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Extension > Horse Extension - Research Updates > 2015

Monday, March 30, 2015

Tendon Boots and Temperature

The application of bandages and tendon boots to the lower limb of horses is widespread and performed for many reasons. Tendon boots are used in training and are applied during some horse competitions. Bandages and tendon boots are supposed to support the anatomic structures, reduce the maximum extension of the fetlock joints and protect the limbs from fractures and trauma; however, there is little scientific data to support their value except in protection against direct trauma.

The objective of this research, conducted by researchers in Austria, was to determine the skin temperature of the cannon bone in horses associated with the use of bandages and tendon boots, compared with the bare limb, at rest and after 20 minutes of lunging.

Skin temperatures at rest were not different with a bare limb, bandage, or tendon boot. Average skin temperatures ranged from 57 to 59°F. Skin temperate of the bare cannon bone after exercise did not increase and remained at 57°F. Skin temperature of the cannon bone in horses increased during exercise when a bandage or tendon boot was used. Skin temperatures under the bandage and tendon boot were 77°F and 70°F, respectively, after exercise.

The authors speculate that both a bandage and a tendon boot accelerate the warmup phase of exercise by increasing the skin temperature. Moderate warmup exercise increases blood flow in tissues, which can help to reduce the risk of injuries. It is not known whether heavy exercise performed with limb bandages or tendon boots is detrimental because of accumulation of heat in the limb and underlying structures. Further research should focus on the effects of warmup and maximum exercise on the temperature of other anatomic structures such as tendons.

For more information, click here. Summarized by: Krishona Martinson, PhD, University of Minnesota.

Selenium Toxicity

Horses are very susceptible to chronic selenium toxicity (selenosis) if grazed on forages grown on high selenium soils for prolonged periods. Selenium toxicity from soils is mostly an issue in the Western U.S.; however, horses on multiple supplements containing selenium can be affected by selenium toxicity. Clinical signs of selenium toxicity include dysplastic or corrugated hoof lesions (see photo), dull hair coat, mane and tail alopecia, and varying lameness with severe cases resulting in untreatable hoof necrosis and sloughing resulting in euthanasia. In this study, conducted by researchers in Utah, mane and tail samples from horses that exhibited classical hoof lesions of chronic selenosis were analyzed.

The horses had grazed for 6 months, from approximately May 15 until November 15, each year for three grazing seasons in a pasture containing forage and water sources with elevated selenium concentrations.

The segmented hair samples showed a cyclic pattern in selenium concentrations in the mane and tail, which corresponded to entering and exiting the contaminated pasture. The selenium concentration in the tail of one horse could be traced for three grazing seasons.

These results demonstrate that in some cases, hair samples can be used to determine selenium exposure in horses for up to 3 years post-exposure. For more information, click here.

Summarized by Krishona Martinson, PhD, University of Minnesota

Magnetic Blankets

Static magnetic blankets often claim to increase blood flow, reduce muscle tension and tenderness, and be beneficial in both prevention and treatment of musculoskeletal injuries in horses. However, there are no studies that confirm the beneficial effects of magnets on muscles of the back in healthy horses.

Research in Sweden set out to investigate whether static magnets sewn into a blanket affect back muscle blood flow, skin temperature, mechanical nociceptive threshold and behavior in healthy horses.

Ten healthy adult horses were evaluated for blood flow by photoplethysmography, skin temperature by use of thermistors in conjunction with digital infrared thermography, and mechanical nociceptive threshold by algometry. Horse behavior was filmed during the procedure and scored on an ethogram. Measurements were performed repeatedly for 30 minutes to establish a baseline. Thereafter, a blanket with active, static magnets (900 gauss) or placebo magnets was placed on the horse and measurements were performed for a 60 minute treatment period and a 30 minute post treatment period.

Blood flow in muscle, skin temperatures, mechanical nociceptive thresholds and behavioral traits did not differ between active and placebo magnetic blankets. Skin temperature increased similarly during both active and placebo blanket treatment.

 In healthy horses, magnetic blankets did not induce additional effects on muscle blood flow, skin temperature, mechanical nociceptive threshold and behavior when compared with nonmagnetic blankets.

