Management Of Horses Research Articles

Stallion management on breeding facilities – a questionnaire

Under wildlife conditions, stallions live in social groups whereas under domestic conditions, most breeding stallions live in individual boxes with limited social contact. This is a welfare issue and known to stimulate aggressiveness stereotypic behavior (De Oliveira and Aurich, J Equine Vet Sci 2021;107:103773). There is an increasing interest in improving stallion management and stabling with the aim to avoid such welfare issues. The aim of this study was to collect information on the worldwide situation regarding handling and housing of stallions used for breeding. We hypothesized that stallion handling practices and housing differ among regions. For this purpose, veterinarians and stallion managers were invited to respond to an online survey presenting several questions with regard to the breeding facility, stallion management, handling and housing. Statistical differences among geographic regions were compared by chi2 analysis (IBM SPSS 28.0). There was a total of 115 responses from breeding centers located in the geographic regions North America (12%), South and Central America (37%), Europe (41%), Middle East (5%), and Oceania (5%). The centers housed 1-3 (35%), 4-6 (29%), 7-10 (12%) or >10 stallions (24%) of various breeds. While stallions in 18% of facilities bred by natural mating only, the majority underwent semen collection (n.s. among regions). In most facilities, semen was collected from each stallioneither 3 times per week (37%) or on demand (46%). Stallions were housed in stallion barns (52%), or mixed barns (48%) with social contact being visual only (64%), visual and tactile (25%) or animals having no contact to each other (10%). Visual and tactile contact of stallions, however, was allowed in more (p<0.01) facilities in Europe (45%) than in other regions of the world (0 to 21%). On the other hand, the time stallions spent in their stables differed among regions with more (p<0.01) facilities stabling stallions all day in Europe (48%) and the Middle East (83%) than elsewhere. Stallions underwent training or were exercised more frequently (p<0.01) in Europe (89%) or North America (86%) than in other geographical regions (42 to 50%). In 64% of facilities, stallions took part in horse shows with differences among regions (p<0.01). Only 9% of facilities stated that they keep stallions together in the same pasture or paddock (n.s. among regions); 24% of the facilities had experienced accidents (some of them very serious) when stallions had been kept together (n.s. among regions). The results demonstrate that housing and management of stallions differs among geographical regions. Improving stallion welfare therefore requires different approaches depending on the country or geographical region and their tradition of horse management.

Comparison of West Nile Virus Disease in Humans and Horses: Exploiting Similarities for Enhancing Syndromic Surveillance.

West Nile virus (WNV) neuroinvasive disease threatens the health and well-being of horses and humans worldwide. Disease in horses and humans is remarkably similar. The occurrence of WNV disease in these mammalian hosts has geographic overlap with shared macroscale and microscale drivers of risk. Importantly, intrahost virus dynamics, the evolution of the antibody response, and clinicopathology are similar. The goal of this review is to provide a comparison of WNV infection in humans and horses and to identify similarities that can be exploited to enhance surveillance methods for the early detection of WNV neuroinvasive disease.

85 Evaluation of an Oral Supplemental Cannabidiol Product for Acceptability in Mature Horses

Abstract Thirty stock type geldings (15 ± 3 y; 556 ± 63 kg BW) were used in a randomized complete design for a 28-d trial to evaluate the influence of cannabidiol (CBD) oil supplementation on health of mature horses by conducting a blood chemistry panel and evaluating the presence of banned substances. Horses were stratified by BW and age, and randomly assigned to 1 of 3 dietary treatments formulated with canola oil to provide.50 mg CBD/kg BW (TRT1; n = 10), 0.75 mg CBD/kg BW (TRT2; n = 10), or 0.00 mg CBD/kg BW (canola oil; CON; n = 10) only as determined by manufacturer (Arrowhead Labs). Treatments were individually fed and top-dressed onto a commercially available concentrate twice daily at 12 h intervals using attachable feed bags. Diets were formulated to meet or slightly exceed nutritional requirements for mature horses at maintenance. Between meals, horses were maintained in adjacent dry lots and received coastal bermudagrass hay ad libitum. Body weight was obtained, and body condition scores (BCS) were assigned every4 d. On d 0 and 28, blood was collected via jugular venipuncture and serum was harvested to perform a blood chemistry panel and drugs of abuse screening at the Texas Veterinary Medical Diagnostic Laboratory (TVMDL; College Station, TX). Data were analyzed using PROC MIXED of SAS (v9.4), and the model included treatment, time, and the treatment × time interaction for BW and BCS. Blood chemistry variables on d 0 were used as a covariate and the main effect tested was treatment. Linear and quadratic orthogonal polynomial contrasts were used to partition sum of squares. Analysis of supplement samples revealed supplemented products contained lower CBD concentrations then indicated from initial testing. Therefore, horses in TRT1 and TRT2 received an average of 0.13 mg CBD/kg and 0.12 mg CBD/kg BW, respectively. Dietary treatments did not affect concentrate intake, BW, or BCS. Supplementation of CBD did not result in the presence of any banned substances in serum, including CBD, 7-carboxycannabidiol, 7-Nor-7-carboxycannabidiol, and tetrahydrocannabinol (THC). Following 28 d of supplementation, gamma-glutamyl transferase (GGT) responded quadratically (P = 0.06) to treatment, with a peak in GGT in horses receiving TRT2. Serum creatinine concentration tended (P = 0.06) to decrease with increasing inclusion of CBD in the diet. In contrast, the main effect of treatment on Ca concentrations was linear (P = 0.01) and characterized by decreased Ca values for TRT1 compared with TRT2 and CON. Canola based CBD oil was well-accepted by mature horses, banned substances were not detectible in blood, and blood chemistry parameters were not adversely affected as a result of supplementation; however, more information is needed to improve stability of CBD used in dietary products.

