The effects of copper supplementation on the prevalence of cartilage lesions in foals

The potential role of dietary copper in the development of cartilage defects in foals was investigated. Twenty-one mares were fed rations containing 13 ppm copper (CuC, control) or 32 ppm copper (CuS, supplemented) during the last three to six months of gestation and first three months of lactation. Their foals were fed pelleted concentrate containing 15 or 55 ppm Cu and were destroyed at 90 (5 CuC and 5 CuS foals) or 180 (6 CuC and 5 CuS foals) days. Focal cartilage lesions were found at multiple sites on necropsy. In foals killed at 90 days, there were over twice (9 versus 4) as many lesions of osteochondrosis and more than four times (9 versus 2) as many articular lesions of osteophyte formation or thinning in CuC foals compared with CuS foals. These differences were due predominantly to a higher number of lesions in one CuC foal. Two 90-day CuC foals had osteochondrosis of articular-epiphyseal (A-E) complex, one with thickenings and separation from subchondral bone and one with subchondral fibrosis. One 90-day CuS foal had a cartilage thickening of the A-E complex in the tibiotarsal joint with separation from subchondral bone. In foals killed at 180 days, there were seven times more articular lesions (21 versus 3) of osteophyte formation or thinning, nearly twice as many lesions of osteochondrosis (13 versus 8) [corrected] in the physis and over five times as many involving the A-E complex (11 versus 2) in six CuC foals compared with five CuS foals.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of stress on gastric ulceration, T3, T4, reverse T3 and cortisol in neonatal foals.

Sixteen neonatal foals stressed by disease underwent endoscopic examination of their stomachs and blood was assayed for triiodothyronine (T3), reverse T3 (rT3), thyroxine (T4) and cortisol, to determine the effects of severe physiological stress and the occurrence of gastric ulcers. compared with eight age-matched controls, six foals had abnormal cortisol, seven had abnormal T3 and 12 had abnormal T4. Eleven of 13 foals had rT3 outside the 95 per cent confidence interval for clinically normal foals of comparable ages. Gastric lesions were seen more frequently in stressed foals, and gastric glandular mucosal lesions were noted in 40 per cent of the stressed foals. Previous studies report low (3 per cent) occurrence of gastric mucosal lesions. The frequency of squamous mucosal lesions was not different from that reported previously, indicating that stress has little effect on the development of lesions at this site.     

Quantitative fecal culture for early diagnosis of Corynebacterium (Rhodococcus) equi enteritis in foals.

Quantitative culture of Corynebacterium (Rhodococcus) equi from feces of 17 foals on a farm (A) with an endemic C. equi infection problem and 26 foals on a farm (B) without the disease in the past decade was done with a selective medium at weekly or monthly intervals from April to August of 1984. Corynebacterium equi was observed in the feces of 16 of 17 foals on farm A, and 19 of 26 foals on farm B. The mean viable count of C. equi in one gram of feces was 4.1 +/- 3.7 (log10) on farm A, and 3.9 +/- 3.4 (log10) on farm B. Corynebacterium equi was recovered from feces of foals as young as two weeks old. Almost all foals at an age between two to four weeks shed the bacteria in the feces. During the observation period two foals showed clinical signs: fever, diarrhea, and cough, at four or five weeks old. At the same time the bacterial count per gram of feces increased from 4 to 7 or 8 (log10). They shed large number of bacteria in the feces and continued to show the clinical signs until death at 10 or 11 weeks old. One of the foals was diagnosed as having had C. equi enteritis and pneumonia by the postmortem recognition of lesions with bacteriological confirmation. The quantitative culture of the feces of foals at weekly intervals after birth on farm A was found to be very useful as an aid in early diagnosis of C. equi enteritis in foals.     

MAGNETIC RESONANCE IMAGING IN FOALS WITH INFECTIOUS ARTHRITIS

The magnetic resonance (MR) imaging findings of foals with infectious and noninfectious arthritis are described. Six foals with infectious arthritis and three foals with noninfectious arthritis were grouped based on synovial fluid analysis results and examined with radiography and MR imaging. Four out of six foals with infectious arthritis had osseous lesions in MR images indicative of osteomyelitis and only 4/19 lesions were detected on digital radiographs. The three foals with noninfectious arthritis had no osseous lesions in MR images or radiographically. Of the six joints that had osseous lesions detected with MR imaging, three had at least one lytic lesion detected radiographically. Osseous lesions in the epiphysis, metaphysis, and physis appeared in MR images as T2W, short tau inversion recovery, and proton density hyperintense foci with a hypointense halo. The same lesions appeared hyperintense in the 3D RSSG water excitation pulse sequence but lacked a surrounding hypointense halo. Most joints of foals with infectious arthritis had heterogenous signals within the synovial fluid whereas all of the nonseptic joints had homogenous synovial fluid signals. MR imaging appears to be better than radiography in the detection of osseous lesions in foals diagnosed with infectious arthritis and may be a valuable screening test for the presence of osteomyelitis.     

