M.E. Persia
Iowa State University
4/16/2012

Type of
Digestion
Enzymatic
Enzymatic
Microbial
Microbial
Microbial
Foregut
Stomach
Small Intestine (70 feet)
Hindgut
Cecum (4 feet)
Large colon (10 – 12 feet)
Small colon (10 – 12 feet)
Capacity % of the
GIT
8-15 L 8
68 L 30
28 – 36 L
86 L
16 L
15
38
9
Adapted: Atlas of Topographical Anatomy of the Domestic Animals,
Popesko, P., W.B. Saunders

• 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.

• 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
Alfalfa – early bloom
Alfalfa – full bloom
Bluegrass
Orchardgrass
DE (Mcal/Kg)
2.42
2.16
2.15
2.2
TDN, %
55
49
50
50.0
CP, %
17.2
15.0
15.0
16.0
DP, %
13.4
10.1
12.6
13.5

• Many warm season grasses contain higher concentrations of oxalates and phytates – can lead to Calcium/Phosphorus concerns.
• Cyanogenic glycosides are high in Sorghum,
Sudan grass, hybrid Johnson grass, and
Sorghum – Sudan hybrids; therefore, not recommended for horses.

• Clostridium, Listeria can be issues with ensiled forages
• Endophyte contamination
• Mycotoxins
• Yellow and White Sweet Clover – Penicillium
spp. – product dicoumarol poisoning
• Toxic plants

• 2 species of concern
– Epicauta vittat
– Epicauta pennsylvanica
• Toxin = cantharidin
• Fatal

• 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

Classification
Mature horses
Growing horses
Mature ponies
Donkeys
Diet type
Hay
Corn silage
Mixed forage + concentrate
Maximal DMI = 3 – 3.2% Body weight
DMI (Kg per 100 Kg BW)
1.8 – 3.2
2.0 – 3.0
1.5 – 5.2
2.3 – 2.6
2.0 – 2.4
0.97
> 2.0

• 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

• What is the management system?

• 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

• 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

• 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%

• 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

• 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

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

• 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

• 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

• Necessary means of managing weight when weighing isn’t possible.
• Farm/Stable Dependent.
• What is function?
• It is dependent on structure