Disposition of orally administered cefpodoxime proxetil in foals and adult horses and minimum inhibitory concentration of the drug against common bacterial pathogens of horses

OBJECTIVES: To determine the disposition of orally administered cefpodoxime proxetil in foals and adult horses and measure the minimum inhibitory concentrations (MICs) of the drug against common bacterial pathogens of horses. ANIMALS: 6 healthy adult horses and 6 healthy foals at 7 to 14 days of age and again at 3 to 4 months of age. PROCEDURE: A single dose of cefpodoxime proxetil oral suspension was administered (10 mg/kg) to each horse by use of a nasogastric tube. In 7- to 14-day-old foals, 5 additional doses were administered intragastrically at 12-hour intervals. The MIC of cefpodoxime for each of 173 bacterial isolates was determined by use of a commercially available test. RESULTS: In 7- to 14-day-old foals, mean +/- SD time to peak serum concentration (Tmax) was 1.7 +/- 0.7 hours, maximum serum concentration (Cmax) was 0.81 +/- 0.22 microg/mL, and elimination half-life (harmonic mean) was 7.2 hours. Disposition of cefpodoxime in 3- to 4-month-old foals was not significantly different from that of neonates. Adult horses had significantly higher Cmax and significantly lower Tmax, compared with values for foals. The MIC of cefpodoxime required to inhibit growth of 90% of isolates for Salmonella enterica, Escherichia coli, Pasteurella spp, Klebsiella spp, and beta-hemolytic streptococci was 0.38, 1.00, 0.16, 0.19, and 0.09 microg/mL, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration at a dosage of 10 mg/kg every 6 to 12 hours would appear appropriate for the treatment of equine neonates with bacterial infections.     

Studies on the immunogenicity of Streptococcus equi vaccines in foals.

The ability of either formalin-treated or heat-inactivated whole Streptococcus equi cell vaccines or partially purified M-protein of S. equi to give rise to protective antibody levels was studied in Standardbred foals by serological means. Two commercial preparations, i.e. a beta-propiolactone killed whole S. equi cell bacterin and a cell-free extract of S. equi cells were included in the study. The mean passive hemagglutination antibody titers (10 X log2) in sera of foals given either four doses of formalin-treated whole cell vaccine or an initial dose of formalin-treated followed by three doses of heat-inactivated vaccine with or without levamisole were significantly higher two weeks after the final dose. These passive hemagglutination antibody titers were higher in foals given formalin-treated whole cell vaccine (6.7 +/- 1.5) than given commercial bacterin (4.5 +/- 2.1). The passive hemagglutination antibody titers in all the groups decreased at 12 to 16 weeks after fourth dose of the vaccine. Foals given a commercial cell-free extract did not show a significant increase in passive hemagglutination antibody titers even up to four weeks after third dose. A group of six pony foals immunized with partially-purified M protein showed mean passive hemagglutination antibody titers lower than those observed in foals given whole cell vaccines. In a challenge experiment with S. equi, two of six foals vaccinated with partially-purified M-protein and all three controls developed clinical disease. The passive hemagglutination antibody of vaccinated foals increased after challenge, while at 28 days postchallenge the passive hemagglutination antibody titers of vaccinates and recovered controls were similar.     

Renal Clearance, Urinary Excretion of Endogenous Substances, and Urinary Diagnostic Indices in Healthy Neonatal Foals

Urine (U) and serum (S) were obtained every 2 hours during a 12- or 24-hour period from eight healthy 96-hour-old pony or horse foals. Dams' milk samples were obtained concurrently. Urine volume was measured during this 12- or 24-hour period. The mean amount of urine produced was 148 +/- 20 ml/kg/day. Baseline urinalyses were evaluated on all foals at two days of age, before any manipulation. Urine generally was dilute (less than 1.008) but the specific gravity was as high as 1.027 in one normal foal. Continuous (12 or 24 hour) urinary catheterization resulted in bacteriuria but not white blood cells in the urine. Prolonged catheterization did not cause foals to become febrile or exhibit clinical signs of cystitis or other illness. Urinary electrolyte excretion, urinary electrolyte clearances, and fractional electrolyte excretions (FE) were measured. When compared with normal values reported in adult horses, excretion, clearance, and FE were similar for sodium (Na) but higher for potassium (K), phosphorus (P), and calcium (Ca). There were no significant differences between data collected during different time periods, and it was concluded that the use of single sample urine/serum estimates of fractional excretion in the neonatal foal was an appropriate indicator of the renal handling of electrolytes, and when viewed in conjunction with urinalysis and other serum parameters, a valuable aid to evaluating renal function.     

