Synaptic

I have assigned a semester-long, original research project (and paper describing that project) in Mammalogy (BIO 342) for years. The paper written by Hannah is one of the strongest I have seen. Not only does her paper do an excellent job of describing her project, but it also perfectly follows the standard format for articles submitted to scientific journals, and she did an excellent job with concise writing. Furthermore, the level of “scientific thinking” displayed in the paper is at the level of a graduate student.

– Dr. Russ Benedict

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Abstract

This study investigated whether grazing duration in domestic horses differs between morning and evening or by breed. The breeds used included Missouri Fox Trotters, Pony of the Americas (POAs), and American Quarter Horses. Horses were observed twice daily for four days, and cumulative grazing time was recorded during ten-minute intervals. Overall, horses grazed slightly more in the evening (5,730 seconds) than in the morning (5,283 seconds), with Quarter Horses grazing the most (3,960 seconds), followed by POAs (3,816 seconds) and Missouri Fox Trotters (3,237). These results did not support the prediction that morning grazing would dominate, nor the hypothesis that grazing time would be similar across breeds. Instead, the data suggests that breed-specific physiological and behavioral traits may influence grazing duration more than time of day. Although limited by small sample size and schedule inconsistencies, this study adds to the relatively scarce research on interbreed grazing differences in horses. Understanding these patterns has practical value for improving feeding and pasture-rotation strategies, ensuring horses receive appropriate forage based on their metabolic needs, and promoting more sustainable pasture management.

Introduction

The purpose of this research is to determine whether domestic horses differ in grazing time between morning and evening and whether grazing time varies by breed. Domestic horses (Equus caballus), members of the order Perissodactyla and the family Equidae, are a subspecies of the wild horse (Equus ferus). They were domesticated by humans approximately 5,000 years ago for transportation and agricultural work. Today, horses are used for riding, sport, herding, and other activities (Animals Network Team).

Domestic horses live in managed environments such as pastures and fields, feeding on high-fiber forage like Timothy grass, Orchard grass, Kentucky bluegrass, Bermuda grass, fescue, ryegrass, clover, and alfalfa (“Different Types of Grasses,” 2025). When fresh pasture is limited, hay and pelleted feeds supplement the diet. Horses typically consume 1.5%-2.5% of their body weight daily, with exact needs varying by activity level, age, breed, metabolism, reproductive status, and environmental conditions (Murray, 2025).

Horses are adapted for continuous grazing, spending 70%-80% of their day eating, often in multiple bouts lasting 10-12 hours total. They rarely go without food for more than three to four hours (“Feeding Behavior”). Horses use mobile lips and strong incisors to crop grass close to the ground while keeping their head lowered. The cheek teeth grind the forage into smaller particles before swallowing (“Feeding Behavior”). Their flat-topped, high-crowned teeth are specialized for grinding fibrous grasses and continue to grow throughout life to replace wear from constant chewing (Benedict, 2025). Grazing peaks around dawn and late afternoon, reflecting temperature and light cycles (“Feeding Behavior”).

The main reason horses eat so much lies in their digestive anatomy. As herbivores that consume fibrous plant material rich in cellulose, horses lack the enzyme needed to break down cellulose directly and must rely on microbial fermentation to extract nutrients (Janis, 1976). Unlike ruminants such as cows, which have multi-chambered stomachs that ferment food in the rumen before digestion, horses are hindgut fermenters. Their microbial fermentation occurs in the cecum and large intestine, structures located later in the digestive tract, resulting in less efficient nutrient extraction because food passes through more quickly. In addition, horses have relatively small stomachs, limiting their capacity to hold and process large amounts of food at once. To compensate for this lower digestive efficiency, horses must graze and eat almost continuously throughout the day to meet their energy requirements (Clauss, et al, 2023).

Horses have the anatomy of running mammals, with adaptations that increase speed, reduce distal limb weight, and withstand the forces of running. Over time, horses have shifted to an unguligrade foot posture, standing on the tip of a single digit. The radius and ulna in the forelimb, and the tibia and fibula in the hindlimb, have fused to provide stability during running, while the bones of the lower leg have elongated, increasing stride length and speed. Most large muscles are concentrated near the body’s core to minimize weight in the lower limbs, which contain very little muscle but are supported by long, powerful tendons (Benedict, 2025). These adaptations give horses the speed and endurance necessary to survive and forage efficiently.

