Chicory (Cichorium intybus) reduces cyathostomin egg excretion and larval development in grazing horses.

Cyathostomins are the most prevalent parasitic nematodes of grazing horses. They are responsible for colic and diarrhea in their hosts. After several decades of exposure to synthetic anthelmintics, they have evolved to become resistant to most compounds. In addition, the drug-associated environmental side-effects question their use in the field. Alternative control strategies, like bioactive forages, are needed to face these challenges. Among these, chicory (Cichorium intybus, Puna II cultivar (cv.)) is known to convey anthelmintic compounds and may control cyathostomins in grazing horses. To challenge this hypothesis, we measured fecal egg counts and the rate of larval development in 20 naturally infected young saddle horses (2-year-old) grazing either (i) a pasture sown with chicory (n = 10) or (ii) a mesophile grassland (n = 10) at the same stocking rate (2.4 livestock unit (LU)/ha). The grazing period lasted 45 days to prevent horse reinfection. Horses in the chicory group mostly grazed chicory (89% of the bites), while those of the control group grazed mainly grasses (73%). Cyathostomins egg excretion decreased in both groups throughout the experiment. Accounting for this trajectory, the fecal egg count reduction (FECR) measured in individuals grazing chicory relative to control individuals increased from 72.9% at day 16 to 85.5% at the end of the study. In addition, larval development in feces from horses grazed on chicory was reduced by more than 60% from d31 compared to control individuals. Using a metabarcoding approach, we also evidenced a significant decrease in cyathostomin species abundance in horses grazing chicory. Chicory extract enriched in sesquiterpenes lactones was tested on two cyathostomins isolates. The estimated IC50 was high (1 and 3.4 mg/ml) and varied according to the pyrantel sensitivity status of the worm isolate. We conclude that the grazing of chicory (cv. Puna II) by horses is a promising strategy for reducing cyathostomin egg excretion and larval development that may contribute to lower the reliance on synthetic anthelmintics. The underpinning modes of action remain to be explored further.

Validation of a serum ELISA test for cyathostomin infection in equines.

Cyathostomins are ubiquitous equine nematodes. Infection can result in larval cyathostominosis due to mass larval emergence. Although faecal egg count (FEC) tests provide estimates of egg shedding, these correlate poorly with burden and provide no information on mucosal/luminal larvae. Previous studies describe a serum IgG(T)-based ELISA (CT3) that exhibits utility for detection of mucosal/luminal cyathostomins. Here, this ELISA is optimised/validated for commercial application using sera from horses for which burden data were available. Optimisation included addition of total IgG-based calibrators to provide standard curves for quantification of antigen-specific IgG(T) used to generate a CT3-specific 'serum score' for each horse. Validation dataset results were then used to assess the optimised test's performance and select serum score cut-off values for diagnosis of burdens above 1000, 5000 and 10,000 cyathostomins. The test demonstrated excellent performance (Receiver Operating Characteristic Area Under the Curve values >0.9) in diagnosing infection, with >90% sensitivity and >70% specificity at the selected serum score cut-off values. CT3-specific serum IgG(T) profiles in equines in different settings were assessed to provide information for commercial test use. These studies demonstrated maternal transfer of CT3-specific IgG(T) in colostrum to newborns, levels of which declined before increasing as foals consumed contaminated pasture. Studies in geographically distinct populations demonstrated that the proportion of horses that reported as test positive at a 14.37 CT3 serum score (1000-cyathostomin threshold) was associated with parasite transmission risk. Based on the results, inclusion criteria for commercial use were developed. Logistic regression models were developed to predict probabilities that burdens of individuals are above defined thresholds based on the reported serum score. The models performed at a similar level to the serum score cut-off approach. In conclusion, the CT3 test provides an option for veterinarians to obtain evidence of low cyathostomin burdens that do not require anthelmintic treatment and to support diagnosis of infection.

Early Castration in Horses Does Not Impact Osteoarticular Metabolism.

