Mare-foal Pairs Research Articles

Characteristics of maternal antibodies transferred to foals raised through maternal equine rotavirus A vaccination

Equine rotavirus A (ERVA) can cause foal diarrhoea and the most common ERVA genotypes are G3P[12] and G14P[12]. Since the introduction of a monovalent killed G3P[12] vaccine, infection in neonates has decreased. We aimed to determine the dynamics and longevity of maternally derived anti-G3P[12] neutralizing antibodies (NAbs) in foals and what, if any, cross-reactivity exists between maternally derived NAbs against G14P[12]. Serum samples were collected from 50 mare-foal pairs before each vaccination and up to 6 months post-foaling for mares and up to 7 months of age for foals. These samples were then used for virus-neutralization antibody assays with both G3P[12] and G14P[12] viruses. We observed that vaccination of mares could increase their serum NAb titers. Pre-nursing serum samples of foals collected at birth before the first nursing contained no detectable NAbs. In contrast, post-nursing serum samples of foals showed a significant amount of NAb levels, thereby confirming that these NAbs are passed through the mare’s colostrum. Our study demonstrated that there is variation in the ratio of NAbs transferred from the serum of mares to the serum of their foals. Results also confirmed evidence of cross-reactivity between maternal antibodies in the serum of G3P[12] vaccinated dams and G14P[12]. Heterologous (G14P[12]) NAb titers were about 2- to 4-fold lower than homologous (G3P[12]) titers in colostrum, milk, and serum samples of both mares and their foals. Our data demonstrate that G3 and G14 NAbs in the serum of foals decreased steadily over time with the lowest point measured at approximately 4 months of age.

Comparing microbiotas of foals and their mares’ milk in the first two weeks after birth

BackgroundThe mare-foal relationship is essential for the well-being and growth of a foal. Mare’s milk provides a foal with nutrients, protective immunity, and microbes. Within the first two weeks of life, there is a risk for a foal to suffer from diarrhea, particularly “foal heat diarrhea” which happens at about the time of a mare’s estrus cycle but is more likely due to transitions in the microbiota in the foal’s gastrointestinal (GI) tract. We hypothesized that this GI microbiota transition could be caused by changes in lysozyme and microbial populations in the mare’s milk. To test this hypothesis, fifteen mare-foal pairs were followed in the first 15 days post-foaling. Every other day milk was collected from mares and rectal swabs were collected from foals. Lysozyme activity in the mare’s milk was measured using a fluorescence assay. Microbial DNA was isolated from the milk and swabs and the V4 domain of 16 S rRNA genes were PCR amplified and sequenced using Illumina MiSeq technology. Microbial populations were analyzed using DADA2 and phyloseq within R.ResultsMare’s milk lysozyme activity peaked for samples at Day 1 and levels dropped to 72.5% of Day 1 activity by Day 15; however, microbial populations in the mare’s milk did not vary significantly over the two weeks. Furthermore, levels of microbial diversity found in foal rectal swabs were initially similar to microbial diversity seen in mare’s milk; however, over the first fifteen days, diversity increased for the foal rectal swab microbiota and swab microbial populations differed from milk microbes. A transition occurred shifting from microbes from the phylum Proteobacteria early in rectal swabs to those primarily from the phyla Firmicutes and Bacteroidota after the first few days post-foaling. These phyla contained several families and genera of microbes that promote utilization of milk components in healthy gut transition. Microbial abundance levels correlated more with days post-parturition than with lysozyme activity and mare’s milk microbial populations.ConclusionsThe findings suggest that much of the microbial populations responsible for the transition of the foal’s gut comes from sources outside of mare’s milk species and levels of lysozyme activity.

Plasma melatonin concentration during the early post-partum period in Thoroughbred mares and their foals.

