Association of growth, feeding practices and exercise conditions with the prevalence of Developmental Orthopaedic Disease in limbs of French foals at weaning

Developmental Orthopaedic Disease (DOD) in limb joints of horses is frequent and is a common cause of pain and lameness. DOD is a multifactorial disease involving genetics, growth, feeding practices and exercise conditions leading to joint injuries. However, there is no clear understanding of the contribution of each factor. The aim of this cohort study was to assess the adjusted effects of breed and gender, growth, feeding practices and exercise conditions on the prevalence of DOD in the limbs of foals at weaning and on the prevalence restricted to osteochondrosis (OC).Twenty-one farms in Normandy, France, were convenience sampled and enrolled in a cohort study. The study sample consisted of 401 foals from 3 breeds, followed from the 8th month of pregnancy of the mares until weaning period at approximately 6 months of age of the foals. Stud farms were regularly visited to collect growth, feeding practices and exercise conditions data. The carpus, the front and hind digits, the hock and the stifle of the foals were X-rayed at the end of follow-up. Foals were categorised as affected or unaffected by DOD or by OC. Two mixed-effects logistic regression models were used to determine risk factors for DOD or OC, adjusting for clustering by farm.Of the 378 foals with complete data, 47% (95% CI: 42–52) were affected by DOD and 36% (95% CI: 31–41) by OC. Risk was significantly increased for DOD and for OC in Warmblood foals compared to Thoroughbreds (OR 2.8; 95% CI: 1.2–6.5 for DOD, OR 2.9; 95% CI: 1.1–7.5 for OC), in foals with a high wither height at 30 days of age, and in foals with a rapid increase of wither height (for DOD only). Exercise conditions such as large area of pasture, some irregular exercise, or some batch changes were also significant risk factors for DOD or OC. No association was found with quantitative feeding practices; it was likely due to the limited variability of horse regimens and to the partial inclusion of nutritional effects in other factors such as breed and growth. In order to reduce the prevalence of DOD or OC in foals, following the growth and reducing nutritional supply in subjects growing fast, limiting the pasture areas offered and providing a regular exercise to foals seems appropriate. To our knowledge, to date the assessment of adjusted effects of potential risk factors for DOD has never been proposed.     

Cryptosporidium parvum infection in a mare and her foal with foal heat diarrhoea

Cryptosporidium infection was molecularly investigated in mares and in their neonatal foals for which the occurrence of foal heat diarrhoea was also assessed. Thirty-seven mare/foal pairs were included in the study. All foals were born in the same stud farm during 2006-2008 breeding seasons. Two faecal samples, one prior to and one after delivery were collected from each mare, whereas three faecal samples were taken from each foal, i.e. at 8, 10 and 12 days of age. All samples (74 from mares and 111 from foals) were divided into two aliquots, one of which was examined for the presence of Cryptosporidium by a commercially available microplate ELISA kit, while the second aliquot of all ELISA-positive samples was molecularly examined. Nine out of 37 examined foals presented foal heat diarrhoea and one of them scored positive for Cryptosporidium, together with its mare. More specifically, four samples belonging to the same mare/foal pair resulted positive for Cryptosporidium upon both ELISA and PCR. The sequence analysis of the COWP gene showed the occurrence of the zoonotic species Cryptosporidium parvum. The possibility that foal heat diarrhoea-like episodes may be due to neonatal cryptosporidiosis and their relevance for the health of horses and of humans handling diarrhoeic neonatal foals and their mares are discussed.     

A case-control study of the congenital hypothyroidism and dysmaturity syndrome of foals.