For more information on this research, click here.  Summarized by: Krishona Martinson, PhD, University of Minnesota

Bedding Materials

It can be a challenge to find suitable horse bedding materials that provide higher moisture absorption, acceptable animal comfort, good fertilizer values, and improve indoor environmental quality.

 Researchers at North Dakota State University set out to determine the water absorption capacity of two bedding materials, flax shive (a newer bedding material) and pine wood shavings which are commonly used by equine facilities. The second objective was to measure ammonia, hydrogen sulfide, and greenhouse gas concentrations emitted from stall surfaces bedded with both materials. 

 The water absorption capacity of bedding materials were measured at 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 hours in a laboratory. A total of eight horses were used for a 14-day study period. Of these, four horses were bedded with flax shive and the other four were bedded with pine wood shavings for week 1. During week 2, the bedding materials were switched between the two groups. Ammonia and hydrogen sulfide were measured in the stalls. Greenhouse gas measurements were collected 6 inches above the bedded stall surface.

The size of pine wood shavings were much larger than flax shive. The smaller particle size might be a precursor of dust, which was noticed in the stalls bedded with flax shive. The water absorption capacity of flax shive was 56% greater than the pine wood shavings when soaked for 24 hours. There were no differences in ammonia, hydrogen sulfide, and greenhouse gas concentrations between the two bedding materials. Mean nutrient content was similar between both fresh bedding materials, except for phosphorous and potassium. As expected (due to the addition of manure and urine), the nutrient content between fresh and soiled bedded samples for each bedding material were different. Total phosphorus and potassium contents of soiled pine wood shavings bedding were approximately 7 and 20 times higher, respectively, than those of fresh pine wood shavings bedding material. Total nitrogen and total phosphorous contents of bedded flax shive were approximately twice than those of fresh flax shive.  

Flax shive shows potential as a new bedding source for use in horse stalls. For more information, click here

 Summarized by: Krishona Martinson, PhD, University of Minnesota.

Managing Laminitis

Excessive bodyweight has become a major health issue in the equine industry. Obesity can contribute to other diseases, including Equine Metabolic Syndrome, laminitis and insulin resistance. Therefore, researchers from Auburn University recently explored methods of rehabilitation used to manage obese horses with laminitis.

 Clinical data from 14 similar laminitis cases were analyzed to evaluate responses to rehabilitation after 5 to 20 months of treatment. Each horse presented as obese and laminitic with no history of a systemic inflammatory disease. The rehabilitation method emphasized a mineral-balanced, low nonstructural carbohydrate diet; daily exercise; hoof trimming that minimized hoof wall loading; and sole protection in the form of rubber hoof boots and/or hoof casts.

 Coffin bone (distal phalanx) alignment within the hoof capsule was improved, and hoof wall thickness was decreased following treatment. Solar depth was also increased. Reduction of heel (palmar) angle measurements was detected in acutely and chronically affected horses. This treatment effect was greater for horses with chronic laminitis than for horses with acute laminitis. Horses were 5.5 times more likely to be sound post-treatment than before treatment.

 Daily exercise, dietary modification, and removal of ground reaction force from the hoof wall were focuses of the rehabilitation program. Hoof care and husbandry as applied to these horses may be an effective method of rehabilitation of horses from obesity-associated laminitis.

 Summarized by Krishona Martinson, PhD, University of Minnesota.

Weeds Commonly Found in Drylots

Laminitis (or founder) is a devastating, painful condition for horses leading to losses in performance, increased veterinary costs, and even death. Diets high in nonstructural carbohydrates are a known trigger for laminitis. Horses that are easy keepers, or overweight, are also at a greater risk of developing laminitis and tend to be classified as having equine metabolic syndrome. Some of the most effective management tools for horses prone to laminitis are to limit their nonstructural carbohydrate intake by testing forage for nonstructural carbohydrate content, restricting amounts of feed to encourage weight loss, and confining to dry lots (i.e. dirt paddocks) in order to avoid access to pasture grasses that are commonly high in nonstructural carbohydrates and digestible energy (i.e. calories).   

