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Extension > Horse Extension - Research Updates > 2013

Monday, November 25, 2013

Stress Response of Young Horses to Changes in Housing

Separating young horses from their group and stalling them in individual boxstalls is stressful.

For initial training, horses are often transferred from group housing to individual boxstalls, which is a potential stressor.

In a study conducted in Austria, salivary cortisol concentrations (an indicator of stress), locomotion activity, and heart rate were analyzed in eight 3-year old mares. Mares were transferred abruptly from group paddock housing to individual boxstalls without paddock access. Data were collected for 4 days while mares were in group housing and for 5 days immediately after the change in housing in individual boxstalls.

Once in boxstalls, mares underwent routine equestrian training for young horses. While in group housing, cortisol concentrations showed a diurnal rhythm with values approximately 0.6 ng/ml in the morning and a decrease throughout the day. When horses were moved to boxstalls, cortisol concentrations increased to 1.8 ng/ml within 30 minutes and did not return to baseline values for 6 hours. On the days following the housing change to boxstalls, a cortisol diurnal rhythm was re-established but at a higher level compared to the level found in group housing. Locomotion activity was higher when mares had access to a paddock than when kept in individual boxstalls and heart rate increased for approximately 60 minutes when mares were separated from their group.

This study confirms what was previously thought; separating young horses from their group and stalling them in individual boxstalls is perceived as stressful.

Friday, November 15, 2013

The effect of different feed delivery methods on time to consume feed in horses

Using obstacles can increase time to consume feed when feeding adult horses.

Management techniques that reduce the insulin response to feeding in horses have application in preventing insulin resistance and potential associations with diseases like laminitis. Eight mature idle horses with a body condition score between 5 and 6.5 and with no previous indication of insulin resistance were fed a meal of concentrate under 4 feed delivery treatments by researchers at North Carolina State University.

Treatments were all based on a bucket of equal dimensions. The treatments included a control and 3 treatments hypothesized to increase time to consume feed: mobile obstacles (BALL) above the feed, stationary obstacles below the feed in the form of a waffle insert (WAFFEL), and feed with water added (water).

Jugular venous blood samples were taken at feed delivery, every 10 minutes for the first hour, and then every 30 minutes until 300 minutes after feed delivery. The time to consume feed was different across treatment and was greater buckets with the BALL and WAFFEL obstacles when compared with the control and water added feed.

Glucose and insulin concentrations increased after feeding and tended to differ among treatments. Peak insulin and glucose concentrations were affected by treatment as were the time to peak insulin and the area under the curve of insulin. Therefore, feed delivery methods that include obstacles effectively increase time to consume feed and attenuate postprandial glucose and insulin concentrations.

A second experiment was designed to determine if the time to consume feed changes associated with BALL and WAFFEL obstacles in experiment 1 remain effective over a 4 day period. Four horses with no recent or regular history of consuming concentrates were fed concentrate meals for 4 consecutive days using the same treatments described in experiment 1. Horses were subject to a 4 day adaptation period and were randomly assigned to 4 day treatment periods using the 4 previously described treatments.

During adaptation, time to consume feed decreased over time. After adaptation, WAFFLE had greater time to consume feed when compared with the control and feed with water added, whereas feed with water added had the lowest time to consume feed overall.

Using obstacles to increase time to consume feed on a daily basis may be an effective method to reduce postprandial glucose and insulin concentrations, thereby decreasing the risk of insulin resistance development in horses.

Seasonal changes of total body water and water intake in Shetland ponies

Water supply during the cold seasons might be more critical than under summer conditions.

Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity.

A recent study conducted by scientists in Germany was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water and total water intake of 10 adult Shetland pony mares were estimated at monthly intervals for 14 months by using the deuterium dilution technique. During the last 4 months, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls.

The total body water in kg was closely related to body mass explaining 86% of the variation. In contrast to total body water in kg, total body water (percentage) remained relatively stable across all measurements. The total water intake showed an increase in summer and a decrease in winter. However, total water intake measured at ambient temperatures less than 0°C did not follow the same trend as total water intake at greater than 0°C. Therefore, removing total water intake values measured at ambient temperatures less than 0°C from the analysis resulted in high correlations with locomotor activity, ambient temperature, and resting heart rate.

Feed restriction had no effect on total water intake and total body water. The total body water content was unaffected by season and physical activity. The comparison of total water intake with published data on drinking water intake revealed that ponies had 1.7 to 5.1 times greater total water intakes when other sources of water such as feed and metabolic water were included. The total water intake was highly influenced by environmental conditions and metabolic rate.

Contrary to expectation, water supply during the cold seasons might be more critical than under summer conditions when water content of grass is high to allow for the compensation of limited availability of drinking water.

Monday, November 4, 2013

The effect of hay steaming on forage nutritive values and dry matter intake by horses

Steaming represents a strategy for reducing dust and mold concentrations and increasing dry matter intake in some hays, but can result in leaching of essential nutrients.

Management strategies for horses with respiratory disease include soaking hay prior to feeding. Hay steaming is an alternative to this practice; however, little is known about its impact on forage nutritive values or intake. The objective of this research, conducted at the University of Minnesota, was to determine the effect of steaming on forage nutritive value and intake by horses.

Two alfalfa-orchardgrass mixed hays were evaluated: a low and moderately moldy hay. Six mature horses were used in a 10 day cross over design. Three horses were assigned to each hay type and treatments were switched on day 6. Each day, one bale of each hay was sampled (pre and post-steaming) and steamed for 90 minutes using a commercial hay steamer. Two flakes of steamed or unsteamed low or moderately moldy hay were weighed and offered simultaneously to each horse in individual hay nets. Horses were allowed access to hay for 2 hours, any remaining hay was collected and 2 hour dry matter intake was calculated. Six additional bales of low and moderately moldy hay were used to evaluate the effect of steaming on total suspended particulate (TSP) or "dust". Flakes of unsteamed or steamed hay were agitated in an electric cement mixer, and TSP was recorded every minute for 30 minutes.