A case-control study was conducted to identify risk factors for the congenital hypothyroidism and dysmaturity syndrome of foals. A questionnaire was used during personal interviews of foal owners and farm managers to collect information on animal signalment, farm environment, and mare management. Information on 39 foals with the congenital hypothyroidism and dysmaturity syndrome were compared with 39 control foals. Foals with the syndrome had a significantly (P < 0.0001) longer gestation (357.6 d) than control foals (338.9 d). Pregnant mares that were fed greenfeed, did not receive any supplemental mineral, left their "home farm" during gestation, or grazed irrigated pasture had 13.1 (P = 0.0068), 5.6 (P = 0.0472), 4.3 (P = 0.0076), and approximately 15.3 (P = 0.0245), respectively, greater odds of producing an affected foal than mares not experiencing these events. Greenfeed often contains high levels of nitrate (NO3-), which is known to impair thyroid gland function. In light of this, forage samples from participating farms were analyzed for nitrate levels. The odds of one or more congenitally hypothyroid and dysmature foals being born on a farm feeding forage with at least a trace of nitrate was 8.0 times greater (P = 0.0873) than the odds of the disease occurring on a farm that fed forage free of nitrate. Further, the odds of a mare producing an affected foal when fed forage containing at least a trace of nitrate were 5.9 times greater (P = 0.0007) than those of a mare fed nitrate free forage. This study suggests that congenital hypothyroidism and dysmaturity syndrome in foals may be the result of diets that contain nitrate or that are low in iodine being fed to pregnant mares.     

The incidence of abnormal limb development in the Irish thoroughbred from birth to 18 months.

A two part survey was carried out in Irish Thoroughbred horses in 1988 and 1989 to establish the incidence and prevalence of developmental skeletal problems, particularly possible manifestations of developmental orthopaedic disease (DOD). Survey One was a retrospective study based on a questionnaire involving the foal crops of 46 stud farms for 3 successive seasons; the 1711 animals initially documented represented 10.46% of Irish foal registrations. The second survey involved repeated monitoring of the 1988 foal crop from birth to 18 months of age on 17 stud farms. The 248 foals initially examined represented 4.24% of foal registrations. Treatment for DOD was deemed necessary for 11.3% of the animals in Survey One. Angular limb deformities and physeal dysplasia ("epiphysitis") together constituted 72.9% of the cases treated. The peak incidence of DOD problems occurred between weaning and the end of December. More than half the animals treated (53.9%) recovered completely, ie achieved expected sale value as yearlings, 27.5% of those treated showed incomplete recovery and mild to moderate loss of sale value and the remaining 18.7% were killed or lost much of their sale value. In the second survey, while 67% of animals exhibited some form of DOD, the incidence and severity of problems treated were not significantly different from those of farms in Survey One. Again, physeal dysplasia and angular limb deformity were the predominant clinical conditions and their severity was greatest during the early winter. During the suckling phase colts had a significantly greater incidence of DOD. At all other stages the incidence and severity of DOD was similar in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of cyathostome infections in mares treated at parturition with ivermectin

Six mares were treated on the day of parturition with an intramuscular injection of 0.2 mg kg-1 ivermectin and placed in a pasture free of equine parasites as soon as possible after foaling. The mares and their foals were compared with a similar group of untreated mares and foals on an adjoining pasture. The experimental data was derived from mare and foal fecal egg counts, foal necropsies and pasture larval counts. Ivermectin administered to mares on the day of parturition, when combined with movement to parasite-free pastures, significantly lowered the cyathostome (small strongyle) egg production for 4 months. This reduced cyathostome exposure was reflected in lower worm-burdens in their foals for 5 months. The results indicate that ivermectin will effectively control equine strongyles when mares and their foals are moved to parasite-free pastures.     

Diseases in neonatal foals. Part 2: Potential risk factors for a higher incidence of infectious diseases during the first 30 days post partum

Reason for performing study: The development of clinical illness in foals is usually predetermined by perinatal history, management or stressful environmental conditions. Objectives: To determine potential risk factors for an increased incidence of infectious diseases during the first 30 days post partum. Methods: The population consisted of Thoroughbred foals born on stud farms in the Newmarket (UK) area in 2005 (n = 1031). They were followed for their first 30 days. Factors suspected to influence the incidence of infectious neonatal diseases were examined in a logistic regression approach for each of the 3 outcomes (total infectious diseases, systemic disease with diarrhoea and total infectious diseases excluding diarrhoea). All 28 factors were either foal or mare or stud farm related. Results: Several significant risk factors for a higher disease incidence, such as birth complications, colostrum intake by stomach tube and leucocytosis 12–48 h post partum were identified. The factor ‘boarding stud’ seemed to be protective against disease. Conclusion: Some factors, such as the mare's time at stud before foaling, the mare's rotavirus vaccination schedule and fibrinogen‐values that empirically had been linked to the outcome previously were not confirmed as relevant. This included the reported useful prophylactic treatment with antimicrobial drugs. Potential relevance: Factors to be considered when evaluating newborn foals include: stud management, the birth process, route of colostrum intake, white and red blood cells, and the date of birth. These may help to detect foals at risk to develop an infection so that targeted prophylactic measures can be initiated.     

