Vet Nutrition Test 2

What are prehension, mastication, and deglutition in horses?

• Prehension: sorting/grabbing food; primarily lips, less so incisors.

• Mastication: chewing in a circular motion; teeth grind food smaller and mix it with saliva.

• Saliva has minimal amylase activity.

• Deglutition: swallowing.

• Horses are obligate nasal breathers.

What is unique about equine teeth

• Horses have hypsodont teeth that continuously erupt through the gum.

• Poor dentition can lead to poor digestion.

What are the major characteristics of the equine stomach?

• Horses are monogastric with a “simple stomach.”

• Small: approximately 9–15 L in a 500-kg horse.

• Has minimal enzymatic digestion and limited microbial fermentation.

• Squamous epithelium: prone to ulceration.

• Glandular epithelium: produces gastric acid.

What occurs in the equine small intestine?

The small intestine is the primary site of enzymatic digestion and absorption of:

• Soluble carbohydrates

• Protein

• Fats and fat-soluble vitamins A, D, E, K

• Minerals such as calcium and phosphorus

• Glucose absorption is highest in the duodenum and lowest in the ileum.

Why are horses considered hindgut fermenters?

• The hindgut = large intestine.

• Large intestine consists of the cecum + ascending colon (large colon).

• Microbial fermentation occurs primarily here.

• Cellulose/lignin-containing feeds are fermented into volatile fatty acids (VFAs).

• Hindgut microbes are sensitive to sudden, drastic dietary changes.

What are the key digestive anatomy takeaways for feeding horses?

• Horses are grazers/trickle-feeders.

• Have a small stomach.

• Plant cells contain cellulose, hemicellulose, and lignin, which provide rigidity and are poorly digestible.

• Mastication is important.

• Poor dentition → poor digestion.

• Microbial fermentation is a symbiotic process occurring primarily in the hindgut.

• Make all feed changes gradually.

What is normal grazing behavior in horses?

• Horses naturally eat frequent, small meals.

• With unlimited pasture access, horses may graze 12–14 hours/day.

• Grazing occurs more during the day than overnight.

What can prolonged fasting and low-forage diets cause?

• Stress

• Stereotypic behaviors

• Gastric ulcers

• Colic

• Other problems associated with prolonged/iatrogenic fasting.

What factors determine a horse's nutrient requirements?

• Body weight

• Workload

• Stage of pregnancy

• Stage of lactation

• Age/growth

What are the protein requirements for horses?

• Most mature horses: 10–12% protein in the diet.

• Growing horses: 13–15%.

• Grass hays: approximately 10–15% crude protein.

• Alfalfa: approximately 15–20%.

• Horses receiving low-protein hay may need protein supplementation, such as a ration balancer.

What mineral does every horse need, and why?

• Salt is needed by all horses.

• It helps improve water consumption.

• Sources include salt blocks such as white, Himalayan, or trace-mineral blocks.

• A 500-kg horse can receive approximately 2 tbsp loose iodized salt/day.

Why might additional mineral supplementation be necessary?

Mineral concentrations vary because of:

• Diet/feed composition

• Drying and storage

• Soil deficiencies

• Geographic differences

• Feed should be analyzed when needed.

• Consult an equine nutritionist when appropriate.

What are the major diet considerations when formulating a horse's diet?

• Forage/roughage

• Concentrates

• Energy requirements

• Maintenance

• Growth

• Reproduction

• Performance/activity level

What nutrient-related factors should be considered when selecting feed?

• Feed quality

• Plant toxins (e.g., fescue)

• Contamination (e.g., weeds)

What animal-related factors should be considered when formulating a diet

• Age

• Body condition

• Underlying disease states

• Housing

• Environmental conditions

How much forage should an adult horse receive?

• Feed forage based on weight, not volume.

• Average adult horse: 1.5–2% of BW/day as dry matter (DM).

• Hay is approximately 90% DM and 10% water.

• DM percentage is often unknown/unaccounted for.

• 1% BW/day is the absolute minimum.

• Horses may consume up to 3% BW/day, depending on factors such as ambient temperature and lactation.

How do you calculate the forage amount for a 500-kg horse receiving 2% BW/day?

• 500 kg × 0.02 = 10 kg DM/day.

• Hay is ~90% DM, so if calculating actual hay as-fed, account for its water content.

