Clinical Nutrition

This part of my blog focuses on feeding strategies for the management and prevention of some nutrient-related diseases and disorders in horses and ponies. This part of the blog is designed to ensure you have a good understanding of the nutritional management of horses and ponies affected with laminitis and obesity, and also dietary management of older horses. By the end of this blog post you should be able to discuss rations for horses with specific nutrition-related disorders.

* Nutritional management of:
  - Horses/ponies susceptible to laminitis
  - Obesity
  - Horses/ponies with weight loss
  - Older horses/ponies

LAMINITIS
* "Barley Disease"- starch overload
* Pasture associated laminitis
  - High WSC
* Survey taken in the 1990's of cases of laminitis in UK
  - 61% at grass
  - 30% combined
  - 9% stabled
* US Survey: 46% of cases linked with pasture

LAMINITIS- PASTURE ASSOCIATED
* Turning out horses/ponies onto:
  - Lush pasture (actively photosynthetic)
  - Stressed pasture (low environmental conditions for growth)
  - Especially spring/summer
* Seems to trigger laminitis
  - When they ingest high WSC
* Recurrent in certain individuals
* Trigger= WSC containing pastures
* Spring/summer
* WSC levels= higher variable
* Varies throughout the day
* Grass species= higher variable
  - Ryegrass> fescue> timothy> grass
* Plant part is important
  - Stems and leaves
* High WSC pastures may influence laminitis in other ways
  - May promote insulin resistance
  - Insulin peaks similar to high starch diets
  - Lower threshold for laminitis to be triggered
* Other threshold lowering factors may be involved
  - Obesity
  - Genetic predisposition

OBESITY AND INSULIN RESISTANCE
* Man
  - Regional adiposity (visceral) is linked to diabetes and heart disease
* Horses/ponies
  - Regional adiposity (crest) is linked with laminitis
* Laminitis also linked to:
  - Generalized obesity
  - Hyperinsulinemia
  - Hyperleptinemia

OBESITY IN HORSES
* No universally accepted definition of obesity in horses/ponies
  - Henneke PCS= 8 to 9
  - 7= overweight
* BCS doesn't account for regional adiposity
  - May signify higher risk of disease
* But:
  - Not all horses/ponies that are obese develop laminitis
  - Not all obese horses are IR
  - Some "acceptable conditioned" animals are IR
  - Other possible risk factors may exist

LAMINITIS- AVOIDANCE
* Consider zero grazing
  - Use suitable forage alternative
* Turnout when fructan/WSC likely at lowest
  - Late at night to early morning
  - Remove from pasture by mid-morning
* Do not graze pastures not well managed
  - Maintain young leafy swards not mature stemmy pastures
* Avoid/restrict turnout in spring and autumn
* No turnout on pastures exposed to low temperatures
  - e.g. frosts followed by warm, bright sunny days
* Do not graze pastures during/following drought
* Grazing muzzles
  - Ensure water intakes
  - Behavioral issues
* Strip grazing
* Mowing and removal of cut grass
* Turnout in an arena (provide alternate forage)
* Rotate paddocks
  - Other species (cattle/sheep) so the grass stays the appropriate height
* Forage- base the diet on forage
* For horses with history of laminitis:
  - Analyse forage- feed forage with less than 10% WSC
  - Many hays in UK higher in WSC
  - Soak in water for atleast 3 hours to help lower WSC content
  - Soaking variable- best to feed lower WSC forage
* Broad spectrum vitamin/mineral supplement
* No evidence to suggest magnesium to lower laminitis
* Supplementary feeding most won't need this
* Avoid feeds that exacerbate IR
  - Cereal grains and NSC pasture
* Use oil instead of cereal grains (unless contraindications)
  - Introduce oil gradually into the diet
  - Add vitamin E at 100-150 iu/100 ml oil
  - No more than 100 ml oil/100 kg BW
* If cereal grains are fed
  - Need to processed by cooking (e.g. micronisation)
  - Increases SI starch digestibility
  - Restrict meal sizes to 0.25kg/100 kg BW of cereal based feed
Ensure overall starch intake is less than 1 g starch/kg body weight
* Other considerations
  - No sudden dietary changes
  - Avoid abruptly starving animals
  - Regular exercise wherever possible
  - Avoid development of obesity
  - Aim= BCS between 4 & 5 (moderate) out of 9
  - If overweight- plan a weight management program

OBESITY- WEIGHT MANAGEMENT
* Eat less and Exercise more
* General principals:
  - Total removal of high calorie feeds (cereal grains and oils)
  - No excessive feeding of treats (carrots, apples, etc)
  - Assess workload- be realistic about workload
  - Set realistic goals
  - Gradual dietary changes- avoid prolonged periods of fasting
  - At target weight- develop a weight maintenance program
  - Long term commitment is 4 to 6 months

WEIGHT MANAGEMENT- HORSE STABLED
* Removal from pasture- ONLY WAY TO CONTROL INTAKE
* Studies shown no change in BW with restricted access to pasture
  - 12 hours restricted access
  - High grass consumption during grazing period
  - Estimated ponies can eat 40% of daily DMI in 3 hours at pasture
* Advisable to begin at 2% BW/day for 6-8 weeks
* If weight loss by feed restriction alone lower the feed provision
* Lower to 1.5% of current BW per day for 8 weeks
  - Divide ration into 3-4 feeds per day
  - Use haynets with small holes

WEIGHT MANAGEMENT- HORSE KEPT AT GRASS
* Restrict access to small well managed paddocks
* Ensure free from toxic plants (hungry animals may eat them)
* Stall for significant portions of the day (feeding forage)
* Strip grazing
* Use grazing muzzle
* Muzzles
  - Not always easy to use
  - Duration of muzzling needs changed as BW changes
  - Horse/pony needs some time without muzzle
** NOTE: Short term removal from grazing by stabling or muzzling is healthier for the horse, although many people think that stalling is not good for their health or well-being.