Traumatic disruption of the suspensory apparatus in foals

Traumatic disruption of the suspensory apparatus is a catastrophic injury in the horse. Although this injury has been described in the adult, little information is available in the foal. This paper describes 3 foals with metacarpophalangeal joint instability caused by traumatic disruption of the suspensory apparatus. Two foals had biaxial proximal sesamoid fractures in a single forelimb, and 1 foal had avulsion of the distal sesamoidean ligaments in 1 forelimb plus biaxial proximal sesamoid fractures in the other forelimb. The foals with single forelimb involvement were managed with splints, and the foal with bilateral disruption of the suspensory apparatus was euthanatized. Both treated foals resumed natural exercise at pasture. Both continue to be pasture sound 2 and 3 years after injury and are to be used for breeding. Management of disruption of the suspensory apparatus causing metacarpophalangeal joint instability using external support was effective for salvage of these 2 valuable foals for breeding.     

Risk factors associated with the incidence of foal mortality in an extensively managed mare herd.

The purpose of this study was to determine the incidence of neonatal mortality in a large, extensively managed mare herd and what risk factors were involved in foal mortality. For a 6 wk period between April 18, 1994, and May 31, 1994, 334 foals were born, of which 74 died before reaching 10 d of age, giving an overall mortality of 22% for this period. Seventy four percent of the foal deaths occurred within 48 h of parturition. The major causes of foal mortality included starvation/exposure 27%, septicemia 26%, and dystocia 20%. Weekly incidences varied significantly, ranging from 67% for week 1 to 14% for week 5 (P < 0.01). Other risk factors that were associated with foal death included failure of passive transfer (P < 0.0001), poor mothering ability (P < 0.0001), the presence of dystocia (P < 0.0001), low birth weight (p < 0.05), lack of rainfall (P < 0.01), and low temperatures (P < 0.1). The effect of sire, mare age, mare body condition, and foal sex were not significant risk factors for foal survival (P > 0.1). Further studies are required to determine if changing management procedures will be effective in reducing the incidence of neonatal foal mortality in this extensively managed herd.     

Epidemiological studies of equine herpesvirus 1 (EHV-1) in Thoroughbred foals: a review of studies conducted in the Hunter Valley of New South Wales between 1995 and 1997.

Sero-epidemiological studies conducted between 1995 and 1997 on two large Thoroughbred stud farms in the Hunter Valley of NSW showed clear evidence of EHV-1 infection in foals as young as 30 days of age. Similarly, serological evidence suggested that these foals were infected with EHV-1 from their dams or from other lactating mares in the group, with subsequent foal to foal spread of infection prior to weaning. These studies also provided evidence of EHV-1 infection of foals at and subsequent to weaning, with foal to foal spread of EHV-1 amongst the weanlings. These data indicated that the mare and foal population was a reservoir of EHV-1, from which new cases of infection propagated through the foal population both before and after weaning. The results of these studies support the long standing management practices of separating pregnant mares from other groups of horses to reduce the incidence of EHV-1 abortion. Also, these results have important implications for currently recommended vaccination regimens, as the efficacy of vaccination in already latently infected horses is unknown.     