Selective breeding has produced significant interbreed variation in morphology and behavior. Height ranges from 70 centimeters to over 2 meters, and weights range from 907 kilograms–1,089 kilograms, with diverse coat colors, gaits, diseases, and temperaments (Librado, 2017). This study examined grazing habits in three breeds: Missouri Fox Trotter, Pony of the Americas (POA), and Quarter Horse. The Missouri Fox Trotter was bred by settlers who needed sure-footed, comfortable horses capable of covering long distances. Its “fox trot” gait creates a smooth, rhythmic motion (“Missouri Fox Trotting Horses”). Missouri Fox Trotters typically stand 1.4–1.6 meters tall, weigh up to 544 kilograms, and live 20–30 years (Gillet, 2025). The Pony of the Americas (POA) was bred to create a small, athletic pony with the speed, stamina, and appearance suitable for young riders.

The breed is known for its rugged build, striped hooves, distinctive spotted coat patterns, and white sclera. They typically stand 1.1–1.4 meters tall and weigh between 295 and 650 and 408 kilograms (“Pony of the Americas”). The American Quarter Horse is one of the most popular and versatile horse breeds, known for its muscular build, speed, and agility. They are widely used in rodeo events, ranch work, and riding disciplines. Quarter horses are typically 1.4–1.6 meters tall, weigh between 408 and 544 kilograms, and display a variety of coat colors, often with distinctive facial and leg markings (Wilson & Dewsbury, 2025).

Given the distinct physical characteristics of these breeds, comparing their grazing activity offers insight into how breed-specific traits may influence feeding behavior. It was hypothesized that grazing activity would be greater in the morning than in the evening because cooler temperatures both reduce heat stress and increase energy demands for maintaining body temperature. A second hypothesis proposed no significant difference in grazing time among breeds, as all horses have high nutritional requirements.

Materials and Methods

This study was conducted using two separate pastures at Grace Therapeutic Riding, consisting of Missouri Fox Trotters, POAs, and Quarter Horses. Observations were made twice daily, once in the morning (between 7:00–8:00) and once in the evening (between 4:30–5:30). During each observation period, one randomly selected horse from each breed was observed for ten minutes. A stopwatch was used to record the cumulative time each horse spent grazing. Grazing, in this experiment, is defined by any time the horse’s head was lowered to the ground. Time on the stopwatch was paused whenever the horse raised its head. After ten minutes, the total grazing time for that breed was recorded. This procedure was repeated for each breed during both observation periods.

To minimize bias, data collectors alternated the time of day and the order in which breeds were observed to account for potential timing differences. For example, if observer A recorded data in the morning one day, they collected data in the evening on the next. Additionally, data was collected only on fair, sunny days with similar temperatures to ensure that weather conditions did not influence grazing behavior.

Results

Overall, the horses spent more time grazing later in the day as they grazed for a total of 5,283 seconds (88 min 3 sec) in the morning and 5,730 seconds (95 min 30 sec) in the evening. Both Missouri Fox Trotter Horses and POA Horses grazed longer in the evening, whereas Quarter Horses grazed longer in the morning (see Figure 1 and Table 1). Among the three breeds, Missouri Fox Trotter Horses spent the least amount of time grazing, with 3,237 seconds (53 min 57 sec), compared to 3,816 seconds (63 min 36 sec) for POA Horses and 3,960 seconds (66 min) for Quarter Horses (see Figure 2 and Table 1).

Discussion

Both hypotheses were rejected, as the data did not support them. Only Quarter Horses grazed slightly more in the morning, spending 50.8% of their total grazing time during this period. Missouri Fox Trotters and POAs grazed 46.7% and 46.1% in the morning, respectively. Overall, Quarter Horses spent the most time grazing, for a total of 3,960 seconds (82.5% of the observation period), followed by POAs at 3,816 seconds (79.5%) and Missouri Fox Trotters at 3,237 seconds (67.4%).

Differences between morning and evening grazing were minimal, with most horses grazing slightly more in the afternoon. Thermal stress was unlikely to influence this pattern, as morning temperatures never dropped below 55°F and evening temperatures never exceeded 90°F. The small variations observed may reflect physiological differences among breeds. Missouri Fox Trotters, known for endurance, may delay feeding due to high energy efficiency, grazing more as energy demands increase later in the day. POAs, being highly social and active, may graze more in the evening following periods of movement and interaction. Quarter Horses, with larger body size and higher metabolic demands, may favor morning grazing to meet energy requirements, consistent with their selection for strength and quick acceleration.

Across the 80-minute observation period, total grazing time was similar for Quarter Horses and POAs, differing by only a few minutes, while Missouri Fox Trotters grazed nine–twelve minutes less than the other breeds. This may relate, speculatively, to their stamina, smooth gait, and efficiency over long distances, which could allow more efficient food use and reduced total grazing time. These explanations would warrant further study.