The authors aimed to determine the plasma melatonin concentration in mares and their new-born foals in the early post-partum period. Blood samples were collected from the jugular vein of 53 mare-foal pairs within twelve hours after parturition. Plasma melatonin levels were measured by ELISA. The melatonin concentration, adjusted for the moment of parturition using a generalised linear model, was34.58 pg mL-1 in mares. It was significantly lower (27.63 pg mL-1) in the new-born foals. However, the melatonin concentration declined differently by the end of the twelve hours, it decreased less in theoffspring than in the mothers. An artificial light supplementation at the end of gestation reduced the melatonin concentration both in mares and their foals by about 10 pg mL-1, compared to the controls. An elevated melatonin production may be related to preparation of mares for parturition and ensures the chances of survival of offspring, therefore the melatonin may reach its peak at the moment of foalingregardless of its actual time. The effect of low melatonin concentration in new-born foals might be associated with the foal's health and subsequent performance. The need to monitor the melatonin concentration in the offspring justifies further studies.

Hair Cortisol and DHEA-S in Foals and Mares as a Retrospective Picture of Feto-Maternal Relationship under Physiological and Pathological Conditions.

Simple SummaryHair hormone concentrations represent an attractive alternative for studies focusing on the prenatal period because a single measurement from hair collected at birth could provide data from a wide but datable prenatal period. Our aim is to evaluate cortisol, dehydroepiandrosterone-sulfate concentrations and their ratio in the trichological matrix of mares and foals to assess maternal and fetal hypothalamus-pituitary-adrenal axis activity in relation to the clinical condition of the neonate and the housing place at parturition. Mare’s endocrine setting influences hormone concentrations detected in foal’s hair, and foals classified as sick at birth have different hormone concentrations than healthy ones. On the other hand, hormone concentrations detected in the hair of mares hospitalized for attended parturitions do not reflect a different hypothalamus-pituitary-adrenal axis activity from those foaled at the breeding farm. Although the specific role of cortisol and dehydroepiandrosterone-sulfate in foals and mares under pathological conditions remains under investigation, this study opens up the use of neonate’s hair as an attractive non-invasive retrospective calendar for the assessment of prenatal adrenal activity in the equine species.Equine fetal hair starts to grow at around 270 days of pregnancy, and hair collected at birth reflects hormones of the last third of pregnancy. The study aimed to evaluate cortisol (CORT) and dehydroepiandrosterone-sulfate (DHEA-S) concentrations and their ratio in the trichological matrix of foals and mares in relation to their clinical parameters; the clinical condition of the neonate (study 1); the housing place at parturition (study 2). In study 1, 107 mare-foal pairs were divided into healthy (group H; n = 56) and sick (group S; n = 51) foals, whereas in study 2, group H was divided into hospital (n = 30) and breeding farm (n = 26) parturition. Steroids from hair were measured using a solid-phase microtiter radioimmunoassay. In study 1, hair CORT concentrations measured in foals did not differ between groups and did not appear to be influenced by clinical parameters. A correlation between foal and mare hair CORT concentrations (p = 0.019; r = 0.312, group H; p = 0.006; r = 0.349, group S) and between CORT and DHEA-S concentrations in foals (p = 0.018; r = 0.282, group H; p < 0.001; r = 0.44, group S) and mares (p = 0.006; r = 0.361, group H; p = 0.027; r = 0.271, group S) exists in both groups. Increased hair DHEA-S concentrations (p = 0.033) and decreased CORT/DHEA-S ratio (p < 0.001) appear to be potential biomarkers of chronic stress in the final third of pregnancy, as well as a potential sign of resilience and allostatic load in sick foals, and deserve further attention in the evaluation of prenatal hypothalamus-pituitary-adrenal (HPA) axis activity in the equine species. In study 2, hormone concentrations in the hair of mares hospitalized for attended parturition did not differ from those that were foaled at the breeding farm. This result could be related to a too brief period of hospitalization to cause significant changes in steroid deposition in the mare’s hair.

Kinetics of the Equid Herpesvirus 2 and 5 Infections among Mares and Foals from Three Polish National Studs.

