Horse Nutrition March 29, 2013 M.E. Persia Iowa State University 4/16/2012

Digestive Anatomy Type of Digestion ForegutCapacity% of the GIT EnzymaticStomach8-15 L8 EnzymaticSmall Intestine (70 feet) 68 L30 Hindgut MicrobialCecum (4 feet)28 – 36 L15 MicrobialLarge colon (10 – 12 feet) 86 L38 MicrobialSmall colon (10 – 12 feet) 16 L9 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 ForageDE (Mcal/Kg)TDN, %CP, %DP, % Alfalfa – early bloom Alfalfa – full bloom Bluegrass Orchardgrass

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 – – 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? – 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 ClassificationDMI (Kg per 100 Kg BW) Mature horses1.8 – 3.2 Growing horses2.0 – 3.0 Mature ponies1.5 – 5.2 Donkeys2.3 – 2.6 Diet type Hay2.0 – 2.4 Corn silage0.97 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? – 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 – related 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 beats/min Elite eventing, racing

Exercise Considerations - Energy Digestible Energy – Light work = ( x BW) x 1.20 – Moderate work= ( x BW) x 1.40 – Heavy work= ( x BW) x 1.60 – Very heavy= ( x BW) x 1.90 Ex. 500 Kg race horse = ( 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 g CP ( g = 675 g CP) Moderate = BW x g Heavy = BW x g Very heavy = BW x g ( = 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