Plasma and pulmonary disposition of ceftiofur and its metabolites after intramuscular administration of ceftiofur crystalline free acid in weanling foals

The objectives of this study were to determine the plasma and pulmonary disposition of ceftiofur crystalline free acid (CCFA) in weanling foals and to compare the plasma pharmacokinetic profile of weanling foals to that of adult horses. A single dose of CCFA was administered intramuscularly to six weanling foals and six adult horses at a dose of 6.6 mg/kg of body weight. Concentrations of desfuroylceftiofur acetamide (DCA) were determined in the plasma of all animals, and in pulmonary epithelial lining fluid (PELF) and bronchoalveolar lavage (BAL) cells of foals. After intramuscular (IM) administration to foals, median time to maximum plasma and PELF concentrations was 24 h (12-48 h). Mean (± SD) peak DCA concentration in plasma (1.44 ± 0.46 μg/mL) was significantly higher than that in PELF (0.46 ± 0.03 μg/mL) and BAL cells (0.024 ± 0.011 μg/mL). Time above the therapeutic target of 0.2 μg/mL was significantly longer in plasma (185 ± 20 h) than in PELF (107 ± 31 h). The concentration of DCA in BAL cells did not reach the therapeutic level. Adult horses had significantly lower peak plasma concentrations and area under the curve compared to foals. Based on the results of this study, CCFA administered IM at 6.6 mg/kg in weanling foals provided plasma and PELF concentrations above the therapeutic target of 0.2 μg/mL for at least 4 days and would be expected to be an effective treatment for pneumonia caused by Streptococcus equi subsp. zooepidemicus at doses similar to the adult label.     

Evaluation of granulocyte transfusion in healthy neonatal pony foals

Granulocyte transfusions (GT), 0.98 X 10(9) neutrophils/kg of body weight, were performed on 7 healthy pony foals between 2 and 7 days old. The mean neutrophil count of the foals was significantly (P less than 0.05) greater than base line (4,830 +/- 1,260/microliter) 1 hour after GT (8,870 +/- 3,350/microliter) and was similar to base line by 15 to 18 hours after GT (6,550 +/- 2,310/microliter). Leukocyte concentrates (LC) used for GT were harvested from clinically normal adult horses by continuous-flow centrifugation leukapheresis (CL), 3 to 6 hours after hydrocortisone sodium succinate was administered to increase the blood neutrophil count. The mean neutrophil count of the LC used for GT was 68,050 +/- 13,990/microliter, and the mean LC volume was 377.4 +/- 79.2 ml (14.82 +/- 3.54 ml/kg). The mean time required to collect the LC used for GT was 232.1 +/- 73.4 minutes. Neutrophils from LC had significantly reduced in vitro stimulated migration to zymosan-activated serum, when compared with peripheral blood neutrophils of the donors (P less than 0.05). Neutrophil phagocytosis and bactericidal capacity were not significantly changed in LC. Mean neutrophil migration indices were not significantly different in foals after GT. Mild depression and transient diarrhea was noticed in 1 foal 30 minutes after the start of the GT. The donor of LC for this foal and 1 other donor experienced depression, piloerection, and muscle tremors during CL, indicating that complement had been activated. Problems were eliminated by the use of new disposable plastic materials for blood processing in each CL procedure.     

