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Extension > Horse Extension - Research Updates > June 2012

Tuesday, June 12, 2012

Hay soaking

Results in dry matter losses.

Summarized by Krishona Martinson, PhD, University of Minnesota

Horse owners have resorted to soaking hay in water to remove water-soluble carbohydrates to manage horses diagnosed with laminitis or Polysaccharide Storage Myopathy (PSSM). Researchers have suggested that complete rations (hay, grain and supplements) contain less than 12 and 10% nonstructural carbohydrates (NSC), which are the starches and sugars in the forage, for horses affected with laminitis and PSSM, respectively. The objectives of this research, conducted by faculty at the University of Minnesota, was to determine the impact of water temperature and soaking length on the removal of carbohydrates and dry matter (DM) from alfalfa and orchardgrass hays.

Hay types included bud and flowering alfalfa, and vegetative and flowering orchardgrass. Flakes were submerged for 15, 30 and 60 minutes in 7 gallons of cold (72°F) and warm (102°F) water and for 12 hours in cold water.

Prior to soaking, both alfalfa hays were below the 10 and 12% NSC recommended for horses diagnosed with PSSM and laminitis, respectively, and would not have required soaking. This is common for alfalfa, since legumes store their carbohydrates as starch, compared to grasses that store their carbohydrates as fructans (a sugar). The orchardgrass hays were above these recommendations (approximately 14% NSC pre-soaking), however, after soaking for 15 to 30 minutes, were at or below 10 to 12% NSC.

Dry matter losses were similar among all hays after soaking for 15, 30 and 60 minutes in either warm or cold water. Dry matter losses after soaking for 12 hours were greater than other treatments.

Owners should rely on forage analysis, both before and after soaking, as the primary method of determining the appropriate hay for horses, especially when feeding horses diagnosed with laminitis and PSSM. Soaking hay for short durations (15 to 60 minutes) is an acceptable management method, but should only be used if preferred hay is not available. Soaked hay should be fed immediately to reduce the chance of mold.

Economic impact of trail riding in Minnesota

$29.4 million gross state product, 522 jobs, $16.9 million in labor compensation, $3.7 million in tax revenues

Summarized by K. Martinson, University of Minnesota

Minnesota has an active equine industry with an estimated 90,140 horses and 13,048 farms, ranking Minnesota 13th in the nation with a $1 billion impact on the state annually. In Minnesota, more than 1,000 miles of horseback riding trails are managed by the Department of Natural Resources, with more than 200 miles of additional trails on other lands. Minnesota is home to over five million people, of whom 4.5% participate in horseback riding. The objectives of this research were to document the profile of recreational horse trail users, their motivations, expenditures, and their economic impact on the state.

Minnesota residents who purchased a state horse trail pass were used to develop the survey database. From this database, a random sample of 804 Minnesota residents was selected. An eight page mail questionnaire was developed, pre-tested and implemented in fall 2008. The questionnaire included sections on experiences, trips and expenditures, and demographics. There was a 60% response rate. Spending and economic impacts were estimated at the destination regions. Estimates from an exit-survey of Minnesota state park visitors were used to determine trip spending for major consumer items. Park attendance data was applied to the average spending to project visitor spending.

Eighty percent of respondents were female, between the ages of 41-50 (55%), and were White, non-Hispanic (90%). Respondents reported an average of 27 years of horseback riding experience. Of the 20 possible motivations for horseback riding, seven were important or very important to more than 75% of respondents, including to view the scenery (96%), be close to nature (94%), get away from the usual demands of life (94%), experience nature (93.1%), explore and discover new things (90%), relax physically (90%), and be physically active (88%).

Respondents spent an average of 23.5 days trail riding within 30 minutes of their home. Trips to nearby trails by residents accounted for 72% of total days spent on horseback trails in the state. Resident horseback riders spent an average of $26.88 per person-day at nearby trails. Horseback riding by residents resulted in almost $43 million in consumer spending. Out-of-state visitors added $6.9 million which increased total spending on Minnesota horse trails to almost $50 million.

It is estimated that total horseback trail riding expenditures produced $34.7 million in output of directly affected businesses, and the gross state product amounted to $29.4 million. Three hundred and fifty-nine jobs were supported by the direct spending, plus an additional 163 jobs from indirect impacts on related businesses and local suppliers. Total labor compensation was estimated at $16.9 million, and state and local tax revenues at $3.7 million.

Average annual per person equipment expenditures for horseback riding included $536.55 in horse feed, $521.91 in truck/trailer maintenance, $243.20 in veterinarian costs, $201.25 in farrier costs, $189.15 in new equipment, and $101.62 in the purchase of used equipment. Total spending reached $530.2 million. This resulted in, $390.9 million in gross state product, and $49.4 million in state and local taxes.

This study demonstrates the importance of the horse industry to the Minnesota economy. Maintenance of existing horse trails and consideration for trail expansion in Minnesota is recommended.

AM vs PM grazing

Horses ate more in the PM, likely in response to increases in nonstructural carbohydrates.

Summarized by Beth Allen, University of Minnesota

Forage composition fluctuates depending on the time of day. In theory, dry matter intake (DMI) should increase throughout the day as nonstructural carbohydrates (NSC) increase. Researchers at North Carolina State University set out to test this theory.

The experiment measured equine forage intake during morning (AM) and afternoon (PM) grazing periods. Six light horse breed geldings were used and randomly allocated into one of two groups: an AM or a PM grazing treatment for 14 days. After the first 14 days, horses were switched to the opposite treatment for an additional 14 days. Morning treatment groups were grazed from 7:00 am to 1:00 pm and PM groups were fed from 12:30 pm to 8:30 pm. Horses were grazed on tall fescue pastures.