Relatively few studies have examined breed-specific differences in grazing time among horses, but research on other grazing species suggests that anatomical and behavioral traits can influence foraging strategies. For example, a comparative study of Highland, Braunvieh, and Angus x Holstein cattle demonstrated clear variation in bite rate, distance traveled, and selectivity while grazing (Pauler, et al, 2020). It was concluded that traits such as energy requirements, body size, and overall foraging strategy could shape how long animals spend grazing. Although this study focused on cattle rather than horses, it supports the broader idea that interbreed differences in anatomy and metabolism could contribute to the variation in grazing time seen in this study’s dataset (Pauler, et al, 2020).

A second study comparing cattle, horses, and sheep found that horses grazed more continuously throughout the day than the other species. Unlike cattle and sheep, which tended to show more distinct peaks in activity, horses maintained a steady grazing behavior across daylight hours (Vidal-Cardos, et al, 2025). This observation suggests that horses may not express strong time-of-day preferences for foraging, and instead might rely on frequent, sustained intake to meet their metabolic needs. When considered alongside this study’s results, this could explain why there was often an unclear, or small, difference in morning and evening preferences (Vidal-Cardos, et al, 2025).

Finally, existing literature on equine nutritional requirements indicates that horses must consume a certain amount of forage relative to body weight, meaning that smaller breeds theoretically need less total intake and may therefore spend less time grazing (Murray, 2025). This helps explain why larger breeds, such as Quarter Horses, showed the highest grazing times. However, it does not fully account for the observation that POAs, despite being smaller, grazed more than Missouri Fox Trotters. These contrasts show that grazing time is shaped by more than body size alone and that breed-specific behavioral and physiological factors likely contributed to the variations observed.

Several sources of error may have influenced the results of this project and could have impacted the accuracy of the data collected. First, the limited sample size reduced the strength of any patterns detected and made the dataset more sensitive to individual variation among the horses. With only around three horses per breed, any unusual behavior on a given day, or any quirks a horse may exhibit, could influence that data for that entire breed. Additionally, observations were conducted on only four days, meaning the total amount of time spent viewing the horses was relatively small. Increasing the number of observation days and total minutes recorded would improve reliability and provide a clearer, more accurate understanding of typical grazing behavior.

Another source of error stemmed from inconsistencies in the feeding schedule. Although observations were conducted at the same time each day, the staff did not always feed the horses on a strict schedule. As a result, some horses on some days were observed either just before feeding or immediately after receiving their pelleted feed. In these cases, the horses tended to wait at the gate or focus on their feed rather than engage in natural grazing behavior. This inconsistency introduced variability in grazing time measurements and made comparisons across days less reliable. A more controlled approach would involve scheduling observations outside of feeding periods or coordinating more closely with staff to ensure feeding occurs at predictable times.

A third source of error involves the high degree of human involvement in the horses’ daily routines. Because each horse has individualized feeding requirements, supplements, and human interactions, their behavior can differ based on factors unrelated to natural grazing patterns. For example, horses accustomed to more frequent handling or specific feeding cues may alter their movement or attention if they anticipate human contact. This reliance on human-managed routines increases the likelihood of inconsistent results, as not every horse is handled or managed in the same way.

Future studies could expand on this project by examining grazing behavior across a wider range of horse breeds and management settings. One potential direction would be to compare breeds with significant differences in body weight, as well as breeds known for long-distance endurance versus those selected for speed, to determine whether these physiological or performance-based traits influence grazing time. Additionally, conducting the study across multiple facilities and including a larger number of horses per breed would help reduce the impact of atypical behavior from any single individual. By broadening both the sample size and the diversity of horses observed, future research could produce more concrete conclusions about how breed characteristics influence grazing patterns. This research contributes to a broader understanding of how breed characteristics shape grazing behavior and highlights important considerations for equine management. Recognizing these differences can improve pasture and feeding strategies, since breeds can vary widely in metabolic rates and nutritional needs. This study also helps fill a gap in the limited research on breed-specific grazing patterns, offering insight into how evolutionary history and physiology influence natural foraging behavior. Additionally, identifying preferred grazing times can support more effective rotational grazing plans, reducing pasture stress and preventing overgrazing. Together, these findings emphasize that grazing behavior is not one-size-fits-all and that tailoring management to the needs of each breed can lead to healthier horses and more sustainable land use.

Acknowledgements

We extend our thanks to Grace Therapeutic Riding for their generous support. Access to their land and horses was essential to the completion of our project, and their willingness to accommodate our research activities is gratefully appreciated.

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