The castration of stallions is traditionally performed after puberty, at around the age of 2 years old. No studies have focused on the effects of early castration on osteoarticular metabolism. Thus, we aimed to compare early castration (3 days after birth) with traditional castration (18 months of age) in horses. Testosterone and estradiol levels were monitored from birth to 33 months in both groups. We quantified the levels of biomarkers of cartilage and bone anabolism (CPII and N-MID) and catabolism (CTX-I and CTX-II), as well as of osteoarthritis (HA and COMP) and inflammation (IL-6 and PGE2). We observed a lack of parallelism between testosterone and estradiol synthesis after birth and during puberty in both groups. The extra-gonadal synthesis of steroids was observed around the 28-month mark, regardless of the castration age. We found the expression of estrogen receptor (ESR1) in cartilage and bone, whereas androgen receptor (AR) expression appeared to be restricted to bone. Nevertheless, with respect to osteoarticular metabolism, steroid hormone deprivation resulting from early castration had no discernable impact on the levels of biomarkers related to bone and cartilage metabolism, nor on those associated with OA and inflammation. Consequently, our research demonstrated that early castration does not disrupt bone and cartilage homeostasis.

Horses discriminate between human facial and vocal expressions of sadness and joy.

Communication of emotions plays a key role in intraspecific social interactions and likely in interspecific interactions. Several studies have shown that animals perceive human joy and anger, but few studies have examined other human emotions, such as sadness. In this study, we conducted a cross-modal experiment, in which we showed 28 horses two soundless videos simultaneously, one showing a sad, and one a joyful human face. These were accompanied by either a sad or joyful voice. The number of horses whose first look to the video that was incongruent with the voice was longer than their first look to the congruent video was higher than chance, suggesting that horses could form cross-modal representations of human joy and sadness. Moreover, horses were more attentive to the videos of joy and looked at them for longer, more frequently, and more rapidly than the videos of sadness. Their heart rates tended to increase when they heard joy and to decrease when they heard sadness. These results show that horses are able to discriminate facial and vocal expressions of joy and sadness and may form cross-modal representations of these emotions; they also are more attracted to joyful faces than to sad faces and seem to be more aroused by a joyful voice than a sad voice. Further studies are needed to better understand how horses perceive the range of human emotions, and we propose that future experiments include neutral stimuli as well as emotions with different arousal levels but a same valence.

Comparison of two molecular barcodes for the study of equine strongylid communities with amplicon sequencing.

Basic knowledge on the biology and epidemiology of equine strongylid species still needs to be improved to contribute to the design of better parasite control strategies. Nemabiome metabarcoding is a convenient tool to quantify and identify species in bulk samples that could overcome the hurdle that cyathostomin morphological identification represents. To date, this approach has relied on the internal transcribed spacer 2 (ITS-2) of the ribosomal RNA gene, with a limited investigation of its predictive performance for cyathostomin communities. Using DNA pools of single cyathostomin worms, this study aimed to provide the first elements to compare performances of the ITS-2 and a cytochrome c oxidase subunit I (COI) barcode newly developed in this study. Barcode predictive abilities were compared across various mock community compositions of two, five and 11 individuals from distinct species. The amplification bias of each barcode was estimated. Results were also compared between various types of biological samples, i.e., eggs, infective larvae or adults. Bioinformatic parameters were chosen to yield the closest representation of the cyathostomin community for each barcode, underscoring the need for communities of known composition for metabarcoding purposes. Overall, the proposed COI barcode was suboptimal relative to the ITS-2 rDNA region, because of PCR amplification biases, reduced sensitivity and higher divergence from the expected community composition. Metabarcoding yielded consistent community composition across the three sample types. However, imperfect correlations were found between relative abundances from infective larvae and other life-stages for Cylicostephanus species using the ITS-2 barcode. While the results remain limited by the considered biological material, they suggest that additional improvements are needed for both the ITS-2 and COI barcodes.

Horses cross-modally recognize women and men.

Several studies have shown that horses have the ability to cross-modally recognize humans by associating their voice with their physical appearance. However, it remains unclear whether horses are able to differentiate humans according to different criteria, such as the fact that they are women or men. Horses might recognize some human characteristics, such as sex, and use these characteristics to classify them into different categories. The aim of this study was to explore whether domesticated horses are able to cross-modally recognize women and men according to visual and auditory cues, using a preferential looking paradigm. We simultaneously presented two videos of women and men's faces, while playing a recording of a human voice belonging to one of these two categories through a loudspeaker. The results showed that the horses looked significantly more towards the congruent video than towards the incongruent video, suggesting that they are able to associate women's voices with women's faces and men's voices with men's faces. Further investigation is necessary to determine the mechanism underlying this recognition, as it might be interesting to determine which characteristics horses use to categorize humans. These results suggest a novel perspective that could allow us to better understand how horses perceive humans.