Horses had higher intake rates in the PM grazing sessions compared to the AM sessions. These results confirm pervious beliefs that horses increase their DMI throughout the day, likely in response to increases in NSC. However, caution should be taken when grazing horses, especially horses prone to laminitis, on grasses high in NSC in the afternoon hours.

Diet affects dental needs of horses

Horses should have a yearly dental evaluation, especially if consuming a diet low in forage or high in pellets.

Summarized by B. Allen and K. Martinson, PhD; University of Minnesota

Have you ever wondered if your horse's diet affects their need for dental work? Previous studies have suggested that temporomandibular or jaw joint (TMJ) kinematics (chewing motion) depended on the type of food being chewed or masticated, but accurate measurements of TMJ motion in horses chewing different feeds has not been published. A group of researchers in the College of Veterinary Medicine at Michigan State University set out to determine if the TMJ has a larger range of motion when horses chew hay compared to pellets (grain).

An optical motion capture system was used to track skin markers on the skull and mandible (lower jaw) of seven horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle.

Frequency of the chewing cycles was lower for hay than for pellets. Excursions (chewing motion of mandible) of the virtual mandibular marker were significantly larger in all three directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the two feeds.

The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets. These findings support the suggestion that horses receiving a diet high in concentrate feeds (grains) may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing compared to horses fed a diet high in forages.

In a separate study conducted at Virginia Tech, chewing direction both before and after dental treatments was investigated. Seventeen horses were observed while consuming small portions of mixed grass-alfalfa hay. Chewing direction was determined by the horse's jaw motion as either counter-clockwise or clockwise.

Horses chewed counter-clockwise 60% of the time before dental work and 37% of the time after dental work. While chewing direction varied between the horses, there was a significant effect of lateral excursion on chewing direction with counter-clockwise chewers having a greater left lateral excursion. There was also a trend for clockwise chewers to have greater right lateral excursion. Dental treatment did not appear to have an impact on chewing direction.

The take home message: horses should have a yearly dental evaluation, especially if the horse if consuming a diet low in forage or high in grains (pellets).

Restricted grazing

Ponies anticipated the restricted grazing time period and ate more quickly.

Summarized by Beth Allen, University of Minnesota

Cool season pastures can contain substantial amounts of non-structural carbohydrates (NSC). Research links over consumption of NSC by grazing horses to laminitis, especially when horses have an existing health condition (i.e. previous history of laminitis). Restricted grazing is a common solution to managing laminitic horses, however, little research has measured pasture intake during periods of restricted grazing. The goal of this project, conducted by researchers in England, was to determine the relative dry matter intake (DMI) of pasture by ponies allowed three hours of grazing time per day and un-restricted access to hay for the remainder of the day over a six week period.

Four ponies were used for the study and were turned out daily in the afternoon into a mixed grass clover pasture. When not grazing, ponies were housed in individual stalls with un-restricted access to water and mixed grass hay. Pasture samples were taken to determine quality and pasture dry matter intake were determined from change in pony body weight over the three hour grazing period. Intake of hay was determined daily for each pony.

Ponies gained an average of 0.7 pounds per day and total daily dry matter intake over the six week period remained constant averaging 2% body weight per day. The proportion of total daily dry matter intake accounted for by grazing rose from 22% to 49% by week 6 representing 0.49 and 0.91% of body weight in weeks one and six, respectively. In conclusion, the increase of 0.49% to 0.91% body weight suggests that as the trial progressed, restricting grazing time for ponies became increasingly less effective in reducing pasture intakes.

In other words, the ponies anticipated the restricted grazing time period and as a result, ate more quickly as the trial progressed.

The effect of water acidity

The lower the pH of the water, the less the horses will consume.

Summarized by Beth Allen, University of Minnesota

Preferred flavors added to food, water, or medications my possibly increase palatability and intake. Although there is some research on certain flavors such as sour, peppermint, and banana, little evidence exists measuring the taste preferences of horses. Researchers at the University of Guelph set out to determine the horse preference or aversion to sourness through alteration of water pH.

Twelve horses were used for the study. All horses received daily turnout with free access to forage and water. Each horse was given a treatment for four consecutive days. Treatments were fed in identical black buckets and consisted of control water (pH 7.5) and control water plus citric acid with either a pH of 5.0, 3.6, or 2.9 (the lower the pH, the more acidic the water). Citric acid is sometimes used to flavor water for horses. Water buckets were refilled and weighed as necessary to determine total amount of water consumed from each bucket. Treatment intake was calculated as the percentage of total daily fluid intake, and these values were used to determine preference.

Preference and aversion were established as percent intake above 60% and below 40%, respectively. Differences of intake were noted in the buckets with a pH of 3.6 and 2.9 (these groups did not differ from each) whereas a pH of 5.0 was moderately aversive and tended to differ from the control bucket, which the horses most preferred. Although acidic treatments were found to be aversive, no treatment was completely rejected by the horses. However, the buckets with a pH of 2.9 were the least preferred.

In conclusion, the lower the pH of the water the less the horses will consume.

Slowing grain consumption

Using obstacles in the feed bucket increased feed intake time.

Summarized by K. Martinson, PhD, University of Minnesota

The rapid intake of grain diets high in soluble carbohydrates can result in increased blood insulin and possible problems with insulin sensitivity and laminitis. Simply slowing feed consumption may reduce blood insulin levels. This was the objective researchers from North Carolina State University set out to investigate.