• The lecture example states 10 kg hay/day for 2% BW

What factors affect forage nutritional quality?

• Plant species

• Soil conditions

• Growing and harvest conditions

• Maturity at harvest

• Moisture content

• Storage conditions

• Weeds/contaminants

How should you choose hay for a horse?

• Select the type that best fits the horse's needs.

• Appearance does not guarantee nutrient quality.

• Greener is not always better.

• Soft, leafy hay may be more palatable.

• Hay analysis provides the nutrient profile.

What hay bales should be rejected?

Reject bales that are:

• Excessively heavy or warm → excess moisture

• Excessively dusty

• Visibly moldy

• Sour-smelling

• Contaminated with soil, weeds, toxic plants, trash, debris, or carcasses

What are concerns with round bales?

Round bales may:

• Contain more mold

• Be associated with respiratory problems

• Be associated with botulism

• Allow horses to over-eat

How can hay feeding be improved?

• Hay feeders reduce wastage.

• Provide enough feeding stations to reduce competition.

• Consider mats around feeders to decrease sand/debris intake.

• Hay nets slow consumption.

• Feeding hay from the ground creates a preferable head position.

What are alternative fiber sources for horses?

• Hay cubes/biscuits

• Hay pellets

• Silage

• Haylage

• Complete pelleted rations

• Weigh pros/cons based on patient needs and availability.

What are concentrate feeds?

• Small-volume, purposeful feeds that are dense in additional nutrients.

• Provide energy through carbohydrates, fat, and/or protein.

• Can provide vitamins and minerals.

• They are NOT complete feeds and are not intended to be fed without forage.

Which horses commonly benefit from concentrates?

• Growing horses

• Lactating mares

• Performance horses

• Geriatric horses

• Horses with underlying disease

What types of concentrate feeds are commonly used?

• Grains: oats, barley, corn

• Grain mixes: sweet/textured feeds

• Processed feeds

• Extruded feeds: may have enhanced digestibility and palatability.

• Pelleted feeds: cheaper.

What is the maximum starch recommendation for an individual concentrate meal, and why?

• No individual grain/concentrate meal should contain >2 g starch/kg BW.

• Larger meals decrease carbohydrate digestion in the small intestine.

• More starch reaches the hindgut and is fermented there.

• This can contribute to excess gas, colic, osmotic diarrhea, dysbiosis, laminitis, and acute/chronic disease states.

How do you calculate the maximum starch allowed in a meal?
Example: 500-kg horse

• Maximum = 2 g starch/kg BW

• 2 g × 500 kg = 1,000 g = 1 kg starch/meal maximum.

• If fed 2 kg of a 50% starch diet:

  • 2 kg × 0.50 = 1 kg starch

  • Therefore, this meal is at the maximum recommended amount.

What supplements can be used in equine diets, and what precautions apply?

• Ration balancer: vitamins/minerals; should be fed if the diet consists of hay only.

• Beet pulp: high-fiber; may contain molasses; available shredded or pelleted.

  • ALWAYS SOAK to reduce risk of esophageal obstruction.

• Fat supplements: introduce gradually to reduce risk of diarrhea.

  • Oils: flax > corn

  • Rice bran

What are the three main nutritional assessment tools used during a physical exam of a horse?

• Body weight

• Body condition score (BCS)

• Cresty neck score (CNS)

What are the methods for estimating a horse’s body weight?

• Scale — most accurate

• Weight tape

• Heart-girth score

What are the limitations of using a weight tape?

• Lack of standardization

• Accuracy varies with age, breed, and body build

• Placement must be consistent

• Best used to track trends, not as an exact weight measurement

• Compare with a scale when possible

What is the heart-girth formula for estimating adult horse body weight?

Weight (lb) = [heart-girth (in)]² × body length (in) ÷ 330

What is the Henneke body condition score (BCS) scale, and what scores are considered healthy?

• 9-point scale

• BCS 4, 5, and 6 are considered healthy/normal.

What does the cresty neck score (CNS) assess?

It assesses fat deposition along the neck, particularly the development of a fatty/“cresty” neck.

What are the major health/nutritional problems addressed in this lecture?

• Weight loss/malnutrition

• Gastric ulcers

• Colic

• Equine metabolic syndrome (EMS)

• Laminitis

When evaluating a horse with weight loss, what question should you ask first regarding malnutrition?

