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Extension > Horse Extension - Research Updates > September 2013

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
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