To investigate the time of grain consumption, four treatments were evaluated: 1) a control; 2) adding four bocce balls to the grain bucket; 3) inserting a waffle-type plate at the bottom on the grain bucket; and 4) wetting down the grain prior to feeding. Time of grain consumption and post-feeding blood insulin samples were taken.

The bocce balls and waffle insert increased time to feed consumption compared to the control and wetted feed. The bocce ball treatment also reduced the concentration of blood insulin compared to all other treatments.

The use of obstacles in a feed bucket effectively increased feed intake time, which resulted in decreased insulin concentrations post-feeding.

Equine grazing preferences

Timothy, Kentucky bluegrass, and quackgrass were most preferred.

B. Allen, K. Martinson, PhD and C. Sheaffer, PhD, University of Minnesota

Cool season grass varieties are being marketed for use in grazing systems, but few are evaluated for palatability under horse grazing. The objective of this research was to evaluate grazing preferences and persistence of twelve cool season grasses under horse grazing.

Research was conducted in St. Paul, MN during the 2010 growing season. Four adult Quarter Horse types were grazed May through October in a cafeteria style grazing trial. Post-grazing grass removal was visually assessed to determine horse preference and percent ground cover was assessed to determine grass persistence.

Timothy, Kentucky bluegrass and quackgrass were most preferred; smooth bromegrass, meadow fescue, tall fescue, perennial ryegrass, and reed canarygrass were moderately preferred; and orchardgrass, creeping foxtail and meadow bromegrass were not preferred by the horses.
Tall fescue, orchardgrass, and meadow fescue were the most persistent grasses while creeping foxtail and timothy did not persist well under horse grazing. Quackgrass, perennial ryegrass, reed canarygrass, meadow bromegrass, Kentucky bluegrass and smooth bromegrass persisted moderately well.

Mixtures of fescues, bluegrass, bromegrass and ryegrass should persist under grazing while being highly preferred by horses.

Shelter use by horses

Shelter access is important in snowy, windy conditions.

Summarized by Krishona Martinson, PhD, University of Minnesota

Have you ever watched your horse on a cold winter day and wondered why they were not in their shelter? Researcher Dr. Camie Heleski at Michigan State University recently researched this question.

She examined daytime shelter-seeking behavior in domestic horses housed outdoors, and studied the relationship of temperature, precipitation, and wind speed with shelter-seeking behavior. Sixty Arabian and draft horses were observed. Horses were divided among 8 pastures containing sheds. During a 12-month period, over 5,000 visual observations of shelter use were recorded. At each observation, researchers noted whether or not a shed was being used. At each sampling time, weather conditions and whether each horse was standing or lying inside or next to shelters were recorded.

Shelter usage ranged from a low of <10% of observations in many weather conditions to a high of 62% of observations when it was snowing and wind speed were greater than 11 mph. When wind was greater than 5 mph, there was a significant effect of both rain and snow on shelter usage, that is, more horses used shelters in snowy or rainy, breezy conditions.

Though overall shelter usage was typically <10%, it appears that shelter access is very important in certain weather conditions.

Equine pasture consumption

Horses consumed more dry matter during the first 4 hours than the second 4.

Summarized by Kristen Cleary, University of Minnesota undergraduate equine intern

It is difficult to calculate whether a horse that is turned out on pasture for part of the day is receiving adequate nutrition from the forage consumed while grazing, or whether they require additional sources of nutrients. This calculation is complex, in part because of the relative lack of data detailing how much forage the average horse consumes per hour when turned out to pasture.

Researchers at NC State Univ. attempted to address this problem by conducting a study to develop a reliable means with which to estimate how much dry matter horses on pasture consume per hour. The experiment was conducted using 8 horses that were accustomed to grazing. The researchers found that on average, the horses consumed more dry matter during the first 4 hours of grazing as compared with the second 4 hours. These findings are important for horse owners who must account for the varying amount of forage that is consumed when grazing.

Continuous vs rotational grazing

Rotational grazing has benefits for pasture yield.

This research was summarized by Kristen Cleary, University of Minnesota undergraduate equine intern

The use of land for horse pasture must be balanced against the negative environmental effects caused by potential mismanagement of these areas. Many opinions exist about whether horses benefit more from continuous grazing of one area or from rotational grazing of many areas, but little research exists detailing which approach results in an improvement in horse health. In an effort to begin to address this issue, researchers at Missouri State University conducted a two-year study, during the summer of 2007 and the summer of 2008, comparing continuous and rotational grazing and evaluating the amount of forage that each method made available to the horses.

In 2007, 8 horses were used, and in 2008, 9 horses were used, to equalize stocking rates based on weight. The researchers found similar changes in body weight for the continuous and rotationally grazed pastures, but the average available forage was significantly higher for the rotationally grazed pastures. Not only does rotational grazing result in less detrimental effects on the environment, but this study concludes that it has additional benefits for pasture yield as well.

Stress during transport

The effects are evident after 6 hours of transport.

This research was summarized by Kristen Cleary, University of Minnesota undergraduate equine intern

As most horse owners are aware, transporting a horse for any length of time is a stress inducing event. Numerous studies have been conducted that document the negative effects of transportation stress including, dehydration and respiratory illnesses. However, there has not been a lot of research into effective methods for reducing this stress and its associated consequences. Researchers at Texas Tech University, began to tackle this problem by performing two studies to analyze the effects of transportation stress on the horse's body.

