Interpretation of the detection of Sarcocystis neurona antibodies in the serum of young horses

Horses that are exposed to Sarcocystis neurona, a causative agent of equine protozoal myeloencephalitis, produce antibodies that are detectable in serum by western blot (WB). A positive test is indicative of exposure to the organism. Positive tests in young horses can be complicated by the presence of maternal antibodies. Passive transfer of maternal antibodies to S. neurona from seropositive mares to their foals was evaluated. Foals were sampled at birth (presuckle), at 24h of age (postsuckle), and at monthly intervals. All foals sampled before suckling were seronegative. Thirty-three foals from 33 seropositive mares became seropositive with colostrum ingestion at 24h of age, confirming that passive transfer of S. neurona maternal antibodies occurs. Thirty-one of the 33 foals became seronegative by 9 months of age, with a mean seronegative conversion time of 4.2 months. These results indicate that evaluation of exposure to S. neurona by WB analysis of serum may be misleading in young horses.     

Maternal antibodies against equine influenza virus in foals and their interference with vaccination.

Foals that were born to mares vaccinated twice a year against influenza had moderate to high haemagglutination-inhibition antibody titers at 24 hours after birth. The foals were vaccinated at six and ten weeks of age, and again at three to five months after birth. Four months after the third vaccination no antibodies against A/H7N7 and A/H3N8 influenza viruses were detected in these foals. Thus, maternal antibodies probably prevented the development of antibodies against equine influenza virus after vaccination. Foals born to the same mares one year later were monitored to determine the rate of decline of maternal antibodies against influenza viruses. Antibody titers of the foals shortly after birth were similar to those of the mares at foaling. The antibodies persisted for three to six months, and their biological half-life was estimated to be approximately 38 days. Two vaccinations of foals against influenza after the maternal antibodies had virtually disappeared resulted in an antibody response in most, but still not all, foals. These findings suggest that foals should not be vaccinated against influenza until maternal antibodies have disappeared.     

A follow up study on antibodies against Lawsonia intracellularis in mares and foals from two breeding farms in Germany

Equine proliferative enteropathy (EPE) caused by Lawsonia (L.) intracellularis is an emerging disease in foals, particularly in North America. Since a case report in Germany exists, the objective of this study was to examine the incidence of L. intracellularis-antibodies in healthy horses from two German breeding farms. In group 1, serum samples from 24 (year 1) and 16 (year 2) Haflinger mares and their foals were taken. In group 2, over a period of five months, serum samples of six warmblood mares and foals were collected monthly from birth until the foals became seronegative. Serum samples were tested using an ELISA system. Results are expressed as Percentage of Inhibiton (PI). All adult mares (100%) of both groups were seropositive at each point in time (PI-value > 30). In group 1,7/24 foals (29.2%) in year 1 and 4/16 foals (25%) in year 2 had antibodies.The seropositive foals from year 2 had the same dams as the seropositive foals from year 1. In group 2 five of six foals were seropositive after birth. Antibodies decreased from March to July in mares and foals. In July, all five foals tested negative for the first time between the ages of 82 and 141 days (median 115 days). PI-values of mares were significantly correlated with PI-values of their foals. Higher PI-values were seen in younger foals and early in spring. Loss of antibodies in foals at the age of three to five months could be a risk factor for infection and appearance of EPE.     

Detection and effects on platelet function of anti-platelet antibody in mule foals with experimentally induced neonatal alloimmune thrombocytopenia

Horse mares carrying mule foals were immunized during the last trimester of pregnancy with whole acid-citrate-dextrose-anticoagulated donkey blood to experimentally induce neonatal alloimmune thrombocytopenia. Thrombocytopenia occurred in the neonatal mule foals born to immunized horse mares within 24 hours after ingestion of their dams' colostrum. Mule foals born to mares not immunized with donkey blood did not develop thrombocytopenia. These findings suggest that antibodies may have been directed against a donkey platelet antigen present in the mule foals but not present in their dams. The objectives of this study were to determine whether anti-platelet antibody could be detected in mule foals with experimentally induced neonatal alloimmune thrombocytopenia, to identify any platelet proteins recognized by serum antibody in these foals, and to determine if platelet function was altered by sera from these mule foals. An indirect enzyme-linked immunosorbent assay demonstrated significantly higher absorption at 1:200 of platelet-bindable immunoglobulin G in serum from thrombocytopenic mule foals, compared with nonthrombocytopenic mule foals. Sera from thrombocytopenic and nonthrombocytopenic mule foals produced similar binding patterns in western immunoblots with donkey platelet proteins separated on sodium dodecyl sulfate polyacrylamide gels. Maximal platelet aggregation and relative slope of aggregation in response to collagen were significantly inhibited after incubation with sera from thrombocytopenic mule foals. These results suggest that mule foals with induced alloimmune thrombocytopenia have serum antibodies that bind to platelets and may compete with collagen binding sites to impair platelet aggregation.     

Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses

OBJECTIVE: To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals. ANIMALS: 484 Thoroughbred and Warmblood foals from 4 farms in California. PROCEDURE: Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were > or = 40 and > or = 160 for S neurona and N hughesi, respectively. RESULTS: Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1 %, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM). CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses < or = 2.5 years of age.     

Serological status of mares in parturition and the levels of antibodies (IgG) against protozoan family Sarcocystidae from their pre colostral foals

Protozoa from the family Sarcocystidae are agents of reproductive and neurological disorders in horses. The transmission of these protozoa may occur via horizontal or vertical means, and the frequency and potential of the later is not fully elucidated in horses. Thus, the aim of study was to correlation levels of antibodies in mares with pre colostral foals seropositive and assess the level and distribuition of antibodies against Neospora spp., Sarcocystis neurona and Toxoplasma gondii, in mares and pre colostral foals at the parturition. The blood samples were collected from mares immediately after parturition and from newborns before the ingestion of colostrum, and sera were analyzed for the presence of IgG by ELISA. It was found that 21.5%, 33.7% and 27.6% of mares were seropositive for Neospora spp., S. neurona and T. gondii, respectively; foals had antibodies at a rate of 8.3%, 6.6% and 6.6% for Neospora spp., S. neurona and T. gondii, respectively. Additionally, paired samples from mares and pre-colostral foals revealed an overall negative correlation between the serum reactivity against these three parasites and suggested that seronegative mares, or those with low to intermediate antibody levels, have a higher risk of giving birth to seropositive foals.     

Serologic prevalence of Sarcocystis neurona, Toxoplasma gondii, and Neospora caninum in horses in Brazil.

OBJECTIVE: To determine serologic prevalence of Sarcocystis neurona, Toxoplasma gondii, and Neospora caninum in horses in Brazil. DESIGN: Prevalence survey. ANIMALS: 101 Thoroughbreds in Brazil. PROCEDURE: Blood samples were obtained from horses and tested for serum antibodies against S neurona by use of an immunoblot procedure with culture-derived S neurona merozoites as antigen, and for serum antibodies against T gondii and N caninum by use of a modified agglutination test with formalin-preserved tachyzoites and mercaptoethanol. RESULTS: Antibodies against S neurona and T gondii were detected in 36 and 16 of 101 horses, respectively. Cross-reactivity between antibodies against T gondii and S neurona was not detected. Antibodies against N caninum were not detected in any samples. CONCLUSIONS AND CLINICAL RELEVANCE: The high prevalence of antibodies against S neurona detected in clinically normal horses emphasizes the importance of examining CSF for antibodies when establishing a diagnosis of equine protozoal myeloencephalitis.     

Sarcocystis neurona-specific immunoglobulin G in the serum and cerebrospinal fluid of horses administered S neurona vaccine

A vaccine against Sarcocystis neurona, which induces equine protozoal myeloencephalitis (EPM), has received conditional licensure in the United States. A major concern is whether the immunoglobulin G (IgG) response elicited by the vaccine will compromise the use of Western blotting (WB) as a diagnostic tool in vaccinated horses with neurologic disease. Our goals were to determine if vaccination (1) causes seroconversion: (2) causes at least a transient increase in S neurona-specific IgG in the cerebrospinal fluid (CSF); and (3) induces an IgG response that can be differentiated from that induced by natural exposure. Horses included in the study (n = 29) were older than 6 months with no evidence of neurologic disease. The presence or absence of anti-S neurona antibodies in the serum of each horse was determined by WB analysis. Seropositive horses had CSF collected and submitted for cytology, CSF index, and WB analysis. The vaccine was administered to all the horses and boostered 3-4 weeks later. On day 14 after the 2nd administration, serum and CSF were collected and analyzed. Eighty-nine percent (8 of 9) of the initial seronegative horses seroconverted after vaccination, of which 57% (4 of 7) had anti-S neurona IgG in their CSE Eighty percent (16 of 20) of the seropositive horses had an increase in serum S neurona IgG after vaccination. Of the 6 of 20 horses that were initially seropositive/CSF negative, 2 were borderline positive for anti-S neurona IgG in the CSF, 2 tested positive, and 2 were excluded because the CSF sample had been contaminated by blood. There were no WB banding patterns that distinguished samples from horses that seroconverted due to vaccination versus natural exposure. Caution must be used in interpreting WB analysis from neurologic horses that have been recently vaccinated for EPM.     