The effect of uterine torsion on mare and foal survival: a retrospective study, 1985--2005

REASONS FOR PERFORMING STUDY: Anecdotal speculation suggests that prognosis for survival of mares and foals following correction of uterine torsion has improved over the past 30 years. OBJECTIVES: To determine statistically the outcome of uterine torsion according to duration of clinical signs, stage of gestation, parity, physical examination findings, method of correction, prognosis for survival and reproductive health of the mare, and prospects for the foal within the neonatal period. METHODS: This retrospective study combined cases from 4 equine referral hospitals. RESULTS: The stage of gestation at which uterine torsion occurred was a risk factor for survival of mare and foal. Overall mare survival was 53/63 (84%); when uterine torsion occurred at < 320 days gestation, 36/37 (97%) of mares survived compared to 17/26 (65%) survival rate when uterine torsion occurred at > or = 320 days gestation. Overall foal survival was 54% (29/54). When uterine torsion occurred at < 320 days gestation, 21/29 (72%) foals survived compared to 8/25 (32%) when uterine torsion occurred at > or = 320 days gestation. Thirty mares were discharged from the hospital carrying a viable fetus following uterine torsion correction and 25/30 (83%) of these mares delivered live foals that survived beyond the neonatal period. CONCLUSIONS: Prognosis for survival for mares and foals following uterine torsion is good and improves if torsion occurs < 320 days compared to > or = 320 days gestation. CLINICAL RELEVANCE: Gestational timing of uterine torsion should be considered when advising clients about the prognosis for survival of the mare and foal. The prognosis for a mare delivering a live foal is good if the mare is discharged from the hospital following uterine torsion correction with a viable fetus.     

Ca2+ ATPase in Dutch warmblood foals compared with Na+, K+ ATPase: intermuscular differences and the effect of exercise

We studied the effects of exercise without or with a subsequent period on pasture on Ca2+ ATPase concentration in foal skeletal muscle, and compared the results with those previously reported on Na+, K+ ATPase. Ca2+ ATPase was measured in homogenates as Ca2+-dependent steady-state phosphorylation from [gamma-32P]ATP. From day 7 after birth, 24 foals were divided into three groups: (i) staying in a box stall (Box); (ii) staying in a box stall with an exercise programme of an increasing number of sprints per day (Exercise); and (iii) staying on pasture (Pasture). Half of the foals (12 with four in each treatment group) were killed after 5 months. The remaining foals stayed on pasture until 11 months. In the 5-month Pasture group, Ca2+ ATPase concentration was 29.4 +/- 4.3 nmol/g wet weight (wt) (n = 4) in gluteus medius muscle, 25.2 +/- 3.3 nmol/g wet wt (n = 4) in semitendinosus muscle (both mixed fibre type), and 4.1 +/- 1.7 nmol/g wet wt (n = 3) in the slow masseter muscle. These values were not altered by exercise or by box rest. This was in contrast to the Na+, K+ ATPase concentration which was not different between the three muscles, but showed a 20% rise in gluteus medius and semitendinosus muscle after exercise. In the period from 5 to 11 months on pasture, there was no change in Ca2+ ATPase in any group. In conclusion, the Ca2+ ATPase concentration in foal muscle is around 6-fold higher in mixed fibres than in slow fibres. Furthermore, the enzyme is not up- or down-regulated by sprint exercise or subsequent rest.     

Impact of reproductive efficiency over time and mare financial value on economic returns among Thoroughbred mares in central Kentucky

Reason for performing study: There have been no studies reporting the impact of reproductive efficiency and mare financial value on economic returns. Objective: To explore the economic consequences of differences in reproductive efficiency over time in the Thoroughbred mare. Methods: Complete production records for 1176 mares were obtained. Production history and drift in foaling date were calculated. Multiple logistic regression was used to identify factors influencing the probability of producing a registered foal in 2005. The ‘net present value’ and ‘internal rate of return’ were calculated for economic scenarios involving different initial mare financial values, levels of reproductive efficiency, and durations of investment. Results: Among mares that did not produce a foal every year (63%), the mean time before failing to produce a registered foal was 3.4 years. The majority of mares drifted later in their foaling dates in subsequent foaling seasons. Increasing mare age, foaling after 1st April, needing to be mated multiple times during the season, and producing a lower number of foals in continuous sequence during previous years decreased the probability of producing a registered foal. Over a 7 year investment period, live foals must be produced in all but one year to yield a positive financial return. Profitability was highest among mares of greatest financial value. Conclusions: Mares are long‐term investments due to the extended period before there is a return on the investment. Improving our understanding of mare, stallion and management factors that affect the likelihood of producing a live foal are critical to ensuring a positive financial return. Additional work is needed to test the robustness of the study's conclusions when the cost and revenue assumptions are varied. Potential relevance: This information can assist in assessing mare profitability and developing management strategies to maximise profitability.     

