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Extension > Horse Extension - Research Updates > August 2013

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
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