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Extension > Horse Extension - Research Updates > November 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.
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