Equid herpesvirus 2 (EHV-2) and 5 (EHV-5) are two γ-herpesviruses that are commonly detected from horses worldwide, based on several cross-sectional molecular surveys. Comparatively few studies examined the dynamics of γ-herpesvirus infection over time in a group of horses. The aim of the current study was to investigate the dynamics of EHV-2/5 infections among mares and their foals at three Polish national studs with different breeds of horses: Arabians, Thoroughbreds and Polish Konik horses. Nasal swabs were collected from each of 38 mare-foal pairs monthly for a period of 6 to 8 months. Virus-specific quantitative PCR assays were used to determine the viral load of EHV-2 and EHV-5 in each sample. All 76 horses sampled were positive for EHV-2 or EHV-5 on at least one sampling occasion. The majority (73/76, 96%) were infected with both EHV-2 and EHV-5. In general, the mean load of viral DNA was higher in samples from foals than from mares, but similar for EHV-2 and EHV-5 at most sampling occasions. There was, however, a considerable variability in the viral DNA load between samples collected at different times from the same foal, as well as between samples from different foals. The latter was more apparent for EHV-2 than for EHV-5. All foals became infected with both viruses early in life, before weaning, and remained positive on all, or most, subsequent samplings. The virus shedding by mares was more intermittent, indicating the existence of age-related differences. Overall, the data presented extend our knowledge of EHV-2/5 epidemiology among mares and foals.

Monitoring Body Length of Hokkaido Native Horse’s Foals Using a Drone

Monitoring Body Length of Hokkaido Native Horse’s Foals Using a Drone

Characterisation of and risk factors for extended-spectrum\xa0\u03b2-lactamase producing Enterobacterales (ESBL-E) in an equine hospital with a special reference to an outbreak caused by Klebsiella pneumoniae ST307:CTX-M-1

BackgroundExtended-spectrum β-lactamase producing Enterobacterales (ESBL-E) are important causative agents for infections in humans and animals. At the Equine Veterinary Teaching Hospital of the University of Helsinki, the first infections caused by ESBL-E were observed at the end of 2011 leading to enhanced infection surveillance. Contact patients were screened for ESBL-E by culturing infection sites and rectal screening. This study was focused on describing the epidemiology and microbiological characteristics of ESBL-E from equine patients of the EVTH during 2011–2014, and analysing putative risk factors for being positive for ESBL-E during an outbreak of Klebsiella pneumoniae ST307.ResultsThe number of ESBL-E isolations increased through 2012–2013 culminating in an outbreak of multi-drug resistant K. pneumoniae ST307:blaCTX-M-1:blaTEM:blaSHV during 04–08/2013. During 10/2011–05/2014, altogether 139 ESBL-E isolates were found from 96 horses. Of these, 26 were from infection-site specimens and 113 from rectal-screening swabs. A total of 118 ESBL-E isolates from horses were available for further study, the most numerous being K. pneumoniae (n = 44), Escherichia coli (n = 31) and Enterobacter cloacae (n = 31). Hospital environmental specimens (N = 47) yielded six isolates of ESBL-E. Two identical E. cloacae isolates originating from an operating theatre and a recovery room had identical or highly similar PFGE fingerprint profiles as five horse isolates. In the multivariable analysis, mare–foal pairs (OR 4.71, 95% CI 1.57–14.19, P = 0.006), length of hospitalisation (OR 1.62, 95% CI 1.28–2.06, P < 0.001) and passing of a nasogastric tube (OR 2.86, 95% CI 1.03–7.95, P = 0.044) were associated with being positive for ESBL-E during the K. pneumoniae outbreak.ConclusionsThe occurrence of an outbreak caused by a pathogenic ESBL-producing K. pneumoniae ST307 strain highlights the importance of epidemiological surveillance of ESBL-E in veterinary hospitals. Limiting the length of hospitalisation for equine patients may reduce the risk of spread of ESBL-E. It is also important to acknowledge the importance of nasogastric tubing as a potential source of acquiring ESBL-E. As ESBL-E were also found in stomach drench pumps used with nasogastric tubes, veterinary practices should pay close attention to appropriate equipment cleaning procedures and disinfection practices.