Steaming increased hay moisture and therefore reduced dry matter to 77 and 81% for low and moderately moldy hay, respectively. In low and moderately moldy hay, steaming reduced phosphorous (P) content by 16 and 17%, respectively. Steaming reduced water soluble (WSC) and ethanol soluble carbohydrates (ESC) by 13% and 27% respectively, for moderately moldy hay, but had no effect on low mold hay. Steaming reduced mold concentrations in both hays by ≥ 91%. Total suspended particulate of moderately moldy hay was reduced by 55%, but TSP in low mold hay was not affected by steaming (P = 0.445). Dry matter intake of low mold hay was increased by steaming; horses ingested 0.64 kg of unsteamed and 2.02 kg of steamed hay. Dry matter intake of moderately moldy hay was not affected by steaming. For low mold hay, steaming decreased P and mold concentrations, increased dry matter intake of the hay, but had no effect on TSP. In moderately moldy hay, steaming reduced P, WSC, ESC, mold concentrations and TSP, but did not affect dry matter intake.

Steaming represents a strategy for reducing TSP and mold concentrations and increasing dry matter intake in some hays, but can result in leaching of essential nutrients.

Thursday, September 26, 2013

Furosemide Use in Thoroughbreds

Decreases in energy generation during exercise found in furosemide-treated horses were attributed to the losses in body weight caused by the drug's diuretic action.

One of the most controversial issues in horse racing is the debate over the use of the loop diuretic furosemide (also known as Salix or Lasix) in the prevention of exercise-induced pulmonary hemorrhage (EIPH), a condition characterized by bleeding into the lungs during intense exercise. It has long been known that furosemide administration improves horses' racing performance when compared to non-medicated horses. Researchers at the University of Kentucky conducted a study to measure the effects of furosemide on horses' energy efficiency during a standardized exercise test (SET).

Six Thoroughbred geldings with an average age of 6.8 years were selected for the study. For 21 days leading up to the SET, all horses received 13 pounds of hay, 9 pounds of grain, and 0.5 pounds of a vitamin/mineral supplement. Horses were not given access to water or feed for the 4 hours leading up to the SET. All horses were weighed 4 hours before the SET, immediately before and after the SET, as well as at 4, 8, 12, 24, 48, and 72 hours after the SET. Heart rate, VO2, and VCO2 were measured at intervals throughout the SET. Blood samples were also taken before, after, and during the SET to measure lactate, glucose, total protein (TP) concentrations, and packed cell volume (PCV). One hour following the SET, all horses were assessed and graded for EIPH by tracheobronchial endoscopy.

In this study, horses treated with furosemide prior to the SET experienced significantly greater weight loss (27 pounds, compared to 12 pounds in untreated horses). Untreated horses had higher heart rates during the SET and greater lactate accumulation, indicating more energy expenditure. Weight-adjusted VO2 and VCO2 measurements did not differ significantly between treated and untreated horses. EIPH incidence after the SET was low and not associated with treatment.

Rather than reduced EIPH, decreases in energy generation during exercise found in the furosemide-treated horses in this study were attributed to the losses in body weight caused by the drug's diuretic action.

Summarized by Sam Beeson, Univ. of Minn. Veterinary Student

Oral Glucosamine Supplementation in Young Horses

There is potential for dietary glucosamine HCl supplementation to have a positive effect on joint inflammation and cartilage turnover in young growing horses.

A recent study conducted at Texas A&M University investigated the effects of oral glucosamine supplementation in young horses. The purpose of the study was to determine whether glucosamine HCl could influence joint inflammation and cartilage metabolism after an inflammatory insult.

In this 98-day experiment, fourteen yearling Quarter horses were housed individually and fed 1% body weight (BW) of grass hay and 1% BW of concentrate per day. Half of the horses also received 30mg/kg BW of glucosamine HCl top-dressed over their concentrate rations.

After 84 days, all horses received carpal joint injections with a solution containing lipopolysaccharide (LPS) from E. coli to elicit inflammation. Each horse also received an injection of equal volume of sterile lactated ringers solution (LRS) into the opposite carpal joint to account for inflammation generated in response to the injection itself. Synovial fluid was collected for analysis from each joint pre-injection and at 6, 12, 24, 168, and 336 hours post-injection.

LPS injections increased levels of the inflammatory mediator prostaglandin E2 (PGE2) and proteins involved in collagen metabolism in the synovial fluid of all horses involved in the study. However, horses receiving the glucosamine supplement showed significantly reduced PGE2 and less evidence of collagen breakdown as well as increased signs of collagen growth when compared to those that did not receive the supplement. These results suggest that there is potential for dietary glucosamine HCl supplementation to have a positive effect on joint inflammation and cartilage turnover in young growing horses.

Tuesday, September 10, 2013

Acceptability and Nutritional Value of Teff for Grazing Horses

Teff grass was found to be readily acceptable to grazing horses.

The warm season annual grass Teff is native to Ethiopia and recognized for drought tolerance, low nitrogen requirement, and productivity in marginal soils. To determine the value of Teff grass as a horse pasture, a single plot was established with minimum preparation to a predominantly barren hill side within a larger, established pasture in Virginia.

The grazing trial began 54 days after the initial planting, when forage had attained the proper grazing height. Within a 23 day time frame, the Teff paddock was grazed during 4 weekly periods by two groups of horses. The groups grazed at different times within 24 hours of each other. Horses were allowed to graze for 1 hour. During the grazing of each group, forage samples were randomly harvested throughout the plot, clipping the Teff to 4". After about 30 minutes of each grazing event, the horses were approached and samples of the long forage were grabbed as the horses began to chew the forage bites. "Stolen" samples were collected from each horse as they grazed for approximately 10 minutes. All samples were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF). Although Teff was a novel grass (i.e. the horses had never grazed the grass) to the horses in this study, all groups grazed the novel forage within 5 minutes of entering the paddock and tended to bite only the upper portion of the plants.

Nutritional data indicated CP did not vary significantly between grazing period, averaging 9% CP for clipped samples. The stolen forage showed higher levels of CP, averaging around 12% CP. NDF averaged 64% in the first two periods, but increased to an average of 65% in the last two periods. NDF was not different between clipped and stolen samples. To the horses in this study, the novel, tall Teff grass was readily acceptable and the upper part of the plant selected by the horses was higher in CP. Further investigation is warranted to determine the value of Teff under greater grazing pressure from horses.