For the first study, 20 quarter horses were hauled for 26 hours. The researchers found increased levels of cortisol, a stress hormone, in the horses after transport. In the second study, 30 horses were hauled for 24 hours. As with the first study, the horses had increased levels of cortisol. However, the increased cortisol levels were found to occur after just six hours of transport and remained elevated for the duration of the transport period. The horse's respiration levels were also elevated during transport at the 6 and 12 hour marks but had returned to normal at the 18 and 24 hour marks.

These studies confirm that horses do experience stress as a result of transport, and that those effects are evident after 6 hours of transport.

Abrupt diet change and body weight

Abrupt change from pasture to hay results in decreased body weight.

K. Franks, H. Spooner, B. Nielson, S. Eberhart, and H. Schott II, Michigan State University.

The use of the horse as a recreational and competitive animal often necessitates management changes that are challenging to the normal behavior and physiological well-being of the horse. In some instances, it is necessary to remove a horse from a free-choice pasture diet and impose an all hay diet (i.e. seasonal changes in MN).

When such changes are made, a loss in body weight (BW) has been observed. It has been speculated that the BW loss is the result of a decrease in a full gut (digestive track), as pasture forage tend to have higher moisture contents related to hay.

However, dry matter intake is correlated to water intake, thus hay-fed animals should be able to maintain a full gut and BW as a result of increased water consumption. This study was undertaken at Michigan State University to examine the effect of an abrupt diet change from pasture to a hay diet on BW and abdominal circumference (AC).

BW decreased immediately following a change from pasture to a hay diet, yet BW was not significantly different than the starting value by day 5.

The immediate decrease was likely a result of decreased feed intake by the horse due to the sudden diet change.

This data is not surprising, but supports that abrupt change from pasture to a hay diet results in a persistent decrease in BW, likely due to a decrease in gut fill.

The research also reinforces the need to change horse diets slowly. Horse owner are frequently reminded to gradually introduce horses to pasture (from hay) in the spring, but should also gradually remove horses from pasture (to hay) in the fall, especially if a reduction in body weight is a concern.

Bedding stall cleaning effects

Wheat straw bedding and partial mucking out were most favorable.

K. Fleming, E. Hessel, and H. Van den Weghe, University of Goettingen, Germany

Indoor air quality in horse barns is a concern for both horses and humans. In a recently published study, researchers compared different types of bedding and mucking out regimes used in horse stables on the generation of particle matter and gases (carbon dioxide, nitrous oxide, ammonia).

The research was carried out in an enclosed stable which had 5 single box stalls housing 4 horses. Three types of bedding materials (wheat straw, straw pellets, and wood shavings) were used. Each type of bedding was used for 2 weeks and was replicated.

Wheat straw bedding generated the least amount of ammonia, followed by wood shavings and straw pellets. Researchers then further investigated wheat straw and the effects of the mucking out regime on the generation of ammonia and particles.

Daily mucking regimes included no mucking, complete mucking, and partial mucking out (just removing feces). The mean ammonia concentrations in the stalls differed significantly between all three mucking out regimes. The highest ammonia values were recorded when the stalls were mucked out completely every day, followed by no mucking and then partial mucking.

Finally, a 6 week bedding regime without mucking out was evaluated with regard to gas and airborne particle generation. The ammonia values did not constantly increase during the course of the 6 week period. It can be concluded from the particle and gas generation patterns found in the results of the experiments that wheat straw was the most suitable bedding of the 3 types investigated, and that mucking stalls out completely on a daily basis should not be undertaken in horse stables.

To view the full article, go to:

Carrying capacity

Horses with wider loins and greater cannon bone circumference can bear weight better.

Powell, Bennett-Wimbush, Peeples, and Duthie; The Ohio State University Ag Tech. Inst.

The amount of weight a horse can safely carry on its back depends upon a variety of physical traits. These may include the horse's size, conformation, body condition, age, the duration of the work to be done, as well as the speed at which the work is being performed.

There are a few methods that are currently being used to help estimate how much weight a horse can carry, however, little research evidence can be found to support these methods. The objective of the study conducted in Ohio was to determine whether horse height, cannon bone circumference, and loin width can be used as indicators of weight carrying ability in light horse.

Horses demonstrated higher work rates both at the trot and canter when carrying 25% and 30% of their body weight compared to carrying 15% or 20%. Heart rates after exercise differed when horses carried 25% and 30% of their bodyweight. Horses tended to have a greater change in muscle soreness and muscle tightness when carrying 25% of their bodyweight, with significant change demonstrated when carrying 30% of their body weight.

Loin width and bone circumference were negatively correlated with change in muscle soreness and tightness, suggesting that the horses having the wider loin area and greater cannon bone circumference became less muscle sore when asked to carry the higher weight loads.

This study shows that when horses are asked to carry over 20% of their bodyweight, the additional weight influences both work rate and heart rate, indicating higher work loads. Further studies using a larger data set will be necessary to assess the importance of loin width and cannon bone circumference when assessing weight carrying capacity in the riding horse.

Composting carcasses

Using stall cleanings is effective in composting.

Thousands of horse carcasses are disposed of every year in the US. Burial, rendering, and use of landfills were once the most frequently used means of carcass disposal, yet environmental and water quality regulations have limited their use. Research exists regarding composting of poultry and swine carcasses, yet little data has been obtained for larger ones. The equine industry needs to explore alternative disposal methods.

The objective of this research, conducted at West Texas A & M University, was to determine the length of time needed to complete the compost process, and the types of composting materials best suited for degrading equine carcasses. Three treatment materials were used; stall cleanings (SC), cattle manure (CM) and a mix of cattle manure and hay (CM+H). Compost pile temperatures during the study indicate that SC was more effective for composting. Treatment CM+H had a higher moisture content as compared to SC and CM. Upon visual inspection, carcass decomposition appeared more complete in SC piles when aerated at 90 days as compared to CM and CM+H.