185 Effects of COVID-19 on horses in-transition: Industry perspectives through survey analysis

Equines currently in transition from one home or vocation to another, known as horses in-transition, present a significant welfare concern for the equine industry. However, there is a lack of research on how major crises, such as the COVID-19 pandemic, affect equine ownership and management strategies which could contribute to the number of horses in this at-risk population. Objectives of this study were to evaluate the impact of the pandemic on equine ownership, management practices and time spent engaged in equine activities. A 23-question online survey was disseminated through QualtricsTM to adults in the United States via email, digital newsletter, and social media (n = 346). Frequency analysis combined with Chi-squared analyses and analyses of variance, identified the impacts of COVID-19 on horse owners, non-horse owners, and equine professionals, with a response rate of 75%, 8%, and 17%, respectively. From survey results, equine ownership remained relatively stable throughout the pandemic with the majority of respondents (68%) reporting they owned the same number of horses as they did before March 2020. The response of “no impact” to changes in equine management was most prevalent across all groups; however, equine professionals did indicate experiencing a larger impact than that of horse owners (P = 0.047). Similarly for the effect on time spent with horses, “no impact” wasthe largest recorded response. For horse owners, a negative correlation between time spent with horses and age was discovered (P < 0.001). The ability to participate in equine events was the only category for which “no impact” was not the most prevalent response. Horse owners and equine professionals reported slight to significant decreases in their ability to participate in equine events due to the pandemic at 67% and 60%, respectively. Type of primary horse use was an influential factor in determining the extent of impact on ability to participate with respondents involved in recreation with horses indicating less impact than those involved in showing and breeding (P = 0.006 and 0.034, respectively). For horse owners, age was shown to have a negative correlation (P = 0.017) with ability to participate in equine events. Based on study results, the COVID-19 pandemic had little impact on equine ownership and management practices; however pandemic quarantine procedures decreased engagement in equine activities in the United States for the parameters measured. Long-term effects of COVID-19 on equine ownership and management decisions should be considered to provide a deeper base of knowledge for how major crises may impact horses in-transition.

162 Evaluating the effectiveness of online equine educational programming on increasing knowledge and management skills of horse owners

The 2015 American Horse Publication Equine Industry Survey results indicated equine clientele receive information from magazines (67%), company/product websites (65%), and social media (60%), but peer-reviewed research and university sources were not commonly mentioned as sources of equine management information. Cooperative Extension systems across the US have a unique opportunity to leverage expertise to provide research-backed information to equine owners through online and virtual platforms. The UGA Horse Owner's Webinar Series was developed to provide timely, evidence-based equine management education to horse owners. The series was held annually via Zoom and each session was focused on specific, relevant, and alternating subject matter. To date, the program had reached 1,688 registrants from over 38 states and 15 countries. Program sessions were evaluated using voluntary surveys conducted in Qualtrics. Surveys were provided at the conclusion of each session and in a follow-up email with an average of 30 returned evaluations per session. The evaluation used Likert-scale questions designed to assess knowledgeincreases, intended behavioral changes and overall response to the program. Resulting data were analyzed via paired t-test using the Excel statistics add-on. Across all 4 years of the webinar series, evaluation data demonstrated increased participant knowledge in the following topic areas from pre to post assessment (P < 0.05): general equine management, basic equine health, advanced equine health, and basic equine nutrition. Additionally, 98% of participants indicated they would use the information provided in the series in their own operations. Based on these data, online equine educational programming may be an effective option for providing horse owners with up-to-date equine management information and for reaching equine clientele who may be unfamiliar with Extension resources. In response to this model, a monthly lunch-and-learn program titled the Equine Exchange was established in 2021 and the UGA Horse Owner's Webinar Series will continue being held on an annual basis.

179 Survey of equine veterinarians: Part 2—Hay feeding practices and horse health

Horse owners often consider veterinarians to be an important source of information about equine nutrition. The objective of this survey was to learn about the perspectives of veterinarians on the relationship between hay feeding practices, horse health and behavior. A survey link (Qualtrics, Provo, UT) was sent to members of Kentucky Association of Equine Practitioners and distributed by equine practices located in Lexington, KY. Descriptive statistics were performed in SPSS V28. The majority of veterinarians thought time spent eating hay was extremely (56%) or moderately important (33%) to health when pasture is not available. Ninety 2 percent of veterinarians said time spent eating is important for increasing saliva production and decreasing the risk of gastric ulcers. When asked about factors that may affect rate of hay consumption, 44% of veterinarians strongly agreed that physical form was important, while only 14% of veterinarians strongly agreed that fiber content was an important factor. Nutrition scenarios for performance and sedentary horses were presented to gauge concern about amount of hay offered. The amount of hay fed to performance and sedentary horses was considered of extreme or moderate concern by 97% and 86% of veterinarians, respectively. Most veterinarians considered the minimum amount of hay forperformance and sedentary horses to be 1.5 lb per 100-lb bodyweight and 1 lb per 100-lb bodyweight, respectively. Supporting digestive function was the most frequently selected reason for recommending a minimum amount of hay for performance (83%) and sedentary (66%) horses. For horses with underweight, overweight, and digestive health issues, the percentage of veterinarians who would discuss hay type with their clients was 97, 90, and 87%, respectively. For these same categories of horses, the percentage of veterinarians who would discuss hay amount with their clients was 92, 80, and 69%, respectively. Only 46% of veterinarians agreed they would discuss hay type and 59% agreed they would discuss hay amount for horses with undesirable oral behaviors or other undesirable behaviors. This survey suggests veterinarians view the type and amount of hay as having important roles in weight management and digestive health compared with affecting equine behavior. In addition, although veterinarians are often considered to be an important nutrition resource, veterinarians in this survey reported clients rarely (51%) or occasionally (37%) asked for feeding advice.