Researchers have recommended a total diet (i.e. hay, grain, supplements, treats) of less than 12% nonstructural carbohydrates for horses diagnosed with laminitis or equine metabolic syndrome. However, recent reports from horse owners indicate horses housed on dry lots are still experiencing recurring bouts of laminitis, despite being fed a low nonstructural carbohydrate diet. Weeds that commonly grow in dry lots may be both palatable to horses and high in nonstructural carbohydrates; therefore, capable of triggering a laminitis episode. The objective of this research, conducted at the Univ. of Minn., was to determine nonstructural carbohydrate content of weeds commonly found in dry lots housing horses or ponies with a history of laminitis.   

During the summer of 2013, 10 farms in Minnesota and Wisconsin were visited three times (spring, summer and fall), and up to four weeds growing in dry lots housing laminitic horses or ponies were collected. Samples were sent to a forage testing laboratory and analyzed.    

Twenty-seven different weed species were collected. The 6 most common weed species included prostrate knotweed, plantain, redroot pigweed, common ragweed, cinquefoil, and purslane. The average nonstructural carbohydrate content of the weed species varied with plantain have the highest and prostrate knotweed the lowest. There were no differences in nonstructural carbohydrate content within weed species across farms; however, nonstructural carbohydrate content was higher during the fall. It is common for plants to have higher nonstructural carbohydrate contents in the fall due to weather conditions. Most plants continually produce nonstructural carbohydrates during the day and utilize them at night. However, plants essential shut down during cool nights and therefore do not utilize nonstructural carbohydrates which contribute to higher levels commonly observed in the fall.

The average nonstructural carbohydrate content of plantain, cinquefoil and ragweed was greater than the maximum 12% total diet recommendation for horses diagnosed with laminitis or equine metabolic syndrome. However, the maximum amount of nonstructural carbohydrate content exceeded this recommendation for all weed species. Nutritive analysis of other components indicated the weeds would be palatable to most horses, especially ones housed in a dry lot on a restricted diet (i.e. horses who might feel hungry). All weed species were relatively low in structural carbohydrate components and high in crude protein. Combined, these results have proven to increase palatability; therefore, it is not surprising the horses consumed the weeds. 

 Although this research did not directly link the ingestion of weeds to laminitis, the wide range of nonstructural carbohydrate content within the weed species suggests horse owners should control weeds in dry lots, especially if used to house laminitic horses and ponies.  

This project was sponsored by a grant from the Minnesota Horse Council. Authors: D. Gunder and K. Martinson, PhD, Univ. of Minn. and J. Wilson, DVM, MN Board of Vet Med.


Bodyweight Estimation

Excessive bodyweight has become a major health issue in the equine industry. The objectives of the study, conducted at he University of Minnesota, were to determine if the addition of neck circumference and height improved existing bodyweight estimation equations; develop an equation for estimation of ideal bodyweight; and develop a method for assessing the likelihood of being overweight in adult equines.

In 2011, 629 adult horses and ponies were measured and weighed at two horse shows in Minnesota (WSCA Champ Show and State 4-H Horse Show). Personnel assessed body condition score (BCS) on a scale of 1 to 9, measured wither height, body length from the point of shoulder to the point of the buttock, neck and girth circumference, and bodyweight using a livestock scale. Individuals were grouped into breed types and equations for estimated and ideal bodyweight were developed. For estimated body weight, the model was fit using all individual equines. For ideal bodyweight, the model was fit using only individuals with BCS of 5. Breed type, height and body length were also considered as these measurements are not affected by fat deposits. Finally, a bodyweight score to assess the likelihood of being overweight was developed and standardized using horses with a BCS of 5.
Breed types included Arabian, stock and pony. Mean BCS was 5.6.  Bodyweight (lbs) was estimated by taking girth (in)1.486 x length (in)0.554 x height (in)0.599 x neck (in)0.173/119 (Arabians), 119 (ponies) or 114 (stock horses). Ideal body weight (lbs) was estimated by taking length (in) x 15.65 + height (in) x 23.47 – 1,344 (Arabians), 1,269 (ponies) or 1,333 (stock horses).
Equines with a BCS of ≥ 7 had a greater likelihood of being overweight and the model suggested cutoffs at the 48th and 83rd percentiles for underweight and overweight horses, respectively. In conclusion, body measurements were successfully used to develop equine bodyweight-related equations.

To encourage use of the equations, the research team developed a mobile app for Apple and Android operating systems. Users enter the body measurements and the app calculates estimated and ideal bodyweight and a bodyweight score.