Results indicate that properly monitored compost piles made with SC maintain a temperature more conducive to composting as compared to CM and CM+H, resulting in a more effective and timely disposal of equine carcasses.


This behavior may be tied to feeding or digestion, instead of stress or boredom.

Cribbing is a repetitive behavior where the horse places its upper incisors against a horizontal surface, arches its neck, pulls backwards with its body and may produce a characteristic grunting sound. The digestive process of cribbing horses may differ from horses that do not crib because cribbing horses have lower gastric pH than normal horses, produce less saliva, have slower orocecal transit times and greater incidence of stomach ulcers and particular types of colic than non-cribbing horses.

Cribbing frequency also increases around concentrate meal feeding times. It is not known if this increase in cribbing behavior is due to the ingestion of the feed itself or whether factors, such as activity levels, diurnal rhythms or digestive physiology might be involved. A recent study at Auburn University was initiated to determine if cribbing activity was correlated to concentrate intake.

Initial analysis indicated that the majority of cribbing activity in this study occurred around the feeding times as previously reported, and higher values were observed during the time period corresponding more closely to concentrate feeding times.

There are many theories as to the cause of cribbing behavior. Stress reduction, isolation or lack of social interaction, genetics, altered digestive or neural physiology have been hypothesized as origins of this behavior. Though the present results do not eliminate these possible causes, they may direct further study around theories that highlight feeding or digestive causes of cribbing. The current study showed that the highest frequency of cribbing behavior followed times of concentrate feeding.

These data suggest that the function of cribbing does not lie in stress reduction or easing boredom, but support the claim that the behavior may be tied to feeding or digestion.

Donkey thistle control

Using donkeys to reduce plumeless thistle infestations in pastures

Vince Crary and Carlyle Holen, PhD, University of Minnesota

Plumeless thistle is the most common species of thistle infesting NW Minnesota pastures. In overgrazed pastures this plant often forms dense patches that limits cattle feeding and reduces pasture productivity. Plumeless thistle infestations can be reduced over time with annual applications of herbicides; however, access by spray equipment to many pastures is limited by steep slopes, rocks, trees, water and other physical barriers.

The purpose of this research was to evaluate the effectiveness of donkeys in reducing plumeless thistle infestations in established pastures. In 2003, a three year study was established in a grass pasture with moderate to heavy plumeless thistle populations at Deer Creek, MN. Treatments consisted of 1) one donkey and one cow/calf pair and 2) two cow/calf pairs.

Some of the observations about feeding preferences include:

  1. There are differences between donkeys in their preference for consuming plumeless thistle blossoms. All donkeys in the project grazed on plumeless thistle but some donkeys have a greater affinity for consuming thistle blossoms than others.

  2. Donkeys prefer blossoms over stems and leaves of plumeless thistle. Donkeys ignore the younger plants and do not begin grazing on plumeless thistle plants until blooms are present.

  3. Plumeless thistle plants with heavy grazing pressure are stimulated to continue to produce additional blossoms. Many of the later blossoms produced by the plant will not produce seed.

The number of plumeless thistle blossoms in sampling areas was reduced by 74% in 2003 and 87% in 2004 in the donkey treatment compared to the cattle grazing treatment. Plant height was reduced by 10% and 40% in the donkey treatment compared to the cattle treatment in 2003 and 2004, respectively. Some pastures may have plumeless thistle populations that are too high for management by donkeys. For more information, please contract Vince Crary at 218-385-3000 or Carlyle Holen at 218-281-8691.

Equine vocalization project

Horses have the ability to produce a distinct and repeatable call.

D. Browning, Browning Biotech; and J. Nadeau, P. Scheifele, and J. Dinger, Univ. of CT.

Equines vary frequency during vocalization, giving them the potential for expression. Of the sounds that horses make, whinnies have the greatest potential for long range communication. The challenge is to build up a large equine vocalization data base to determine if a particular acoustic spectrum might be associated with a particular situation.

An analysis of previously recorded whinnies indicates that, in general, there are two principal components: a tonal or constant frequency component; and a frequency dependent component, typically characterized by a rapid increase in frequency followed by a more gradual decrease. The latter produces the sound we usually associate with a whinny and we refer to as the "call".

The objective of this research conducted at the University of Connecticut was to find a situation where a number of whinnies were collected under constant, known condition.

A total of 100 sonograms form four separated mare/foal pairs were collected. The acoustic structure of the whinnies were very consistent. There was a tonal structure, which tends to be slightly different for each mare's "voice", comprising of a basic frequency and its harmonics. Imbedded in this, however, was a distinct persistent call with a characteristic frequency structure: a sharp rise to about 2,000 Hertz and then a gradual decline. The call was consistent throughout the whinnies of an individual mare and was very similar when comparing different mares.

Based on this initial research, it appears that horses have the ability to produce a distinct and repeatable call as part of a whinny. The spectra of the call in the whinnies recorded were similar to a softer call made by a mare looking for her foal while being relocated to the barn. What is not known at this time is whether this particular call might apply to other situations too. As a horse is primarily visually oriented, most whinnies occur when vision is.

The next step is to determine if whinnies can contain distinctly different calls under different circumstances as a tool for communicating information, stress, or feelings to other horses or people.

Euthanasia drug and compost

Avoid using compost containing sodium pentobarbital as fertilizer.