Species interactions, stability, and resilience of the gut microbiota - Helminth assemblage in horses.

The nature and strength of interactions entertained among helminths and their host gut microbiota remain largely unexplored. Using 40 naturally infected Welsh ponies, we tracked the gut microbiota-cyathostomin temporal dynamics and stability before and following anthelmintic treatment and the associated host blood transcriptomic response. High shedders harbored 14 species of cyathostomins, dominated by Cylicocyclus nassatus. They exhibited a highly diverse and temporal dynamic gut microbiota, with butyrate-producing Clostridia likely driving the ecosystem steadiness and host tolerance toward cyathostomins infection. However, anthelmintic administration sharply bent the microbial community. It disrupted the ecosystem stability and the time-dependent network of interactions, affecting longer term microbial resilience. These observations highlight how anthelmintic treatments alter the triangular relationship of parasite, host, and gut microbiota and open new perspectives for adding nutritional intervention to current parasite management strategies.

Characterization of Myeloperoxidase in the Healthy Equine Endometrium.

Myeloperoxidase (MPO), as a marker of neutrophil activation, has been associated with equine endometritis. However, in absence of inflammation, MPO is constantly detected in the uterine lumen of estrous mares. The aim of this study was to characterize MPO in the uterus of mares under physiological conditions as a first step to better understand the role of this enzyme in equine reproduction. Total and active MPO concentrations were determined, by ELISA and SIEFED assay, respectively, in low-volume lavages from mares in estrus (n = 26), diestrus (n = 18) and anestrus (n = 8) in absence of endometritis. Immunohistochemical analysis was performed on 21 endometrial biopsies randomly selected: estrus (n = 11), diestrus (n = 6) and anestrus (n = 4). MPO, although mostly enzymatically inactive, was present in highly variable concentrations in uterine lavages in all studied phases, with elevated concentrations in estrus and anestrus, while in diestrus, concentrations were much lower. Intracytoplasmic immunoexpression of MPO was detected in the endometrial epithelial cells, neutrophils and glandular secretions. Maximal expression was observed during estrus in mid and basal glands with a predominant intracytoplasmic apical reinforcement. In diestrus, immunopositive glands were sporadic. In anestrus, only the luminal epithelium showed residual MPO immunostaining. These results confirm a constant presence of MPO in the uterine lumen of mares in absence of inflammation, probably as part of the uterine mucosal immune system, and suggest that endometrial cells are a source of uterine MPO under physiological cyclic conditions.

Early castration in foals: Consequences on physical and behavioural development.

BACKGROUND: The impact of very early castration of foals has not yet been studied despite the many positive effects observed in dogs and cats. OBJECTIVES: The objective of the study was to compare castration at 3 days and 18 months and assess their subsequent morphological and behavioural development. STUDY DESIGN: This was a randomised, blinded clinical study. METHODS: Twenty-two Welsh ponies underwent either early (3-day old, EC group, n = 11) or traditional (18-month old, TC group, n = 11) castration. Animals were followed up to 3 years of age. All ponies were castrated using a primary closure technique under general anaesthesia. Weight and morphometric measurements were monitored monthly from birth until 8 months of age in both groups. Then, measurements were taken every 3 months until 2 years of age and then every 6 months until 3 years of age. Temperament tests were performed on all animals when they were 1- and 3-years old. RESULTS: No differences were observed between the EC and TC groups in terms of physical development from birth until 40 months of age or in terms of temperament and behaviour at either 1 or 3 years of age. MAIN LIMITATIONS: The study included only one breed (Welsh ponies) and only 22 animals that were castrated before 2 years of age, precluding comparison with castration performed at older ages. CONCLUSIONS: We demonstrate that early castration at 3 days does not interfere with morphological or behavioural development.

Horses form cross-modal representations of adults and children.

Recently, research on domestic mammals' sociocognitive skills toward humans has been prolific, allowing us to better understand the human-animal relationship. For example, horses have been shown to distinguish human beings on the basis of photographs and voices and to have cross-modal mental representations of individual humans and human emotions. This leads to questions such as the extent to which horses can differentiate human attributes such as age. Here, we tested whether horses discriminate human adults from children. In a cross-modal paradigm, we presented 31 female horses with two simultaneous muted videos of a child and an adult saying the same neutral sentence, accompanied by the sound of an adult's or child's voice speaking the sentence. The horses looked significantly longer at the videos that were incongruent with the heard voice than at the congruent videos. We conclude that horses can match adults' and children's faces and voices cross-modally. Moreover, their heart rates increased during children's vocalizations but not during adults'. This suggests that in addition to having mental representations of adults and children, horses have a stronger emotional response to children's voices than adults' voices.