 Information on the “Healthy Horse” app can be found here.   For more information on this research, click here

 Summarized by Krishona Martinson, PhD, University of Minnesota

Equine Neglect Investigations

Every state in the US has regulations prohibiting acts of neglect and cruelty against animals. Local law enforcement and animal control agencies are responsible in many communities to enforce these statutes. As society’s perception of horses has changed from their origin as livestock to companion animals in modern times, owners have transitioned their care and management.  

 The goal of this study, conducted at the University of California Davis, was to identify the role and capacities of local animal control services in the US that investigate equine neglect, cruelty, and abandonment investigations, and to identify challenges and outcomes of the investigations.

 A 128-question on-line survey was accessible for animal agencies to complete. A total of 165 respondents from 26 states completed all or the majority of the questions. A total of 6864 equine investigations were initiated between 2007 and 2009 by 90 agencies, which extrapolates to 38 investigations annually per agency. A typical agency has an average annual budget of $740,000, employs 7 animal control officers, and spends about $10,000 annually on equine cases. Neglect was ranked as the most common reason for investigation. Owner ignorance, economic hardship and lack of responsibility were the highest ranked causes of neglect and cruelty. Individual cases were provided by 91 agencies concerning 749 equines. The physical condition of the horse was the primary factor of investigation, and low body condition, parasite infestation, and compromised dental condition were present in most seized horses.

 Over half of the equine owners previously had been investigated or charged with neglect or cruelty of animals or were identified with cruelty or abuse offenses to people. Less than 3% of the cases advanced to adjudication, and these were likely to be decided by a judge rather than a jury. Judgments of guilty verdicts and pleas were nine times more common than acquittal.

 Challenges for equine investigations cases included lack of funding, limited availability of facilities for horses, and providing educational materials for horse owners to aid in prevention and resolution of neglect cases.

 Summarized by Krishona Martinson, PhD, University of Minnesota


Stress During Transport

Acupuncture has been shown to have the beneficial effect of reducing stress responses in animals and humans. Pharmacopuncture is the injection of subclinical doses of drugs into acupoints to give therapeutic results without side effects. This study, conducted by researchers in Brazil, compared the effects of injecting the usual dose of acepromazine (ACP; 0.1 mg/kg, intramuscularly [I.M.]) with those of pharmacopuncture (1/10 ACP dose at the governing vessel 1 [GV 1] acupoint) on the stress responses of healthy horses undergoing road transport for 2.5 hours.

 Four different treatments were applied immediately before loading, with 8 animals/treatment: injection of saline or ACP (0.1 mg/kg, I.M.) at the base of the neck; and injection of saline or 1/10 ACP (0.01 mg/kg) at the GV 1 acupoint.

 The road transport increased heart rate (HR), respiratory rate, body temperature, and serum cortisol of the untreated horses (injected with saline at the base of the neck). Pharmacopuncture at GV 1 reduced the average HR and transport-induced increase in HR at unloading, without changing the other variables. On the other hand, ACP (0.1 mg/kg) produced significant sedation and reduced the transport-induced increase in respiratory rate but without preventing the stress-induced increase of cortisol.
Other acupuncture points and drugs should be tested to verify the beneficial effect of this therapy to reduce stress in horses during road transport.

 Summarized by: Krishona Martinson, PhD, University of Minnesota



Teff Grass for 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

Equine Shade Preference

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

Risk Factors Affecting Horses Welfare

Horses are used for a wide variety of purposes, from being used for recreational purposes to competing at an international level. With these different uses, horses have to adapt to numerous challenges and changes in their environment, which can be a challenge in continuously safeguarding their welfare. The objective of this study, conducted in the Netherlands, was to assess the prevalence of health disorders with clinical examination and identify possible risk factors of health disorders affecting horse welfare in horses in the Netherlands.

 With the use of fixed protocols for recording health aspects in horses, 150 horse farms voluntarily participating in the study were evaluated by trained assessors. On each farm, 20 horses were clinically examined; in total, almost 3,000 animals. The study recorded (based on clinical examinations) information on the respiratory system (abnormal breathing: 1%, coughing: 1%, nasal discharge: 2%), body condition (19% were fat and 6% were in poor body condition), locomotion (14.5% exhibited irregularity of locomotion and 5% were lame), back palpation (23% had a light response and 8% had a moderate to severe response), mouth (irregularities on mouth corners were found in 3%, while 3% had bars), and ocular discharge was found in 12%.