Summarized by Shanna Privatsky, University of Minnesota

Preference of Shade for Domestic Horses in Hot, Sunny Weather

Results indicated that individually-housed horses prefer to utilize shade when it is available in hot, sunny environments.

Provision of shade is recommended by best practice guidelines for horses living in hot, sunny environments despite a lack of research focused on potential benefits of shade for horses. A previous study showed that horses with no access to shade showed greater rectal temperature, respiration rate, and exhibited more sweat than horses that were completely shaded. Yet, this apparent benefit is dependent on horses choosing to stand under the shade provided. The objective for the study, carried out by researchers at the University of California Davis, was to assess horse preference for shaded and unshaded areas in hot, sunny, summer weather.

Twelve healthy, adult horses were used in three different trials, with four horses being used in each trial. The trials consisted of two days of acclimation and 5 to 7 days of observation. Horses were housed individually in dry lots. The southern half of each pen was covered by an open-sided shade structure. The amount of the pen shaded varied throughout the day with an average of 51% of the pen shaded throughout the day. Rectal temperature, respiration rate, skin temperature and sweat score were measured once in the morning, afternoon and evening each day. The horses' behavior was also observed and recorded. The behaviors recorded were horses' location relative to shade, and time spent walking, foraging and standing. Horses were considered to be "in shade" if at least two hooves were shaded by the shade structure.

Results showed that more horses were located in the shade and performed more walking and foraging behavior in the shaded area. In addition, horses spent more time at night beneath the shade structure than in the uncovered area. These results indicate that individually-housed horses do prefer to utilize shade when it is available in hot, sunny environments. These results support recommendations for access to shade when developing best management practice guidelines for horses.

Summarized by Shanna Privatsky, University of Minnesota

Voluntary Water Intake in Horses When Fed a Dry versus Mash Grain in Two Different Seasons

Horses consumed less water in the winter compared to the fall. Feeding mash to horses was helpful in increasing overall water intake.

Many horse owners in northern climates feed a grain mash (i.e. grain plus water) to horses in cold weather. It is thought that by providing an additional source of water, potential dehydration related colic could be avoided. Water intake varies according to both outdoor temperatures and the temperature of water. Cold weather has been reported to decrease water intake by 6 to 12%. In addition, consumption of water decreases as total dry matter intake in the diet decreases. Therefore, it is unknown if the horse simply drinks less liquid water in response to increased water present in the mash. Thus, water intake in two different seasons in horses fed a dry grain or a mash was compared by researchers at the University of Wisconsin River Falls.

Ten mature horses were used and were housed in individual stalls, in a heated barn for trial 1 (Winter), and an unheated barn for trial 2 (Fall). Horses were divided into two groups, one which received pelleted concentrate at 0.5% of their body weight, and one which received the same pelleted feed with water added at a rate of 0.25 gallons per pound of feed. Alfalfa hay was offered at a maximum of 2% of their body weight, divided into two equal feedings, morning and night. A total of 8.5 gallons of water was provided in two buckets at each feeding. Any water and feed remaining was measured prior to the next feeding. Horses were on their respective treatments for four days and then returned to their original pastures for at least two days before switching treatments. The same study was then repeated during the winter.

In the winter, horses on the mash diet had a tendency to consume more water than the horses on the dry concentrate, but no difference was observed in the fall. Horses did consume significantly less water in the winter compared to the fall. There was a significant interaction between treatment and season, with horses consuming dry grain in the winter drinking significantly less water than mash fed horses in the winter and fall. Therefore, feeding mash to horses does appear to be helpful to increase their overall water intake. Horses consuming mash drank equal to or more water than horses on the dry grain, in addition to the water they consumed in their feed.

Summarized by Shanna Privatsky, University of Minnesota

Wednesday, August 14, 2013

Effect of Meal Frequency in Horses

This research confirms that feeding several small meals throughout the day is preferred for healthy horses.

Several studies have investigated the order of feeding (i.e. hay first then concentrate vs. concentrate then hay) and its impact on plasma glucose concentrations in horses. An Australian study recently looked at the effect of feeding frequency on plasma glucose.

A hay common to Australia (wheat hay) was fed to 6 Thoroughbred mares at 2.0% body weight ; a concentrate pellet was fed at 0.5% body weight. Horses were fed either once, twice, or three times daily, with the ration equally divided among meals. The pelleted concentrate was offered either 15 minutes before or after the hay was given for a period of 7 days and blood samples were taken while horses consumed each meal.

Researchers determined that the order of feeding, hay first then concentrate or concentrate then hay, had no effect on plasma glucose values, regardless of number of meals fed. Horses fed two meals per day had higher peak glucose compared to the other frequencies, and morning meals resulted in the highest peak glucose concentrations. Horses fed only one meal per day had the highest overall glucose response to their meal when compared to horses fed at multiple times throughout the day.
These results show that a horse's response to glucose is highest in the morning, and that the number of meals fed per day does affect blood glucose. Even though horses fed one meal per day had the highest overall glucose concentrations, horses fed three times a day had a greater glucose response. This is most likely due to the fact that only a limited amount of glucose is able to be absorbed from the gut during a meal. Feeding one large meal will have a pronounced and immediate effect on blood glucose, whereas spreading it out over several meals results in a larger amount of glucose absorbed.

This research confirms that feeding several small meals throughout the day is preferred for healthy horses.

Summarized by Emily Glunk, MS, University of Minnesota

Effect of Day-time vs. Night-time Grazing in Horses

Owners with horses prone to laminitis should try to avoid grazing their horses at the end of the day, when grasses peak in NSC concentrations.

Non-structural carbohydrates (NSC) are often associated with increased risk of laminitis and insulin resistance in horses. NSC are highly fermentable carbohydrates and excessive consumption can lead to negative consequences in horses such as accelerated hindgut pH which has been implicated in pasture associated laminitis. NSC are a component of all forage species, including cool-season grasses such as fescues, ryegrasses orchardgrass, bluegrass, and bromegrass. Concentrations of NSC can fluctuate throughout the growing season, in response to stresses (i.e. drought), and throughout each day, usually increasing during the daylight hours and falling during the night. The fluctuation in NSC throughout the day is due to the amount of photosynthetic activity occurring. Because of the potentially high NSC concentrations that can occur at different times of day, researchers from North Carolina State University wanted to obtain a better estimation of NSC concentrations and its role in pasture-associated laminitis. The goal of the study was to determine how time of day affected daily pasture NSC concentrations, fecal pH, fecal lactate concentrations, and total volatile fatty acid concentrations.