122 US senior horses: When are they considered “old” and how does that affect their management?

Depending on the age definition applied (e.g., chronologic, demographic, physiologic), a horse may be considered old at 15 years, 20 years, or even at an older age. The management of a horse is likely adjusted once it is considered old, however, details concerning these changes are currently sparse. Similarly, it is unclear at what age owners typically consider their horses to be old and why. To learn more about these and other topics related to older horses, a US-wide survey was conducted with owners of horses aged ≥ 15 years. The objectives of the present subsection of this survey were to 1) determine at what age horses were considered old by their owners, 2) identify the reasons for this decision, and 3) assess management changes made because the horse was considered old. The anonymous survey was distributed through social media and a press release and was online from Oct. 15th to Nov. 21st, 2020. 2717 of 2927 started surveys were eligible for analysis. Responses were received from all US states with southeastern states being most represented (38%; n = 2607). Data were analyzed descriptively with frequency counts expressed as percentages. Percentages amounted to maximally 100% for single-choice questions (s-c q.) but could exceed 100% for multiple-choice questions (m-c q.). All responses were discrete variables. At the time of the survey, about half (47.4%)of the participants considered their horse to be old (n = 2528 total responses to question; s-c q.). Most indicated to have first considered their horse old at an age of 20 (22.8%) or 25 years (14.1%) (n = 1181; s-c q.). Other ages were overall less commonly reported and hence grouped: < 15 years (1.0%), 15–19 years (24.0%), 21–24 years (22.4%), 26–30 years (13.9%), and > 30 years (1.9%). The top 3 reasons for considering their horses old were: 1) horse showed reduced ability to work/exercise (43.6%), 2) horse showed first signs of age-related disease/disorder (43.5%), 3) horse's hair turned gray/increase in gray hair (29.3%) (n = 1153; m-c q.). Ninety-one percent (90.6%) made changes to their horse's management once it was considered old (n = 1187; m-c q.). The top 3 changes were: 1) changed diet and/or supplements (65.9%), 2) exercised horse less intensely (31.3%), and 3) stopped riding/driving exercise (29.6%) (n = 1187; m-c q.). In conclusion, horses were often considered old at distinct ages (20 and 25 years), with changes in fitness level, health status, and physical characteristics (i.e., gray hair) reported as the main reasons. For almost all horses, management was adjusted once they were considered old, and changes mainly pertained to exercise regimen and diet.

98 Environmental impacts and daily voluntary movement of horses housed in pasture tracks as compared to conventional pasture housing

Pasture tracks are a recent trend in equine management. Tracks are a way to increase movement by theoretically mimicking patterns of wild horses, though this has not been proven. To test movement patterns of horses housed in pasture tracks as compared with conventional pastures, a track (3.5m in width) was created around the perimeter of a rectangular 2.0 ha pasture with feeding troughs placed roughly equidistant around the track. Eight horses were paired and rotated between 3 treatment locations: the track (T), the small 2 ha pasture housed within the track (SP), and a larger 12 ha pasture on the same farm (LP). Movement was tracked using a GPS watch (Amazfit Bip U by Zepp Health) attached to the crown of a halter. Testing occurred over a 10-week period in which horses were randomly rotated in pairs to each location with testing in each location occurring simultaneously. Horses were acclimated to each location for 3 d and then tested over a 4-d period during which one horse in each pair would wear the GPS monitor for 2 d followed by the second horse. At the conclusion of the 10-week study, 4 horses on 2 additional farms with existing track systems were monitored for a one-week period to compare their movement patterns to those collected in the test location as controls. Environmental impact of the pasture tracksystem was evaluated by comparing erosion measurements of the track to the small pasture. Erosion was evaluated via quantification of vegetative cover (as measured by standing biomass) and sediment relocation (as measured using an adapted mesh-bag technique). Data was collected on days −7, 14, 33, 67, and 86 of horses being placed on the track. GPS data was analyzed using Minitab v.21 (State College, PA, USA) with housing as a treatment effect. Erosion measurements were run as a repeated-measures over time with location as the treatment effect. Results indicate no differences in daily distance traveled between T and SP (5.7 vs 5.4 km, P = 0.60) or between T and LP (5.7 vs 6.2 km, P = 0.36). Though not comparable, horses on the private farm tracks walked a similar daily distance of 6.1 ± 0.2 km/d avg. There was a decrease in vegetative cover on the track (P < 0.001) from beginning to end of the study, which resulted in sediment relocation (P = 0.013). Collectively, this data does not support the use of pasture tracks as a beneficial management practice to increase movement, and potential environmental impacts of the use of tracks should be considered.