Effects of repeated Strongylus vulgaris inoculations and concurrent ivermectin treatments on mesenteric arterial lesions in pony foals

Eight of 10 pony foals reared under helminth-free conditions were inoculated PO with 50 Strongylus vulgaris infective larvae/week for 4 weeks, at which time 1 foal died of acute verminous arteritis. Inoculation of 7 remaining foals continued at 2-week intervals for 20 weeks. Of the 7 foals, 3 were treated with ivermectin (0.2 mg/kg of body weight) in an oral paste formulation at experiment weeks 8, 16, 24; 4 foals were not treated. Two foals were not inoculated or treated and served as controls. After the first ivermectin treatment, ivermectin-treated foals had fewer days (12 +/- 2.9) with rectal temperatures greater than 38.6 C than did nontreated foals (23.3 +/- 3.8). Mean baseline rectal temperatures were 38 +/- 0.2 C. Adverse clinical reactions to ivermectin treatment were not observed in foals. Foals were euthanatized and necropsied 3 weeks after the last ivermectin treatment (week 24). Ivermectin was effective in reducing S vulgaris arterial larval and intestinal adult parasite numbers by 100% in 3 treated foals. Strongylus vulgaris arterial larvae and/or adults were recovered from all 4 nontreated inoculated foals. One nontreated inoculated foal lacked arterial larvae or active arterial lesions, indicating that protective resistance had developed in this individual. Marked gross and histopathologic lesions typical of chronic S vulgaris infection were observed in the 3 nontreated inoculated foals with arterial larvae. Repeated killing of intra-arterial S vulgaris fourth-stage larvae in ivermectin-treated foals did not exacerbate lesions associated with verminous arteritis or induce unique lesions associated with repeated destruction of arterial larvae.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exploratory celiotomy for suspected urinary tract disruption in neonatal foals: a review of 18 cases

The medical records of 18 neonatal foals, in which exploratory celiotomies were performed for suspected urinary tract lesions, were reviewed. Despite clinical signs and laboratory values indicative of disruption of the urinary tract, three foals did not have a site of urinary tract leakage at surgery. Eight foals had ruptured bladders and seven foals had urachal lesions. Ultrasonography was used as a pre-operative diagnostic procedure in eight foals to evaluate the presence of free peritoneal fluid and urinary tract integrity. Nine foals were alive six months after discharge. Seven of the nine non-surviving foals died or were destroyed because of fungal or bacterial infections.     

Pathological findings in horses dying during an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection.

In 1988 an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection occurred on a stud farm and several animals died. This provided an opportunity to perform detailed pathological investigations to gain insights into the pathogenesis of this spontaneous disease. Two paretic mares, three foals, an aborted foetus and its non-paretic dam were examined. The endotheliotropism of the virus was clearly demonstrated by the use of an indirect immunoperoxidase (IP) stain. At autopsy, evidence of viral infection was widespread in the foetus and foals, but limited or absent in the mares, probably reflecting differences in their immune status. Vascular lesions were present in the central nervous system (CNS) of the foals as well as the adults; they resulted in minimal neural lesions in the foals. Severe changes in the upper and lower respiratory tracts were a particular feature in the foals, two of which exhibited extensive vasculitis and thrombosis in the lungs. The IP technique was of great value in locating antigen-containing cells in the CNS of one mare when virus isolation was negative. It also revealed the presence of virus in less well documented sites such as the pancreas, gut, thyroid, uveal tract and the skin of the nares.     