Serum antibodies in mares and foals to Actinobacillus equuli whole cells, outer membrane proteins, and Aqx toxin

Actinobacillus equuli is carried in the alimentary tract of mares and can cause severe septicemia of neonatal foals. A hemolytic subspecies, A. equuli subsp. haemolyticus, and a non-hemolytic subspecies, A. equuli subsp. equuli, have been identified. Hemolytic strains produce the RTX toxin Aqx. The purpose of this study was to demonstrate sequentially in two sets of mare-foal pairs antibodies to A. equuli whole bacterial cells, outer membrane proteins, and recombinant Aqx and to compare the transfer of antibodies to these antigens between mares and their foals. Two mare/foal sets of sera were evaluated. Cohort A consisted of 18 mare-foal pairs obtained in the spring of 2005. Cohort B consisted of 10 mare-foal pairs obtained in the spring of 2006. For both sets, mare and foal sera were obtained immediately after foaling and prior to nursing (time 0) as well as at 12 and 24h and daily thereafter for 7 days. For Cohort B, sera were also obtained 30 days after birth. At parturition all mares had detectable antibodies to A. equuli whole cells and outer membranes; however, of those mares, two in Cohort A had undetectable antibodies to Aqx and their foals likewise had undetectable anti-Aqx antibodies. Antibodies against whole cells, outer membrane proteins, and Aqx were readily transferred from mares to foals. In most cases, there were significant correlations (p<0.05) between antibodies against whole cells, outer membrane proteins, and Aqx in mares' sera at the time of parturition and foal sera 24 after birth. Antibodies against the three antigen preparations had declined insignificantly (p>0.05) by day 30.     

Immunoglobulin isotypes in sera and nasal mucosal secretions and their neonatal transfer and distribution in horses

OBJECTIVE: To determine concentrations of IgA and IgG subclasses in serum, colostrum, milk, and nasal wash samples of adult horses and foals. ANIMALS: Seven 2-year-old Welsh ponies, 27 adult mixed-breed horses, and 5 Quarter Horse mares and their foals. PROCEDURE: Serum was obtained from ponies and adult horses. Colostrum and milk were obtained from mares and serum and nasal wash samples from their foals immediately after parturition and on days 1, 7, 14, 28, 42, and 63. Nasal wash samples were also obtained from 23 adult horses. Concentrations of immunoglobulins were determined by use of inhibition ELISA. To determine transfer of maternal isotypes to foals, concentrations in colostrum and milk were compared with those in foal serum. Serum half-lives of isotypes in foals were also determined. RESULTS: IgGb was the most abundant isotype in serum and colostrum from adult horses, whereas IgA was the predominant isotype in milk. The major isotype in nasal secretions of adult horses and foals > or = 28 days old was IgA, but IgGa and IgGb were the major isotypes in nasal secretions of foals < or = 14 days old. Serum half lives of IgGa, IgGb, IgG(T), and IgA in foals were 176, 32, 21, and 3.4 days, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The early immunoglobulin repertoire of neonatal foals comprised IgGa, IgG(T), and IgA; endogenous synthesis of IgGb could not be detected until 63 days after birth. The restricted repertoire of immunoglobulins in foals may influence humoral immune responses to vaccination.     