94 Age and feeding behavior associated with dental disorders in Western horses

Dental disorders can lead to discomfort and chronic pain in horses, affecting their behavior, management, and athletic performance. There is a lack of research on equine management and epidemiology of dental problems in horses trained in Western disciplines. Our main goal is to investigate dental disorders in Western riding horses located in West Texas and their association with management and behavior. For each horse, a Texas Veterinary Board of Medical Examiner (TVBME) licensed Equine Dental Provider investigated the oral environment with a bright headlight, speculum, mirror, probe, and endoscope, assisted by veterinarians for sedation and health evaluation. All findings and pictures were documented through the Pimbury Dental App and approved by an equine dental veterinarian. We developed a dental scoring system to quantify the dental findings ranging from 0 (no abnormalities) to 120 (fractures, periodontal disease, severe pathologies such as hypercementosis, and oral ulcerations associated with all teeth), where higher dental scores indicated worse dental conditions. Horse owners filled out a survey for each horse, which included feeding, medical, riding, and behavioral history. Wecorrected for multiple testing using Bonferroni adjustment, and the significance level was set to α ≤ 0.01. Forty-seven horses with adult dentition (out of the same planned study with over 200 horses) were included in the preliminary correlation analyses. Dental scores ranged from 10 to 60 points (Mean = 32.89, SD ± 11.306). Older age is significantly correlated with increased dental scores (P < 0.001). Commonly reported hay-eating behavioral issues, such as several pauses (P < 0.01) and dropping hay (P < 0.001), show significant correlations to higher dental scores. Dental care history demonstrates a trend toward significance. Horses with no history of dental care scored on average 7.6 points higher than individuals with past dental care (P = 0.03). While we are still adding individuals to the analysis, the preliminary results demonstrate that disruptive hay-eating behaviors could be a sign of dental issues. Furthermore, age is a strong factor influencing dental problems, with a lack of previous dental care as a possible component in Western horses.

170 Revisiting perceived needs of Arizona horse owners to update and focus cooperative extension horse educational programming and resource development directions

In 2021, a voluntary, anonymous online livestock/equine survey (originally distributed in 2015), was readministered using Qualtrics® software and disseminated to Arizona livestock/equine industry stakeholders through email listservs, social media, personal connections, and attendees of cooperative extension events. The goal was to compare the 2021 data from horse owners (118/237 overall responses) to the 2015 responses (280 horse owners/484 total respondents) to review, update and if necessary, change the focus of our educational programming to topics perceived to be of moderate to critical need by 2021 Arizona horse owners. Survey results from both years came from all 15 Arizona counties and grouped by number of horses owned (1–3, 4–6, 7–9, and ≥ 10). The 2 data sets were analyzed independently using Chi-Square contingency tests, with significance declared at (P < 0.05). In both 2015 and 2021, more respondents owning 1–3 horses used their horses for recreation only (P < 0.05), and more respondents owning ≥ 10 horses used them for business (P < 0.05). In 2015, preferences for methods of information delivery were significantly affected by the age of respondent, with ≥ 70 years choosing newsletters/emails and both 50–69 years and ≥ 70 years preferring hands-on field days (P < 0.05). Additionally, more 50–69year-old respondents wanted fact sheets (P < 0.05). In 2021, ≥ 70 year-old respondents were less receptive to virtual seminars (P < 0.05). Survey takers ranked each of 22 topics related to horse feeding, management, training, horse health, business planning, etc. by no, slight, moderate, or critical need. Highest ranking topics in both 2015 and 2021, (with > 60% of ratings ranging from moderate to critical need), included toxic plants, vaccination programs, training and behavior, hoof care, heat stress, utilizing AZ forage, and lameness. In 2015, more respondents owning ≥ 10 horses chose “no need” for horse training/management (P < 0.05) and heat stress (P < 0.05), but in 2021 the “no need” for heat stress education difference was no longer apparent. In 2015, owners with 1–3 horses did not perceive a critical need for heat stress education, but they did in 2021 (P < 0.05). Topics with the highest perceived need were similar in 2021 and 2015, allowing us to continue with our current programming areas and priorities, although we found the age of respondents affected their preferences for methods of information delivery, and we need to continue heat stress education for recreational horse stakeholders owning 1–3 horses.

132 Management of horses transported by road in the US on journeys of three hours or less

Horses are regularly transported short distances by road in the US; however, general management practices when traveling less than 3 h are undefined. To investigate, we created an online survey through Qualtrics with questions about the management of an individual horse, plus a few opinion questions about transportation. A subset of 1169 responses from a larger survey were used; each describing a horse who was transported 3 h or less by road between March 2021 to 2022. The most common breeds represented were Quarter Horse (21.2%), Thoroughbred (16.7%) and Warmblood (9.9%). While the majority of horses were adults (60%, ages 5 to 15), 30% were 16 years or older; 58% of horses were geldings and 39% mares. Horses were most often used, and transported, for pleasure or trail riding (44.3%,) followed by showing and competition (31.2%). The majority of horses resided in the Southeast (41.6%) or Midwest (21.2%). A gooseneck (52.2%), slant load (48.4%) trailer with a step-up rear (52.5%) was most commonly used. Ventilation typically consisted of roof vents (71.9%) and side windows (81.9%); rubber mats (86.8%) and shavings or sawdust (61.4%) were the most common flooring and bedding types. Most horses were reported to have been tied (76.6%) at or above eye level (69.2%) during transport. While almost all horses wore halters (95.1%), 26.5% also wore some form of hoof or leg protection when being transported.Within the hour before transport the majority of horses had access to hay or pasture and water (60.2%) and 15.7% received an ulcer preventative or treatment. The majority of horses had access to hay during the transportation (65.6%), and 70.3% had access to hay or pasture and water within the hour following transport. The likelihood of a horse owner taking the temperature, pulse, and/or respiration (TPR) before or after transportation by road increased as the duration of trip increased beyond 3 h; however, 90% reported that they did not take TPR before or after a journey of 3 h or less. When asked various ways to monitor their horse during transport 60% of horse owners said they would be interested in using, or already used, video monitoring and 39% were interested in heart rate monitors. The biggest concern when transporting horses by road was injury to the horse (26.7%), followed by stress (23.1%) and dehydration or overheating (15.6%). The biggest factors when planning to travel were season or weather (24.1%), trip length (21.9%), horse health (16.8%) and traffic (15.5%). The results from the survey show how horse owners are managing horses when transporting by road over short distances in the US

