feeding horses student version 2013

7/28/2019 Feeding Horses Student Version 2013

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227.208 Equine Nutrition

Erica Gee BVSc, PhD, Dip ACTRoom 1.21

[email protected] 2013

Acknowledgement: Dr Simone Hoskins

Equine Nutrition Lectures

Monday 29th April 11am SSLB6

Thursday 2nd May 9am SSLB6

Monday 6th May 11am SSLB6

Powerpoints on Stream, plus required reading

Who am I?

Senior lecturer in Equine Science

Equine nutrition and reproduction

[email protected]

Learning objectives

Evaluate the diet of a horse

Explain the main principles of feeding horses

Discuss the benefits and potential problems of

pasture based diets for horses

Discuss the effects of nutrition on health and

well-being of horses

Lecture outline

The basics of feeding horses (and why the horse isnot a cow!)

The role of fibre

Assessing fatness and adequacy of diet

Pasture as a nutrient source

Where problems occur & how to prevent them by

feeding practice

Why feeding is both art & science

Prior knowledge assumptions

Equine GI tract anatomy

Equine GI tract physiology

Nutrients & nutrient digestion

Protein & amino acids

Lipids

Carbohydrates & fibre

Vitamins & minerals

Some knowledge of equine management, behaviour,breeds etc
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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The digestive system

Foregut

Mouth

Oesophagus

Stomach

Small intestine

What is happening in the small

intestine?

Enzymes, bile, other digestive juices

Feed passes through in 30-90 minutes

Digestion

Soluble carbohydrates (sugars and starch)

glucose

What enzyme is rate limiting for starch digestion?

Most protein from grains

Oils and fats

Calcium, phosphorus, B vitamins, vitamins A, D, E, K

The equine digestive system

The hindgut

Caecum

Large colon

Small colon

Rectum

What happens in the hindgut?

Giant fermentation vat

Bacteria break down fibre volatile fatty

acids (VFA)

B vitamins

Fermentation takes days

Quality

Water reservoir

Features of GI tract Lips, tongue, teeth

High degree of selectivity

Fibre grinders

Stomach

Small capacity, fast passage

Cardiac sphincter = one way valve

Normally rarely empty & highly buffered

Small intestine

Relatively fast passage

Urea secretion terminal ileum

Gall bladder

Large intestine & caecum

Big capacity

Slow passage

Mucus & motility

Bends & flexures

Microbial fermentation

Absorption VFAs, H2O, NH3, vits

Acetic, butyric & proprionic

Designed for high fibre diet low in soluble

carbohydrate & no sudden changes in diet


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Natural feeding behaviour

14-18 hours per day grazing

Covering 10-15 km per day Grasses preferred with some legume/ browse

The domesticated horse

The equine athlete Sources of energy

Horse at pasture

75 to 80% of energy from VFAs (ie hindgut

digestion

Horse in heavy work (fed lots of grain)

obtain 70 to 75% of their energy from starch and

oil digested in the small intestine

How do we know a diet is adequate?

The horse can

Perform as desired

Maintain appropriate body condition and weight

Excess dietary energy not desirable

Assessing fatness/adequacy of diet

Humans

Weight Skinfold thickness

BMI

Waist circumference

Bioelectric impedance analysis, MRI and CT

And the horse?

Weight

Condition score


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Body condition scoring

Condition Scores: Texas A&M

1 POOR

Horse is extremely emaciated. The backbone, ribs, hipbones and tailhead project prominently. Bone

structure of the withers, shoulders and neck easily noticeable. No fatty tissues can be felt.

2 VERY THIN

Horse is emaciated. Slight fat covering over vertebrae. Backbone, ribs, tailhead and hipbones are

prominent. Withers, shoulders and neck structures are discernible.

3 THIN

Fat built up about halfway on vertebrae. Slight fat layer can be felt over ribs, but ribs easily discernible. The

tailhead is evident, but individual vertebrae cannot be seen. The hipbones cannot be seen, but withers,

shoulder and neck are emphasized.

4 MODERATELY THIN

Negative crease along back. Faint outline of ribs can be seen. Fat can be felt along tailhead. Hip bones

cannot be seen. Withers, neck and shoulders not obviously thin.