Influence of liver copper status of mare and newborn foal on the development of osteochondrotic lesions

REASON FOR PERFORMING STUDY: To elucidate the highly contentious role of copper in the pathogenesis of osteochondrosis. HYPOTHESIS: There would be no relationship between liver copper concentration of mares and foals and incidence of radiographically detectable osteochondrotic lesions in foals and yearlings was tested. METHODS: Liver copper concentration was assessed in biopsies taken within 4 days after birth from both mares and foals and from the same foals at age 5 months. Biopsies were taken in the standing, sedated animal under ultrasonographic guidance. Radiographs were taken of both hocks (lateromedial, dorsoplantar and dorsomedial-plantarolateral oblique views) and stifles (lateromedial and caudolateral-craniomedial oblique views) at ages 5 and 11 months and scored for the presence and severity of osteochondrotic lesions. RESULTS: Copper concentrations in newborn foals were high with a large variation (351 +/- 201 mg/kg DM). They declined until reaching values comparable to those in mature animals at 5 months (20 +/- 8 mg/kg DM; mares: 19 +/- 20 mg/kg DM). Radiographic osteochondrotic lesions decreased in number and severity from 5 to 11 months. This pattern was more predominant in the stifle than in the hock, as has been described previously. CONCLUSIONS: There was no relationship between foal or mare liver copper concentration and osteochondrosis status at either 5 or 11 months. However, osteochondrotic lesions in foals with low-level copper status at birth decreased significantly less in number and severity than those in foals with high-level copper status at birth. POTENTIAL RELEVANCE: It is concluded that copper is not likely to be an important factor in the aetiopathogenesis of osteochondrosis, but this study indicates that there may be a significant effect of high copper status on the natural process of repair of early lesions.     

Bronchointerstitial Pneumonia and Respiratory Distress in Young Horses: Clinical, Clinicopathologic, Radiographic, and Pathological Findings in 23 Cases (1984–1989)

Twenty-three foals, between 1 and 7 months old, with signs of acute respiratory distress, were examined at the Veterinary Medical Teaching Hospital (VMTH), University of California, Davis, between 1984 and 1989. Characteristic features included sudden onset of severe respiratory distress and tachypnea, cyanosis unresponsive to nasal oxygen, pyrexia, hypoxemia, hypercapneic respiratory acidosis, poor response to treatment, and histopathologic lesions of bronchiolitis and bronchointerstitial pneumonia. Seven of the 23 foals were normal before the onset of respiratory distress, 3 foals were found dead, aqd 13 foals were being treated for respiratory tract infections at the time of presentation. Laboratory data obtained for 13 horses showed increased plasma fibrinogen concentration (630.7 ±193 mg/dL), leukocy-tosis (18,607 ± 7,784/μL), and neutrophilia (13,737 ± 8,211/μL). Thoracic radiographs showed a diffuse increase in interstitial and bronchointerstitial pulmonary opacity and, in 5 foals, an alveolar pulmonary pattern of increased density was also seen. In 3 foals heavy interstitial infiltration proceeded to a coalescing nodular radiographic appearance. Microbiological culture of tracheobronchial aspirates (TBA) from 9 foals yielded bacterial growth, but no one bacterial species was consistently isolated. Microbiological culture of postmortem specimens of the lung from 6 foals yielded growth of bacteria that included Escherichia coli, Enterobacter spp., Proteus mirabilis, Klebsiella pneumonias, Rhodococcus equi, or β-hemolytic Streptococcus spp. Tracheobronchial aspirates from 4 foals and lung samples collected from a further 4 foals at necropsy yielded no bacterial growth. Cultures were not taken from two foals premortem or postmortem. Virologic examination of TBA, lung tissue, or pooled organ tissue from 12 foals was negative. Viral culture of TBA from 1 foal showed cytopathic effects and positive immunoflu-orescence for equine herpes virus type II (EHV-II). In addition to the 3 foals that were found dead, 11 foals died or were euthanatized. Pathologic lesions were limited to the lungs in 50% of the foals; the remainder also had bowel lesions suggestive of hypoxic injury. The predominant histopathologic pulmonary lesions included bronchiolitis, bronchiolar and alveolar epithelial hyperplasia, and necrosis. Many bronchioles were filled with mucoid and fibrinocellular exudate. The peribronchiolar interstitium and adjacent alveolar spaces were also infiltrated with inflammatory cells and contained proteinaceous edema fluid. Type II cell hyperplasia and hyaline membrane formation were observed in the majority of foals and in 2 foals alveolar multinucleate giant cells were also present. Nine of 13 foals (69%) on which treatment was attempted at the VMTH survived after aggressive medical care that included external thermoregulatory control, oxygen by nasal insufflation, antimicrobial drugs, bronchodilating agents, nonsteroidal anti-inflammatory drugs, and corticosteroids. Persistent radiographic evidence of increased interstitial density was noted up to 24 months after initial presentation, and one horse remained exercise intolerant for at least 15 months after discharge. The exact etiopathogenesis of this disorder and long-term sequalae in the survivors have yet to be fully determined. However, it is likely that a number of different insults rather than a single agent may initiate the pulmonary damage that leads to severe interstitial pneumonia and subsequent acute respiratory distress or apparent sudden death in foals. (Journal of Veterinary Internal Medicine 1993; 7:277–288. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Strongylus vulgaris in the tunica media of arteries of ponies and treatment with ivermectin