Is the horse being fed enough?

What should be evaluated if inability to eat is suspected?

Can the horse properly prehend, chew, and swallow food? This may indicate dysphagia.

What is hyporexia vs. anorexia?

• Hyporexia: reduced appetite

• Anorexia: absent appetite
  Ask whether the horse shows interest in food.

What other causes of weight loss should be considered besides inadequate intake?

Increased nutrient demands

• Malabsorption

• Inability to eat

• Reduced/absent appetite

What is a key question when evaluating possible malabsorption?

Is the horse losing weight despite everything else being normal?

What type of disease are gastric ulcers considered in horses?

A “lifestyle” or management disease.

What are the major risk factors for equine gastric ulcers?

• Stress

• Social stress

• Illness/hospitalization

• Transportation

• High-grain diets

• Stall confinement

• Meal-feeding

• Intense exercise

• Exercise >5 days/week

• Chronic NSAID use

Why can high-grain diets contribute to gastric ulcers?

High-concentrate feeding is associated with increased ulcer risk; reducing concentrates is part of ulcer prevention.

How can feeding frequency help prevent gastric ulcers?

Provide frequent, small feedings (“grazing”) rather than large meal feedings.

How should forage be provided to help prevent gastric ulcers?

Increase forage

• Use good-quality forage

• Provide constant/free-choice (ad libitum) access when appropriate

• Hay nets or slow feeders can help extend forage consumption

What should be done regarding exercise and feeding to help prevent gastric ulcers?

Feed 1 hour before exercise

What dietary changes can help prevent gastric ulcers?

• Increase forage

• Decrease concentrates

• Consider omega-3 fatty acid supplementation

• Alfalfa can help buffer stomach acid and is referred to as “Horse Tums.”

What is colic?

Abdominal pain that can originate from gastrointestinal or non-gastrointestinal causes.

How can colic be categorized?

• Gastrointestinal vs. non-gastrointestinal

• Medical vs. surgical

What feeding-related factor increases the risk of colic?

A recent or abrupt feed change and the type of feed being provided.

What management changes can increase colic risk?

• Changes in activity

• Increased confinement

• Changes in access to water

What healthcare-related factors can affect colic risk?

• Dental care

• Deworming

• Recent deworming or lack thereof

What is equine metabolic syndrome (EMS) commonly associated with?

Easy-keeper” horses that are predisposed to insulin dysregulation and abnormal fat deposition.

Which horse breeds/types are listed as having a predisposition to EMS?

• Morgans

• Mustangs

• Arabians

• Saddlebreds

• Paso Finos

• Iberian breeds

• Warmbloods

• Ponies

• Miniature horses/donkeys

What contributes to an individual horse’s risk for EMS?

A genetic predisposition plus a characteristic phenotype.

What is the typical phenotype associated with EMS?

• Regional adiposity ± generalized obesity

• High CNS

• High BCS

What does a high CNS and/or BCS suggest regarding insulin regulation?

The horse is more likely to have insulin dysregulation.

What major disease is associated with insulin dysregulation in EMS?

Laminitis (“founder”), particularly associated with high insulin levels.

What happens metabolically during weight loss/starvation?

• Carbohydrates and fat are used for energy first

• Catabolism of protein is a last resort

• Protein is broken down from skeletal, cardiac, and GI smooth muscle

• 60–90 days of starvation → recumbency

• Recumbency >72 hours carries a grave prognosis

What are the major causes of weight loss in horses?

• Inappropriate husbandry

• Inability to eat/dysphagia

• Reduced appetite

• Increased nutrient demands

• Malabsorption of nutrients

How is an underweight horse defined, and what diagnostics should be performed?

• BCS <4/9

• Thorough history and physical examination

• CBC, chemistry, fibrinogen

• Fecal flotation

• Sedated oral examination

• Targeted diagnostics such as ultrasonography or biopsies

What is the most important principle when treating an underweight horse?

Address the underlying cause of the weight loss.

Which horses are at highest risk for refeeding syndrome?

• Horses with BCS <2/9 are at highest risk

• Losing >50% of body weight carries a poor prognosis for survival

What electrolyte abnormalities can occur with refeeding syndrome?
Within 7 days of feeding, horses can develop low:

• Potassium

• Phosphorus

• Magnesium
  They may also develop acute thiamine deficiency.

What are the potential consequences of refeeding syndrome?