Weaned horses, especially females, still prefer their dam after five months of separation.

Under natural conditions, foals stop nursing from their dam at approximately-9 months old, but their bond persists until 1.5-2.5 years of age. In contrast, in horse breeding, foals are generally artificially weaned and totally separated from their dam at 5-7 months. However, it is not known whether the bond between the dam and her foal is maintained after artificial weaning. The aim of this study was (1) to assess whether foals still recognise and prefer their dam over other familiar mares several months after weaning and (2) to evaluate whether the preference for the dam is more pronounced in fillies or colts. Fifteen fillies and 19 colts were weaned at the age of 7 months old (complete separation from the mother). At the age of one year (i.e., 5 months after the separation), they underwent a test evaluating their preference for their dam or a familiar mare from their natal group. Significantly more foals first approached their dam; they also sniffed and tended to look more often at her. This finding indicates that artificially weaned horses remember and still exhibit a preference for their dam, suggesting that the bond persists even after 5 months of separation. Moreover, fillies exhibited a stronger preference for both mares than colts: they looked at them more frequently, sniffed them for a longer duration and spent more time in proximity to both mares than colts. This suggests that fillies generally have an even stronger attachment to their dam as well as to other mares from their natal group. This study calls into question the practice of artificial weaning at 5-7 months of age.

Pet-directed speech improves horses' attention toward humans.

In a recent experiment, we showed that horses are sensitive to pet-directed speech (PDS), a kind of speech used to talk to companion animals that is characterized by high pitch and wide pitch variations. When talked to in PDS rather than adult-directed speech (ADS), horses reacted more favorably during grooming and in a pointing task. However, the mechanism behind their response remains unclear: does PDS draw horses' attention and arouse them, or does it make their emotional state more positive? In this study, we used an innovative paradigm in which female horses watched videos of humans speaking in PDS or ADS to better understand this phenomenon. Horses reacted differently to the videos of PDS and ADS: they were significantly more attentive and their heart rates increased significantly more during PDS than during ADS. We found no difference in the expressions of negative or positive emotional states during PDS and ADS videos. Thus, we confirm that horses' perception of humans can be studied by means of video projections, and we conclude that PDS attracts attention and has an arousing effect in horses, with consequences on the use of PDS in daily interactions with them.

Investigation of equine testis contribution to vitamin D bioactivation.

Although vitamin D acts in various biological processes, it plays a critical role in the maintenance of bone health, and regulates calcium homeostasis. In humans and rodents, the main tissues involved in vitamin D metabolism are the liver and the kidneys, however it has been shown that the testis has strongly participated in its bioactivation. Indeed, in these different species, enzymes metabolizing vitamin D (CYP27A1, CYP27B1 and CYP2R1) have been demonstrated in this tissue. Moreover, men with hypogonadism have shown a decrease in circulating levels of vitamin D. In equine species, the castration of males is a regular practice to reduce the behavior of stallions deemed too aggressive. Castration is carried out at various ages: in foals during their growth or in adulthood once they have reached their optimum size. Although horses exhibit atypical vitamin D metabolism with low circulating levels of vitamin D, it was suggested that testis may contribute to its activation as has been described in rodents and humans; castration could therefore be likely to affect its metabolism. In this study, blood levels of bioactive form of vitamin D (1 α,25[OH] 2 vitamin D 3 ) were measured before and after castration at different ages: 1 wk, after puberty (2 yr) and at adulthood (6 yr). The gene expression of enzymes involved in vitamin D metabolism has been sought in the testis of different experimental groups. No change in bioactive vitamin D3 levels was observed after castration regardless of the age at the time of surgery. The exceptional status of equine species is confirmed with a low or a lack of testis contribution to vitamin D metabolism, regardless of testicular development. This is demonstrated by a low or a lack of signal from enzymes involved in vitamin D bioactivation. Therefore, horses constitute a unique model in comparative endocrinology.

Integrative biology defines novel biomarkers of resistance to strongylid infection in horses.