A preliminary investigation was made into the effect of fourth-stage Strongylus vulgaris larvae sequestered in the tunica media of ileocolic arteries of pony foals treated with ivermectin. The foals had been reared parasite-free, inoculated with infective larvae and given orally a placebo or ivermectin paste. Two foals received subsequently one or two further inoculations with larvae and treatment with ivermectin. Arteriography was used to identify the lesions in the ileocolic artery following inoculation and their regression following treatment. At necropsy, foals were examined for lesions and larvae grossly and histologically. Ivermectin was highly effective against fourth-stage larvae and those present in the media appeared not to unduly affect the integrity of the ileocolic artery. Increased numbers of larvae were not found in the media of foals receiving repeat inoculations and repeat treatments. Larvae were not found in the media of foals treated with a placebo. The major pathological changes in the arterial wall of all foals were attributed to infection with S. vulgaris and there was no strong tendency for the damaged arteries to return to normal after the S. vulgaris were removed.     

Endoscopic evaluation of changes in gastric lesions of Thoroughbred foals

Gastroendoscopic examinations were conducted on thirty-two 2- to 60-day-old Thoroughbred foals on 5 breeding farms. Repeat gastroendoscopic examinations were performed 35 to 135 days after the initial examination, with the age of foals ranging from 39 to 190 days. On initial endoscopic examination, lesions consisting of ulcers and/or erosions were most prevalent in the stratified squamous epithelial mucosa adjacent to the margo plicatus along the greater curvature of the stomach (15 of 32 foals), and were observed much less frequently at other sites within the stomach. In addition to ulcers and erosions, squamous epithelial desquamation at the margo plicatus was observed in 16 of 19 foals less than 30 days old and in 3 of 13 foals 30 to 60 days old, and was not seen in any foal on repeat endoscopy. At the time of repeat endoscopic examination, the frequency of ulcers and erosions at the margo plicatus was significantly (P less than 0.01) less than at initial examination (4 of 32 foals vs 15 of 32 foals). Lesions had healed in 14 of the 15 foals with lesions at the margo plicatus on the initial examination. Lesions were observed in the glandular mucosa of the fundus in 3 of 32 foals on initial examination and in 6 of 32 foals reexamined. Lesions in the glandular fundus observed on initial examination had healed in 2 of 3 foals, and of the 6 foals with glandular mucosal lesions on reexamination, 5 had developed lesions since the initial examination.(ABSTRACT TRUNCATED AT 250 WORDS)     

Articular / epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: influences of growth of the foal and prenatal copper supplementation of the dam

AIMS: To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. METHODS: Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4-8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically. RESULTS: Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birthweight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions. CONCLUSIONS: Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.     

Rhodococcus equi foal pneumonia: protective effects of immune plasma in experimentally infected foals

The immunoprophylactic capacity of specific immune plasma was evaluated in pony foals infected experimentally with Rhodococcus equi. Immune plasma, produced by repeated parenteral administration of viable R. equi to adult horses, was harvested and frozen. Group I (six control foals) and Group II (six principal foals) received lactated Ringers solution and immune plasma respectively at three and five days of age. R. equi were aerosolised into a caudal lung lobe of all foals at seven days of age. Clinical signs, haematological alterations, immune responses, thoracic radiographs and technetium99m pulmonary perfusion scans were monitored. All foals were destroyed and complete post mortem examinations performed. All foals developed pneumonia as evidenced by clinical, radiographic and perfusion alterations, but the survival rate of principal foals was significantly (P less than 0.01) greater than that of control foals. Five control foals developed terminal disease, whereas all principal foals recovered. There was no significant (P greater than 0.05) difference in temperature response, or peripheral blood leucocyte, neutrophil or fibrinogen concentrations between groups. ELISA values for R. equi antibody were significantly (P less than 0.001) greater in principal foals following treatment, but there was no significant (P greater than 0.05) difference in IgG or IgM concentrations between groups. Results of the haemolysis inhibition assay indicated that equi factor neutralising antibodies were transferred by immune plasma to the principal foals. Post mortem examinations of five control foals destroyed at approximately three weeks post infection because of terminal disease, revealed severe pyogranulomatous pneumonia. One control and all principal foals were either free of lesions or had resolving lesions and/or minimal scar formation at three months post infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Articular/epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: Influences of growth of the foal and prenatal copper supplementation of the dam