WEIGHT MANAGEMENT- EXERCISE
* Weight loss increases when diet decreases and exercise increases
* 10 minutes walking in hand twice daily for first week
* Gradually increased to 1 hour daily
* As exercise increases feed restriction can be lowered

WEIGHT MANAGEMENT- MONITORING
* Not all animals lose weight at the same rate
* BCS not useful for short-term monitoring (less than 3 months)
* Horses should be checked weekly
* Using weighbridge or weight tape

HORSES/PONIES WITH WEIGHT LOSS
* Reasons:
  - Disease (needs investigation)
  - Poor nutrition (neglect or ignorance)- inadequate energy provision
  - Horses that are mis-managed are likely to eat food when offered
  - Diseased horses will not eat when offered food
* Some diseased horses eat and still lose weight
  - Poor absorption
  - Excessive loss or metabolism of nutrients
* A number of contributing factors may be present
  - e.g. marginal diet and poor dentition
* Considerations:
  - Teeth
  - Anthelmintic program
  - Evaluate the diet
* Absence of disease
  - Higher intake of digestible nutrients
  - Diet depends on extent of weight loss and age (growing)
* Severe cases (less than 3.5 of Henneke BCS Scale)
  - Gradual changes essential (re-feeding syndrome)
  - Usually occurs 3 to 5 days post change in diet
  - Electrolyte imbalances associated with high NSC feeding
* Re-feeding:
  - High fat, low NSC
  - Lucerne- High protein, low NSC
  - Grass hay- soak for atleast 3 hours
  - Small (0.5 kg) frequent meals (6 times daily) of forage
  - Gradual increase in amount over 10 days
  - Then gradually add higher energy dense feed
  - Maintain weight mid-point BW current and desired BW
  - Then increase feed gradually to reach desired weight
  - Oil is good- needs to be added gradually
  - Check electrolyte intake

OLDER HORSES
* Some studies shown lower digestibility
  - CP, phosphorus and fiber digestibility
* Others shown no difference
* Attributed to:
  - Damage to large colon (chronic parasitism)
  - Poor dentition
* Thus can assume older, healthy horses can be fed as per normal adult horse guidelines

OLDER HORSES- PROBLEMS
* Weight loss is most common nutritional problem
* Can be several causes:
  - Dental abnormalities
  - Renal and hepatic disease
  - Cushing's Disease
* Incidence or periodontal disease
  - One study: 60% in horses over 15 years of age
  - Second study: similar incidence in horses over 20 years of age
* Dietary Management
  - Grass is easier to chew than long-stem hay
  - Turnout is desirable
  - Feed high quality forage (high leaf to stem ratio)
  - Chop if required
* Severe cases
  - Commercial senior feed
  - Mixed with high fiber cube (alfalfa pellets or cubes)
  - Soak before feeding (warm water= higher palatability)
  - High volume of feed will lower daily DM intake
  - Oil can be added (if not in commercial feed)
  - Add Vitamin E if oil used (100 IU/100 ml oil)
  - Small, frequent feedings

OLDER HORSES- OTHER CONSIDERATIONS
* Often high quality and/or quantity of feed can increase intake and BCS
* Some horses increase intake if fed with companion horses
* Soak feed in warm water
* Add molasses or pureed apple
* Add flavorings i.e. crushed ginger cookies
* Older horses usually lower pecking order in field
  - Feed separately to increase intake
* Older horses may have OA
  - Feed from raised container to increase intake- OA of forelimbs
  - Raised container for hay (no haynet)- OA of neck

CLINICAL NUTRITION CONCLUSION
* Diet can impact on development of disease
* Good dietary management can prevent disease
* Dietary management can improve health
* Diet is integral to health
* PREVENTION IS BETTER THAN A CURE!!!!!!!!!!!!!!!

Abbreviations used in this section:
 

ADF = acid detergent fibre

BCS = body condition score

BW = bodyweight

Ca = calcium

CH4= methane

CHO = carbohydrate

CF = crude fibre

CO2= carbon dioxide

CP = crude protein

DE = digestible energy

DM = dry matter

DP = degree of polymerisation

G = grams

GIT = gastrointestinal tract

H2O = water

HT = High temperature

LAB = lactic acid bacteria

LI = large intestine

LW = live weight

IR = insulin resistance

Mg = milligrams

MJ = megajoules

NSC = non-structural carbohydrates 

 

VIDEOS TO WATCH REGARDING LAMINITIS

Dietary Management

This part of my blog focuses on ensuring you have a good understanding of different types of feeds that can be included in your horse's diet no matter the age or work load. By the end of this blog you should be able to define the nutrient requirements of horses and ponies and provide recommendations on rations.

DETERMINING BODY WEIGHT
* Essential part of dietary management
* Can be done by:
  - Weigh tape
  - Weighbridge
  - Measuring tape
* Equation: BW(kg)= [heart girth (cm) x 2x length (cm)

CONDITION SCORING
* 0 to 5 system
  - Carroll & Huntingdon, 1988
  - Ideal= between 2 to 3
* 1 to 9 system
  - Henneke, 1983
  - Ideal= between 5 to 7
* Henneke- scored on 1 to 9 scale
* Areas of body are graded 1 to 9
  - Average taken
* Areas assessed:
  - Loin
  - Ribs
  - Tailhead
  - Withers
  - Neck
  - Shoulders

CONDITION SCORING- THIN HORSE
* Loin
  - Negative crease
* Ribs
  - Very prominant
  - Easily seen and felt
  - No fat padding
* Tailhead
  - Prominent
* Withers
  - Affected by confirmation
  - Easily visible
* Neck
  - Can see bone structure of neck
* Shoulder
  - Prominent