In vitro bactericidal efficacy of equine polymorphonuclear leukocytes against Corynebacterium equi

Polymorphonuclear leukocytes from adult horses were separated from whole blood, using a 2-step Percoll gradient, and were tested for bactericidal function against Corynebacterium equi. Staphylococcus aureus, an organism against which equine neutrophils have proved efficacy, was a positive control. The percentage of uptake after a 15-minute preincubation of the neutrophils and bacteria in the presence of normal horse serum was also calculated. The results indicated that equine neutrophils effectively phagocytosed and killed C equi and S aureus. The percentage of uptake for S aureus (95% +/- 3%) was greater than that for C equi (85% +/- 6%) (P less than 0.001), but the bactericidal efficacy was equivalent. More than 90% of the ingested or attached bacteria were destroyed during the 3-hour incubation period (mean percentage of C equi killed = 96 +/- 2%; mean percentage of S aureus killed = 91 +/- 8%). These results indicated that a failure of bacterial killing by neutrophils is unlikely to be important in the pathogenesis of C equi pneumonia in the horse.     

Length of gestation periods of horses and ponies belonging to different breedsDurée de gestation des juments de différentes races de chevaux et de poneysTragezeiten von stuten verschiedener pferde- und ponyrassen

The mean gestation periods of mares belonging to different horse and pony breeds common in The Netherlands have been calculated using data from the birth registers of five stud-book societies. The following mean values have been determined: Fjord pony: 342.2; Haflinger pony: 341.3; Draught horse: 343.3; Shetland pony: 337.2; and Frisian horse: 337.7 days. The variation in the mean gestation period is greater in horses than in cows, sheep or pigs. Colts are carried a little longer than fillies. Differences between years are not significant, but differences between the various breeds have been determined. Shetland foals born before 1 June are carried longer than those born after 1 June. The gestation period for mares of this breed mated at 2 years, is significantly longer than for those mated at more than 2 years.The length of the gestation period in horses is possibly affected by physiological factors other than those influencing the gestation period in some other farm animals.     

Variations in equid SLC11A1 (NRAMP1) genes and associations with Rhodococcus equi pneumonia in horses

Rhodococcus equi is an important intracellular pathogen of horses, most commonly causing chronic, suppurative bronchopneumonia in foals. Although most foals likely are exposed to environmental R. equi within the 1st few days of life, only some develop R. equi pneumonia, and the basis of differences in susceptibility among foals currently is unknown. In this study, we investigated solute carrier family 11 member 1 (SLC11A1) gene sequences in the 5' untranslated region, exon 1, and a portion of intron 1 for variations in 3 equid species (horse, donkey, zebra) and compared variants within 3 independent horse breeding farms for associations with R. equi pneumonia by use of an age-matched case-control design. Seven novel variants in the 5'untranslated region were identified as specific for one or both of the non-horse equid species sampled. In addition, a single novel horse variant in the 5'untranslated region, -57C/T, was identified in 4 breeds. The -57C/T variant was found on 2 of the 3 farms with endemic R. equi pneumonia, representing 2 different horse breeds. Significant allelic and genotypic associations with susceptibility to R. equi pneumonia were observed for the -57C/T variant in foals from these farms. Although the functional impact of this novel variant remains to be determined, this study represents an important step in our understanding of natural resistance to R. equi foal pneumonia and other intracellular bacterial diseases affecting equids.     

Cellular and humoral immune response of foals to vaccination with Corynebacterium equi.

Transformation of peripheral blood lymphocytes from pony foals vaccinated and subsequently infected with Corynebacterium equi was studied. Three foals were vaccinated on two occasions using a formalinized C. equi vaccine with aluminum hydroxide as an adjuvant. Three nonvaccinated foals served as controls. Foals were challenged intratracheally with 9 x 10(9) C. equi six weeks after the initial vaccination.Foals survived this infection for one to two weeks. Significant lymphocyte transformation in response to C. equi antigens was detected in two vaccinated foals at the third week after initial vaccination and in all vaccinated animals at the fifth week. No statistically significant transformation was seen in nonvaccinated foals before infection. Vaccinated and nonvaccinated foals showed responsive lymphocytes following challenge. Vaccination offered no obvious protection against experimental challenge but this failure was probably due to an excessive infective dose of organisms. Low levels of humoral antibodies were detected in some challenged foals. The pathological changes in the lungs of infected animals were comparable with, but more fulminating than, changes observed in the natural disease.     