The widespread failure of anthelmintic drugs against nematodes of veterinary interest requires novel control strategies. Selective treatment of the most susceptible individuals could reduce drug selection pressure but requires appropriate biomarkers of the intrinsic susceptibility potential. To date, this has been missing in livestock species. Here, we selected Welsh ponies with divergent intrinsic susceptibility (measured by their egg excretion levels) to cyathostomin infection and found that their divergence was sustained across a 10-year time window. Using this unique set of individuals, we monitored variations in their blood cell populations, plasma metabolites and faecal microbiota over a grazing season to isolate core differences between their respective responses under worm-free or natural infection conditions. Our analyses identified the concomitant rise in plasma phenylalanine level and faecal Prevotella abundance and the reduction in circulating monocyte counts as biomarkers of the need for drug treatment (egg excretion above 200 eggs/g). This biological signal was replicated in other independent populations. We also unravelled an immunometabolic network encompassing plasma beta-hydroxybutyrate level, short-chain fatty acid producing bacteria and circulating neutrophils that forms the discriminant baseline between susceptible and resistant individuals. Altogether our observations open new perspectives on the susceptibility of equids to strongylid infection and leave scope for both new biomarkers of infection and nutritional intervention.

Ivermectin treatment in lactating mares results in suboptimal ivermectin exposure in their suckling foals.

The management of equine strongyles has become problematic over the last decade because of an increased prevalence of drug-resistant isolates worldwide. Therapeutic options are therefore limited, leaving macrocyclic lactones as the most often effective drug class. However, their lipophilic properties result in a long-lasting elimination that could favour drug resistance selection. As a result, ivermectin treatment in lactating mares could promote suboptimal exposure of their foal parasites to ivermectin, thereby selecting for more resistant worms. To test for this putative transfer, we selected two groups of six foal-mare pairs, one group of mares receiving ivermectin and the other being left untreated. We compared faecal egg count trajectories in foals from the two groups and quantified plasma ivermectin concentrations in ivermectin treated mares and their foals during seven days. Our results showed limited but sustained plasmatic exposure of foals associated with non-significant faecal egg count reduction (P = 0.69). This suggests that ivermectin treatment in lactating mares results in suboptimal exposure to the drug in their foal.

Feed Concentrate Palatability in Welsh Ponies: Acceptance and Preference of Flavors.

In horses, it is well established that nutrients and the palatability of feed material (odor and taste) play an important role in diet selection. For example, high-fiber feed taste is not well accepted by horses. Consequently, manufacturers have begun to supplement horse feed with flavors to mask feed bitterness, to overcome feed neophobia and to encourage water drinking. However, only few studies have been performed to evaluate the acceptance and preference of flavors in horses. The aim of this study was to evaluate the acceptance and preference of flavors supplemented on top of concentrate offered to ponies. Thirty-three female Welsh ponies aged between four to 13 years were enrolled in the experiment. Ponies were offered 4 flavored concentrates and one control with no flavor. The flavored concentrates were anise, caramel, raspberry and apple. The inclusion rate of the flavors was 300 g/t on an as-is basis. During the adaptation period (one week), the ponies were gently guided to each bucket containing the flavored concentrate (200 g) during 10 sec/bucket for olfaction only. During the test period, ponies were allowed to freely choose flavored concentrates for 2 minutes. The flavors and the position of the buckets in front of the ponies were randomized. Each period was video-recorded and number of chews were counted during test period. The concentrate intake, eating time, and animal behavior were recorded during the test period. The apple concentrate was consumed the most at 116 g/2-min offering, whereas the raspberry and control concentrates were consumed the least, at 85.31 and 90.80 g/2-min offering, respectively. Apple flavor was preferred over caramel, raspberry and anise as indicated by higher consumption rate (g/sec) (chi-squared=16.68, df=4, P<0.05). There was no effects on chews, smell or headshaking time per sec between treatments. In conclusion, the ponies accepted a wide range of flavors with a preference for apple over raspberry flavored concentrate.

Human Face Recognition in Horses: Data in Favor of a Holistic Process.

Recent studies have demonstrated that horses can recognize humans based simply on visual information. However, none of these studies have investigated whether this involves the recognition of the face itself, or simply identifying people from non-complex external clues, such as hair color. To go beyond this we wanted to know whether certain features of the face were indispensable for this recognition (e.g., colors, hair or eyes). The 11 horses in this study had previously learned to identify four unfamiliar faces (portrait view and in color) presented repeatedly on a screen. We thus assessed whether they were able to identify these same faces spontaneously when they were presented in four other conditions: profile view, black and white, eyes hidden, changed hairstyle. The horses' performances remained higher than chance level for all the conditions. In a choice test under real conditions, they then approached the people whose face they had learned more often than unknown people. In conclusion, when considering all the individuals studied, no single facial element that we tested appears to be essential for recognition, suggesting holistic processing in face recognition. That means horses do not base their recognition solely on an easy clue such as hair color. They can also link faces from photographs with people in real life, indicating that horses do not process images of faces as simple abstract shapes.