The incidence and consequences of failure of passive transfer of immunity on a Thoroughbred breeding farm

Circulating IgG concentration was determined between 12 and 24 hours after birth for 323 foals born on a Thoroughbred breeding farm over 3 consecutive years. The incidence of failure of passive transfer (FPT) of maternal immunoglobulins (foal circulating IgG concentration < 8 g/L) was found to be 9.6%. Foals born late in the season (October to December) were found to be at increased risk for the development of FPT. The degree of assistance required at parturition and the presence of a periparturient problem in the mare or foal also significantly influenced the subsequent incidence of FPT. Passive immune status significantly influenced the likelihood of foals developing septic illness (joint ill, septicaemia, pneumonia) in the first month of life, but had no significant effect on the development of diarrhoea or Rhodococcus equi pneumonia. The results of the current study support the value of routine monitoring of passive immune status and the early speculative treatment of foals considered to be at risk for the development of FPT.     

Neonatal isoerythrolysis involving the Qc and Db antigens in a foal.

In 1992, a multiparous 13-year-old Thoroughbred mare and her 48-hour-old colt were examined because of possible neonatal isoerythrolysis (NI). Supportive treatment was administered, and the foal recovered without requiring a transfusion. According to the owners, the mare had delivered foals without incident during 1987 and 1991. The mare was barren during 1993, but in 1994, delivered a filly that developed severe NI. The foal was given 3 transfusions and eventually recovered without complications. Blood typing analysis of the mare and its foals indicated that all 4 foals were positive for the Qc, Db, and Dq antigens, and the 3 most recently born foals were positive for the Ua antigen; however, the marc was negative for the Qc, Db, Dq, and Ua antigens. The mare did not have alloantibodies against Ua and did not react to the Dq antigen. However, in 1994, the mare reacted against the Db (the reaction was characterized by strong agglutination and an increase in titer at the time of parturition and a subsequent decrease) and Qc (the reaction was characterized by weak lysis and an increase in titer at the time of parturition and a subsequent decrease) antigens. Results of testing in this mare and foals suggested that although approximately 90% of all cases of NI in horses are attributable to the Aa or Qa antigen, other antigens may be involved.     

Specific immune response of mares and their newborn foals to Actinobacillus spp. present in the oral cavity

Oral swab samples, serum and colostrum was taken from 15 mares and 14 of their foals, within 24 h of birth. The presence of antibody against Actinobacillus spp. isolated from the oral cavity was investigated using agar gel immunodiffusion. Antibodies against 48 out of the 77 Actinobacillus isolates from all horses in the study were present in the respective sera of 13 mares and 9 foals. In 11 mother-foal pairs, the antibody content of the foal serum was similar to that of the mare, and in 9 cases this was reflected in the antibody content of colostrum from the mare. The results indicate that an immune response to Actinobacillus spp. colonising the oral cavity is present in many adult horses and that this immune response can be transferred from mother to foal via colostrum.     

Associations between the Exposure to Airborne Virulent Rhodococcus equi and the Incidence of R equi Pneumonia among Individual Foals

Rhodococcus equi is a significant cause of pneumonia, resulting in disease and sometimes death of foals. It is believed that infection occurs by inhalation of dust contaminated with virulent R equi. Although association between the airborne concentration of virulent R equi and the incidence of foal pneumonia at breeding farms has been documented, studies at the level of individual foals have not been reported. Thus, the objective of this study was to determine whether the magnitude of airborne virulent R equi was significantly associated with risk of R equi pneumonia for individual foals. The concentration of virulent R equi was significantly (P < .001) greater in stalls than paddocks among samples collected from 47 foals at a breeding farm in central Kentucky. The presence of airborne virulent R equi in stalls was significantly (P = .045) more likely at 7 days of age for foals subsequently found to be affected by rhodococcal pneumonia. Additionally, airborne concentrations of virulent R equi in stalls were significantly greater at 7 and 14 days of age than at birth. Presence of the mare and foal at the time of sampling was significantly (P < .001) associated with increased airborne concentrations of virulent R equi in stalls. These findings suggest that environments containing airborne virulent R equi during the first week of life may influence the risk of subsequent disease for a foal.     