Twelve mature, idle, light-horse geldings were enrolled in the study during the fall and were rotated through 3 treatments. The three treatments consisted of 1) 24 hours of continuous grazing beginning; 2) 10 hours of grazing over-night beginning at 9 pm; and 3) 10 hours of grazing during full daylight beginning at 10 am. The highest pasture NSC concentrations occurred around 9 pm, peaking at 20% NSC. NSC content at 7 am was 17%. Fecal pH and volatile fatty acid concentrations and ratios were highest in the continuously grazed group. Time of day does effect grass NSC content without significantly influencing fecal pH and volatile fatty acid production.

Length of grazing did have an impact on fecal pH and volatile fatty acid production. Even though pH was lower in both of the 10-hour grazing groups, it was not low enough to be of concern for causing any detrimental health effects. This is most likely due to the fact that pasture NSC content likely did not reach high enough levels to induce any problems. However, owners with horses prone to laminitis should try to avoid grazing their horses at the end of the day, when grasses peak in NSC concentrations.

Summarized by Emily Glunk, MS, University of Minnesota

Body Weight Loss in Obese Horses and Ponies

Researchers found that obese Standardbred horses lost significant amounts of body weight and condition when fed only hay, but the Andalusian and pony groups did not lose weight as easily.

Obesity in horses and ponies has become a significant problem, often increasing the risk of diseases such as insulin resistance, laminitis and equine metabolic syndrome. It has been thought that weight loss may be achieved more easily in some breeds compared to others, and should be carefully monitored to avoid adverse effects including hyperlipidemia (abnormally high lipid concentrations in the blood).

In a study conducted in the United Kingdom, obese (BCS ≥7) ponies, Standardbreds and Andalusians were used to compare weight loss with and without the addition of daily exercise. A total of 12 equines were studied. A body condition score (BCS) of ≥ 7 is characterized by a moderate to obvious crease down the back; fat accumulation over the ribs, tail head and behind the shoulders; and a cresty neck.

All animals were housed and fed individually on a dry lot (dirt paddock) for up to 12 weeks on a restricted diet of 1.25% body weight of grass hay daily; nutritionists generally recommend a daily intake of 2% body weight. Half of the horses were exercised daily on a horse-walker for 25 minutes, while the other 6 were not exercised. Researchers recorded changes in body weight, BCS, and body fat percentage. Once the animals reached a BCS of 5, considered an optimal body condition score, the dietary restriction was stopped.

Researchers found that obese Standardbred horses lost significant amounts of body weight and condition when fed only hay, but the Andalusian and pony groups did not lose weight as easily. During the dietary restriction, Standardbreds reduced their body fat by 57% body fat while the other two breeds reduced their body fat by only 27%. While it took the Standardbreds 6 weeks to achieve a BCS of 5, it took ponies and Andalusians 12 weeks to achieve the same results. Amount of exercise was found to have no effect on rate of body weight loss or reduction of BCS and body fat%.

This study illustrates the differences in the ability of different horse breeds to lose body weight. While exercise was not found to contribute to weight loss in this study, it is still advised for horses and has many physiological benefits.

Summarized by Emily Glunk, MS, University of Minnesota

Monday, June 24, 2013

The Effect Of Hay Net Design On Rate and Amount of Forage Consumed By Adult Horses

The objectives of this study were to investigate the effect of hay net design on the rate and amount of forage consumed by adult horses.

Horses have evolved to consume several small forage-based meals throughout the day, often spending ≥16 hours grazing each day. Modern horse management systems alter this behavior by limiting the amount of time horses spend foraging. The objectives of this study, conducted at the University of Minnesota, were to investigate the effect of hay net design on the rate and amount of forage consumed by adult horses.

Eight adult horses in light work, with an average body weight of 513 kg were fed in individual boxstalls. Horses were fed hay off the boxstall floor (control), or from one of three hay nets: large net (LN, 15.2 cm openings), medium net (MN, 4.4 cm openings) and small net (SN, 3.2 cm openings). During data collection periods, horses had access to hay inside the nets for two 4 hour periods: 0700 to 1100 and 1600 to 2000 each day. Throughout the trial, grass hay was fed at 1% BW twice each day. Horses had ad libitum access to water. To determine forage consumption rate, stopwatches were started once horses began eating, and stopped once horses either finished all offered hay, were no longer interested in eating, or the 4 hour time period had expired. All refuse hay was collected and weighed. Total forage consumed was calculated by subtracting amount of refuse from hay offered.

Mean consumption rates were 1.49, 1.33, 1.11 and 0.88 kg/h (SE ± 0.025) for the control, LN, MN and SM, respectively, with all treatments being different from one another. Horses were able to consume all hay from the control and LN during the 4 hour feeding period, but not all horses finished the hay meal when fed from the MN and SN. Mean percentage of offered hay consumed was 95, 95, 89 and 72% for the control, LN, MN and SN, respectively. There was no difference between the control and LN; however, these treatments were different from the MN and SN, which were also different from one another.

These results demonstrate that the MN and SN were effective in decreasing both rate and amount of forage consumed by adult horses.

Preference of Twelve Perennial Grass Pasture Mixtures Under Horse Grazing

To maximize forage use and promote uniform grazing, mixtures containing meadow fescue, Kentucky bluegrass, perennial ryegrass, and timothy should be planted in horse pastures in the North Central U.S.

Perennial grasses are the foundation of horse pastures in the North Central U.S. Horses are selective grazers, and recent research has shown that horses have a strong preference for Kentucky bluegrass, timothy, and meadow fescue. However, horse pastures are rarely planted to a single species. Planting mixtures is common; however, mixtures are rarely evaluated under horse grazing. The objective of this research, conducted at the University of Minnesota, was to evaluate horse preference of perennial grass pasture mixtures.