CONDITION SCORING- OBESE HORSE
* Loin
  - Crease down back
* Ribs
  - Not seen
  - Very difficult to feel
* Tailhead
  - Bulging fat
* Withers
  - Bulging fat
* Neck
  - Thick all around "Cresty"
* Shoulder
  - Bulging fat, especially behind the elbow

NUTRIENT REQUIREMENTS
* Categories:
  - Maintenance
  - Pregnancy and lactation
  - Growth
  - Work
* Requirements are additive
  - Maintenance + activity
* Under/over supply of nutrient
  - Limit performance/productivity
  - Affect health
* Balancing diet begins with maintenance

MAINTENANCE
* Horses that are not:
  - Pregnant
  - Working
  - Growing
* Requirements depend on:
  - Bodyweight
  - The environment
  - Individual digestive and metabolic efficiency
* Feed intake
  - Generally 2% of bodyweight
* Forage only (with forage balancer)

BREEDING- PREGNANCY
* Pregnancy
  - Gestation= 11 months
  - First 4 months= maintenance
  - Last 7 months= adjust ration
* Requirements
  - Increased energy and protein
  - Reduced intake
  - Due to fetal growth
* Feed intake
  - Can reduce to 1.75% of BW
* Feed energy dense feeds (e.g. oils) and high protein feeds

BREEDING- LACTATION
* Lactation
  - Early and late lactation
  - Early lactation= 0 to 12 weeks
  - Late lactation= 12 weeks to weaning
* Requirements
  - High energy requirements
  - Early lactation= 2x maintenance
  - Late lactation= 1.75x maintenance
* Feed intake
  - Can increase to 2.5% of bodyweight
* Ensure ad lib water available
* Feed good quality forage
* Feed a stud mix
  - No more than 40% of the ration
  - Feed little and often
* Monitor condition
  - Feed more mix if losing weight
  - For easy keepers use a forage balancer to reduce calories

BREEDING- STALLION
* Breeding season
  - Naturally starts in spring
* Requirements:
  - Non breeding season feed for maintenance
  - Breeding season feed 1.2x maintenance energy and protein
  - Increased vitamin and mineral requirements
  - Depends on the number of mares covered
* Feed intake
  - 2 to 2.5% of bodyweight
* Feed broad spectrum vitamin and mineral supplement
* Feed good quality forage
* Can feed a stud mix
  - During breeding season
  - Feed little and often
* Monitor condition
  - Obesity affects breeding performance

GROWING HORSES
* Aims:
  - Steady increase in size and bodyweight
  - Avoid very rapid growth rates
  - Avoid compensatory growth spurts
  - Avoid getting overweight
* Foals:
  - Newborn= 10% of bodyweight
  -  One year old= 60 to 70% of adult weight (80 to 90% of adult height)
* Feed intake
  - 0 to 3 months eating solely mother's milk
  - 3 months mare's milk decreases and foal's requirements rise
* Feeding the foal
  - Begin to introduce feeds at 3 months to ready for weaning
  - Weaning occurs between 4 and 6 months of age
* Feed types
  - Good quality protein feeds
  - Low starch
  - Good vitamin and mineral levels
  - Good quality forage (e.g. grass)
  - Feed a youngstock pellet
  - Easy keepers should have balancer only
* Yearlings to 2 years
  - Growth rate begins to slow down
  - Correct feeding still essential
* Feeding:
  - Feed ad lib forage
  - Feed a forage balancer
  - Good quality forage should meet energy and protein requirements
  - Some youngsters may need supplementary feeding (stud feed)
* Two years onwards
  - Requirements affected by training (racehorses)
  - If not in training then forage alone
  - Growing horses in training have higher nutrient requirements
  - Diet should still be good quality forage plus supplementary feed

WORKING- LIGHT WORK
* Light work
  - Recreational riding
  - Beginning of training program
* Requirements:
  - Appetite= 2% BW
  - Good quality forage
  - Possibly supplementary feeds deepening on individual
  - Forage should comprise 70% of the ration
* Supplementary feeds
  - Low energy mix, sugar beet pulp, alfalfa, oil
* Feed broad spectrum vitamin and mineral supplement

WORKING- ENERGY SOURCES
* Dietary energy sources:
  - Oil
  - Carbohydrate (fiber, starch and sugars)
* Type of energy source required depends on:
  - Intensity of exercise
  - Duration of exercise
  - Temperature of the horse
  - Any clinical conditions
* Energy- calories
  - Horse diets use megajoules (1 MJ= 239 calories)
* Digestible energy (DE) is digested in the GIT
* Fiber as an energy source:
  - Slow release energy
  - Essential for gut health
* Starch as an energy source:
  - Instant energy
  - May cause excitability
  - Not suitable for obese horses/for horses with certain clinical conditions
* Oil as an energy source
  - Slow release of energy (high energy content)
  - Less excitable behavior
  - Must be introduced gradually (100 ml per week)
  - No more than 100 ml oil/100 kg BW (Vitamin E should be added to high oil diets)

WORKING- MODERATE WORK
* Moderate work:
  - Novice/intermediate level eventer
  - Dressage horse (medium level)
  - Grade A Showjumper
* Requirements:
  - Appetite= 2.25% BW
  - Good quality forage
  - Supplementary feeds
  - Forage should comprise minimum 60 to 70% of the ration
* Supplementary feeds:
  - Mix, sugar beet pulp, HT alfalfa, oil

WORKING- HEAVY WORK
* Heavy work:
  - 3 day eventer
  - Endurance horse (7o to 100 mile rides)
* Requirements:
  - Appetite= 2.5% BW
  - Good quality forage plus supplementary feeds
  - Forage should comprise minimum 50 to 60% of the ration
* Supplementary feeds
  - Mix
  - Sugar beet pulp
  - HT alfalfa
  - Oil