 Statistical analysis found several risk factors for health aspects. Horses used for instruction (i.e. riding lessons) were almost two times more at risk to develop moderate to severe back pain compared to horses used for recreation or for competition. Horses used for instruction, breeding, or recreation all had a higher risk for irregular locomotion or lameness compared to competition horses. Horses used for recreation were more prone to have a higher body condition score compared to horses used for breeding and instruction.

These results may provide the basis for horse welfare and health programs on farm in the Netherlands and beyond. With the development of a valid welfare monitoring system for the horse industry, the welfare of horses can be increased through improving awareness and changes in management.

 Summarized by: Krishona Martinson, PhD, University of Minnesota


Bandaging, Healing, and Proud Flesh

Many horse owners fear limb injuries, not only because of potential lameness issues, but because of the intense care that usually accompanies them. Recently, two studies investigated the use of different ointments and/or bandaging strategies in wound healing and granulation tissue (i.e. proud flesh) formation in limbs.

Researchers in Virginia set out to determine whether povidone iodine ointment or two forms of silver sulfadiazine applied topically to wounds on horse limbs affected the rate healing and the influence of bandaging on proud flesh formation. Six healthy adult horses were used. Six standardized skin wounds per horse were distributed between the dorsomedial surfaces of the metacarpi and metatarsi. One of the following 6 treatments was applied to each wound: 1% silver sulfadiazine cream with bandage, 1% silver sulfadiazine slow-release matrix with bandage, 1% silver sulfadiazine slow-release matrix without bandage, povidone-iodine ointment with bandage, untreated control with bandage, and untreated control without bandage. Wound area, proud flesh area, and perimeter were measured using digital images, and proud flesh was removed when present. Days until healing, rate of healing, rate of contraction, and epithelialization were compared among wound treatment groups.

Healing parameters did not differ among any of the wound treatment groups. All bandaged wounds produced proud flesh tissue, which was surgically removed; none of the un-bandaged wounds produced proud flesh tissue. When the proud flesh tissue was removed, rates of healing were not different among wound treatment groups, whether bandaged or un-bandaged.

In a separate study, researchers from Australia came to a similar conclusion. Their objective was to evaluate the effect of a non-occlusive dressing incorporated in a 3-layer bandage on limb would healing. Seventeen horses were bandaged with a non-occlusive dressing covered by gauze-coated cotton wool that was compressed with adhesive tape, while 16 horses were left un-bandaged. Standardised wounds were made on the skin overlying the dorsomedial aspect of the mid-metacarpus. Wounds were photographed weekly for nine weeks and the images were analyzed electronically.

There were significant effects associated with bandaging. In bandaged wounds, proud flesh tissue required regular trimming, but not in un-bandaged wounds. There was no difference between groups in the total days to healing or the overall rate of healing. If excessive granulation tissue was excised regularly, bandaging had no effect on total time to healing.

Both studies concluded that bandaging limb wounds resulted in the formation of proud flesh. However, if the proud flesh was removed, bandaging (or not bandaging) had no effect on total time to healing.

Summarized by: Krishona Martinson, PhD, Univ. of Minnesota


Ideal Weight Load

Recently, there has been considerable discussion regarding the ideal weight load (rider and tack) of horses and ponies. In a recent study conducted at Kitasato University in Japan, researchers aimed to determine the load capacity of a trotting Taishuh pony by gait analysis using a motion analysis system.

 Seven Taishuh ponies (5 mares and 2 geldings) and their rider were fitted with a marker and recorded by 2 high-resolution digital DVD cameras as they were trotting along a straight course. Each horse performed 7 tests: 2 tests with 154 pound loads and 5 tests with random weights between 176 and 265 pounds. Among ponies, symmetry in the 265 pound test was significantly lower than that in the 154 pound test, and stabilities during the 220 and 265 pound tests were significantly less than that in the 154 pound test. The time lag between the time series of horse and rider in the 265 pound test was significantly greater than that in the 154 pound test.