• Neurologic disease

• Kidney failure

• Heart failure

• Respiratory failure

• Death

What type of forage should be used when feeding an emaciated horse?

• High-quality, low-starch forage, such as alfalfa

• Analyze the hay

• Avoid hay containing >10% non-structural carbohydrates (NSC = starch + sugar)

How should feeding be initiated in an emaciated horse?

• Start with <50% of nutritional needs, based on predicted healthy BW

• Use a low-calorie ration balancer

• Provide multiple small feedings/day

• Monitor blood electrolytes and minerals

• Bran can be used as a phosphorus supplement if needed

How can feeding be modified for a thin horse with poor dentition?

To reduce risk of choke and impaction colic:

• Soak feedstuffs

• Use soft, easily digestible pasture

• Introduce hay pellets/cubes and pelleted feeds

• Consider alfalfa for protein and palatability

• Use complete pelleted feeds

• Fat/oil supplements may be added

How can you encourage a thin horse with reduced appetite to eat?

• Feed whatever the horse will eat

• Refresh feed frequently

• Improve access by elevating feed

• Allow grazing when possible

• Warm feed

• Flavor with fenugreek, banana, cherry, ginger, or garlic

• Use honey or molasses as sweeteners

• Regularly clean feed/water tubs

What is the concern with garlic supplementation in horses?

• Garlic can cause Heinz-body anemia

• Feed <15 mg/kg

What are the major causes of obesity in horses?

• Overfeeding

• Inappropriate husbandry

• Inactivity

• Genetics

What health problems are associated with obesity in horses?

• Pro-inflammatory state

• Increased risk of insulin dysregulation/equine metabolic syndrome (EMS)

• Arthritis and other orthopedic conditions

• Heat intolerance

• Reduced conception rates

How is an obese horse identified and what is the general treatment

• Obesity = BCS 7–9/9

• Owner recognition may be poor

• Dietary management + exercise → weight loss

• Pharmaceuticals may be used in some cases, e.g. levothyroxine in EMS

• Aim for approximately 50 lb weight loss every 1–2 months

What are the initial dietary changes for an obese horse?

• Eliminate alfalfa

• Eliminate high-calorie feeds

• Maximize forage

  • Teff and Bermuda grass are generally lower energy

  • Analyze hay

• Provide a ration balancer

How should forage be managed for an obese horse with unlimited hay access?

• Weigh the forage

• Offer 2% of current BW/day

• Feed small, frequent meals

• Use hay nets to slow consumption

• Simply controlling access may be enough to induce weight loss

If diet control and exercise aren't enough, how should forage intake be adjusted?

• Feed 2% of target BW/day in forage

• Remember: 1 BCS point ≈ 50 lb

• Example: a 6/9 horse should lose ~50 lb

• Intake can be decreased to 1.8% or 1.5% BW

How can soaking hay help an obese horse?

• Soaking hay for 1 hour reduces NSC (sugar + starch)

• Rinse the hay afterward

• Do not allow the horse to consume the sugar-rich soaking water

When is a ration balancer particularly important for an obese horse?

Especially when forage is restricted to 1.5% BW/day, a ration balancer helps provide nutrients while limiting calories

How often should an obese horse's weight-management plan be reassessed?

• Every 2–4 weeks

• Reassess:

  • BCS

  • Cresty neck score (CNS)

  • Body weight

• Owner can provide photos from the side and back

What should you do if the horse continues losing weight during follow-up

Make no change to the plan if weight loss is continuing appropriately.

What should you do if the horse's weight is static after 1 month?

• Adjust recommendations

• Decrease daily intake

What is hepatic lipidosis?

• A consequence of negative energy balance

• Occurs when the horse is using more calories than it consumes

• Can occur with starvation, disease, or dramatic feed reductions

What happens during hepatic lipidosis

• Fat stores are mobilized for energy

• This causes increased fat in the blood and liver

• Hyperlipemic plasma can result

What is the key rule when making dietary changes in horses?

Make all changes gradually to minimize metabolic complications, including hepatic lipidosis

What is the difference between managing an emaciated vs. obese horse?

• Emaciated: carefully increase nutrition while preventing refeeding syndrome; start <50% of predicted needs and use small, frequent meals.

• Obese: restrict calories safely, maximize appropriate forage, control intake, and use exercise/weight monitoring.