AIMS: To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age.

METHODS: Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4–8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically.

RESULTS: Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birth-weight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions.

CONCLUSIONS: Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.     

A XERORADIOGRAPHIC STUDY OF OSTEOCHONDROSIS IN THE METACARPOPHALANGEAL REGION OF TWO FOALS

Using xeroradiographic techniques, both metacarpophalangeal regions of six quarter horse foals were radiographed at 1 day of age and at 2-week intervals until they were 6 weeks old, and then at 4-week intervals until they were 12 months old. Lateromedial and dorsopalmar xeroradiographs of each metacarpophalangeal region were made per examination; dorsomedial-palmarolateral projections of the left metacarpophalangeal joint of foal 6 were also made. The foals were weighed and measured at the withers immediately prior to each examination. Representative xeroradiographs were selected to demonstrate progression of the osteochondrosis (OCH) lesions in two of these foals. Radiographic evidence of osteochondrosis in the metacarpophalangeal region was first detected at 10 weeks and followed through 12 months of age. In one foal the lesions were bilaterally symmetric and involved the dorsoproximal aspect of the sagittal ridge of metacarpal 3; in the other, the left medial proximal sesamoid bone was affected. One of the sagittal ridge lesions progressed to osteochondritis dissecans by 26 weeks; the other sagittal ridge lesion and that of the sesamoid bone healed spontaneously, but residual radiographic evidence of the disease persisted throughout the study in both foals.     

Early lesions of articular osteochondrosis in the distal femur of foals

Failure of the cartilage canal blood supply to epiphyseal growth cartilage has been implicated in the pathogenesis of articular osteochondrosis in horses and other animal species. In a previous study of the developmental pattern of the blood supply in the tarsus of foals, early lesions of osteochondrosis were consistently found in regions where the cartilage canal vessels traversed the chondro-osseous junction. The developmental pattern of blood vessels has also been described in the distal femoral epiphysis; however, the group of foals examined in that study did not have lesions of osteochondrosis in this location. Therefore, the relationship between the occurrence of early lesions of osteochondrosis and the developmental pattern of the blood supply to epiphyseal growth cartilage in this site in foals has not been examined. Distal femora were collected from 30 fetuses and foals (up to 11 months old) submitted for postmortem examination. Sections from the lateral trochlear ridge and medial femoral condyle of both hind limbs were examined histologically. Sixteen cartilage lesions were found in 7 of the 30 fetuses and foals. All lesions contained evidence of cartilage canal necrosis and ischemic chondronecrosis. The lesions were located in regions where cartilage canal vessels traversed the chondro-osseous junction, as previously observed in the tarsus. The location and morphology of lesions indicated that a subclinical stage of ischemic chondronecrosis existed that preceded and predisposed to the development of osteochondrosis dissecans and subchondral bone cysts.     

Effect of hyperimmune plasma on the severity of pneumonia caused by Rhodococcus equi in experimentally infected foals

This study evaluated the prophylactic effectiveness of hyperimmune plasma (HIP) as an aid in the prevention of pneumonia caused by experimental infection with Rhodococcus equi. Thirty neonatal foals were administered R. equi HIP or saline at 2 days of age and were infected with virulent R. equi at 7 days. All foals developed signs or symptoms of respiratory disease. Radiographic scores on day 28 and neutrophil concentrations on day 49 were significantly greater in control foals, and time to respiratory effort score of 2 or higher was significantly shorter for control foals. Three foals, all in the principal group, died or were euthanized before the end of the study, but there was no significant difference in mortality between groups. VapA titers were significantly greater in principal foals. Administration of R. equi HIP decreased the severity of radiographic lesions and prolonged time to increased respiratory effort due to R. equi-induced pneumonia.     