102 Detecting coprophagy in foals and its relationship with foal gut health

Abstract Consumption of maternal feces is commonly observed in foals; however, the role of this activity in foal health is unknown. Therefore, this study aimed to determine the occurrence of coprophagy in foals and how it relates to foal gut health. Milk samples and foal feces were collected from 12 mare-foal pairs at 12 h, 3, 5, 7, 10, 14, and 21 d after foaling. Milk yield was estimated after muzzling foals for 2 h intervals at 7 and 14 d postpartum. To detect coprophagy in foals, nine mares were fed chromic oxide (10 g/d) with their concentrate in nosebags twice daily. Mares had ad libitum access to forage. Fecal samples were collected immediately after defecation and used to enumerate cellulolytic bacteria, lactobacilli, and lactate-utilizing bacteria using culture-based techniques. Enumeration data were log10 transformed before statistical analyses. Frozen feces were used to analyze neutral detergent fiber (NDF) using a Fiber Analyzer (Ankom Technology, NY, USA), then ashed and digested to analyze chromic oxide via atomic absorption. Fecal scores were recorded daily to monitor for signs of diarrhea. Changes over time were evaluated using repeated measures ANOVA and relationships between variables were analyzed using Pearson’s correlation coefficient (SAS 9.4). Coprophagy was detected as early as 3 d after birth and detected in all foals by 7 d of age. Peak coprophagy occurred at 14 d after birth. Milk yield was negatively related to fiber and chromic oxide in foal feces (r = -0.64 and -0.70, respectively; P &amp;lt; 0.05). Chromic oxide in foal feces was positively related to the number of cellulolytic bacteria and NDF (r = 0.97 and 0.79, respectively; P &amp;lt; 0.05). Bouts of diarrhea tended to be negatively related to chromic oxide (r = -0.59; P = 0.0928). Maternal feces is likely an important source of fiber and microbial inoculum for foals, aiding in colonization of beneficial microbes.

Is similarity in Major Histocompatibility Complex (MHC) associated with the incidence of retained fetal membranes in draft mares? A cross-sectional study.

The failure of the maternal immune system to recognize fetal antigens and vice versa due to MHC similarity between the foal and its dam might result in the lack of placental separation during parturition in mares. The aim of the study was to investigate the influence of MHC similarity between a mare and a foal on the incidence of retained fetal membranes (RFM) in post-partum mares. DNA was sampled from 43 draft mares and their foals. Mares which failed to expel fetal membranes within three hours after foal expulsion were considered the RFM group (n = 14) and mares that expelled fetal membranes during the above period were the control group (n = 29). Nine MHC microsatellites of MHC I and MHC II were amplified for all mares and foals. MHC compatibility and MHC genetic similarity between mares and their foals was determined based on MHC microsatellites. The inbreeding coefficient was also calculated for all horses. The incidence of RFM in the studied population was 33%. Compatibility in MHC I and MHC II did not increase the risk of RFM in the studied population of draft mares (P>0.05). Differences in MHC similarity at the genetic level were not observed between mare-foal pairs in RFM and control group (P>0.05). We suspect that RFM in draft mares may not be associated with MHC similarity between a foal and its dam. Despite the above, draft horses could be genetically predisposed to the disease.

Early colonisation and temporal dynamics of the gut microbial ecosystem in Standardbred foals.

Even if horses strictly depend on the gut microbiota for energy homeostasis, only a few molecular studies have focused on its characterisation and none on the perinatal gut microbial colonisation process. To explore the perinatal colonisation process of the foal gut microbial ecosystem and the temporal dynamics of the ecosystem assembly during the first days of life. Longitudinal study. Thirteen Standardbred mare-foal pairs were included in the study. For each pair, at delivery we collected the mare amniotic fluid, faeces and colostrum, and the foal meconium. Milk samples and faeces of both mare and foal were also taken longitudinally, until day 10 post-partum. Samples were analysed by means of next-generation sequencing of the 16S rRNA gene on Illumina MiSeq. Our findings suggest that microbial components derived from the mare symbiont communities establishes in the foal gut since fetal life. After birth, an external transmission route of mare microorganisms takes place. This involves a rapid and dynamic process of assembling the mature foal gut microbiome, in which the founder microbial species are derived from both the milk and the gut microbial ecosystems of the mare. The inability to discriminate between live and dead cells, the possible presence of contaminating bacteria in low biomass samples (e.g. meconium and amniotic fluid), the limits of the phylogenetic assignment down to species level, and the presence of unassigned operational taxonomic units. Our data highlight the importance of mare microbiomes as a key factor for the establishment of the gut microbial ecosystem of the foal.

Vertical transmission of hepatitis C virus-like non-primate hepacivirus in horses.