Female horses spontaneously identify a photograph of their keeper, last seen six months previously.

Horses are capable of identifying individual conspecifics based on olfactory, auditory or visual cues. However, this raises the questions of their ability to recognize human beings and on the basis of what cues. This study investigated whether horses could differentiate between a familiar and unfamiliar human from photographs of faces. Eleven horses were trained on a discrimination task using a computer-controlled screen, on which two photographs were presented simultaneously (32 trials/session): touching one was rewarded (S+) and the other not (S-). In the training phase, the S+ faces were of four unfamiliar people which gradually became familiar over the trials. The S- faces were novel for each trial. After the training phase, the faces of the horses' keepers were presented opposite novel faces to test whether the horses could identify the former spontaneously. A reward was given whichever face was touched to avoid any possible learning effect. Horses touched the faces of keepers significantly more than chance, whether it was their current keeper or one they had not seen for six months (t = 3.65; p < 0.004 and t = 6.24; p < 0.0001). Overall, these results show that horses have advanced human face-recognition abilities and a long-term memory of those human faces.

Effect of cumulus cell removal and sperm pre-incubation with progesterone on in vitro fertilization of equine gametes in the presence of oviductal fluid or cells.

In spite of many attempts to establish an in vitro fertilization (IVF) technique in the equine, no efficient conventional IVF technique is available. The presence of oviductal fluid or oviductal cells during IVF helps to improve embryo production in vitro but is not sufficient to reach high fertilization rates. Thus, our aim was to perform equine IVF either after sperm pre-incubation with oviductal fluid or in the presence of oviductal cells, and to evaluate the effect of cumulus removal from the oocyte or sperm pre-incubation with progesterone. In experiments 1 and 2, IVF was performed in the presence of porcine oviduct epithelial cells. The removal of cumulus cells from equine oocytes after in vitro maturation tended to increase the percentage of fertilization when fresh sperm was used (1/33 vs. 4/31, p > 0.05) but had no effect when frozen sperm was used (1/32 vs. 1/32). Equine sperm pre-incubation with progesterone did not significantly influence the fertilization rate when fresh or frozen sperm was used (2/14 vs. 2/18 for fresh, 1/29 vs. 1/25 for frozen). In experiments 3 and 4, IVF was performed after pre-incubation of sperm with porcine oviductal fluid. The removal of cumulus cells tended to increase the percentage of fertilization when fresh sperm was used (1/24 vs. 3/26, p > 0.05). Sperm pre-incubation with progesterone did not significantly influence the fertilization rate when fresh or frozen sperm was used (2/39 vs. 2/36 for fresh, 2/37 vs. 1/46 for frozen), but two 3-4 cell stage zygotes were obtained with fresh sperm pre-incubated with progesterone. This is an encouraging result for the setting up of an efficient IVF procedure in equine.

Artifact Induced by a Transponder During In Vivo Magnetic Resonance Imaging on Horse Brain.

Magnetic resonance imaging (MRI) is now widely used in equine veterinary practice. However, the mandatory European legislation regarding horse identification imposes the implantation of a transponder within the fatty tissue of the neck cervical ligament. While performing brain MRI for scientific purposes in ponies, we faced artifacts produced by such transponder and reported here this problem. Indeed, pony mares were anesthetized for 2 hours and placed, bedded on their back, in a 3T MRI scanner. A four-element flexible antenna positioned around the head was used. Three MRI sequences were performed on each animal: three-dimensional T1, three-dimensional T2, and two-dimensional T1. The anesthesia allowed the acquisition of MRI for 2 hours. The images for the three MRI sequences for each pony exhibited great quality on all the anterior parts of the brain but began to become distorted posteriorly to the pineal pituitary axis and completely disappeared at the level of the cerebellum. To find the origin of the artifact, the transponder used for the identification of the animal was inserted in an inert gel and imaged in the same conditions as the ponies. The images obtained looked similar to the observed artifact. Our study thus advocates for the further exploration of such kind of artifact when using 3T MRI in brain imaging in horses.