Condition Scores: Texas A&M

5 MODERATE Back is level. Ribs can be felt but not easily seen. Fat around tailhead beginning

to feel spongy. Withers are rounded and shoulders and neck blend smoothly into the body.

6 MODERATELY FLESHY May have a slight crease down the back. Fat on the tailhead feels soft.

Fat over the ribs feels spongy. Fat beginning to be deposited along the sides of the withers, behind

the sholders and along the neck.

7 FLESHY A crease is seen down the back. Individual ribs can be felt, but noticeable filling

between ribs with fat. Fat around tailhead is soft. Noticeable fat deposited along the withers,

behind the shoulders and along the neck.

8 FAT Crease down back is prominent. Ribs difficult to feel due to fat in between. Fat around

tailhead very soft. Area along withers filled with fat. Area behind shoulders filled in flush with the

barrel of the body. Noticeable thickening of neck. Fat deposited along the inner buttocks.

9 EXTREMELY FAT

Obvious crease down back. Fat is in patches over rib area, with bulging fat over tailhead, withers,

neck and behind shoulders. Fat along inner buttocks may rub together. Flank is filled in flush withthe barrel of the body.

Optimal body condition

Varies with

discipline

Individual variation

Evidence for

optimal body

condition

Racehorses

Endurance horses

Overall weight and

body condition score

What is normal?

Depends.

Age

Sex

Purpose

Season

Breed

Etc etc etc


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Body weight

In humans excessive body weight may be

associated with

Cardiovascular disease

Type 2 diabetes

Sleep apnea

Osteoarthritis

Visceral fat is important.

Fat animals?

Not desirable in meat producing

animals

Overfat heifers have decreased lifetime

milk production

Cats and dogs associated with

increased risk for diabetes

And a fat horse?

Excessive fatness and obesity is a growing problem

Predisposed to laminitis, metabolic disease

Risk factor for hyerlipidemia

Athletic performance

Heat tolerance

Exacerbate osteoarthritis

Reproductive performance???

Developmental orthopaedic disease???

Condition scores for athletes

BCS for broodmares

Start of breeding season:


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Typical body condition scores

Dressage 2.5-3/5

Endurance 1.5-2/5

Eventing ~2/5

Show horses 2.5-3/5

Race horses 1.5-2.5/5

1.5 trim, poor-moderate

2.5 fleshy, mod-good

3.5 heavy, good-fat

What horses evolved to eat

Evolved on prairie/ rangeland

10-20 km per day travel

Native grasslands

Big variety in mostly perennial species

Predominantly grasses, but also herbs & legumes

Unselected for digestibility or performance

Diet

Highly fibrous, high in minerals, low protein

Energy mainly from VFAs not glucose

Pasture too good?

But horses evolved as

pasture grazers didnt

they??

Modern pasture ok for modern horses?

No, modern pastures designed for ruminants

High sugar, low fibre

Not great for pasture ornaments

Yes, modern pastures are great for some

Rapid growly young horses, pregnancy, lactation,

horses in hard work

Yes, poor/older pastures are great for some

Pasture chemical composition

% DM Leafy RG Seeding RG

Soluble sugars 14 10

Hemicellulose 16 26

Cellulose 21 27

Lignin 3 7

Protein 15 6

Lipid 9 5

Ash 8 6

Waghorn et al, (2007) NZSAP Occ.Publ. 14.

Whats wrong with high soluble

carbs/ low fibre?

MAY result in:

Digestive disturbance, rapid fermentation

Hindgut acidosis, risk factor for

Laminitis

Colic

Azoturia, Exertional Rhabdomyolysis etc

Behavioural problems

Metabolic disorders, insulin resistance

Developmental Orthopeedic Disease?


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Nutrition and laminitis

Pasture-associated

laminitis Fructans

Soluble sugars

Grain overload

Undigested grain in

hindgut, rapid

fermentation

Can pasture be ok as sole diet?

It can be too good

Pasture can provide enough energy & protein

Similar growth of TB youngstock on NZperennial ryegrass pasture as pasture + grain

overseas

However, macro & micro minerals?

