Horse NutritionMarch 29, 2013

M.E. PersiaIowa State University4/16/2012

Digestive Anatomy

Type of Digestion

Foregut Capacity % of the GIT

Enzymatic Stomach 8-15 L 8

Enzymatic Small Intestine (70 feet)

68 L 30

Hindgut

Microbial Cecum (4 feet) 28 – 36 L 15

Microbial Large colon (10 – 12 feet)

86 L 38

Microbial Small colon (10 – 12 feet)

16 L 9

Adapted: Atlas of Topographical Anatomy of the Domestic Animals, Popesko, P., W.B. Saunders

Purpose of Feeding

• Physiological Stage• Growth, pregnancy, lactation• Geriatrics

• Environment• Health & Well Being (body condition)• Clinical Conditions• Exercise

Feeding Behavior and General Considerations

• Feeding behavior affects feed intake• Forages of considerable variety are primary diets consumed by wild horses

• 65% Grasses and Sedges• 25% Shrubs• 5% forbs (such as wildflowers)

• Preference between wild and domestic horses for grasses is similar but difficult to measure and data are inconsistent.

• Highly selective grazers and will graze down to ground level.

• Prefer young, rather than mature plants

• Grasses are preferred to legumes and herbs.

Appropriate & Palatable Forage Species

• Cool Season Grasses– Perennial ryegrass, meadow fescue, timothy, orchardgrass, creeping red

fescue, Kentucky bluegrass, brome grass, tall fescue• Warm Season Grasses

– Bermuda grass, crabgrass, prairie grass, India grass, canary grass, wheat grass, switch grass

• Legumes– Alfalfa, white clover, vetch

• Herbs– Dandelion, ribgrass, chicory

• Cereals– Oats, barley

Soft brome

Forage quality

Forage DE (Mcal/Kg) TDN, % CP, % DP, %

Alfalfa – early bloom 2.42 55 17.2 13.4

Alfalfa – full bloom 2.16 49 15.0 10.1

Bluegrass 2.15 50 15.0 12.6

Orchardgrass 2.2 50.0 16.0 13.5

Anti – Nutrients in Forage

• Oxalates & Phytates– Many warm season grasses– Calcium/Phosphorus concerns

• Cyanogenic glycosides– high in Sorghum, Sudan grass, hybrid Johnson

grass, and Sorghum – Sudan hybrids; therefore, not recommended for horses.

Anti-Nutrients in Forage

• Clostridium, Listeria can be issues with ensiled forages

• Endophyte contamination• Mycotoxins• Yellow and White Sweet Clover – Penicillium

spp. – product dicoumarol poisoning• Toxic plants

Insect Contamination - Blister beetles

• 2 species of concern– Epicauta vittat– Epicauta pennsylvanica

• Toxin = cantharidin• Fatal

Grazing Time• Constant Grazers

– http://www.youtube.com/watch?v=s5FJgsHx6gY– Accounts for up to 1.5 – 3 miles per day– Move more than cattle (damage to pasture)

• Horses will graze for 10 – 17 hours per day– Compared to cattle? – http://www.youtube.com/watch?v=L5xRBoyNIzc

• Affected by light and season– 20 – 50% nocturnal (higher in summer)

• Affected by group– Herd animals > single

• Affected by gender, age, breed– Mares > stallions– Mature > weanlings– Yearlings > 2 year olds– Arabians > Thoroughbreds

Crowell-Davis, et al., 1985; Kaseda, 1993; Mesochina et al., 2000, Rogalski, 1977

How much will a horse eat?

Maximal DMI = 3 – 3.2% Body weight

Classification DMI (Kg per 100 Kg BW)

Mature horses 1.8 – 3.2

Growing horses 2.0 – 3.0

Mature ponies 1.5 – 5.2

Donkeys 2.3 – 2.6

Diet type

Hay 2.0 – 2.4

Corn silage 0.97

Mixed forage + concentrate > 2.0

General Feeding Considerations

• Meet nutrient needs while maintaining normal feeding behaviors.