Composting is one option for disposing of a horse carcass after euthanasia. Researchers at West Texas A&M recently conducted a study to determine if residues of sodium pentobarbital, used in euthanasia, might remain in compost. Horses that had been euthanized by a veterinarian were composted with layers of hay and stall cleanings and mechanically aerated every 90 days. After six months, samples from eight different compost piles contained from 0.008 to 3.16 parts per million (ppm) sodium pentobarbital.

The research team is conducting further research to assign relevance to these numbers and learn more about the environmental fate of pentobarbital. Currently, researchers recommend avoiding the use of compost containing sodium pentobarbital as fertilizer. Care should be taken to compost euthanized animals in areas where residues are less apt to leach into ground water or run off into ponds or streams. Reprinted with permission of The Horse (

Feeding concentrates and cribbing

Free access to concentrate feeds can decrease cribbing but result in health problems.

This research was summarized by Kristen Cleary, University of Minnesota undergraduate equine intern

Cribbing in horses is an undesired behavior that causes property damage and has the potential to harm the horse's health. It is known that the frequency with which a horse engages in cribbing increases during the times that concentrate feeds are fed. A recent study indicated that providing horses free access to concentrate feeds resulted in a decrease in cribbing behavior, but allowing free access to concentrate feeds can create a myriad of health problems.

Because of this, researchers at Auburn University and Tuskegee University set out to determine whether feeding small measured amounts of feed on an hourly basis also resulted in less cribbing.

Each of the ten horses in the study received the same total amount of feed per day, but different amounts at individual feedings; either in two larger feedings or twenty-four smaller feedings. The researchers found that providing the horses with small meals each hour did not reduce cribbing behavior. This was because the frequently fed horses spent more time at the feeder, resulting in more cribbing when compared with the horses that only went to the feeder two times per day.

Combining this data with the information from the previous study, the researchers concluded that it is likely the amount of concentrates that a horse consumes rather than how often they eat that affects the frequency with which they crib.

Reference: McCall, C., P. Tyler, W. McElhenney, and T. Fenn. 2009. Effect of hourly concentrate feed delivery on crib-biting in horses. Abstract. Journal of Equine Veterinary Science. 29:5 427-428.

Feeding horses with PSSM

Avoid hay with nonstructural carbohydrate content of greater than 16%

Authors: L. Borgia and S. Valberg, U of M; K. Watts, Rocky Mtn Res.; and J. Pagan, KER. Reprinted with permission of The Horse

Researchers at the University of Minnesota have been examining the effects of feeding horses hay with varying levels of nonstructural carbohydrate content (NSC) in order to determine the best diets for horses with polysaccharide storage myopathy (PSSM). The study objectives were to determine if there is a difference in blood glucose and insulin response to feeding hay types with varying NSC content between horses with PSSM and control horses.

Horses' glucose and insulin levels were measured after feeding hay with high (17%), medium (11%), and low (4%) NSC content. In the control horses, significantly higher insulin responses were observed when horses were fed high NSC hay, but the blood glucose levels did not differ.

In the PSSM horses, a greater insulin response to the high NSC hay compared to medium or low sugar hay was detected, but this group's insulin concentrations were less than the controls on high NSC hay.

Blood insulin response appears to be a more sensitive indicator of the metabolic effects of high NSC hay than glucose response.

Researchers suggest that owners or managers avoid feeding PSSM horses hay with an NSC of greater than 16 %; they recommend hay with less than 11% NSC for these horses because it does not produce a significant elevation in blood sugar or insulin. Analyzing your hay for quality will determine NSC content.


Feeding TMR cubes

Effectiveness of total mixed rations (TMR)

Total mixed rations (TMR), wherein all the nutritional needs of the animals are met in a single feedstuff that is available free choice, are used in other species but not commonly for horses. In geographic areas, or years when a consistent, quality source of forage (either hay or pasture) is limited, TMR cubes may be a solution.

Research conducted at Rutgers University evaluated feeding forage based TMR cubes as the sole feed source to weanling draft horse crosses in 2004 to 2006. In the study, all 24 weanlings that were fed the TMR cubes maintained good health and body condition scores, while growing more efficiently than the 24 matched weanlings fed traditional hay/ concentrate (grain) diets.

Based on the results of these trials, feeding TMR cubes to weanling draft horse crosses can be an effective alternative to traditional forage (hay or pasture), especially during times of limited, quality forage.

Foal rib fractures

Rib fractures in foals may be occurring more frequently than previously thought.

The National Institute for Animal Agriculture

Rib fractures in foals may be occurring more frequently than previously thought. That's the conclusion of a University Of Montreal study. The study also revealed that ultrasonography is more effective than radiography for detecting rib fractures in foals.

During physical, radiographic and ultrasonographic examinations on 29 Thoroughbred foals admitted to an emergency unit for reason other than thoracic trauma, researchers found that 69 percent had at least one rib fracture.

Fillies had almost twice as many fractures than colts, and fractures were often occurring on the left side. Researchers believe these variances are due to the difference in thoracic cage flexibility between genders and positioning during parturition (labor).

Although x-rays showed some foals without a fracture, ultrasonography revealed a different story. The more sensitive technique found fractures in 82% of the foals that looked normal on x-rays. Moreover, ultrasonography enabled researchers to identify additional rib abnormalities not visible on radiographs.

Researchers contend that ultrasonography justifies its routine use, calling it the "gold standard" technique in diagnosing rib fractures in neonatal foals.

For additional information on this study, see the March 2007 issue of the Equine Veterinary Journal.

Gastric ulcer syndrome and hay

Alfalfa hay may help with gastric ulcers.