2 Effects of extra-label bisphosphonate use on growth parameters and endocrine biomarkers of bone health in juvenile horses

Extra-label bisphosphonate use in juvenile horses is widespread despite limited scientific understanding of biological and welfare impacts on skeletally immature, exercising horses. The objective of this study was to determine the effects of bisphosphonate (clodronate disodium; CD) on endocrine regulation of bone growth, hypothesizing there would be no effect. To test this, 32 Quarter Horses were stratified by age (500 ± 13 d of age), BW (336 ± 26 kg), sex (n = 16 males, n = 16 females), and initial bone optical density by aluminum equivalence into 4 treatment groups for a 168-d trial. The experimental period was divided into 2 phases mimicking sales preparation (Phase I: d 0–83) and early performance training (Phase II: d 84–168). Horses were housed in individual stalls (3.6 m × 7.3 m) and fed diets formulated to meet nutrient requirements. Investigators were blinded, and all horses received iso-volumetric intramuscular injections of either 1.8 mg/kg BW CD (OSPHOS®) or saline (placebo) on d 0, 42, 84, and 126. Treatments consisted of control (CON; n = 8), single-dose CD (1X; n = 8; d 84), 2-dose CD (2X; n = 8; d 0, 84), and 4-dose CD groups (4X;n = 8; d 0, 42, 84, 126). Physical measurements including BW, wither height (WH), hip height (HH), body length (BL), and heart girth (HG) circumference were recorded every 42 d from d 0. Likewise, serum samples were collected every 42 d before treatment administration to quantify growth hormone (GH), calcitonin (CT), parathyroid hormone (PTH), and ionized calcium. Data were analyzed using PROC MIXED of SAS. All physical growth measurements increased over time (P ≤ 0.01) but were not affected by treatment (P ≥ 0.62). Similarly, there was no effect of treatment (P = 0.44) for GH, but concentrations tended to decrease over time as growth rate slowed (P = 0.09). A treatment ´ time interaction was observed for PTH (P = 0.05) where concentrations increased following 2 clodronate doses. Specifically, concentrations increased on d 84 in 4X and on d 126 in 2X following the second administration of clodronate while 1X and CON remained unchanged. There was no effect of treatment (P = 0.98), time (P = 0.33), nor treatment × time interaction (P = 0.61) for CT despite the increase in PTH. Ionized calcium concentrations decreased over time (P < 0.01) with no effect of treatment (P = 0.26) or treatment × time interaction (P = 0.32). These results suggest that while administration of bisphosphonate has no effect on growth morphometrics, its repetitive use alters PTH concentrations after 2 doses.

134 Late-gestation maternal overnutrition alters gene expression and histomorphology in neonatal foal testes

While obesity has deleterious effects on metabolism, performance, lameness, and health in mature horses, little is known about the impacts to reproductive health in foals from overfed dams. The objective of this study was to determine the effects of maternal overnutrition on neonatal foal testicular development. To test this, 16 Quarter horse mares were used in a completely randomized design and stratified by expected foaling date, body weight, and body condition score into one of 2 dietary treatments offered twice daily beginning on gestation d 235: control (CON; n = 8) fed to meet 100% of nutrient requirements and overfed (HIGH; n = 8) fed to 140% of nutrient requirements. At 5 h postpartum, foals were humanely euthanized, and testes were harvested, weighed, and stored for analyses. Testicular weight included the tunica dartos with the epididymis removed. RNA was extracted using the PureLink RNA Mini Kit (Life Technologies, Austin, TX) and submitted for RNA sequencing (Novogene, Sacramento, CA). Histomorphometric evaluations were performed using a hematoxylin and eosin stain. Ten 10X images per animal were analyzed using ImageJ software for individual seminiferous tubule (ST) area, ST number, and % area of STs per 10X field relative to interstitial tissue. Sertoli cell numbers were determined at 40X using 20 seminiferoustubules per animal. Data were analyzed using the MIXED procedure in SAS. Testes from HIGH male foals (n = 4; LSMeans ± SEM; 32.93 ± 1.93 g) were 61% larger than testes from CON male foals (n = 4; 20.50 ± 1.93 g; P < 0.01). RNA sequencing revealed 56 differentially expressed genes between HIGH and CON groups (P-adjusted <0.05). These genes represent biochemical pathways involved in oxidative phosphorylation, fatty acid metabolism, and thermogenesis, which are integral for testicular development and function. Gene ontology analyses revealed differential gene expression was associated with biological processes relevant to reproductive function and spermatogenesis, including cellular respiration and mitochondrial function. Histological analyses revealed no difference in individual ST area (P = 0.76) or Sertoli cell number within STs (P = 0.57); however, testes from CON foals had 2.3x more STs per 10X field (21.68 ± 2.48) than HIGH foals (9.35 ± 2.48; P = 0.01) along with STs representing a greater percentage of the image area relative to interstitial tissue (CON 3.66% ± 0.61%; HIGH 1.60% ± 0.61%; P = 0.05). These data from the neonatal foal indicate that late-gestation maternal overnutrition alters fetal testicular development with potential long-term implications.