Risk factors for Clostridium piliforme infection in foals

OBJECTIVE: To determine risk factors for Clostridium piliforme infection in neonatal foals on a Thoroughbred breeding farm in California. DESIGN: Case-control and retrospective cohort studies. ANIMALS: 322 neonatal Thoroughbred foals either born on the study farm or born elsewhere but traveled to the farm with their dam during the 1998, 1999, and 2000 breeding seasons. PROCEDURE: Mare and foal records from 1998, 1999, and 2000 were examined, using case-control design methods to determine variables associated with increased risk of C. piliforme infection in foals. Important risk factors identified in the case-control study were then reevaluated by use of a retrospective cohort design, using data from all neonatal foals present on the farm during the 3-year study period. RESULTS: Foals born between March 13 and April 13 were 7.2 times as likely to develop C. piliforme infection as were those born at any other time of the foaling season. Foals of nonresident (visiting) mares were 3.4 times as likely to develop disease as were foals born to mares that were permanent residents of the study farm. Foals of mares < 6 years of age were 2.9 times as likely to develop disease as were foals born to older mares. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this research can be used to better understand the epidemiologic factors of C. piliforme infection in horses. High-risk foals can be closely monitored to aid in early diagnosis and treatment, resulting in the best possible clinical outcome for affected individuals.     

Immunologic Profiles of Peripheral Blood Leukocytes and Serum Immunoglobulin G Concentrations in Perinatal Mares and Neonatal Foals (Heavy Draft Horse)

The purpose of this study was to examine sequential changes in the immunologic parameters of perinatal mares and neonatal foals of the heavy draft horse. Blood samples were collected from clinically healthy pregnant mares and their newborn foals every week from 1 month before the expected foaling date, and 1 hour, 1 day (24-48 hours), and 1, 2, 3, and 4 weeks after foaling. Peripheral blood samples were used to examine total leukocyte counts (n = 20), differential leukocyte counts (n = 20), lymphocyte subpopulations (n = 13), lymphocyte responses to mitogens (n = 10), neutrophil phagocytic function (n = 12), and serum immunoglobulin G (IgG) concentrations (n = 10). In perinatal mares, remarkable changes observed included increased neutrophils, decreased lymphocytes, decreased CD4⁺ T lymphocytes, and decreased lymphocyte responses to mitogens at delivery. These changes were speculated to be the result of physical stress associated with delivery. In neonatal foals, increase in the phagocytic function of neutrophils, and increase in serum IgG concentration after suckling colostrum and increase of lymphocytes accompanied by physiologic growth were observed. Compared to dams, foals showed lower phagocytic function of neutrophils before suckling and fewer lymphocytes and lower lymphocyte responses to mitogens within 1 day after birth. This study revealed immunologic dynamics in perinatal mares and neonatal foals. Immunologic functions are suppressed in foaling mares and are immature in neonatal foals, especially before colostral intake. We expect these data will be useful for further studies in the field of clinical immunology, and preventive medicine.     

The importance of vertical transmission of Neospora sp. in naturally infected horses

Neospora spp. is a intracellular protozoan phylogenetically closely related to Toxoplasma gondii and Sarcocystis neurona, and it can infect horses leading to the development of reproductive or neurological diseases. We determined the presence of antibodies to Neospora sp. in mares at their parturition time and determine the frequency of vertical transmission in healthy foals to verify the importance of transplacental transmission. The samples were analyzed by indirect immunofluorescence antibody test, showing that seroprevalence in mares is higher than in foals and seropositive mares are likely to transmit the neosporosis to their offspring. This shows that endogenous challenge occurs in horses, and it suggests that this protozoan can be disseminated by means of transplacental transmission in horse species.     

Studies of passive immunity in foals to equine viral arteritis

The capacity of colostral samples collected from mares immune to equine viral arteritis to neutralize arteritis virus was two or more times greater than that present in the dams' sera. This activity in the mammary secretions was very low or undetectable after 1 week. The capacity of sera from eight of the nine foals born to immune mares to neutralize arteritis virus was high at 1 week of age. All of the titres had declined to extinction after 2–6 months. Arteritis virus neutralization was not detected in serum collected from foals prior to nursing or in samples from non-immune mares and their foals.Foals from immune mares developed mild signs or no signs of disease when inoculated nasally with virulent arteritis virus at 6 days of age.Seven- to nine-day-old foals from non-immune mares responded to vaccinationas they had appreciable serum-virus neutralizing antibody titres 6 months after vaccination and did not develop signs of disease when inoculated nasally with virulent virus. Foals of the same ages from immune mares did not respond to the vaccine since antibody could not be detected 6 months after vaccination and they either died or experienced clinically severe disease when inoculated nasally with virulent arteritis virus.     