Non-primate hepacivirus (NPHV), a recently discovered hepatotropic virus infecting horses, is phylogenetically the closest known homologue of hepatitis C virus (HCV). The main route for acquiring HCV infection in childhood is vertical transmission. However, nothing is known about the natural mode of transmission for NPHV. To investigate the possibility of vertically transmitted NPHV infection in horses, 20 Thoroughbred broodmares and their foals were monitored during foaling season 2015 until 6 months post-partum. Prepartal serum was taken from the mares, and during foaling umbilical cord blood and colostrum samples were collected. Postnatal serum samples were taken from the foals after delivery. In addition, serum was taken at 3 and 6 months after foaling from all mares and foals. Samples were analysed for the presence of NPHV RNA by quantitative real-time PCR and for the presence of anti-NPHV NS3 antibodies by luciferase immunoprecipitation system. Identified NPHV isolates were sequenced and phylogenetic analysis of the viral glycoproteins was used to track the course of naturally occurring infections and the circulation of distinct isolates within the herd. At parturition, 16 mares were seropositive, including four viraemic mares. Vertical transmission occurred in one of these four mare-foal pairs. Interestingly, NPHV isolates of newly infected foals and mares after 3 and 6 months cluster in their respective pasture herds suggesting another horizontal route of transmission.

Genetic and serological surveillance for non-primate hepacivirus in horses in Japan

Non-primate hepacivirus (NPHV) is a recently discovered homolog of the hepatitis C virus in horses. The frequency and distribution of NPHV infections among horses in Japan is unknown. In this study, serum samples from 453 horses across Japan were screened for NPHV RNA using real-time RT-PCR and anti-nonstructural 3 protein (NS3) antibodies using the Gaussia luciferase immunoprecipitation system assay. In order to monitor the course of NPHV infection in horses, we examined 31 stored samples (9 adult horses and 22 young horses) obtained one year ago and compared the results to the recent data. Stored sera from 7 mare–foal pairs were also examined. The NS3 region sequences of 14 NPHV strains from NPHV RNA positive serum samples were determined and analyzed phylogenically. Of the 453 serum samples tested, 33.55% were positive for anti-NS3 antibody and 13.68% were positive for NPHV RNA. We found a higher rate of NPHV RNA detection in serum obtained from young horses (1–2 years of age) than that of adults, in two geographically distinct areas. We observed higher variation in the course of infection over one year in young horses than in adult horses. The foals were infected with NPHV after the weaning period. Phylogenic analysis revealed that while NPHV NS3 genes isolated in Japan clustered with sequences previously classified as NPHV, but the genetic diversity of the Japanese NPHV strains we detected was not correlated with their geographic origin. In conclusion, Japanese horses exhibit a high prevalence of NPHV. Young age appears to be a risk factor for such viral infection in Japan, although the infectious route was not determined.

Effect of Weaning Age on Stress-Related Behavior in Foals (Equus Caballus) by Abrupt - Group Weaning Method

Weaning is one of the most stressful periods in a foal’s life. The traditional and most common weaning method is total and abrupt in China. The purpose of the research was to examine the stress-related behavioral response of foals and find the optimal weaning age by using abrupt and group weaning method. A total of 15 thoroughbred mare-foal pairs were divided into three groups A (6-month foals, n=5), B (7-month foals, n=5) and C (8-month foals, n=5) according to the weaning age. These foals were observed for 3 days before weaning and 9 days after separation, and 15 behavioral patterns were compiled. All statistical analysis was performed by R2.14.2 (R Development Core Team). Comparing to pre-weaning, frequency of drinking, urination, fast-moving, aggression behaviors increased and the frequency of standing, lying and individual rolling behaviors decreased after separation for three groups. On the weaning day (Day 0), drinking, urination, social game, friend were most pronounced and standing, slow-moving, individual rolling was least pronounced in foals of group A (p<0.05). Except for the same pronounce with group A, the frequency of fast-moving and individual nibbling were the highest in foals of group B (0.53 ± 0.49, 0.77 ± 0.15 times /h, respectively) and the frequency of defecation, social kidding, individual nibbling behaviors were the highest in foals of group C (0.38 ± 0.11, 1.75 ± 0.87, 0.71 ± 0.08 times /h, respectively) on the weaning day, whilst the frequency of slow-moving were strongly decreased in foals of group B (10.88 ± 0.69 times /h) and the frequency of social suck were strongly decreased in foals of group C (0.33 ± 0.07 times /h ) on the weaning day. 8, 12 and 13 behavior categories had changes in group A, group B and group C during the observation phase. Weaning is associated with stress but 6-month years old was least pronounced in foals by abrupt - group weaning method in China.