Research was conducted in 2011 and 2012 in MN. Four adult horses grazed eight commercially marketed and four experimental perennial grass pasture mixtures. Mixtures contained four to six of the follow species; orchardgrass, reed canarygrass, meadow fescue, Kentucky bluegrass, perennial ryegrass, smooth bromegrass, meadow bromegrass, timothy or festulolium. Individual plots were 1.8 x 6.0 m, and horses were given access to the entire plot area (37 x 22 m). Grazing was initiated when most grasses averaged 20 cm. Horses were allowed to graze the area for 5 days, averaging 4 hours of grazing each day. This grazing length was selected to achieve a minimum average residual height of 9 cm to avoid overgrazing. After grazing, manure was removed, plots were mowed to 9 cm and allowed to regrow. Horses were given ad libitum access to water, housed in a dry lot, and fed grass-alfalfa hay when not grazing. Immediately after grazing, plots were visually assessed for percent of available forage removal on a scale of 0 (no grazing activity) to 100 (100% of existing vegetation grazed to a 9 cm height) to determine horse preference.

Horses showed distinct preferences among the mixtures. Mixtures that included meadow fescue, Kentucky bluegrass, perennial ryegrass, and timothy were the most preferred with ≥86% of the forage removed by horse grazing. Deviating from this combination reduced horse preference. Simply adding orchardgrass to the most preferred mixtures reduced horse preference to 71%. Removing meadow fescue or Kentucky bluegrass and timothy from the most preferred mixtures and adding meadow bromegrass and/or orchardgrass resulted in the least preferred mixtures with a preference of 55%. This agrees with previous research that showed horses did not prefer orchardgrass or meadow bromegrass.

To maximize forage use and promote uniform grazing, mixtures containing meadow fescue, Kentucky bluegrass, perennial ryegrass, and timothy should be planted in horse pastures in the North Central U.S.

Authors: KL Martinson and CC Sheaffer

The Interaction of Grazing Muzzle Use and Grass Species on Forage Intake Of Horses: A Preliminary Study

Preliminary results suggest that the effectiveness of grazing muzzles in reducing herbage mass intake depends on the grass being grazed.

Excessive pasture intakes have been linked to the increase in incidence of equine obesity. Previous research with grazing ponies showed that grazing muzzles reduced pasture intake by 83%. However, horses are selective grazers, and forage grasses have different growth morphologies (i.e. upright and prostrate). Both of these factors could impact the effectiveness of grazing muzzles; however, this has not been researched. The objective of this experiment, conducted at the University of Minnesota, was to determine the effectiveness of grazing muzzles at reducing forage intake when horses were allowed access to different grass species.

Four adult horses, with a mean body weight of 460 kg were grazed in. Prior to grazing, horses were acclimated to wearing the grazing muzzle (Weaver, Mt. Hope, OH) and to grazing for the prescribed amount of time. Four species of perennial, cool-season grasses were grazed, including Kentucky bluegrass, meadow fescue, perennial ryegrass, and reed canarygrass. Kentucky bluegrass and meadow fescue were previously determined to be preferred by horses, while perennial ryegrass and reed canarygrass were less preferred. Kentucky bluegrass and perennial ryegrass have prostate growth habits, while meadow fescue and reed canarygrass have upright growth habits.

Horses were grazed in June and August of 2012 in St. Paul, MN. Horses were allowed to graze a small pasture (4.5 x 9.9m) for 4 hour each day for 4 consecutive days each month. On days 1 and 2, horses were given access to one grass species either with or without a grazing muzzle. On days 3 and 4, horse were given access to a different grass species either with or without a grazing muzzle. Prior to each grazing event, a 0.9 x 3.3 m strip was mechanically harvested from the pasture to determine available initial herbage mass. Post grazing, an adjacent 0.9 x 3.3 m strip was harvested to determine residual forage mass. The difference (on a dry matter basis) was used to estimate horse pasture intake. After grazing, manure was removed and pastures were mowed and allowed to re-grow.

Grazing muzzles decreased the amount of herbage mass consumed by 45, 38, 30, and 4% when horses grazed perennial ryegrass, Kentucky bluegrass, meadow fescue, and reed canarygrass, respectively. The combination of prostrate growth and low preference resulted in the greatest reduction in forage mass consumed when muzzled horses grazed perennial ryegrass. Although reed canarygrass had an upright growth habit, low horse preference resulted in a minimal reduction of forage mass consumed when grazed by muzzled horses.

These preliminary results suggest that the effectiveness of grazing muzzles in reducing herbage mass intake depends on the grass being grazed. This study will be continued in 2013.

Authors: EC Glunk, CC Sheaffer, MR Hathaway, and KL Martinson

Horse Prices and Seller Reasons from Sale Barns in Minnesota, Wisconsin and Texas

Research revealed that horse sale prices varied by location; however, economics were identified as the main reason for selling across all three locations.

The problem of unwanted horses in the U.S. has increased over the past several years. The general decline in the economy and increased cost of feed were recently identified as significant contributors to the unwanted horse problem. Anecdotal claims of horses being abandoned at sales barns also exist but have not been confirmed. The goals of this research, conducted by the University of Minnesota and Texas A & M University, were to document the prices of horses passing through sale barns and identify reasons consigners were selling the horse(s).

Horse sale barns in Minnesota, Wisconsin, and Texas were each visited 6, 5 and 5 times, respectively, from March 2012 to January 2013. Horse sale price, breed, age, and gender were collected, and consignees were asked to complete a short survey identifying the reason for selling. Reasons for selling were placed into four general categories: economics, failure to meet expectations, owner-related issues, and business was horse training/trading.

The average sale price of 512 horses sold at a Minnesota sale barn was $350 and ranged from $1,950 to free. The majority (29%) of horses sold were American Quarter Horses. The average sale price of 605 horses sold at a Texas sale barn was $698 and ranged from $4,800 to $10. The majority (41%) of these horses were American Quarter Horses. The average sale price of 845 horses sold at a Wisconsin sale barn was $916 and ranged from $5,500 to $10. The majority (64%) of horses sold were Standardbreds. Most of the Standardbreds sold at the Wisconsin sale barn originated from harness racing tracks and were sold to the Amish and Mennonite community as buggy horses.