WORKING- VERY HEAVY WORK
* Very heavy work:
  - Racehorse
* Requirements:
  - Appetite= 2.25% BW
  - Good quality forage
  - Plus supplementary feeds
  - Forage should comprise minimum 50% of the ration
* Supplementary feeds
  - Mix
  - Sugar beet pulp
  - HT alfalfa
  - Oil

RULES OF FEEDING
* Provide adequate forage
* Feed concentrates little and often
* Feed consistently: amount and type
* Provide a good water source
* Control parasites
* Check teeth
* Monitor condition (and weight)
* Provide regular exercise

THE DIETARY MANAGEMENT CONCLUSION
* Feed high quality forage
* Use high degradable fibrous feeds
* Feed cereal grains in moderation
* Feed little and often
* Monitor bodyweight

Abbreviations used in this section:
 

ADF = acid detergent fibre

BW = bodyweight

Ca = calcium

CH4= methane

CHO = carbohydrate

CF = crude fibre

CO2= carbon dioxide

CP = crude protein

DE = digestible energy

DM = dry matter

G = grams

GIT = gastrointestinal tract

H2O = water

HT = High temperature

LAB = lactic acid bacteria

LI = large intestine

LW = live weight

Mg = milligrams

MJ = megajoules

NSP = non-starch polysaccharide

P = phosphorus

RAO = recurrent airway obstruction

SI = small intestine 

 

HORSE WEIGHT CALCULATOR

http://www.thehorse.com/tools/horse-weight-calculator

HORSEration APP

https://itunes.apple.com/us/app/horseration-free/id577847790?mt=8&ign-mpt=uo%3D2

Nutrient Sources

This part of my blog focuses on nutrient sources for horses and ponies. I am hoping at the end of this blog you will have a good understanding of different types of feeds that can be included in a horse's diet. You will learn advantages and disadvantages of various feeds and how knowledge of this can enhance the dietary management of horses to ensure good health, maximize performance and prevent nutrition-related diseases/disorders.

FORAGE
* Constitutes the higher portion of diet of all classes of horses and ponies
* Entire diet for horses and ponies in the wild and many domesticated horses and ponies
* Grazed directly (fresh) or conserved

FRESH FORAGE
* Natural environment for horse= grazing on fresh pasture
* Many domesticated horses still spend more time at pasture
* Some competition horses spend much less time at pasture
* Natural diet= low quality herbage
* Domesticated horse= improved pastures (higher nutritive value)

GRASSLANDS
* Chemical Composition
  - Extremely variable
  - CP= 3 to 30%
  - CF= 20 to 40%
  - WSC= 3 to 40%
  - Lipid= 1.5 to 3.5% (unsaturated)
  - Ash= 4 o 8%
  - DE (energy)= 7.5 to 12 MJ/kg DM (depending on time of year)
  - DE of legumes higher= 10 to 12 MJ/kg DM
  - Minerals= Higher in pastures containing legumes
* The amount of nutrition grass can provide depends on:
  - Time of year
  - Environment
  - General management of the pasture
  - Number of animals grazing the area
* Time of year:
  - Rapid in spring and early summer
  - Often more produced than animals can eat
  - Grazing pasture often cropped for conservation in spring
  - Used for grazing in summer
  - Less growth in autumn
  - Very little growth in winter
  - Ground damage in winter
  - Thus animals housed and fed conserved forages
  * Hay
  * Silage
  * Haylage
  * High-temperature dried

NUTRITIVE VALUE
 Dependent on:
* Stage of growth
  - Most important factor in nutritive value of grass
* Plant species
* Soil type
  - Grass responds well to soil with high fertility
  - Soil type can limit plant growth and nutrient content
* Environmental conditions
  - Temperature
  - Light
  - Rainfall

NUTRITIONAL INTAKES
* Nutritional quality and growth higher in spring and summer
* Difficult to estimate amount of grass eaten
* Most horses/ponies 2% of BW per day
* In spring/summer too much grass can be consumed
  - 1 acre will feed 3 to 4 horses
* Intakes lower in winter
  - 1 acre will feed 1 horse or 2 ponies

REQUIREMENT FOR CONSERVED FORAGE
* Seasonal growth needs to be conserved for winter feeding
* Provides forage when demand exceeds supply
* Some horses are stabled year round
* Grassland management tool
  - Grazing exceeds grazing needs

OBJECTIVES OF FORAGE CONSERVATION
* Preserve a product with high digestible nutrients
  - Quality of preservation key to:
  * Palatability
  * Longevity
  * Nutritional quality
  * Hygienic quality

METHODS OF FORAGE CONSERVATION
* By removing the moisture for aerobic storage
  - Dried in field, or barn, or part both
  - Haymaking and artificial dehydration
* By acidification in an anaerobic environment
  - Fermentation and storage of moist crop
  - Silage/haylage making

CONSERVED FORAGE- HAY
* Plant materials dried to 15% moisture content
* Usually field dried= good weather dependent
* Cut at late stage of maturity
* Stable at ambient conditions
* Changes during storage
* UK= grass hay
* Variable quality
  - Nutritionally
  - Hygienically
* Low energy (DE= 4 to 8 MJ/kg)
* Dust (RAO)
* Soak (10 minutes or steam)
* North America= Lucerne (alfalfa)
* UK too wet
* Higher protein
* Higher energy (DE= 10 MJ/kg)
* UK= conserved by HT drying

CONSERVED FORAGE- HT FORAGES
* Dried at very high temperatures
  - Efficient but very expensive
* Young forage= higher digestibility
  - Drying has little effect on nutritional quality
* Used as a short chop added to bucket feed
* Lucerne (alalfa)
  - DE= 10 MJ/kg DM
* Grass (readigrass)
  - No data in horses
* Alfalfa/straw mix
  - Lower energy