T. Lybbert, P. Gibbs, N. Cohen, and D. Sigler. Texas A & M University

Equine gastric ulcer syndrome (EGUS) is recognized as a health problem in horses and can be detrimental to a horse's athletic performance. The increased availability of endoscopic equipment suitable for performing equine gastroscopy has facilitated more routine evaluation of horses for EGUS.

Up to 93% of racehorses and over 60% of arena performance horses have ulcers of varying severity. Factors implicated as contributors to EGUS include stress, feed deprivation, stall confinement, increased intraluminal pressure with dorsal displacement of acid during exercise and intensive training, retention of gastric acid, and diet. These factors may be directly linked to excessive acid secretion and decreased pH, which increases the opportunity for acid-induced injury.

Research has demonstrated stomach ulcers will heal spontaneously if provided a more basic environment. The relationship of diet and gastric ulcers has been the focus of numerous investigators, including a proposal that proteins in alfalfa may offer some buffering capabilities within the stomach and a strong correlation between dietary alfalfa hay and lower degree of gastric ulceration.

The objective of this study was to further investigate antiulcerogenic properties of alfalfa hay. Twenty-four Quarter Horse yearling geldings, in an exercise program, were used and fed either alfalfa or grass hay.

There was no significant difference in ulcer severity score between the groups at day 0, when the study was initiated. There was a significant effect of diet on ulcer score. Horses fed grass hay had higher ulcer scores. The effect of diet was strong, with an estimated effect of increasing the ulcer score by 1.5 times. The alfalfa hay contained 1.5 times the amount of protein and 3.4 times the amount of calcium than the grass hay and may have had buffering capabilities.

Whether or not the differences observed in ulcer score were due to protein intake, protein quality intake, or calcium intake, could not be determined. Additional research is needed to better determine those characteristics in alfalfa that contribute to a decreased severity of gastric ulcers compared to horses eating grasses. In this study, alfalfa hay exhibited preventative or therapeutic capabilities of gastric ulcers in horses.

GPS and pasture grazing behavior

In 36 hours, horses traveled an average of 7 miles.

C. Clingman, W. Staniar, T. Smith, and B. McIntost. Virginia Tech

Global positioning systems (GPS) are useful tools for measuring distance, speed, and position in grazing horses. These measures were previously estimated through physical observation, which is difficult to standardize, therefore a quantifiable method of determining activity levels on pasture is needed. Improved accuracy and precision from GPS data will be a useful tool to answer questions regarding equine behavior on pasture, examine possible effects of different management strategies, and provide potentially better estimates of equine energy expenditures and requirements.

Ten Thoroughbred mares were acclimated to a 12 acres pasture. The GPS units were affixed to the horses halters and recorded data for 36 hours. Each GPS unit recorded data (speed and position) every 30 seconds.

During the first 24 hours, the horses traveled an average of 4 miles. Over the entire 36 hour period, the horses traveled an average of 7 miles. The average speed over the entire period was <1 mile per hour. Analysis of differences between night and day revealed a slight increase in both speed and distance traveled during the night.

Quantitative measurements of speed, distance, and position are exciting additions to equine nutrition and behavior research. Data from this study confirms the usefulness of small, inexpensive GPS units in equine pasture research.

Human bone cements work in horses

Magnesium cement performs the best.

This article has been edited from a National Institute for Animal Agriculture Publication.

The fate of Barbaro has intensified the interest in identifying a bone cement that would help the equine community and potentially accelerate bone repair.

A biodegradable magnesium phosphate bone cement that is being investigated to repair human fractures may be a valuable veterinary tool for equine bone fractures. A recent study at The Ohio State University (OSU) compared two bone repair cements, the new magnesium cement and a calcium phosphate cement currently used in humans. The magnesium product is currently under FDA review as a bone void filler for use in people.

The OSU study involved replicating a wedge fracture in the second and fourth metatarsal bones of clinically normal horses, and then replacing the triangular fragments using the magnesium cement, the calcium cement or nothing. Radiographs were taken at regular intervals during the seven-week healing period. The metatarsal bones were examined using computed tomography (CT) and bone histology for adverse reactions, and for signs of healing and callus formation.

Study results showed that when compared to either calcium cement or no treatment, fragments affixed with the magnesium cement were significantly closer to the parent bone during all stages of healing. Mature woven bone and fibrous tissue were also more abundant in the sites treated with magnesium, indicating that healing was occurring.

Additionally, the magnesium cement outperformed the calcium cement when it came to remaining at the fracture site. Magnesium cement stayed at the site 94 percent of the time while calcium cement persisted in only 25 percent of the treated fractures.

While both cements were similar in handling characteristics, the researchers found that immediate adhesion was not a shared characteristic. Magnesium cement provided immediate adhesion while calcium cement did not. The calcium cement was biocompatible and provided some cementing once hardened.

Previously reported in the American Journal of Veterinary Research.

N fertilizer application rates and timings

The optimum time to apply N is early May and early August.

D. Cosgrove, PhD, UWRF

Split nitrogen (N) applications have long been recommended on rotationally grazed pastures. However, the most efficient timing for these nitrogen applications to rotationally grazed pastures has not been established.

Research conducted by Wisconsin Extension faculty determined that the optimum time to apply nitrogen is early May and early August. Mid-June applications are not productive because cool season grass (i.e. timothy, orchardgrass, and bromegrass) growth is slowed by summer heat and reduced precipitation.