The interaction of Rhodococcus equi and foal neutrophils in vitro

Polymorphonuclear neutrophil leukocytes (PMNL) from 8 healthy foals (2-14 weeks of age) and 2 foals with bacterial pneumonia were separated from whole blood using a 2 step Percoll gradient. Purified PMNL were tested for bactericidal function against Rhodococcus equi and Staphylococcus aureus in the presence of normal horse serum. The percentage uptake after a 15-min pre-incubation of PMNL and bacteria was also calculated. Ultrastructural examination of the interaction of R. equi and normal foal PMNL was performed after 15 min incubation. Results indicated that foal PMNL effectively phagocytose and destroy R. equi and S. aureus in the presence of normal horse serum. The mean percent uptake for R. equi was 99.3 +/- 0.4% and for S. aureus 99.9 +/- 0.1%. Further, 97.8 +/- 0.1% ingested R. equi and 98.4 +/- 0.1% ingested S. aureus were destroyed in the 15-min incubation period. Over the 3-h incubation, 91.9% of remaining R. equi were killed, but only 49.2 +/- 31.9% of S. aureus (P less than 0.01). Total bactericidal effect of foal PMNL, however, was 99.3 +/- 0.4% against R. equi and 99.9 +/- 0.1% against S. aureus. The percentage uptake and total bactericidal efficacy of neutrophils from sick foals was greater than 95%. Ultrastructural examination of the PMNL-R. equi interaction after 15 min incubation revealed phagocytosis of the bacteria and morphologic changes consistent with neutrophil degranulation. This study suggests that a defect in PMNL bactericidal capability is not likely to be a contributing factor in the pathogenesis of R. equi pneumonia in foals.     

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)     

Microcytosis, hypoferremia, hypoferritemia, and hypertransferrinemia in standardbred foals from birth to 4 months of age

At birth, 24 Standardbred foals were assigned at random to 1 of 2 groups and were given a placebo supplement (group 1) or an iron supplement (248 mg of iron/treatment; group 2). Foals were given iron supplement or placebo 4 times during the second and third weeks after birth. Hematologic variables and general health were monitored until foals were 4 months old. Mean PCV in foals of both groups decreased during the first 2 weeks after birth, but values remained within adult horse reference ranges. During the first 6 weeks after birth, foal erythrocytes were smaller than adult horse erythrocytes, but foal erythrocyte glucose-6-phosphate dehydrogenase activity was greater than that in adult horses. At every measurement, indices of anisocytosis were lower in foals, compared with adult horse reference values, suggesting that foals have a homogeneous population of microcytic erythrocytes during early foalhood. In 2-week-old foals of both groups and in 4-week-old placebo-treated foals, mean serum iron concentration was lower than that in adult horses. In foals at birth and during the first 4 months, total iron-binding capacity values were above the adult reference range. In newborn foals, transferrin saturation percentage values decreased to below the reference range in foals from 2 weeks to 4 months after birth. When foals were born, serum ferritin concentration values were above the adult horse reference range, but decreased to within the reference range by the time foals were 1 day old. From 2 through 6 weeks after birth, foal ferritin concentration values were below the adult reference range.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rhodococcus (Corynebacterium) equi: bactericidal capacity of neutrophils from neonatal and adult horses

The capacity of hematogenous polymorphonuclear neutrophilic leukocytes (PMNL) to kill Rhodococcus equi was compared in horses of various ages. A radioisotope bactericidal assay was used to determine the capacity of PMNL to kill R equi. Assays were conducted on PMNL from horses in 3 groups: group I, 13 foals with a mean age of 3.3 days; group II, 10 group-I foals at a mean age of 35.7 days; and group III, adult dams of group-I foals. Bacteria were obtained from the lungs of a foal with R equi pneumonia and opsonized with fresh adult equine serum that contained R equi specific antibody. The mean peak percentage of R equi killed by PMNL was 78.9 for group I, 90.1 for group II, and 87.9 for group III. There was no significant difference (P greater than 0.05) among groups; however, 15% of foals in group I (2 foals) had a mean peak percentage of 30.5 killed, which was significantly (P less than 0.05) lower than the percentage for other foals in group I. The results of our investigation indicated that the capacity of PMNL to kill opsonized R equi is similar in neonatal, young, and adult horses. However, some neonatal foals have a substantially lower capacity to kill R equi, which may be an important factor in the pathogenesis of R equi infections.     