CONSERVED FORAGE- HAYLAGE AND SILAGE
* Fermentation of low DM crop
* Difference between haylage and silage= DM content
* Generally made from grass
  - Legumes (e.g. lucerne)
* Cut, wilted, ensiled

CONSERVED FORAGE- HAYLAGE
* Haylage
  - Typically grass haylage
  - Popular feed for horses
  - Higher DE than hay
  - Low dust
  - Palatable
  - Less need for cereal grains
  - Less aerobic stability

CONSERVED FORAGE- SILAGE
* Silage
* Clamp or big bale (clamp not usually fed to horses)
* Perceived as high risk
  - Acidity (no difference in faecal pH of horses fed silage compared to hay)
  - Laxative effect (only small difference in faecal DM)
  - Hygienic quality (can contain Listeria spp. or Clostridium botulinum)
  - Hygienic quality important- horse can't metabolize certain toxins
  - Haylage contains less moisture for microbial growth

CEREAL GRAINS
* Nutritional value:
  - CP: 80-120 g/kg DM
  - Low in protein quality (low essential aa)
  - Lipids: 10-60 g/kg DM (unsaturated)
  - Low calcium (less than 1 g/kg DM)
  - High phosphorus (3-5 g/kg DM)
  - Poor Ca:P ratio
  - High energy (starch)- DE12- 16 MJ/kg
  - Less variable than forage
* Commonly utilized grains:
  - Oats (40% starch, fiber content [hull]- naked oats those with no hull)
  - Barley (55% starch, high energy value)
  - Maize (70% starch, needs to be processed)
* Other grains:
  - Wheat
  - Rye
  - Sorghum
  - Triticale

OATS
* 40% starch
* Fiber content- hull
* Naked oats- no hull

BARLEY
* 55% starch
* Higher energy than oats

MAIZE
* 70% starch
* Higher energy than oats and barley
* Needs to be processed

BOTANICAL SOURCE OF STARCH
* No affect on TT digestibility= completely digested
* SI digestibility is affected

CEREAL PROCESSING
* Improves availability of nutrients
* Simple mechanical processing:
  -Rolling
  - Grinding
* More sophisticated techniques
  - Microsination (heat and mechanical pressure- infrared technology)
  - Extrusion (high temperature steam- then rolled into a flake)
* Cereals need to be processed for horses
* Improves SI digestibility
* Prevents grains passing to LI
 - = disturbance

STARCH INTAKES
* 500 kg horse- 0.5 kg starch per meal. No more than 1.2 kg oats per meal
1.2 kg x 40% starch= .48 kg

CEREAL GRAIN OVERVIEW
* Energy dense feed
* Consistent nutritional value
* Starch is only okay for horses in fast work (race horses)
* Needs to be processed
* Fed in moderation & small, frequent meals
* Utilize more high energy fibrous feeds

CEREAL BY-PRODUCTS
* Wheat Bran- major milling product fed in UK
  - Arising from milling of cereal grains
* Nutritional value is poor
  - High levels of lignin
  - Low calcium and High Phosphorus (poor ratio)
* High H20 holding capacity
* Easy way to administer medication
* Palatable= good appetite stimulent

FIBROUS BY-PRODUCTS
* Sugar beet pulp- commonly fed to horses
  - Soaked to prevent choke and stomach distention
* Residue after extraction of sucrose
  - Dried
  - Shredded or pelleted
  - Available with or without molasses
* Nutritional value
  - High fiber content; High fiber digestibility
  - Moderate CP content
  - High Ca content
* Sugar beet pulp- very good cereal replacer
  - Uniform composition
  - More favorable Ca content
  - Low risk of LI disturbances
  - High DM digestibility (85%)
  - DE of almost 13 MJ/kg DM
* Uses
  - Found in compound mixes
  - Added to bucket feed
  - Generally valued and under used

MOLASSES
* Residue following sugar extraction from the sugar beet root
* Thick residue after sugar separated from water extract
  - High soluble sugars
  - Often added to sugar beet pulp
  - And proprietary mixes, mineral "licks"
* Nutritional value
  - DE= 11 MJ/kg
  - CP= 50 g/kg
  - High CHO content

OIL AND OIL BY-PRODUCTS
* Vegetable oils- most commonly fed to horses
  - Corn oil (most palatable)
  - Soy oil
  - Sunflower oil
  - Rapeseed oil
  - Linseed oil
* Fish oils (particularly cod liver oil)
* Most oils have energy content= 9 Mcal/kg
* 2.25 more than CHO
* Use of oil in horse rations
  - Mainly to provide high energy content to the ration
* Other benefits seen
  - Improved energetic efficiency
  - Improved athletic performance
  - Enhanced body condition
  - Less excitable behavior
  - Improved health
* Oil by-products
  - Seeds grown for high oil content- oil extracated
  - Residue remaining- oil seed meal
* Oil seed meal
  - High protein
  - Generally used as protein supplement
  - Some oil content (1- 1.5% solvent or 4-5% mechanical)
* Types (High quality protein- High lysine)
  - Soybean meal
  - Linseed meal
  - Hempseed meal

NUTRIENT SOURCES CONCLUSION
* Feed high quality forage
* Use high degradable fibrous feeds
* Feed cereal grains in moderation and ONLY as a supplement to a fiber-based diet

Abbreviations used in this section:
 

ADF = acid detergent fibre

BW = bodyweight

Ca = calcium

CH4= methane

CHO = carbohydrate

CF = crude fibre 

CO2 = carbon dioxide

CP = crude protein

DE = digestible energy

DM = dry matter

G = grams

GIT = gastrointestinal tract

H2O = water

HT = High temperature

LAB = lactic acid bacteria

LI = large intestine

LW = live weight

Mg = milligrams

MJ = megajoules

NSP = non-starch polysaccharide

P = phosphorus

RAO = recurrent airway obstruction

SI = small intestine 

 

 

Digestion In The Equine Gastrointestinal Tract

This second part of my blog focuses on nutrient digestion in the equine gastrointestinal tract. My goal is to ensure you have a good understanding of nutrient digestion in the various segments of the gastrointestinal tract.