Of all horses consigned (n=2,125), 6% were not sold due to failure of meeting a minimum price. During this time period, no horses were abandoned at the sale barns. Two-hundred seventeen consigner surveys were collected. Forty-one percent of consignees listed economic reasons (i.e. cost of feed, too many horses), 25% cited issues related to the owner (i.e. lost interest, illness), 18% were horse traders, and 16% indicated the horse failed to meet expectations as the primary reason for selling. Some consignees (n=83) had attempted to sell the horse privately, most commonly via the internet, and most sellers (93%) indicated they owned at least one additional horse.

This research revealed that horse sale prices varied by location; however, economics were identified as the main reason for selling across all three locations. This information will be used to develop educational efforts aimed at prospective horse owners, including costs of horse ownership and proper matching of horse and owner.

Authors: WJ Weber, SK Beeson2, J Wilson, DH Sigler, EC Glunk, JL Zoller, and KL Martinson

Investigating The Unwanted Horse Problem in Minnesota, Wisconsin, and Texas

Data indicates that early detection and intervention with humane cases and education focusing on the costs and responsibilities associated with horse ownership are key steps toward addressing the issue of unwanted horses.

The recent increase in the number of unwanted horses in the U.S. has gained national attention. Before education efforts can be developed and targeted, a better understanding of the scope and costs of the unwanted horse problem is necessary.

The goal of this project, conducted at the University of Minnesota and Texas A & M University, was to document factors and costs associated with unwanted horses in Minnesota, Wisconsin and Texas. From March through August 2012, the Minnesota Animal Humane Society (MN AHS) collected data on equine-related humane investigations, including live horses involved, carcasses found on-site, horses seized, other animals found on site and mileage associated with the investigations. Between March and May 2012, a Minnesota renderer collected data on number of horses rendered, breed, age, manner of and reason for death, and cost of rendering. From March through August 2012, four equine rescues located in Minnesota (n=2), Wisconsin (n=1), and Texas (n=1), collected data on number of horses rescued, adopted out, and euthanized, as well as costs associated with these horses. The rescues also provided a summary of fundraising and marketing efforts. Data collection continued through February 2013.

The MN AHS investigated 53 properties, involving 349 live horses. Of the live horses investigated, 28 were seized. The investigations uncovered 2 equine and 1 bovine carcasses, and other animals present on the properties included dogs, cats, llamas, donkeys, poultry, small ruminants, and cattle. Humane agents logged 4,297 miles investigating these cases at a cost of $2,389 (federal reimbursement rate of $0.556/mile).

The renderer picked up 37 equine carcasses. The average age of rendered horses was 18 years, and the dominant breed was the Quarter Horse (n=20). A majority of the horses were chemically euthanized (n=32), and injury and advanced age of the horse were the two most common reason given for euthanasia; however, this information was not always available. Two horses were euthanized due to being unwanted. The average cost of rendering was $168 per horse.

Combined, the four rescues took in 89 horses, of which 7 were returned from previous adoptions. Ten of these were euthanized. Of the remaining horses (n=79), 21 were placed into foster homes, 35 were adopted, 3 were transferred to another rescue; the rest were kept onsite. The average cost for euthanasia was $237; however, some rescues received discounts from veterinarians. On average, rescues invested $285 per horse in veterinary and shipping costs. Rescues listed a number of methods to raise funds and improve adoptability of horses, including trainers' challenges, social media, and newspaper stories.

This data indicates that early detection and intervention with humane cases and education focusing on the costs and responsibilities associated with horse ownership are key steps toward addressing the issue of unwanted horses.

SK Beeson, WJ Weber, JH Wilson, DH Sigler, EC Glunk, and KL Martinson

The Effect of Steaming on Dust Concentrations in Hay

Results indicate that steaming represents a viable management strategy for reducing dustiness in hay containing elevated dust levels.

New management strategies for feeding horses with respiratory disease include steaming hay prior to feeding to reduce dustiness; however, little is known about the effectiveness of this practice.
The objective of this study, conducted at the University of Minnesota, was to determine the effect of steaming on dust concentrations in hay. Dust levels of two alfalfa-orchardgrass hays (low mold [LM] and moderately moldy [MM]) were measured pre- and post-steaming using a commercial hay steamer (The Professional Hay Steamer; Happy Horse Products, Ltd., Palmyra, VA). Prior to steaming for 90 minutes, one flake (1.70 ± 0.23 kg, DM) was removed from the center of each bale (control or non-steamed flake), and the remaining hay was re-tied. Dust content of the control flake was measured while the bale was steamed. After steaming, one flake of steamed hay (1.56 ± 0.34 kg, DM), was removed from the center of the bale, and dust content was measured. To measure dust, each flake was placed inside the drum of an electric cement mixer with two lead weights (3.0 kg) to encourage agitation of the hay. The cement mixer operated at 20 rpm, and total suspended particulate (TSP) levels were measured at the mouth of the drum using a tapered element oscillating microbalance sampler (1400a; Thermo Fisher Scientific, Waltham MA). Instantaneous TSP concentrations were recorded every 60 sec for 30 min. Measurements were averaged over 30 minutes; and the average expressed on a weight (kg) basis.

Initial dust content measurements were different between the two hays; 758 and 406 µg/m3 per kg DM for MM and LM, respectively. Steaming reduced the dust content of the MM hay to 345 µg/m3 per kg DM; however, dust content in the LM hay was not significantly affected by steaming (257 µg/m3 per kg DM).

Limited data is available regarding typical, or acceptable, concentrations of dust in feedstuffs commonly fed to horses. However, steaming of the MM hay reduced dustiness to levels comparable to the LM hay, which was considered an acceptable hay for horses. Additional research needs to determine acceptable levels of dust; until then, results from this study indicate that steaming represents a viable management strategy for reducing dustiness in hay containing elevated dust levels.

Authors: JE Earing, CC Sheaffer, BP Hetchler, LD Jacobson, JC Paulson, MR Hathaway and KL Martinson

Pasture Best Management Practices on Horse Farms in MN and WI

Data suggests that farm owners are aware of some recommended pasture best management practices for horse farms, but practices are not fully or consistently implemented.