Lung surfactant function and composition in neonatal foals and adult horses

BACKGROUND: Lung surfactant function and composition are varied and adapted to the specific respiratory physiology of all mammalian species. HYPOTHESIS: Lung surfactant function and composition are different in neonatal foals as compared to adult horses. ANIMALS: Six adult horses, 7 term foals (<24 hours old), and 4 premature foals were used. Animals were part of the Auburn University teaching herd except for 3 client-owned premature foals. METHODS: Bronchoalveolar lavage fluid (BALF) was obtained from all animals. Ultracentrifugation of cell-free BALF separated surfactant into crude surfactant pellets (CSP) and supernatant. Both fractions were analyzed for phospholipid and protein content with the Bartlett and bicinchoninic acid method, respectively. Phospholipid composition of the CSP was determined by using high-performance liquid chromatography with an evaporative light scatter detector. Surface tension of the CSP was measured with a pulsating bubble surfactometer. Results from term foals (<24 hours old) were compared statistically to those from adult horses. Values of P < .05 were considered significant. RESULTS: BALF phospholipid content was similar between adult horses and term foals, but BALF protein content was significantly decreased in term foals. Phosphatidylglycerol was significantly decreased, phosphatidylinositol was significantly increased, and the minimum surface tension was significantly increased in the CSP from term foals compared to adult horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Surface tension and phospholipid composition of surfactant in neonatal foals are significantly different compared to adult horses. These changes may influence biophysical and immunologic functions of surfactant.     

Cochet-Bonnet aesthesiometer-determined corneal sensitivity in neonatal foals and adult horses

Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- 2.1 mm wetting in sick neonatal foals, normal neonatal foals, and adult horses, respectively. Reduced corneal sensation and lower tear production may be associated with ulcerative keratitis and slow corneal healing in some foals.     

In vitro phagocytosis and killing of Corynebacterium equi by alveolar macrophages of foals

Bronchoalveolar lavage was performed 5 times, sequentially, on 3 healthy foals while each foal was 6 to 63 days of age. Phagocytosis and bactericidal assays were performed on recovered alveolar macrophages. Corynebacterium equi and alveolar macrophages at a ratio of 10:1 were incubated for 1 hour in medium containing 1% heat-inactivated rabbit anti-C equi serum. After incubation, greater than 90% of the alveolar macrophages contained at least 1 ingested bacterium and each alveolar macrophage contained 9.4 +/- 1.0 bacteria (mean +/- SE). After alveolar macrophages and C equi were incubated for 1 hour in medium containing heat-inactivated pooled normal horse serum, approximately 24% of the alveolar macrophages contained at least 1 bacterium and each alveolar macrophage contained 0.8 +/- 0.7 bacteria. From 6 to 61 days of age, each foal had significantly (P less than 0.05) decreased phagocytic activity by alveolar macrophages, but a significant change in killing of C equi by alveolar macrophages was not found in the foals from 21 to 61 days of age. After incubating alveolar macrophages and C equi for 4 hours in vitro, approximately 75% of ingested C equi remained viable.     

Measurement of plasma colloid osmotic pressure in normal thoroughbred neonatal foals