The relationship of coprophagy to fecal microbial species richness in neonatal foals

It is commonly accepted that neonates are born with sterile gastrointestinal (GI) tracts and that the normal GI bacteria are established at some point after birth. In horses, the consumption of maternal feces by the neonatal foal has been suggested as an important mechanism for establishing the resident GI bacterial flora. The aim of this study was to determine if coprophagy plays a role in the colonization of commensal bacteria species in the neonatal equine GI tract. Thoroughbred mare-foal pairs (n ¼ 5) were monitored starting immediately post-foaling for 4 d via surveillance cameras. Cameras were positioned in stalls or day-pens to allow continual observation of mares and foals. Recordings were downloaded to a computer and watched to observe the frequency of coprophagy by foals. Fecal samples were collected from the mare and foal by rectal palpation starting with the passing of the foal’s meconium and at approximately 0.5, 1, 2, 3, and 4 d after foaling. Samples were frozen at -20 � C and later processed. Microbial DNA was extracted and the small ribosomal subunit (16s rRNA gene) was amplified then subjected to PCRdenaturing gradient gel electrophoresis (PCR-DGGE) using a 40-60% gradient. Comparisons between banding patterns in fecal samples of a mare and her foal were made using Dice 0 s index and UPGMA. Data are reported as percent similarity between mare and foal at 0, 0.5,1, and 4 d. When PCR-DGGE was performed on the meconium of foals, no bands were observed (% similarity ¼ 0). By 0.5 d, only 3 of 5 foals had developed banding on gels, resulting in a simi

Identification of periparturient mare and foal associated predictors of post parturient immunoglobulin A concentrations in Thoroughbred foals

Prior to the start of endogenous production of immunoglobulins (Igs), absorption of maternal Igs is important to protect against pathogens in the early neonatal period. It is possible that mare- or foal-associated factors may influence neonatal IgA concentrations. The temporal relationships among serum and milk IgA concentrations in Thoroughbred mare-foal pairs were explored to determine if periparturient mare- and foal-associated factors contribute to the prediction of foal serum IgA concentrations. Blood and milk samples as well as complete veterinary records, were collected for 84 Thoroughbred mare-foal pairs from one month before to 2 months after parturition. Samples were tested using enzyme-linked immunosorbent assay (ELISA) for concentrations of IgA. Pairwise correlation coefficients were estimated (P < 0.01) and simple linear regression used to investigate unconditional associations between mare IgA levels, mare and foal risk factors and foal serum IgA concentration at 12 h. Backwards, stepwise elimination of nonsignificant factors was used to create a final model. There were significant temporal relationships among mare serum IgA and among colostrum and milk IgA concentrations within mares (P < 0.01). Mare serum IgA concentrations up to one month before parturition were associated with foal serum IgA concentrations at all time points and with colostrum and milk IgA concentrations. Mare serum IgA at -28 days and parity were associated with foal serum IgA concentration at 12 h (P < 0.001). Mare serum IgA concentrations up to 28 days before parturition, together with mare parity, are indicative of neonatal foal serum IgA concentrations. Mare serum and colostrum IgA concentrations may be useful peripartum predictors of neonatal mucosal immune status, enabling earlier intervention to prevent the consequences of mucosal infections.

Real-time PCR and typing of Clostridium difficile isolates colonizing mare–foal pairs

Clostridium difficile infection can occur in the dams of sick foals, but it is unknown if mares and foals share the same isolates. In this study, C. difficile isolates from fecal samples of 11 mares paired with 11 foals were genotyped by arbitrarily primed PCR; two mares and three foals in five mare-foal pairs had diarrhea. Fecal immunoassays were utilized to detect C. difficile common antigen and toxin A. Quantitative real-time PCR (qPCR) systems were developed to detect genes for toxins A and B, as well as for binary toxin B. Sequences of all toxins were present in all isolates, although only one horse was positive for toxin A on fecal immunoassay. Identical strains of C. difficile were present in 4/11 (36.4%) mare-foal pairs. Mare-foal pairs can harbor C. difficile subclinically and are potential reservoirs for colonization of each other.