80 Preliminary investigation of gastro-well on Equine Glandular Gastric Disease prevalence in competition horses

The European College of Equine Internal Medicine (ECEIM) has expanded the nomenclature surrounding EGUS to 2 distinct diseases with differences in pathophysiology, risk factors, treatment response, and grading systems: Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD). Although the mechanism, risk factors and pathophysiology of ESGD is well characterized, the mechanism of EGGD still requires elucidation, which may explain the ECEIM recommendation to move away from using fasting models to investigate therapeutic efficacy of nutraceuticals and drugs in naturally occurring disease states. Further most of the previous work in nutraceuticals either does not delineate location of ulcer or focuses on squamous tissue. Recently, the nutraceutical, Gastro-Well (GW; Probiotech International Inc.), was able to reduce naturally occurring EGUS in competition horses after 4wk but did not specify the ulcer location. The objective of this preliminary study was to examine GW, a proprietary blend of minerals, prebiotics, yeast, and psyllium, on performance horses with EGGD. Six mature (7–16y) competition horses with a history of EGGD were enrolled in the study. Two weeks before the initialgastroscopes, all nutraceuticals and medications for EGGD ceased. Gastroscopes were performed on d 0 and after 30d of GW supplementation at 360g/d. Because the ECEIM recommends a descriptive system to assess glandular ulcers without a numeric designation as in the squamous scoring system, images of the glandular ulcers from the gastroscopic examinations were sent in randomized pairs to a veterinarian blinded to order, to determine which image looked healthier based on the ECEIM description of EGGD or if there was no difference. Positive response to GW was determined when the post-image was deemed healthier. The binary data was analyzed by Chi-squared to determine statistical significance (P < 0.05) and trends (P < 0.10). There was a trend (P = 0.08) for positive response to GW. The result demonstrates that GW may have the potential to support glandular gastric health in at-risk competition horses with EGGD. Further research is warranted to replicate these findings with a larger sample size.

72 A survey of North American horse diets: What are we missing?

Balanced nutrition is critical for the health and well-being of horses. To date, there is limited information on the composition of North American equine diets. Here, we describe an analysis of 200 equine diets and how they compare with NRC requirements. Owners from the US and Canada submitted their diets for review by a nutritionist. They were asked to provide information on their horses’ age, weight, exercise level, diet composition, and health concerns. They were also asked to classify their horses' body condition as underweight (UW), slightly underweight (SU), normal weight (NW), slightly overweight (SO), overweight (OW), or obese (OB). Our sample population includes mature horses of various breeds and exercise levels. Diet nutrient composition was based on guaranteed analyses provided by manufacturers and an average hay analysis corrected for variations in regional soil mineral contents, or the hay analysis submitted by the horse owner where available. Nutrient intakes were compared with each horse's requirements based on their exercise level and body weight, obtained from the NRC, to calculate nutrient intake as a percentage of requirements. Wilcoxon Signed Rank Tests and descriptive statistics were used to analyze the data in Prism. Data are presented asmean intakes as a percentage of requirements ± SEM. Our results revealed that diets were providing an adequate amount of selenium (113 ± 8%) and vitamin E (106 ± 7%). Diets were slightly over-supplying energy (118 ± 1%; P < 0.0001), zinc (125 ± 5%; P = 0.0002), copper (151 ± 6%; P < 0.0001), manganese (132 ± 5%; P < 0.0001), and vitamin A (138 ± 8%; P = 0.001). Protein (191 ± 3%), lysine (203 ± 4%), iron (352 ± 6%), phosphorus (192 ± 4%), calcium (292 ± 7%), magnesium (264 ± 4%), and potassium (680 ± 9%) were appreciably over-supplied (P < 0.0001), and sodium was under-supplied (65 ± 5%; P < 0.0001). Interestingly, all horses except those classified as obese were over-consuming energy (P < 0.004), with average intakes for UW horses being the highest (145 ± 8%), followed by SU (127 ± 5%), OW (122 ± 4%), SO (118 ± 3%), and NW horses (116 ± 2%). Understanding the degree to which horses are meeting or exceeding their nutritional requirements is fundamental for formulating recommendations to support performance, longevity, and overall health. This may inform future avenues of research and outreach to improve the health and well-being of the North American equine population.