Effect of intermittent oral administration of ponazuril on experimental Sarcocystis neurona infection of horses

OBJECTIVE: To evaluate the effect of intermittent oral administration of ponazuril on immunoconversion against Sarcocystis neurona in horses inoculated intragastrically with S neurona sporocysts. ANIMALS: 20 healthy horses that were seronegative for S neurona-specific IgG. PROCEDURES: 5 control horses were neither inoculated with sporocysts nor treated. Other horses (5 horses/group) each received 612,500 S neurona sporocysts via nasogastric tube (day 0) and were not treated or were administered ponazuril (20 mg/kg, PO) every 7 days (beginning on day 5) or every 14 days (beginning on day 12) for 12 weeks. Blood and CSF samples were collected on day - 1 and then every 14 days after challenge for western blot assessment of immunoconversion. Clinical signs of equine protozoal myeloencephalitis (EPM) were monitored, and tissues were examined histologically after euthanasia. Results: Sera from all challenged horses yielded positive western blot results within 56 days. Immunoconversion in CSF was detected in only 2 of 5 horses that were treated weekly; all other challenged horses immunoconverted within 84 days. Weekly administration of ponazuril significantly reduced the antibody response against the S neurona 17-kd antigen in CSF. Neurologic signs consistent with EPM did not develop in any group; likewise, histologic examination of CNS tissue did not reveal protozoa or consistent degenerative or inflammatory changes. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of ponazuril every 7 days, but not every 14 days, significantly decreased intrathecal anti-S neurona antibody responses in horses inoculated with S neurona sporocysts. Protocols involving intermittent administration of ponazuril may have application in prevention of EPM.     

Duration of maternally derived antibodies against equine influenza in newborn foals

Serum antibody concentrations against influenza A-equi-1 virus and A-equi-2 virus were measured in a group of 18 foals from birth to 4 months of age. More than 50% of the foals were seronegative to A-equi-1 virus infection by 4 weeks of age, with titers of less than or equal to 1:16. For A-equi-2 virus, more than 50% of the foals were seronegative by 2 weeks of age, with titers of less than or equal to 1:8. Passively derived antibodies against influenza A-equi-1 virus and A-equi-2 virus in foals obtained from recently vaccinated mares and from mares not vaccinated within 6 months before foaling were low in titer. The duration of passively derived antibodies was also short-lived.     

Effects of blood contamination of cerebrospinal fluid on western blot analysis for detection of antibodies against Sarcocystis neurona and on albumin quotient and immunoglobulin G index in horses.

OBJECTIVE: To determine effects of blood contamination on western blot (WB) analysis of CSF samples for detection of anti-Sarcocystis neurona antibodies, and on CSF albumin and IgG concentrations, albumin quotient (AQ), and IgG index in horses. DESIGN: Prospective in vitro study. SAMPLES: Blood with various degrees of immunoreactivity against S neurona was collected from 12 healthy horses. Cerebrospinal fluid without immunoreactivity against S neurona was harvested from 4 recently euthanatized horses. PROCEDURE: Blood was serially diluted with pooled nonimmunoreactive CSF so that final dilutions corresponded to 10(-3) to 100 microliters of blood/ml CSF, and WB analysis was performed on contaminated CSF samples. Number of RBC, albumin and IgG concentrations, AQ, and IgG index were also determined. RESULTS: Antibodies against S neurona were detected in CSF contaminated with 10(-3) microliters of strongly immunoreactive blood/ml. In CSF samples contaminated with 10 microliters of blood/ml, AQ remained within reference range. Volume of blood required to increase IgG index varied among blood samples and was primarily influenced by serum IgG concentrations. Number of RBC in contaminated samples was correlated with volume of blood added, but not with degree of immunoreactivity detected in contaminated CSF samples. CONCLUSIONS AND CLINICAL RELEVANCE: During collection of CSF from horses, contamination with blood may introduce serum antibodies against S neurona at concentrations sufficient for detection by WB analysis, thus yielding false-positive results. When blood is moderately or strongly immunoreactive, the amount of contaminating albumin may be small enough as to not increase AQ above reference range. In these cases, AQ and IgG index should be interpreted with caution.     