WHAT IS IN HORSE FEED?
General Constituents Of Feed:

WATER
* Essential component of the diet
* Water required for:
  - Transport of nutrients around the body
  - Thermoregulation
  - Metabolism
  - Excretion of water products
  - Gut function
* 80% of foal's BM= water
* Water makes up 65-75% of a mature horse
* Water requirements depend on:
  - Age
  - Level of exercise
  - Type of feed (horses drink less on high moisture diets)
  - Environmental conditions (i.e. temperature & humidity)
* Water in food
  - Referred to as moisture content
  - Many horse feeds have high moisture content
  _ Dry matter calculated to compare nutrients

CARBOHYDRATE (CHO)
* Collective name for:
  - Starches
  - Sugars
  - Dietary fiber
* CHO Definitions
  - Structural (fiber)
  - Non-structural (sugar, starch and fructan)
* CHO primary ingredient required for energy

STRUCTURAL CHO
* Components constitute fibrous fraction of plant
  - Structural role in plants (hence name structural CHO)
  - Dietary fiber
  - Major energy source to horses
* Cell wall components
  - Cellulose
  - Hemicellulose
  - Pectin
  -  Lignin
* Degraded by microbes in LI
  - VFA
  - Gases
  - Not digested in SI
* Feeds high in fiber
  - Grass
  - Hay
  - Straw
  - Sugar Beet Pulp

LIGNIN
* Lignin is non-CHO polymer
* Closely associated with NSP fraction
* Negatively correlated to digestibility
  - Gives plant strength but highly resistant to chemical and microbial degradation
  - Also some plant CHO & proteins "bound" to lignin= lowering their digestibility
* Lignin content higher with maturity
* Mature plants, hay and straw rich in lignin

STRUCTURAL CHO- STAGE OF MATURITY
* Primary factor in nutritive value of forages
* High maturity= hugh structural material (i.e. stem)
* Result= lower nutritive value

FIBER ANALYSIS 
* Acid detergent fiber (ADF)
  - Measures cellulose and lignin
* Neutral detergent fiber (NDF)
  - Total cell wall (including ADF fraction)

NON-STRUCTURAL CHO
* Associated with cell contents
* Components constitute storage CHO of plant
* Storage CHO of forage crops:
  - Fructan
  - Starch

NON-STRUCTURAL CHO- FRUCTAN
* Major storage CHO of grasses
* Located primarily in the stem
* Polymers of fructose
* Soluble in H2O
* Digestion:
  - Fermented in LI
  - Horse has no enzymes in SI to break down fructose
  - Large intakes of fructan can cause digestive upset (laminitis)

NON-STRUCTURAL CHO- WSC FRACTION
* Grasses also store simple sugars
  - Glucose
  - Fructose
  - Sucrose
* Fructan + Simple Sugars= Water soluble CHO (WSC) fraction

WSC CONTENT OF GRASS= HIGHER VARIABLE
* Season
  - Early spring: Higher growth= lower WSC
  - Late spring/summer: Lower growth= higher WSC
  - Year effects

Notice in 2nd chart above (in blue) studies reported highest incidence of laminitis in May)

WSC CONTENT OF GRASS= HIGHER VARIABLE
* Time of day
  - Balance b/w photosynthetic activity & utilisation
  - Affected by light & temperature
  - Higher during the day
  - Peaks late afternoon/early evening
  - Declines during hours of darkness

WSC- FACTORS AFFECTING ACCUMULATION
* Environmental & management factors
  - Temperature: Lower temperature= higher WSC
  - Light intensity: Higher light= higher WSC
  - Water stress: Lower water= higher WSC
  - Fertilizer application: Higher fertilizer= lower WSC
  - Cutting/mowing: Higher cutting= lower WSC

STARCH
* Major source of NSC found in many plants
  - Cereal grains
  - Forage legumes
  - Roots & tubers
  - Leaves and stems of grass

NON-STRUCTURAL CHO- STARCH
* Starch content varies with plant species
  - Very low in leaves and stems of grasses
  - Forage legumes= 5% of DM
  - Cereal grains= 40-70% of DM
* Digestion
  - Broken down in SI
  - Amylases break starch down to simple sugars
  - Horse can digest limited amounts of starch in SI
  - Excess travel to LI= causing disturbance

FATS AND OIL
* Horse diets typically lower in fats and oils
* Fats and oils are digested in SI by lipases
* Horses don't require high levels of fat and oils in their diet
* Can add fats and oils to diet to increase energy content
* Double energy of CHO

PROTEIN
* Required for various functions
  - Structural (e.g. muscle, skin, hair)
  - Enzymes (catalysts that effect the rate of reactions in the body)
  - Hormones (chemical messengers that regulate metabolic processes)
  - Immune compounds (for fighting infection)
  - Transport compounds (e.g. transport of nutrients)
* Consists of chains of amino acids
* Essential and non-essential amino acids
* Non-essential: synthesised by the animal
* Essential (need to be supplied in the diet)
  - Lysine (first limiting: present in the least amount relative to requirement)
  - Methionine
  - Threonine
  - Isoleucine
  - Valine
  - Arginine
  - Trytophan
  - Histidine
  - Phenylalanine
* Protein breakdown begins in the stomach
  - Acidity denatures the proteins
  - Pepsin partially degrades proteins into smaller peptides
  - No protein absorption in the stomach
* Further broken down in SI
  - Proteases break down proteins to aa
  - Absorbed across SI gut wall
* Protein associated with the plant cell wall- fermented in LI
* Protein digested in SI- used by the horse
* No aa absorption in LI
* Microbes in LI degrade protein
  - Used for microbial growth
  - No biological value to horse