A well-managed horse pasture can reduce environmental impacts from erosion and runoff and can promote overall horse health by providing constant access to forage. The objective of this project, conducted at the University of Minnesota, was to determine what pasture best management practices (BMPs) were being used on horse farms in Minnesota and Wisconsin.

Data was collected from 26 horse farms that were enrolled in the University of Minnesota Pasture Management Program. Best management practices evaluated at each farm included the use of a sacrifice lot, rotational grazing use, percent ground cover, soil nutrient management, weed control, and manure storage.

Of the 26 enrolled farms, 22 were used for personal recreation, two for therapeutic riding facilities, and two were boarding facilities. Five farms had been purchased recently and had no existing pasture or horses on site; these farms were not included in the summary of data.

Of farms with existing pastures (n=21), the average number of acres allocated to pasture was 10. The average number of horses per farm was 5, resulting in a stocking density of 2 acres per horse. Seventeen farms had designated sacrifice lots. The average pasture ground cover was 88% with Kentucky bluegrass, smooth bromegrass and reed canarygrass being the predominant grasses. Three farms had used herbicide for weed control in the last three years; however, none of the farms utilized mowing as a weed control strategy. Fourteen pastures contained weeds listed as noxious weeds with Canada thistle being most prevalent, and two pastures contained plants poisonous to horses. Six farms used some form of rotational grazing, and 10 farms exhibited signs of overgrazing. Nine farms stockpiled their manure, while 7 farms had no manure management plan and essentially did "nothing" with their manure. Only 2 farms were aware of manure storage regulations. Running water (i.e. streams) or wetlands were found in, or adjacent to, pastures on 9 farms. Only 1 farm had soil sampled and fertilized previously, and soil analysis indicated that fertilization for at least one of the three primary macronutrients (nitrogen, phosphorus, potassium) was necessary on all farms.

This data suggests that farm owners are aware of some recommended pasture BMPs for horse farms, but practices are not fully or consistently implemented.

Authors: SL Privatsky, JE Earing, JA Lamb, CC Sheaffer and KL Martinson

Foal Weight Gain on Pasture

A positive relationship was identified between foal average daily gain (ADG) and rainfall, suggesting ADG's will be higher during periods of greater rainfall.

Researchers from the University of Kentucky have shown that pasture growing conditions can influence average daily gain (ADG) in foals.

A group of 320 Thoroughbred foals were regularly weighed between birth and weaning. Estimates of ADG were calculated for all foals at 3 or 4 months of age in May, June, July, and August. During these months, foals (and mares) were kept on predominantly cool-season grass pastures. Information on daily rainfall was also collected.

A positive relationship was identified between ADG and rainfall, suggesting ADG's will be higher during periods of greater rainfall. Results showed that ADG was within or above suggested ranges during May, but below ranges during June, July, and August. Higher rainfall, paired with the cooler temperatures of May likely increased pasture growth, nutrient availability, and subsequent foal ADG. However, in later summer months, ADG was below expected rates, suggesting supplementation may be necessary when pasture growth is depressed due to weather conditions.

Summarized by: Jennifer Earing, PhD, Univ. of Minn.

Thursday, June 6, 2013

Social Separation and Training

There were no significant differences between singly trained mare and mares trained in pairs.

The intensity with which a horse responds to separation from its group and subsequently to being alone is relevant for both horse and handler safety. Identification of training methods that may reduce responses to separation would be useful in practice. The objective of this research, conducted at the Swedish University of Agricultural Science, was to investigate whether the initial presence of a familiar companion horse modifies responses to separation from the group, lowers stress levels (as measured by heart rate) and increases training efficiency. Researchers hypothesized that habituation to separation proceeds more quickly if the horse is first trained with a companion, and heart rate is lower when the horse is subsequently trained alone, compared to control horses trained individually from the start.

Young mares, kept in groups of 4, were exposed to social separation: 2 horses of the group were trained singly and the remaining 2 horses were trained first with a companion and then alone. The training comprised of three steps whereby distance from the group was gradually increased. The final learning criterion was met when a horse fed calmly alone inside a test arena. Horses that were trained in a pair had to succeed in the final learning criterion (feeding calmly alone inside a test arena) together before they repeated the steps alone. Feeding behavior and heart rate were recorded.

There were no significant differences between singly trained mare and mares trained in pairs, indicating that the initial pair-training did not reduce stress responses in pair trained horses. However, heart rate was significantly lower when horses were trained in pairs compared to when the same horses were subsequently trained alone.

It may not be efficient to habituate naïve young horses to social separation initially with a partner as these horses appear to have to relearn being in the test situation alone when switching to the individual training method.

Summarized by Krishona Martinson, PhD, Univ. of Minn.

Tuesday, April 30, 2013

Adding Supplements to Water

Adding supplements or electrolytes to water can decrease intake in horses.

A 1,000 pound horse should drink about 8 to 10 gallons of water each day. In order to encourage horses to drink, especially when away from home, owners frequently "flavor" (i.e. peppermint) their water; however sometimes electrolytes or supplements are added, which are different than flavors. The objective of this study, conducted by Land O'Lakes Purina, was to test the hypothesis that horses decrease water intake when supplements or electrolytes are added to water.

Six mature horses were offered both plain water and water with one of 4 different supplements. Additives included 2 electrolyte preparations (Farnam Apple Dex and Land O'Lakes Calf electrolyte), a vitamin/mineral (Farnam Red Cell) additive, and a joint additive (Finish Line Fluid Action). All additives were offered at a rate of 28 g per 5 gallons of water. Water intake from buckets was recorded via weight and replenished at 7:00 am and 6:00 pm each day. Horses were fed the same diets, had unlimited access salt, and were housed individually.

There was an effect of adding supplements and electrolytes to water as horses preferred plain water with a mean daily intake of 3 gallons versus 1 gallon for supplement or electrolyte water; horses drank over twice the amount of plain water compared to supplement or electrolyte water. There was no difference within the additive treatments for water intake. There was a trend for water intake to be affected by time of day, with the greatest volume consumed overnight. This trend may have been influenced by timing of water weighing and replenishment, and/or housing management conditions.
Adding supplements or electrolytes to water can decrease intake in horses. This may lead to dehydration, poor performance or other adverse health effects in horses. If planning to add supplements or electrolytes, acclimate the horse before traveling or placing the horse in a stressful condition.