Evaluation of serum concentrations of biomarkers of skeletal metabolism and results of radiography as indicators of severity of osteochondrosis in foals

OBJECTIVE: To determine whether serum concentrations of biomarkers of skeletal metabolism can, in conjunction with radiographic evaluation, indicate severity of osteochondrosis in developing horses. ANIMALS: 43 Dutch Warmblood foals with varying severity of osteochondrosis. PROCEDURE: 24 foals were monitored for 5 months and 19 foals were monitored for 11 months. Monthly radiographs of femoropatellar-femorotibial and tibio-tarsal joints were graded for osteochondral abnormalities. Serial blood samples were assayed for 8 cartilage and bone biomarkers. At the end of the monitoring period, foals were examined for macroscopic osteochondrosis lesions. RESULTS: Temporal relationships were evident between certain serum biomarkers and osteochondrosis severity in foals during their first year. Biomarkers of collagen degradation (collagenase-generated neoepitopes of type-II collagen fragments, type-I and -II collagen fragments [COL2-3/4C(short)], and cross-linked telopeptide fragments of type-I collagen) and bone mineralization (osteocalcin) were positive indicators of osteochondrosis severity at 5 months of age. In foals with lesions at 11 months of age, osteochondrosis severity correlated negatively with COL2-3/4C(short) and osteocalcin and positively with C-propeptide of type-II procollagen (CPII), a collagen synthesis marker. Radiographic grading of osteochondrosis lesions significantly correlated with macroscopic osteochondrosis severity score at both ages and was strongest when combined with osteocalcin at 5 months and CPII at 11 months. CONCLUSIONS AND CLINICAL RELEVANCE: The ability of serum biomarkers to indicate osteochondrosis severity appears to depend on stage of disease and is strengthened with radiography. In older foals with more permanent lesions, osteochondrosis severity is significantly related to biomarker concentrations of decreased bone formation and increased cartilage synthesis.     

Osteopetrosis in two foals

This account describes two neonatal foals affected with osteopetrosis. One of these foals, a full term Peruvian Paso, was born alive, was bright and alert but was unable to stand and was euthanized at two days of age. The second foal, an Appaloosa, was also born alive at full term and was blind, weak, uncoordinated and unable to stand. Postmortem examination of both foals revealed generalized osteopetrosis and brachygnathia inferior. The osteopetrosis was characterized by failure of bone remodelling resulting in spicules of mineralized and nonmineralized cartilage covered by osteoid occupying the medullary areas of bones.

It was not possible to determine whether this condition has an hereditary basis in horses. Circumstantial evidence suggested that the condition might be inherited in the Peruvian horse.

The condition described in foals in this report and in one previous report is compared and contrasted with the disease in cattle. The lesions of osteopetrosis are similar in both species, but slightly less severe in horses.

     

Endoscopic appearance of gastric lesions in foals: 94 cases (1987-1988)

Of 183 foals examined by use of gastroendoscopy during 1987 and 1988, 94 had gastric lesions. Sixty-eight of 120 foals in the 1- to 85-day-old age range had endoscopically confirmed gastric lesions, and 26 of 63 foals in the 90- to 310-day-old age range had gastric lesions. Lesions were observed most frequently in the stratified squamous mucosal epithelium, particularly adjacent to the margo plicatus. Lesions were observed in the gastric glandular mucosa in 26 of the 94 foals with gastric lesions, and with a greater frequency in foals with a clinical disorder than in foals with no disorder (27% vs 3%). In young foals, lesions were consistently observed in the stratified squamous mucosal epithelium adjacent to the margo plicatus along the greater curvature of the stomach at 2 specific sites. These lesions were frequently associated with desquamation of the stratified squamous mucosal epithelium, which was observed in 69 of the 82 foals less than or equal to 30 days old and in 13 of the 101 foals greater than 30 days old. Lesions in the stratified squamous mucosal epithelium adjacent to the margo plicatus were associated with concurrent clinical disorders in foals greater than 90 days old, but developed with identical frequency in foals less than 90 days old with or without a clinical disorder. Lesions in the stratified squamous mucosal epithelium along the lesser curvature of the stomach were observed only in foals with concurrent clinical disorder, and with a higher frequency in foals greater than 90 days old than in younger foals (24% vs 3%).