrospective cohort study. Methods: Radiographs of 1962 Thoroughbred yearlings were retrieved from clinical records obtained between 2005 and 2013. Pedigree information was ...
Mair TS.Larval cyathostomiasis was diagnosed as the cause of an outbreak of illness in a group of five young horses. One had the typical clinical signs of larval cyathostomiasis--sudden onset diarrhoea, weight loss, ventral abdominal oedema and pyrexia, but the other four suddenly started to lose weight rapidly and had limb and ventral abdominal oedema and pyrexia, in the absence of diarrhoea. Large numbers of cyathostome larvae were found in the faeces. Four of the five horses recovered after being treated with anthelmintics and steroids.