Summarized by Krishona Martinson, PhD, University of Minnesota

Thursday, April 4, 2013

Microchip Identification

The objectives of a study conducted at Pennsylvania State University were to characterize the inflammatory response after microchip insertion, evaluate pain response and swelling at the microchip insertion site, and measure migration of the microchips.

The inflammatory process during insertion and occurrence of migration are major concerns of horse owners when determining the usefulness of microchip identification. The objectives of a study conducted at Pennsylvania State University were to characterize the inflammatory response after microchip insertion, evaluate pain response and swelling at the microchip insertion site, and measure migration of the microchips.


Eighteen mature Quarter Horse mares were assigned randomly to three treatment groups. The microchip group (n = 7) had microchips inserted using a sterile needle and syringe; the "sham" group (n = 7) had a needle inserted but no microchip; and the control group (n = 4) had no insertion. The insertion site was visually determined by a veterinarian to be within the nuchal ligament on the left side of the horse, with a transverse position halfway between withers and poll, and dorsal position several centimeters below the crest of the neck.


The inflammatory response was measured over a 2-week period by measuring dermal temperature, response to pressure and swelling at the insertion site, and plasma serum amyloid A (SAA). SAA is expressed in response to inflammatory stimuli.
For the migration component of the study, radiographs of the seven microchipped horses were taken over 6 months after insertion. These radiographs allowed measurement between a select vertebral point and the microchip.


The microchip and sham insertion did not cause a detectable increase in temperature. Algometer readings, used to quantify pressure necessary to induce a pain threshold response, indicated that microchip insertion area was more sensitive than sham insertion at 2 hours on day 1, and day 3 post insertion. Visible swelling began 2 hours post-insertion and resolved by day 3. SAA concentrations were affected by day following insertion, but not by treatment group. Increases in SAA concentration could not be matched with local insertion reactions. Migration was not detected in any of the horses during the 6 months.
Microchip identification is a viable alternative form of identification for equids. It does not cause excessive inflammation or continued tissue irritation after insertion. It also does not migrate if implanted within the nuchal ligament on the left side of the horse halfway between the withers and poll.


However, it may be important to continue to assess the microchips for migration in young growing animals. For some breed registries, identification has to be obtained on registration, so microchip insertion will have to be performed at less than 1 year of age. Although the microchip may not actually be moving, the development of the tissues around the microchip could put it in a different position than anticipated. Future studies should investigate ideal location as affected by age for microchip insertion.


Summarized by Krishona Martinson, PhD, University of Minnesota


Monday, April 1, 2013

Grazing Muzzles

Grazing muzzles are an effective means of restricting pasture intake by ponies.

Grazing muzzles can be used to reduce pasture intake and are alternatives to isolating horses in dry lots and stalls. There is limited information on the extent of intake restriction imposed by grazing muzzles. Therefore the objective of this study, conducted by researcher in England, was to quantify the effect of wearing a grazing muzzle on forage intake by ponies.

Four mature ponies were used for this study. Pasture intakes were measured on four, 3 hour occasions per pony when fitted with a muzzle or grazing without a muzzle. Pasture intake was determined by change in body weight after grazing.

Pasture intakes were significantly reduced when ponies were fitted with a grazing muzzle. Ponies averaged 1 pound of forage per 3 hours with grazing muzzles compared to 7 pounds of forage per 3 hours without a muzzle, representing a 83% reduction in pasture intake for ponies wearing grazing muzzles compared to those without. Pasture dry matter intake by ponies without grazing muzzles averaged 0.8% body weight during the 3 hours, which is equivalent to one half to two-thirds of the recommended daily energy requirement.

This evidence suggests that grazing muzzles are an effective means of restricting pasture intake by ponies.

Summarized by Beth Allen, University of Minnesota

Hay Steaming

Steaming represents a management strategy for reducing dust and mold levels and increasing dry matter intake in some hays. However, steaming should not replace the main goal of feeding good quality (i.e. low in dust and mold) hay.

Management strategies for horses with respiratory disease include soaking hay prior to feeding. Hay steaming is an alternative to this practice; however, little is known about its impact on forage nutritive values or intake. The objective of a study recently conducted at the University of Minnesota was to determine the effect of steaming on forage quality and intake by horses.

Two alfalfa orchardgrass mixed hays were evaluated: a low and moderately moldy hay. Each day, one bale of each hay was steamed for 90 minutes using a commercial hay steamer (Happy Horse Products). Two flakes of steamed or un-steamed low or moderately moldy hay were offered simultaneously to six adult horses in individual hay nets (thee horses per treatment). Horses were fed for 5 days and then switched hay types for 5 additional days. Horses were allowed access to hay for 2 hours and dry matter intake was calculated. Flakes of un-steamed or steamed hay were also agitated in an electric cement mixer, and dust concentrations were recorded every min for 30 minutes using a tapered element oscillating microbalance (TEOM) sampler.

Steaming increased hay moisture and therefore reduced dry matter to 77 and 71% for low and moderately moldy hay, respectively. In both low and moderately moldy hay, steaming reduced phosphorus content. Steaming reduced water soluble and ethanol soluble carbohydrate content by 13% and 27%, respectively, for moderately moldy hay, but had no effect on low mold hay. Steaming reduced mold levels in both hays. Dust concentrations of moderately moldy hay were reduced by 55%; however, dust levels in low mold hay were not affected by steaming . Dry matter intake of low mold hay was increased by steaming; however, dry matter intake of moderately moldy hay was not affected by steaming.

For hay with low mold levels, steaming decreased mold levels, increased dry matter intake of the hay, but had no effect on dust level. In moderately moldy hay, steaming reduced mold and dust levels, but did not improve dry matter intake. Steaming represents a management strategy for reducing dust and mold levels and increasing dry matter intake in some hays. However, steaming should not replace the main goal of feeding good quality (i.e. low in dust and mold) hay.

Co-authors: J. Earing, PhD, M. Hathaway, PhD, C. Sheaffer, PhD, B. Hetchler, L. Jacobson, PhD, and J. Paulson, University of Minnesota and Tennessee Farmers Cooperative.





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