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.

Foal-related risk factors associated with development of Rhodococcus equi pneumonia on farms with endemic infection.

To identify foal-related risk factors associated with development of Rhodococcus equi pneumonia among foals on farms with endemic R. equi infection. Prospective case-control study. 220 foals at 2 equine breeding farms in Texas during a 2-year period. Information collected for each dam included age, time housed on the farm prior to parturition, whether there were any peripartum illnesses, parity, and health of previous foals. Information collected for each foal included breed, sex, gestational age, month and year of birth, location of birth, type of flooring and bedding in stall, postpartum management and preventive health care, passive immunity status, supplementation of immunoglobulins, exposure to other farms or foals affected with R. equi pneumonia, stall and pasture exposure, commingling with other mare-foal pairs, age at weaning, and whether the foal developed R. equi pneumonia. 32 of the 220 (15%) foals developed R. equi pneumonia, of which 4 (13%) died. Foals at 1 of the 2 farms and foals born during the second year of the study were more likely to develop R. equi pneumonia. Foal-related factors that were examined were not significantly associated with risk of R. equi pneumonia in multivariate analyses. Results suggest that there are farm- and year-related effects on the risk that foals will develop R. equi pneumonia. Other foal-related factors significantly associated with R. equi pneumonia were not identified.

Effects of Abrupt vs Gradual Weaning on Cortisol and Immune Function Responses of Foals

This study evaluated the effects of two weaning methods on cortisol and peripheral blood leukocyte (PBL) population of foals. Twelve mare-foal pairs were randomly assigned to abrupt weaning (AW) or gradual weaning (GW) treatments. Foals were weighed on d –30, –23, –16, –9, –2, 7, and 12 relative to weaning (d 0). The activity levels of foals were measured at 12-h intervals. Plasma cortisol was measured daily through d 5. On d 0, 1, 3, and 5, PBL were counted, and lymphocytes were cultured in a proliferation assay. Average daily gain declined (P<0.05) post-weaning, but did not differ between treatments. Cortisol and activity did not differ between treatments, but activity was elevated (P<0.05) for both treatments at 12, 72, and 108h post-weaning. Total neutrophil (P<0.05) and white blood cell counts (P<0.01) were greater for foals on the AW treatment on d 0, 1, and 3, but there were no treatment effects on lymphocyte proliferation to phytohemagglutinin (PHA) or pokeweed mitogens (PWM). A day × treatment interaction for Concanavilin A (Con A)-stimulated proliferation revealed a greater (P<0.01) response in foals on the AW treatment on d 1. No treatment differences were observed in the percentage of cells staining positive for lymphocyte markers. Yet, the percentage of B cells was greatest (P<0.001) on d 3. We concluded that foals on the AW and GW treatments showed similar decreases in ADG and similar cortisol response to weaning. Immune function immediately post-weaning, based on measures obtained in this study, did not seem to be affected greatly by weaning method.

Self-grooming by mares and foals of the Welsh pony ( Equus caballus)

Self-grooming behaviour of 15 mare-foal pairs was studied weekly for the first 24 weeks of the foal's life. Mares self-groomed at mean rates of 1.2–2.2 times h −1 depending on the 4-week period. Foals self-groomed more often, with a peak rate of 12.3 times h −1 occurring during Week 5–8 and a subsequent decline to 6.0 times h −1 by Weeks 21–24. Self-grooming bouts of mares and foals also differed in the proportion devoted to each type of self-grooming. During a greater proportion of their total self-grooming bouts, foals scratched their head and neck with a hind limb or bit and scratched the trunk or hind limbs with the teeth. The mares spent a greater proportion of their self-grooming bouts rubbing their head or neck on an inanimate object, another pony, or their fore limb, or rolling on the ground. Particular types of individual self-grooming bouts were engaged in for different lengths of time. Foals had longer bouts of scratching the head and neck with a hind limb, scratching or biting the fore limb or hind limb with the teeth, and rubbing the head and neck on an inanimate object, while mares had longer bouts of rolling. Some of the differences in preference for particular types of self-grooming may be the result of differences in relative size of various body parts and, consequently, relative ease of a given type of self-grooming.