A normal plasma colloid osmotic pressure (COP) interval was established for foals and compared to values for adult horses. Plasma samples were obtained from 38 Thoroughbred foals that had normal findings on postfoaling examination and 10 healthy Thoroughbred adult horses. Samples were analyzed using a commercially available colloid osmometer. Fifty samples were obtained from 38 foals. Twelve foals had 2 samples taken, 1 during the 1st 24 hours of life and the 2nd between 24 and 72 hours of life. For foals with 2 samples, only 1 randomly selected value was used in group analysis. Total plasma protein, albumin, and globulin concentrations were measured on all samples from foals. The mean measured plasma COP for foals was 18.8 +/- 1.9 mm Hg for the 38 samples analyzed. Measured plasma COP did not differ significantly over the time period examined for either the 12 paired samples (P = .13) or with regression analysis of the 38 samples (P = .13). Calculation of mean COP, based on previously published quadratic equations using total protein, albumin, and globulin concentrations, underestimated mean measured foal COP values except for when total protein measured by refractometer was used in the Landis-Pappenheimer equation. In conclusion, the plasma COP interval (95% CI: 15.0 mm Hg, 22.6 mm Hg) obtained for healthy foals in this study was found to be lower than that of healthy adult Thoroughbreds (20.6 +/- 0.7 mm Hg, P = .006).     

Effects of plasma sample storage on blood ammonia, bilirubin, and urea nitrogen concentrations: cats and horses

Ten horses, a pony, and 13 cats were used to evaluate base-line blood ammonia, bilirubin, and urea nitrogen concentrations and to determine The effects of prolonged cold storage (-20 degrees C) before assay. Base-line plasma ammonia concentrations in cats (0.992 +/- 0.083 [SE] micrograms/ml) did not change significantly after 48 hours of storage (0.871 +/- 0.073 micrograms/ml); however, they were increased 4.2- and 13-fold after 168 and 216 hours of storage, respectively. In contrast to base-line plasma-ammonia values in cats, those of horses were significantly (0.265 +/- 0.044 micrograms/ml) lower, and significantly increased from base-line values after 48 hours of storage (0.861 +/- 0.094 micrograms/ml) and continued to increase 25.6-fold at 168 hours and 18.4-fold at 216 hours. Plasma urea nitrogen concentrations in cats (25.8 +/- 1.06 mg/dl) and horses (11.2 +/- 0.749 mg/dl) did not change significantly during 168 hours of storage. Total plasma bilirubin values from both cats (0.19 +/- 0.049 mg/dl) and horses (0.75 +/- 0.064 mg/dl) also did not change significantly during storage. These results indicate that feline plasma samples for ammonia determinations may be stored at -20 degrees C for up to 48 hours, whereas equine plasma ammonia values tend to increase during that time. The reason for the increase remains unexplained. Both feline and equine plasma urea nitrogen and total bilirubin are stable for at least 168 hours of storage at -20 degrees C.     

D-xylose absorption in the growing foal

Seven healthy foals (five ponies and two horses) were maintained on grass pasture with their dams. All foals had normal faeces at the time of testing. An oral xylose absorption test was performed on each foal at one, two and three months of age. Following an 8 h fast, 0.5 g/kg D-xylose as a 10 per cent solution was given via a nasogastric tube. Control and 30 min interval plasma samples were collected for 3 h and the plasma was analysed for xylose using the phloroglucinol microassay technique. Maximum xylose concentration levels were reached between 30 and 60 mins for each of the foals. The mean (+/- sem) peak xylose concentration at one, two and three months of age was 3.14 +/- 0.29, 2.19 +/- 0.30 and 1.25 +/- 0.22 mmol/litre respectively, which were all significantly different from each other. Xylose absorption capacity decreased, therefore, with age, becoming similar to the adult horse by three months of age. The oral xylose absorption test can be used to evaluate small intestinal absorptive capacity in the foal provided that the results are compared with foals of the same age group.     

Description of an epizootic and persistence of Streptococcus equi infections in horses

The age-specific attack rates of Streptococcus equi infections of the upper respiratory tract and lymph nodes (strangles) in horses for the different age groups were 17.6% for broodmares, 47.5% for 1-year-old horses, and 37.5% for foals. Streptococcus equi was isolated from nasal, pharyngeal, or lymph node specimens in 31 (60.8%) of 51 sick horses. A male 1-year-old horse, shipped from Kentucky to farm A, was considered to be the index case. Six (19.4%) of 31 horses with strangles remained as shedders of S equi after clinical signs of the disease had ended. Shedders of S equi were not identified from horses that were exposed to infected horses but never developed strangles.