171 Enrollment and participant satisfaction in online horse courses for adult learners

The University of Minnesota Equine Extension Program offers 7 online courses to help equip horse owners and professionals with practical knowledge, research updates, and resources to improve horse care and management on their farms. The courses include Basic Nutrition, Carcass Composting, Growing and Feeding Hay, Horse Biosecurity, Managing Overweight Horses, Manure Management, and Pasture Establishment and Management. Each course is offered annually in January and runs for 6 weeks. An online platform is used to facilitate a semi-self-paced format. Learners meet course objectives by viewing weekly asynchronous lectures, exploring additional resources, and completing weekly assignments (e.g., quizzes). Participating in assignments and scoring at least 70% on quizzes is needed to earn a certificate of course completion. Since 2016, 1,256 learners have taken the courses. The objective of this presentation is to evaluate enrollment and assess participant satisfaction in recent years. The data were analyzed using ANOVA models (α = 0.05) followed by Tukey HSD tests with enrollment and certificate completion as response variables and year and course as fixed effects. From 2021 to 2023, the courses had a total of 697 registrations generating an income of $52,050. Registrants were from 10 countries and 39 states, with many from Minnesota (39%). While enrollment numbers did not vary by year (P = 0.06), they didvary among courses (P < 0.001). On average, Basic Nutrition had the highest annual enrollment (81 enrolled) followed by Pasture Establishment and Management (49 enrolled). For 2021 and 2022, course (P = 0.09) and year (P = 0.06) did not affect the proportion of learners that earned a certificate (59 to 85%). Feedback evaluations that asked Likert questions were used to assess participant (n = 12) satisfaction of the newly added Carcass Composting course. All agreed or strongly agreed that they were satisfied with the course and the information taught was useful for their farm. Perceived learner knowledge increased 41% during the course. Most learners agreed or strongly agreed (58%) they planned to make at least one management change on their farm based on content knowledge. Overall, consistent enrollment numbers from 2021 to 2023 indicate that the courses continue to be valuable resources for horse owners and professionals. Learners were particularly interested in areas of nutrition and pasture management, which suggests efforts to implement similar programs regionally could be worthwhile. Positive feedback from newly added courses highlights the success of a variety of topics that can be taught online to improve outreach efforts.

147 Needs assessment: Evaluating interest in the Nebraska horse racing industry

Nebraska passed an expanded legalized gambling bill in 2020 allowing casinos at licensed horse racing tracks. As of January 2023, Nebraska has 5 operational horse racing tracks that have been approved for expanded gambling. As a result, a positive impact on the horse racing industry in Nebraska is expected. As the number of tracks, races, and casinos increases there is also a growing need for horses to compete. Since passage of the bill, there has been an increase in the number of mares bred (72%), registered foals (55%), and active stallions (38%) in Nebraska as reported by The Jockey Club in 2023. To determine individuals' current and potential level of interest in actively participating in Nebraska horse racing a 16-question needs assessment survey was made using Qualtrics to develop extension programming. The survey included quantitative and qualitative items and was distributed online through various equine related social media platforms and sent via email invitation to multiple listservs targeting Nebraska residents. Survey questions focused on basic demographics, current and potential involvement in horse racing, personal goals, and management topics related to Nebraska horse racing. Data was collected from 123 respondents who were approximately 70% female (n = 85) and 30% male (n = 36) and 33.8% of the respondents (n = 45) work in the agriculture industry. Respondents completed a 5-point Likert scale (1 = no involvement to 5 = extremely involved) over their current involvement in different aspects of horse racing. The top 3 levels of involvement were breeding mares (1.91 ± 1.38 SD), mare and foal care (1.80 ± 1.23 SD), and working as a groom (1.64 ± 1.23 SD). When asked about their goals most (23.60%) were unsure and 21.12% identified wanting to own a quality racehorse. The top 3 areas respondents were most interested in being involved in were breeding mares (15.12%), caring for mares and foals (14.63%), and 13.17% were unsure. Respondents ranked 14 horse racing industry related topics 1 to 14 (1 = most interested, 14 = least interested, lowest mean = most interested) based on their level of interest in learning more about them. Based on rankings, they were most interested in learning about racehorse care (5.39 ± 3.11 SD), Nebraska bred races (5.66 ± 3.83 SD), and racehorse nutrition (5.68 ± 3.16 SD). Participants indicated their interest in horse racing stems from family being involved in the industry. Respondents show interest in both Thoroughbred and Quarter Horse racing. From these data, a conference is being developed to educate individuals on the topics identified with the goal of bringing more individuals into Nebraska horse racing.

182 Feed intake and metabolic responses in horses in transition from haylage feeding to pasture grazing

The transition from winter-feeding to pasture involves a considerable diet change that might compromise health of horses, and info on the metabolic responses in horses on pasture are scarce. The objective of the study was to investigate how the transition from haylage feeding to strip grazing affected feed intake (FI) and metabolic responses (blood glucose (GLU)-insulin (INS) and cecal pH). Four cecum-cannulated Norwegian cold-blooded trotter geldings were used in a longitudinal study consisting of 3 periods: 1) haylage only (d 0 to 8) reflecting winter-feeding, 2) transition (d 9 to 20) reflecting a diet where the proportion of forage decreased and grazing increased (0 min to 2 × 3 h per d), and 3) grazing only (d 21 to 28) reflecting horses on pasture (2 × 3 h per d). Strip grazing was used to control and measure daily FI in period 2 and 3. From d 9 to 28 the horses were allowed access to a new strip of grass for a specified time-period. The remaining grass was cut each day after grazing, collected, weighed, and compared with the amount of grass from a strip of ungrazed pasture. It was possible to estimate FI for all horses and calculate an average FI per horse. Haylage and grass samples from every 4th d were analyzed for nutritional composition (neutral detergent fiber excluding residual ash (aNDFom), water soluble carbohydrates (WSC), and crude protein (CP)) and used to estimate dry matter (DM) and nutrientintake. On d 8 and 28, blood and cecal samples were collected before and each h after feeding (2 kg haylage as fed vs. 3 h of grazing) for 8 h. ?Area under the curve (AUC) of GLU and INS were calculated using GraphPad Prism. The effect of d on nutrient content, FI, body weight (BW), AUC and peak GLU and INS, and minimum pH were compared using PROC mixed in SAS and considered different if P < 0.05. Grass yield increased (P < 0.001) over time as the grass matured (0.32 to 0.54 kg DM/m2). Plant maturity of the grass affected the nutrient content (P < 0.001) as aNDFom increased (545 to 636 g/kg DM), and CP decreased (158 to 101 g/kg DM). The WSC content varied (P < 0.001) over time (73 to 128 g/kg DM). Similar BW was measured on d 8 and 28 (568 ± 31 kg). The DM intake was 1.62 kg (0.29% of BW) on d 8 and estimated to be 3.7 kg (0.65% of BW) on d 28. There was no effect of d on AUC and peak GLU and INS, but cecal pH was higher (P < 0.001) when feeding haylage (6.89) on d 8 than pasture (6.57) on d 28. In conclusion, FI was controlled by strip grazing, BW was maintained, and metabolic responses were within the expected ranges. However, a longer grazing time would probably result in increased FI and undesired BW gain.