MINERALS
* Required for various functions:
  - Growth
  - Co-factors to enzymes
  - Involved in transport of energy
* Mineral digestion
  - Majority absorbed in SI
  - Majority of P absorbed in LI
* Two categories of minerals:
  - Macro-minerals
  - Micro-minerals
* Macro-minerals:
  - Required in relatively large quantities (g/day)
 * Micro-minerals:
  - Needed in very small quantities (mg/day)
* Amounts important- also ratios of minerals (e.g. ca:p)
* Two categories of minerals:
Macro Minerals
** Required in g/day
- Calcium (Ca)
- Phosphorus (P)
- Sodium (Na)
- Potassium (K)
- Magnesium (Mg)
- Sulpher (S)
- Chloride (Cl)
Micro Minerals
** Required in mg/day
- Cobalt (Co)
- Copper (Cu)
- Molybdenum (Mo)
- Zinc (Zn)
- Maganese (Mn)
- Iron (Fe)
- Floride (F)
- Iodine (I)
- Selenium (Se)
- Chromium (Cr)
* Amounts important- also ratios of minerals (e.g. ca:p)

VITAMINS
* Required in small amounts- but vital for many bodily functions
  - Vision, immunity, growth, bone development, blood clotting, etc
* Two categories
  - Fat soluble (A,E,D,K)
  - Fat soluble= associate with fat to be absorbed & transported in blood
 - Water soluble (C, B Complex)- dissolve easily in water
* Water soluble vitamins not stored
  - B vitamins need to be supplied regularly
  - B vitamins produced by microbial synthesis in LI
  - But- disruption to LI environment (e.g. high starch diets) can affect this
  - Vitamin C synthesised in the liver

Abbreviations used in this section:
ADF: Acid Detergent Fiber
BW= Body Weight
Ca= Calcium
CH4= Methane
CHO= Carbohydrate
CO2= Carbon Dioxide
DM= Dry Matter
G= Grams
GIT= Gastrointestinal Tract
H20= Water
LAB= Lactic Acid Bacteria
LI= Large Intestine
LW= Live Weight
MG= Milligrams
NSP= Non Starch Polysaccharide
P= Phosphorus
SI= Small Intestine
VFA= Volatile Fatty Acid
WSC= Water Soluble Carbohydrate

VIDEO "3D HORSE DIGESTION GUIDE"

Anatomy and Physiology of the Equine Digestive Tract

This part of my blog focuses on the anatomy and physiology of the equine gastrointestinal tract. Most horse owners do not have a background in equine nutrition. By the end of this blog post you should be able to describe the anatomy of the gastrointestinal tract of the horse.

NATURAL ENVIRONMENT OF THE HORSE
Horses are highly sociable animals and having social time gives them a higher chance of survival. Horses communicate by body language since they can't actually "talk". Horses are prey animals and have a fight or flight instinct (hide or run).
 * Horses travel 4-16 miles per day
* Horses graze little and often
  - Grazing 16-20 hours per day
  - Low quality feeds, high in fiber

DIET
 Horses are non-ruminant herbivores known as a "hind-gut fermenter". This means that horses have only one stomach, as humans do. However, unlike humans they have to digest plant fiber that comes from grass and hay. Unlike ruminants which digest fiber in plant matter by use of a multi-chambered stomach, horses use microbial fermentation in a part of the digestive system known as the cecum or caecum to break down the cellulose.

In practical terms, horses prefer to eat numerous small feedings steadily throughout the day, as they do in the wild when grazing on pasture. This isn't always possible in modern times due to stabling practices and human schedules that favor feeding horses twice per day. It is important to remember the underlying biology of the animal when determining what to feed; how often and amounts.

The digestive  system of the horse is very delicate. Horses are unable to regurgitate food, except from the Esophagus. So if they overeat or eat something poisonous or fermented, vomiting is not an option. They also have a long, complex large intestine and a balance of beneficial microbes in their cecum that can be upset by rapid changes in feed. Because of these factors, they are very susceptible to colic which is a leading cause of death in horses. To prevent this, horses require clean, high-quality feed, provided at regular intervals and may become ill if subjected to abrupt changes in their diets. Horses are also sensitive to molds and toxins. So it is very important not to feed contaminated fermentable materials such as lawn clippings. Fermented silage or "haylage" is fed to horses in some places; however contamination of failure of the fermentation process that allows any mold or spoilage may be toxic.
* Intestinal system designed to process:
  - Higher amounts of low quality forage
  - Ingested on almost continual basis
  - Principal diet should be forage

DEPARTURE FROM NATURAL STATE
* Continual grazing and moving
* Not voluntarily confined

CHANGED USE
 * Mechanisation of agriculture:
  - Working animal to leisure or sports horse
 * Types of feedstuff changed
  - Include energy dense feeds- cereal grains
  - Meet energy requirements of sports horse

CHANGED FEEDING MANAGEMENT
 * Meal feeding:
  - Large meals of cereal grain 2x's daily
* Grain supplementation greater than forage
  - Often less than recommended
  - Minimum 1kg DM forage/100kg LW
* Whilst intestinal system requires largely unmodified

ENCOUNTERED SOME PROBLEMS
 * Health Implications
  - Gastric ulceration
  - Hind-gut acidosis
  - Azoturia
  - Laminitis
  - Colic
* Outcomes
  - Poor performance
  - Irreparable damage
  - Euthanasia