 These results suggests that the maximum permissible load weight of the Taishuh pony at a trot over a short distance is less than 200 pounds, which is 43% of the bodyweight of the pony.

 Although other research has shown that horse can safely carry up to 30% of their body weight, it s generally accepted that a horse can carry up to 20% of their body weight. However, there are other factors than just weight that impact how much weight a horse or pony can carry, including conformation of the horse, the horse's fitness level, rider fitness, and rider ability level. For example, a fit horse with ideal conformation can carry more weight if the rider is also fit and well balanced.

 Summarized by: Krishona Martinson, PhD, University of Minnesota


Wednesday, March 25, 2015

Herd Rank in Young Horses

Researchers in the Czech Republic recently studies the factors influencing dominance position in young horses, with emphasis on the role of the mother. Horses form stable linear dominance hierarchies based on agonistic interactions. Higher dominance positions are believed to be connected, in both genders, to better condition and higher reproductive success. Many variables play a role in forming the dominant-submissive relationships between horses; however, the maternal effect upon the dominance position of the offspring still remains unclear, as do the possible mechanisms of transference (“inheritance”).

Researchers hypothesized that the maternal dominance position, plus differences in suckling parameters or maternal style, may be responsible for later outcome of the offspring's dominance position, characterized by two variables: index of fighting success and rate of winning encounters. Researchers studied 8 groups of loose-housed lactating mares with foals and subsequently four groups of the same foals at 3 years of age.

Researchers found that the impact of age on the dominance position of the young horses and residence in the group impacted dominance position, not the maternal dominance position. Older foals reached higher dominance positions, independent of the dominance position, age, or experience of the mother. Researchers did not find support for direct inheritance of maternal rank on foal dominance position.

However, foals born to the same mare in two consecutive seasons tended to have the same dominance position they obtained at three years of age. This suggests an important constant effect of the mother on the social success of her progeny. However, researchers did not find a significant effect of any of the tested variables describing maternal characteristics or maternal care.

Dominance position depended significantly on the foal's age at observation, and the residence in the herd formed via sequential introducing of later-weaned groups of foals. The most dominant horses were mainly recruited from the first-weaned group of the season, and thus were also the oldest individuals in the herd. Further research is needed to discover the role of foal personality and mare style, and their links to possible dominance behaviors in a herd.

For more information, click here

Summarized by Krishona Martinson, PhD, University of Minnesota




Aged Horse Nutrition

Figure 1.  Aged horse.In species other than horses, such as humans, rats, and dogs, altered nutritional requirements associated with aging include a decrease in energy requirement. However, there is little published work comparing digestibility in healthy adult versus healthy aged horses. Researchers at Michigan State University hypothesized that there would be no differences in macronutrient digestibility between eight adult (5 to 12 years) and nine aged (19 to 28 years) horses fed three diets.    

Seventeen stock-type mares were randomly assigned for a 5-week period to one of three diets: only, hay plus a starch- and sugar-rich concentrate, or hay plus a fat- and fiber-rich concentrate. Each diet period comprised 3 weeks of outdoor group drylot feeding, 2 weeks of indoor stalled individual feeding, followed by a 72-hour digestibility trial including total urine and fecal collection. All horses were clinically healthy for the duration of the experiment. Feed, fecal, and/or urine samples were analyzed to determine dry matter, crude protein, fat, energy, calcium, phosphorus, apparent retention and apparent digestibility. Neutral detergent fiber digestibility was also determined.

Mean body weight was lower in aged than in adult horses (1,003 pounds vs. 1,102 pounds), but body condition score (BCS) did not differ between groups (aged horses: 4.8 BCS and adult horses: 5.1 BCS). No age differences in digestibility, apparent digestibility, or apparent retention were seen for any of the variables measured.

 Based on the results of this study, total tract macronutrient digestibility appears to be similar between healthy adult and aged horses. Data from this study support the hypothesis that older horses in good health and body condition do not automatically require changes to their core diet. However, owners should monitor changes in body condition and muscle mass as horses age. It is also important to note that the nutrient digestibilities of diseased aged horses and those with dental disorders may differ. For more information, click here.  

Summarized by: Krishona Martinson, PhD, University of Minnesota



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