22 Evaluating the core bacterial microbiome of 1,787 horses

The core bacterial microbiome can be defined as the bacteria that are consistently prevalent within a given population. Determining the core microbiome of the equine gastrointestinal tract would allow for the development of probiotics, prebiotics, and management techniques to promote the growth of these taxa and subsequently support horse health. The Microbiome Quotient project (MQ; Purina Animal Nutrition, Gray Summit, MO) aims to determine the core bacterial microbiome from a repository of rectal swabs obtained from thousands of horses across various locations, breeds, ages, and diets, among other factors. To this end, the bacterial DNA of 2,057 rectal swabs were extracted using the Quick-DNA Fecal/Soil Microbe Miniprep kit (Zymo Research, Irvine, CA) and the V3-V4 hypervariable region of the 16S rRNA gene was sequenced by following the Illumina 16S Protocol (San Diego, CA). Data were initially filtered with DADA2 within the QIIME2 pipeline. The data were filtered again in R (4.2.2) to remove samples with missing data points as well as samples with low sequencing depth (<1,000 sequences). In total, 1,787 samples were considered for downstream analysis. The core microbiome was determined by using the Microbiome and qiime2R packages in R to aggregate taxa at the genera level across allsamples with the criteria that the taxa must exceed 0.1% relative abundance in over 70% of the samples (prevalence ≥ 0.7). The data were then analyzed within the following top 5 breeds: Quarter Horse (n = 567), Thoroughbred (n = 314), Warmblood (n = 177), Paint (n = 105), and Arabian (n = 79). The top 15 genera across all samples consisted of Rikenellaceae RC9 gut group (12.58%), uncultured genus (6.79%), Erysipelotrichaceae UCG-004 (4.80%), Ruminococcaceae UCG-002 (4.09%), Akkermansia (3.89%), Ruminococcaceae UCG-010 (3.62%), Arcanobacterium (2.84%), Phascolarctobacterium (2.33%), Streptococcus (1.90%), Treponema 2 (1.75%), Prevotellaceae UCG-001 (1.71%), Mycoplasma (1.64%), Prevotellaceae UCG-004 (1.63%), Clostridium sensu stricto 1 (1.57%), and Alloprevotella (1.56%). Three unique genera were observed between the top 5 breeds and were Campylobacter (Warmblood), Bacteroides (Arabian), and Ruminococcaceae UCG-004 (Paint). Further investigation of this growing database within and between other variables related to health (e.g., age, Body Condition Score, and history of disease) is necessary to fully characterize and understand the function of the equine gastrointestinal core microbiome and to determine the best practices for supporting gastrointestinal health.

64 A preliminary study: Effect of hay nets on horse hay usage, dental wear, and dental conditions in mature adult horses

Hay nets are a commonly used management practice to decrease intake rate and reduce hay waste but can create unnatural foraging conditions that may impact horse health. The objectives of this study were to compare hay usage, dental wear, and dental conditions between horses fed with or without hay nets. Researchers hypothesized horses consuming hay from hay nets would use less hay and have no differences in dental health compared with horses fed without hay nets. In September 2021, 13 mature adult horses were blocked by bodyweight (BW) and randomly assigned to a hay net or no hay net treatment for one year. Horses were housed in adjacent dry lots with shelter, ad libitum water, and free choice access to grass round bales with or without hay nets (4.45cm openings) depending on assigned treatment. Blinded dental work was completed for all horses by an equine veterinarian and dentist in September 2021 (baseline) and 2022 (conclusion of year 1, start of year 2) and included measurements of incisor and canine lengths and recordings of dental conditions before and after dental work. After dental work in 2022, horse groups switched treatments. Horse BW, body condition score (BCS), and softtissue damage on their gums or lips were assessed and recorded monthly. Round bales were weighed before being placed in the dry lot and the date fed was recorded to calculate hay usage (intake and waste). Data were analyzed using PROC MIXED in SAS with significance set at P ≤ 0.05. Horse BW, BCS, and hay usage were greater in horses consuming hay without hay nets (P ≤ 0.05). When pre- and post-length of incisors were evaluated, no differences were observed between treatments (P > 0.05). Incisor length between 2021 and 2022 increased by 3.77 and 3.19mm for horses feeding from no hay net and a net, respectively. Presence of incisor bevels after one year and notation of monthly soft tissue damage did not differ between treatments (P > 0.05). These preliminary data suggest that hay nets do not result in negative impacts on dental health over one year but can significantly reduce hay usage and help control horse BW. This study is ongoing and will be completed in September 2023.