Passive transfer of naturally acquired specific immunity against West Nile Virus to foals in a semi-feral pony herd

Horses naturally exposed to West Nile Virus (WNV) or vaccinated against WNV develop humoral immunity thought to be protective against development of clinical disease in exposed or infected animals. No reports evaluate the efficacy of passive transfer of naturally acquired specific WNV humoral immunity from dam to foal. The purpose of this study was to investigate passive transfer of naturally acquired immunity to WNV to foals born in a herd of semi-feral ponies, not vaccinated against WNV, in an endemic area, with many dams having seroconverted because of natural exposure. Microwell serum neutralization titers against WNV were determined in all mares and foals. Serum IgG concentration was determined in foals by serial radial immunodiffusion. Differences in IgG concentration between seropositive and seronegative foals were examined by means of the Mann-Whitney U-test. Linear regression was used to evaluate the association between mare and foal titers. Seventeen mare-foal pairs were studied; 1 foal had inadequate IgG concentration. IgG concentration was not different between seronegative and seropositive foals (P = .24). Mare and foal titers were significantly correlated in foals with adequate passive transfer of immunity (Spearman's rho = .84; P < .001); >90% of the foal's titer was explained by the mare's titer (R2 = 0.91; P < .001). Passive transfer of specific immunity to WNV is present in pony foals with adequate passive transfer of immunity born to seroconverted mares.     

Effect of altrenogest‐treatment of mares in late gestation on adrenocortical function,blood count and plasma electrolytes in their foals

Reasons for performing study: Mares with compromised pregnancies are often treated with altrenogest to prevent abortion. However, there is only limited information about effects on the foal when altrenogest treatment is continued during final maturation of the fetus. Objectives: To determine effects of altrenogest treatment during late gestation in mares on maturity, haematology changes, adrenocortical function and serum electrolytes in their newborn foals. Methods: Six mares were treated with altrenogest (0.088 mg/kg bwt) once daily from Day 280 of pregnancy until foaling and 7 mares served as controls. Results: Foals born to altrenogest‐treated mares had a significantly lower neutrophil/lymphocyte ratio on the first day after birth than control foals (P<0.05). Basal plasma cortisol concentrations immediately after birth were higher in foals of altrenogest‐treated mares than in control foals (P<0.05). Cortisol release in response to exogenous adrenocorticotropic hormone (ACTH) ‐ except for higher values 15 min after ACTH injection in foals of altrenogest‐treated mares on Day 1 ‐ revealed no differences in adrenocortical function between the groups of foals. Plasma potassium concentration in foals from altrenogest‐treated mares compared to control foals was significantly lower immediately after birth (P<0.05) and plasma ionised calcium concentration was significantly lower 3 h after birth (P = 0.01). Conclusions and potential relevance: Altrenogest treatment of pregnant mares prolonged labour had no major effects on adrenocortical function in foals. A reduced neutrophil/ lymphocyte ratio in these foals may suggest either immunomodulatory effects of altrenogest or dysmaturity of the foals.     

The effects of maternal health and body condition on the endocrine responses of neonatal foals

Reasons for performing the study: Chronic and acute alterations in maternal nutrient intake during pregnancy alter pancreatic and hypothalamo‐pituitary‐adrenal (HPA) axis function in the offspring, before and after birth. Little is known about these effects. Objective: To determine whether maternal nutrient restriction caused by natural infection with Streptococcus equi altered endocrine function in neonatal foals born from mares fed a maintenance or high plane of nutrition throughout pregnancy. Methods: Ten primiparous mares received either a diet to maintain moderate body condition score (Moderate, n = 5) or a near ad libitum feeding regime to maintain a high body condition score (High, n = 5) throughout pregnancy. All mares inadvertently became infected with Streptococcus equi in mid gestation and lost approximately 10% body mass. Results: Maternal insulin and glucose concentrations decreased (P<0.05) during, and one month following, the weight loss period. High mares weighed more (P<0.05) at parturition than Moderate mares; all foals were healthy. Gestational age, foal bodyweights, placental and clinical parameters after birth were no different between the 2 groups. Foal plasma cortisol and glucose responses to exogenous adrenocorticotrophic hormone and insulin, respectively, were similar for both groups. Insulin concentrations during glucose tolerance test were significantly higher (P<0.05) in foals from Moderate than High mares and compared with foals studied previously from healthy, well‐fed mares, suggesting that the β cell sensitivity to glucose was enhanced in Moderate. Conclusion: Acute nutrient restriction in mid gestation caused by maternal illness and inappetence, superimposed on a maintenance feed intake throughout pregnancy, enhanced insulin secretion to glucose in foals. Nutritional programming of pancreatic β cells, but not the HPA axis, appeared to depend on the level of nutrition before and after the weight loss period. Potential relevance: Disturbances in neonatal pancreatic β cell function programmed during pregnancy may predispose foals to metabolic problems in later life.