Background: Anthelmintic treatment is a risk factor for intestinal disease in the horse, known as colic. However the mechanisms involved in the onset of disease post anthelmintic treatment are unknown. The interaction between anthelmintic drugs and the gut microbiota may be associated with this observed increase in risk of colic. Little is known about the interaction between gut microbiota and anthelmintics and how treatment may alter microbiome function. The objectives of this study were: To characterise (1) faecal microbiota, (2) feed fermentation kinetics in vitro and (3) metabolic profiles following moxidectin administration to horses with very low (0 epg) adult strongyle burdens. Hypothesis: Moxidectin will not alter (1) faecal microbiota, (2) feed fermentation in vitro, or, (3) host metabolome.Results: Moxidectin increased the relative abundance ofDeferribacterspp. andSpirochaetesspp.observed after 160 h in moxidectin treated horses. Reduced in vitro fibre fermentation was observed 16 h following moxidectin administration in vivo (P = 0.001), along with lower pH in the in vitro fermentations from the moxidectin treated group. Metabolic profiles from urine samples did not differ between the treatment groups. However metabolic profiles from in vitro fermentations differed between moxidectin and control groups 16 h after treatment (R² = 0.69, Q²Y = 0.48), and within the moxidectin group between 16 h and 160 h post moxidectin treatment (R² = 0.79, Q²Y = 0.77). Metabolic profiles from in vitro fermentations and fermentation kinetics both indicated altered carbohydrate metabolism following in vivo treatment with moxidectin.Conclusions: These data suggest that in horses with low parasite burdens moxidectin had a small but measurable effect on both the community structure and the function of the gut microbiome.

Respirable dust in conserved forages can pose problems with equid respiratory health, thus soaking (W) and high temperature steaming (HTS) are employed to reduce the levels in hay. The aim of this study was to characterize the viable bacterial community profile of four hays from two different locations in UK following pre-feeding wetting regimens. Hypothesis: (1) Viable microbial community profile of hays will not differ between different pre-feeding regimens. (2) Hay type and location will not influence microbial community profile. Replicates of each of the four hays were subjected to dry (D), HTS conducted in a HG600, W by submergence in 45 L tap water, 16°C for 12 hours. From each post-treated hay, 100 g samples were chopped and half (n = 36) treated with Propidium monoazide dye, the remaining half untreated. Bacterial DNA were extracted for profiling the V4-V5 region of 16S rRNA gene from all 72 samples, then sequenced on the Illumina MiSeq platform. Bioinformatics were conducted using QIIME pipeline (v1.9.1). Linear discriminate analysis effect size (LEfSe) was used to identify differences in operational taxonomic units and predicted metabolic pathways between hays and regimens. HTS reduced proportions of microbiota compared to W and D hay (P < 0.001, df 3, F 13.91), viability was reduced within regimens (P = 0.017, df 1, F 5.73). Soaking reduced diversity within and between regimens. Core bacterial communities differed between hays and regimens, however pre-feeding regimen had the greatest effect on the bacterial community profile. W and HTS reduced viable bacteria (P< 0.05) known to cause respiratory disease, for HTS both respiratory and dental disease, with the greatest reductions overall from HTS without reducing bacterial diversity. Soaking increased Gram-negative bacteria and reduced bacterial diversity. Collectively these findings add to a body of evidence that suggest HTS is the most suitable pre-feeding regimen of hay for equid health.

Despite our improved understanding of equid digestive health and accurate rations formulations, obesity in the UK horse population remains high. Study aims: (1) to determine how owners are feeding their horses and what influences their choices, (2) to understand owners’ knowledge of haylage and (3) to identify key areas that require additional education. Data were collected in 2020 from 1338 UK horse owners via two online surveys. Survey 1 was on general feeding practices, and Survey 2 was specifically on the feeding of haylage. Data were processed using chi square analyses + Bonferroni tests, with a significance p < 0.05. Equal numbers of leisure and performance horse owners completed both surveys. For Survey 1, 67% fed hay as the only forage, 30% fed forage (hay/haylage) + balancer, 36% fed haylage and hay to manage energy intake, 84% added a cube or coarse mix, 88% did not do forage analyses, 74% did not see the need for it and 16% did not know analyses could be done. In Survey 2, those who were not feeding haylage, 66% were not sure how to feed it, 68% worried about aerobic spoilage and 79% said the bale size was unsuitable. Body weight measurements (Survey 1 and Survey 2) were rarely performed (11%). Aspects of ration formulations, the value of feed analyses and how to interchange hay and haylage require additional education to owners for improved ration compilation.