Split applications of nitrogen or a single, well-timed application resulted in the highest yield. Three applications of 50 units of nitrogen each, and a single application on May 1 provided the highest overall yield. Single applications of 50 units of nitrogen on either May 1 or August 1 provided the greatest forage increases per pound of nitrogen applied. The single 50 unit application on June 15 consistently provided the lowest yield increase and the lowest yield increase per pound of nitrogen applied.

The greatest return per dollar were realized with the May 1 application and the three 50 unit applications. The lowest return was from the June 15 single application. It is important to realize, in early May, that pasture growth may already be greater than the animals' ability to utilize it. Nitrogen applications at this time will only exacerbate this problem.

In order to capture this increased growth, pastures may need to be mechanically harvested, have a reduced resting period, or stocked with higher than normal stocking rates.

Pasture fertilizing

Incorporating stall material into the soil can reduce use of inorganic fertilizers.

S. Dilling, L. Warren and A. Peters, Univ. of FL

Inorganic fertilizers (man made), which contain readily available nutrients and little to no organic matter (OM), are commonly used to maintain soil fertility in pastures. Unprocessed (non-composted) organic materials, such as horse manure, while high in OM, may not contain nutrients in the readily available state. Land application of composted horse manure represents a management strategy that could replenish soil OM, and reduce the need for inorganic fertilizer.

The objective of this study conducted at the University of Florida was to evaluate soil and forage characteristics in response to fertilization with inorganic fertilizer, unprocessed stall materials or composted horse manure that has been introduced by soil incorporation (tillage) at the time of pasture establishment.

Incorporation of horse stall material into soil, whether unprocessed or composted, produced similar forage yield to that observed with inorganic fertilizer in newly established pasture. Soil OM was not impacted by any of the fertilizers. An increase in soil OM may require more than one yearly application of compost, particularly on sandy soils.

The results of this study suggest that the incorporation of unprocessed or composted horse stall materials into soil can reduce or replace the use of inorganic fertilizers when establishing grass pastures with minimal reduction in forage quality or production. Such a practice could decrease the cost of manure disposal and purchased inorganic fertilizer, recycle nutrients, and reduce environmental degradation by stabilizing nutrients that may threaten water quality.

Spreading horse manure (whether composted or not) on an existing pasture has different guidelines than above. If you have less than one horse for every two acres of pastures, you may be able to spread additional manure on the pasture without increasing the parasite load. If you have more than one horse for every two acres of pasture, then spreading additional manure is not recommended.

Pasture turnout and horse fitness

Pastured horses have greater fitness and bone density.

Horses are better able to maintain fitness when turned out on large pasture. In the project, researchers divided mature horses into three groups:

  • Group 1. Full-time turnout on a 100 acre hilly pasture;

  • Group 2. Stalled during the day with light exercise five times per week;

  • Group 3. Stalled during the day, not exercised.

Groups 2 and 3 spent nights in half acre paddocks. After 14 weeks, the horses in both the pastured and exercised groups had lower heart rates, faster recovery, lower blood lactate levels, lower rectal temperature, and lower peak CO2 blood concentrations after an exercise test, indicating a greater level of fitness.

Additionally, only the pastured horses showed an increase in bone density over the course of the study.

Reprinted with permission from The Horse (

Pelleted bedding

Easier to clean than shavings, but dustier.

Authors: J. Thorson & C. Hammer, NDSU

Controlling ammonia and dust in barns can be a challenge. A study at North Dakota State Univ. recently looked into different bedding types and their ability to reduce ammonia smell and dust.

Bedding treatments consisted of an aspen and wheat based pellet and wood shavings. Ammonia levels were lower for stalls bedded with the pelleted product (3.9 ppm) than with the shavings (8.4 ppm). Also, ammonia levels increased to a greater degree over the length of the treatment period in stalls bedded with shavings compared to stalls bedded with pellets.

Stalls bedded with pellets were easier to clean than stalls bedded with shavings, however, they were dustier.

Stalls bedded with pellets tended to have more waste removed during the trial period. Also, the amount removed remained similar each day for stalls bedded with shavings, while in contrast, bedding removed from stalls bedded with pellets increased throughout the trial period. Its was hypothesized that this was due to increased absorbency of the pelleted product.

Stalls bedded with shavings required additional bedding to be added sooner than stalls bedded with the pelleted product. A substantial difference in total bedding used was observed, with an average total weight of 45 kg/stall for shaving and 136 kg/stall for the pelleted product. This could possibly be a hindrance to horse owners who have limited storage capacity. However, a benefit of the pelleted bedding is that it did not require additional bedding through the trial period.

Overall, the pelleted product performed well. Researchers thought it was easy to clean and handle, and no adverse affects were observed in any of the horses bedded on this material.

Using round bale feeders

It is important to use a feeder to reduce waste.

Round bales are a common bale type in Minnesota. Past research has focused on reducing round bale waste associated with proper storage (stored inside or tarped on a pallet).

Research recently conducted at Texas Tech evaluated waste associated with feeding round bales. Both alfalfa and grass round bales were fed with and without a round bale feeder.

The alfalfa round bales fed with a feeder had a 9.1% loss, compared to a 31.5% loss without a feeder. The grass round bales fed with a feeder had a 1.8% loss, compared to a 38.1% loss without a feeder.

As with feeding any bale type, some loss is expected. It is not clear why there is a difference is loss when comparing alfalfa and grass. The round bales fed in a feeder lasted 8 to 9 days, compared to only 6 days without a feeder. The reduction in days is a reflection of the increased waste that was either soiled by manure and urine or trampled, and was no longer suitable for consumption.

This research may not be surprising, but draws attention to the importance of using a feeder when feeding round bales.

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