• Forage based rations– Benefits? – Grain by-products, pasture, harvested forages– Forages should be a minimum of 1% of the body

weight. – Example: 1,000 Lb horse• 1% = 10 Lb forage minimum

Feeding Considerations• What is the management system?

Feeding Considerations

• Does diet affect behavior? • http://www.youtube.com/watch?v=NyYLfUlwfMs– Goal is to prevent boredom that could lead to stable

“vices” and “sterotypies”• Orosensory sensations of feeds are extremely

important for horses and contribute to palatability. – Smell, texture, and taste– Prefer variety

Feeding considerations – oral behaviors

• Lack of fiber, too much grain in the diet– Reduce gastric pH (3.3 compared to 5.5)– Lower saliva production– Associated with increase oral behaviors such as “cribbing”

• Hay should be at least 14 Lb per day if pasture can’t be offered.

• Feed at least 2 types of forage, provide pasture if possible.• Feeding frequency of grain (more often is not better)• Limit concentrate feeding

– http://www.youtube.com/watch?v=b4lmVaIqZIo&feature=related

Considerations for Senior Horses• Age related changes in nutrient digestion, absorption

and metabolism may occur – Reduction in digestion and absorption in the large intestine

(5% lower digestion of CF)– 5-10% reduction in protein digestibility

• Supplemental lysine (20 g/d) and threonine (15 g/d) – may help reduce the lean tissue loss

• Dental issues• Energy requirements – decrease 15 – 20% – In the absence of disease– With disease can increase as much as 40%

Considerations for heat and cold stress

• Water – during hot periods, voluntary water intake increases 30 – 75%

• Salt should be available during hot weather• Additional vitamins and minerals do not seem to

be useful• During cold weather – DE should be increased 2 –

3%• Hay should be offered ad lib to allow horses to

feed to energy requirement

Considerations for exercise• How exercise is defined

• Light • 1-3 hours weekly• Mean heart rate is 80 beats/min• Recreational trail riding

• Moderate• 3-5 hours weekly• Mean heart rate is 90 beats/min• Show horses, light ranch work

• Heavy• 4-5 hours weekly• Mean heart rate is 110 beats/min• Eventing, race training

• Very Heavy• 6-12 hours weekly (or 1 hour speed work)• Mean heart rate is 110-150 beats/min• Elite eventing, racing

Exercise Considerations - Energy

• Digestible Energy– Light work = (0.0333 x BW) x 1.20– Moderate work = (0.0333 x BW) x 1.40– Heavy work = (0.0333 x BW) x 1.60– Very heavy = (0.0363 x BW) x 1.90

Ex. 500 Kg race horse= (0.0363 x 500) x 1.9 = 34.5 Mcal per day (> 70% more energy than light working)

Exercise Considerations - Protein• Protein requirement for maintenance

– BW x 1.26g CP/Kg BW– 500 Kg horse x 1.26 = 630 grams Crude Protein– Range of 1.08 – 1.44 as the multiplier

• Exercise losses in protein are due to: – Muscle gain– Nitrogen lost as sweat– Add protein to basal requirement

• Light = BW x 0.089 g CP (630 + 44.5 g = 675 g CP)• Moderate = BW x 0.177 g• Heavy = BW x 0.266 g• Very heavy = BW x 0.354 g (630 + 177 = 807 g CP)

– 20% more protein needed than lightly worked horses

Clinical Nutrition

• Hyperkalemic periodic paralysis (HYPP) • Polysaccharide storage myopathy (PSSM)• Developmental orthopedic disease (DOD)• Laminitis• Nutritional Secondary Hyperparathyroidism• Gastric ulcer syndrome• Colic• Enterolithiasis• Recurrent airway obstruction• Obesity

Laminitis

• Multifactorial – inflammatory • Associate with carbohydrate overload including over feeding

of grains, lush pastures– Frosted pastures

• Nitrogen compound overload– Pastures where nitrate fertilizers used– Pastures high in clover

Body Condition Scoring• Necessary means of managing weight when

weighing isn’t possible. • Farm/Stable Dependent.• What is function? • It is dependent on

structure

BCS = 1

BCS = 2

BCS = 3

BCS = 4

BCS =5