WHAT CAN WE DO?
 * Consider digestive anatomy and physiology
  - Maintain gut health
* Understand behavioral needs
  - Maintain good welfare
* Develop dietary management regimes that avoid or even overcome diet-related problems

GIT AS A WHOLE
* Horses are classified anatomically as non-ruminant herbivores
  - Non-ruminants= enzymatic digestion (limited fiber degradation in LI)
  - Ruminant= fiber digestion in the rumen
  - Horse= sit between these
* GIT begins at lips and ends at anus
* GIT consists of 3 functional regions
  - Stomach
  - Small Intestine
  - Large Intestine
(Stomach and Small Intestine being the foregut & Large Intestine being the hindgut)

GIT CONSISTS OF:
 - Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Caecum
- Large Colon
- Small Colon
- Rectum
ASSOCIATED ORGANS CONSIST OF:
- Teeth
- Tongue
- Salivary Glands
- Liver
- Pancreas

 THE MOUTH
* Digestion begins in the mouth
* Upper lip guides food into the mouth
* Feed torn by upper and lower incisors
* Molars and premolars grind the forage into smaller particles
* Chewing is essential for digestion (regular dental checks are important)
* Horses chew 70-90 times per minute and saliva is produced in response of chewing

THE STOMACH
* Size- relatively small and inelastic
  - Capacity of 8 litres (size of a rugby ball)
  - Important not to over fill (no more than 2 kg per meal)
  - Reason why we feed little and often
* Divided into 2 sections (non-glandular and glandular)
  - Non-glandular section is where food enters (no mucous layer)
  - Glandular is where hydrochloric acid is produced (protected by mucous layer)
* Acidic- pH 1.5 to 2 in the glandular region
* Little digestion of feed- some protein breakdown (no absorption)
* Rate of passage- rapid (20 minutes)

THE SMALL INTESTINE
* Size- a 21 to 25m long narrow tube
  - 30% of horse's GIT volume (75% of its length)
  - Joins the stomach to the large intestine
* Three main parts
  - Duodenum (first part after the stomach)- mixing and neutralizing
  - Jejenum
  - Illeum (last part before the LI)- absorption of nutrients
* pH of digesta entering the SI ranges from 2.5 to 3.5
* Bile (secreted from the liver) buffer the pH to approximately  7 to 7.5 (no gall bladder)
* Brunner's Glands secrete bicarbonate into the lumen- further neutralize digesta

THE SMALL INTESTINE CONT'D
* Neutral pH required for:
  - Transport of nutrients across gut wall
  - Optimal activity of enzymes (anylases, lipases, etc)
* Surface area increased by:
  - Villi (0.5 to 1mm long)
  - Crypts (covered by columnar epithelium)
  - Crypts secrete enzymes and mucous to cover intestinal surface
* Absorption greatest in proximal jejenum
* Rate of passage between 45 minutes and 2 hours
  - Depends on diet, type of food, meal size and amount of forage in the diet
* Digesta moves at 30 cm per minute via peristalsis (muscular contractions)

THE LARGE INTESTINE (ALSO KNOWN AS THE HINDGUT)
 * Size- approximately 7 metres long (capacity 150 litres)
  - 60% of horse's GIT volume
* Three main parts
  - Caecum (first part after the ileum)
  - Large colon
  - Small colon
  - Rectum
* Large intestine lined with mucous-secreting glands- no digestive enzymes
* Digestion & absorption in LI depends on microbial fermentation feed residues from SI
* Caecum- 1.2 metres long (capacity of 30 litres)
  - 15% of horse's GIT volume
  - Large blind-ended sack-like structure
  - Digesta enters LI through ileo-caecal valve; leaves through the caeco-colic valve (both at top)
  - Large fermentation vat (similar to the rumen of the cow)
* Large Colon- 3 to 3.5 metres long (capacity of 90 litres)
  - Right and left ventrical colon
  - Left and right dorsal colon
  - Four parts connected by bends known as flexures (often sites of impaction)
* Small Colon
  - Same length as large colon
  - Smaller diameter
  - Main function= absorb water
* Horses do not produce enzymes to digest fiber
* Microbes ferment digest- produce end products
  - Volatile fatty acids (VFA)= acetate, butyrate and propionate
  - Gases= carbon dioxide (CO2) and methane (CH4)
* Microbes- over 400 species (probably more)
  - Bacteria
  - Fungi
  - Protozoa
* pH of LI= 6 to 7 (very important to maintain correct pH)
  - Bicarbonate and phosphate salts secreted
  - Rapid absorption of VFA
* Microbes need time to adapt to any changes in diet
* Abrupt changes:
  - Reduced diet digestibility
  - Colic
  - Acidosis
* Hindgut designed to process fiber
* Problems occur when low fiber diets are fed
* Particularly when high levels of starch are included in diet
* High amount of starch and sugars in LI
  - Undesirable
* Rapidly fermented:
  - High levels of VFA
  - Lactic acid produced
  - Low pH
* Adverse affect on LI environment
  - Death of fiber degrading bacteria
  - Colic
  - Acidosis/laminitis

THE GIT- CONCLUSION
 * Designed to process fibrous feeds
* Fibrous feeds require for:
  - Healthy gut
  - Satisfy behavioral needs
* Sudden changes to diet or inappropriate diets can lead to:
  - GIT disturbance
  - Reduced diet digestibility
  - Ill health

Abbreviations used in this section:
LW= Live Weight
DM= Dry Matter
LI= Large Intestine
SI= Small Intestine
GIT= Gastrointestinal Tract
VFA= Volatile Fatty Acid
CO2= Carbon Dioxide
CH4= Methane
LAB= Lactic Acid Bacteria 

VIDEO "THE HORSE'S DIGESTIVE SYSTEM"