Search

Strongyles are nematode parasites that affect the large intestine and cecum of the horse, with symptoms ranging from loss of condition to colic. Thirty horses from the University of Connecticut campus were used to study the effect of gastrointestinal strongyles on the equine gut microbiome, immune response, body condition, and skin and hair coat conditions. This study included young (n = 16) and adult (n = 14) horses each fall and spring from Fall 2020 to Spring 2022, with young horses 1 to 5 years old and adult horses 6 to 19 years old. Fecal flotation analysis was performed at the beginning of each fall and spring season to classify horses as susceptible to parasites if they had 300 or more strongyle eggs per gram (EPG) or resistant to parasites if they had less than 300 strongyle EPG. Fecal and blood samples were collected each fall and spring to assess gut microbial composition, complete cell counts, and differential cell counts. Body condition scores and body weights were assessed twice per season. Dermatological conditions were recorded once monthly. A split plot design with age as the main effect and fecal egg count (FEC) as the split plot effect was used. Adult and young horses that were susceptible to parasites had significantly increased percentages oflymphocytes and neutrophils and decreased percentages of monocytes and eosinophils compared with horses that were resistant to parasites in Fall 2021 and Spring 2022 (P < 0.05). In adult horses, linear correlation analysis revealed that as parasite load increased, body weight decreased (r = −0.29) and complete cell count decreased (r = −0.29), although these trends were not observed in young horses. Ten percent of the variation seen in microbial community structure was due to phenotype. Linear correlation analysis revealed some changes in skin and hair condition, such as an increase in skin moistness (r = 0.32), tailhead moistness (r = 0.36), and hair thickness (r = 0.44) as parasite load increased and a decrease in hair luster (r = −0.32) as parasite load increased. The effects of strongyle infection on dermatology are still unclear as some of the effects seen contradict previous literature and warrant further investigation. Strongyle load may affect body weight in adult horses. Strongyle infection may affect immune response, but have a minimal effect on microbial composition. [ABSTRACT FROM AUTHOR]

Horses are hindgut fermenters with a highly complex microbiome populating the cecum and colon. This microbiome contributes an abundance of physiological functions to the host, including immune stimulation, defense against pathogens, neutralization of toxins, and regulation of gene expression in epithelial tissues. During bouts of infectious disease, antibiotic administration can disturb this microbiological environment, leading to adverse effects such as colitis and acute diarrhea. Horse owners often provide probiotics to horses receiving antibiotics in an attempt to protect against these adverse effects despite a lack of evidence for their efficacy. Thus, the purpose of the current study was to evaluate the effect of probiotics in horses receiving concurrent antibiotic treatment. Sixteen actively racing Standardbred horses were randomly allocated to one of 4 treatment groups [Antibiotics (A; Sulfadiazine/Trimethoprim), Probiotics (P; Herbs for Horses PROBIOPlusⓇ, Herbs for Horses, Guelph ON), A+P, or control (C)] in a 4-way crossover design. A and A+P horses received antibiotics from Day 0–10, P and A+P received probiotics from Day 0–28, and C horses received the same diet with no probiotic or antibiotic for 28 d. Fresh fecal samples were collected on days −1, 0, 1, 2, 9, 10, 11, 28, 29 and 30 from each horse. Analyses include fecal dry matter (DM; %), fecal pH, and fecal scores (FS; 0 – 9) were measured on all fecal samples. Data were analyzed using a 2-way RM-ANOVA (SigmaPlot Version 12) with fixed effects as horse, trial, day, and treatment and random effects as the intercept for the crossover design. Significance was accepted at P < 0.05. Fecal score in C horses (2.6 ± 0.3) was higher than in A+P horses (1.9 ± 0.2) on Day 10 (P = 0.04); FS of C horses (2.7 ± 0.3) was also higher than P horses (1.6 ± 0.3) on Day 9 (P = 0.02). Fecal DM was lower in C horses (26.9 ± 2.5%) than A+P horses (30.3 ± 2.5%; P = 0.03) overall, but there were no differences at any individual time point. Fecal pH was higher in C horses (6.6 ± 0.04) than P horses (6.5 ± 0.04; P = 0.008) and A+P (6.4 ± 0.04) overall; on Day 9 and 10, pH was lower in A+P (6.3 ± 0.1 and 6.2 ± 0.1, respectively) than C horses (6.7 ± 0.1 for both days). The antibiotic treatment had no differences on dry matter or pH between treatments. Interim results demonstrate that treatment with A+P is associated with an increase in fecal DM and concomitant reduction in FS. Fecal pH is reduced in horses receiving P and A+P. The practical implications of these data are as yet unclear but will be clarified upon completion of microbiome analysis which is currently ongoing. [ABSTRACT FROM AUTHOR]