A preliminary investigation of the use of a foal image to reduce mare stress during mare–foal separation

The data for this study were collected from 7 mares (10 ± 1.6 years old) when their foals were 4-, 15-, 30-, 45-, or 60-days-old. On each occasion, the foals were anesthetized and placed out of sight of the mare and the mares’ behavior, heart rate, and cortisol response to foal separation in either the presence of a foal phantom, a square shape, or no visual stimuli were measured. In the presence of the foal phantom, anxious (P = 0.119) and agitated (P = 0.524) mare behavior was not significantly different from baseline values. The mares had significantly elevated behavior scores for 5 out of 6 criteria when the square phantom was presented and were significantly more active (higher scores for fidgety and active criteria) when no visual stimuli (control) were provided. Based on the data presented in this study, the use of a phantom image of a foal with neutral ear and tail position may be an effective nonchemical method of calming mares during separation from their foal.     

Successful induction of lactation in a barren thoroughbred mare: growth of a foal raised on induced lactation and the corresponding maternal hormone profiles

The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, follicle-stimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and raised by their natural mothers, was 17 kg at 24 weeks old, when the foals were weaned. However, the adopted foal and the control foals had almost the same weight at 35 weeks old and later. The first ovulation after hormonal treatment was confirmed 10 days after the end of hormonal treatment and then the normal estrous cycle resumed. Furthermore, the changes in plasma progesterone, estradiol-17β, follicle-stimulating hormone, and luteinizing hormone showed regular patterns after the first ovulation. Conception was confirmed in the fifth ovulation. Meanwhile, another study demonstrated that conception was confirmed in the first ovulation after hormonal treatment. The present study is the first to demonstrate the hormonal profiles during and after induction of lactation in a Thoroughbred mare. This approach is useful for solving the economic and epidemic problems of introducing a nurse mare to an orphan foal.     

Clinical and clinicopathological characteristics of the septicaemic neonatal foal: review of 38 cases

In an effort to identify improved methods for diagnosis of infection in the neonatal foal, clinical records from 38 septicaemic foals of less than one week of age were examined for trends in history, physical examination and clinicopathological findings. The survival rate of septicaemic foals, 26 per cent, was markedly less than the rate for all other foal admissions. Blood cultures were valuable in diagnosis and treatment of septicaemia and identified a preponderance of Gram-negative infection. Zinc sulphate turbidity test results were abnormally low in all septicaemic foals tested. The clinical course was often distinguished by severe complications and multiple organ dysfunction, leading to death. Conditions present in the mare pre-partum resulted in weak or diseased foals; bacterial placentitis, vaginal discharge and premature lactation were most common. There was no single diagnostic criterion of the septicaemic foal. Fever was not a consistent finding. The most useful white blood cell parameters were neutropenia, the presence of band neutrophils (greater than 0.2 X 10(9)/litre) and toxic changes in the neutrophil population. Hypoglycaemia, metabolic acidosis and hypoxaemia were also common findings.     

Studies on equine prematurity 1: Methodology

This paper describes the general management of mares and foals during the perinatal period and the methodology used in a collaborative research project on equine prematurity. Sixteen mares with dated pregnancies delivered 45 foals over three breeding seasons (1981 to 1983). In the majority, parturition was induced with oxytocin and/or fluprostenol; the remainder were allowed to foal spontaneously. Pre-colostral milk analysis provided a means of assessing the pre-foaling status of the mare. All were observed and monitored before, during and after parturition and the sampling protocol for both mare and newborn foal is discussed in detail. The foals were assessed for their degree of maturity at birth using behavioural, haematological, acid-base status and other criteria; they were then assigned to groups for further study and tests.