But can be difficult to assess quantity/ quality

Pasture vs requirementsPasture/ hay MJ DE/kg DM g CP/kg DM

PRG/WC NZ

Leafy spr ing 12 230

Stalky summer 8 100

USA

Bermudagrass 10 125

Kentucky BG 9 175

Native Meadow (h) 7 87

Native Prairie (h) 7 64

Requirements* MJ DE/kg DM g CP/kg DM

Maintenance 8 80

Growth 4-6mo 12 145

*NRC (1989) Nutrient requirements of horses (USA)

Pasture problems

Too little

Too much

Damage to pastureand soil

Overgrazing

Encouraged growth ofweeds eg docks

Horse sick paddock:faecal rejection

Pasture

Not just for exercising

Nutrient content

variable

Faecal rejection and

overgrazing

Horse sick pastures

Infective parasite

larvae

But all horses need forages!

Forage basis of diet: min 1.5% BW as DM

Essential for hindgut fermentation

Pasture, hay, preserved forages

Grass, alfalfa/lucerne, clover

Quality importance

Smell, colour, dust, stem:leaf

Not energy dense

Variable energy, digestibility and palatability withmaturity

Variable nutrient


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Conserved forages for horses Hay (soaking vs not soaking)

Grass vs legume mix:

Lucerne, clover, pea-vine, herb high protein, Ca

leaf:stem, smell, dust, mould, damp, weeds etc

Chaff (chopped legume hay or oat straw)

Commonly lucerne, red clover, oaten, pea-vine

Hage, baleage, silage

Lucerne and chopped oat hage custom made for horse

Conventional pit pasture silage not recommended (bewaresecondary fermentation, clostridium)

Baleage/ haylage lower risk

Pasture and macrominerals

Ca:P min ratio 1.5:1 vital

Forages tend to be high Ca, grains high P

K - reqts easily met by forages

Na - specific reqts not known, adaption to Na

restriction, pasture likely to be limiting?

Cl - specific reqts unknown, adequate when Na reqts

met with NaCl

Pasture Ca P Cu Se

PRG/WC 3.3-4.2 3.0-3.8 7.5 0.02

Tall Fescue 3.0 3.1 6.3 0.02

Reqts.* Ca P Cu Se

Maint. 2.4 1.7 10 0.1

Growth 4-6

months

5.6-

6.8

2.2-3.4 10 0.1

Pasture vs requirements mins

*NRC (1989), Hoskin & Gee (2004)

g/kg DM mg/kg DM

Nutritional-secondary

hyperparathyroidism NSHP Millers, Bran or Big Head Disease

From diet with low Ca:P, low [Ca], oxalates (kikuyu

grass)

High P levels or oxalates can impair utilization of Ca

which result in low blood Ca levels.

Stimulation of parathyroid gland which results in Ca

removal from bones

Often caused by high feeding levels of wheat bran

(Ca:P ratio, 1:12), tropical grasses like kikuyu (oxalates)

Microminerals

Mg - deficient pastures causing Mg tetany in

ruminants ok for horses?

Behavioural problems w spring pasture, low Mg?

Lots of supplements sold

Research required

Microminerals

Co*, pastures inadequate for ruminants ok for horses

Cu, important for growth, developmental orthopaedic

disease prevention, potential interaction with other

minerals, NZ soils deficient

I*, deficiency = goiter, abnormal oestrus

Mn*, Mo* not deficient in NZ pastures?

Se, NZ soils deficient = white muscle disease,

nutritional myopathy, toxicity w overdose supplements

Fl* Zn*, Fe*?

* Not specifically determined for horses


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Vitamins Fat & water soluble vits high in fresh forage

Hay storage reduces vit content

Soaking hay leaches vits

B & K synthesised by hindgut bacteria

But absorption may vary

High fibre diet needed

Deficiencies may occur w low fibre pasture, acidosis, concentratefeeding

D, need ultraviolet light (stables & covers)

Vit C synthesised in hepatic tissues

Biotin supplementation above adequate enhanced hoofgrowth in some horses

But

We usually dont know the nutrient content of

pastures or hays for horses!

Review lecture 2

Pasture is a good, cheap source of nutrition for horses,especially young horses, broodmares

PRG good energy and protein, marginal Ca? NB usually dont know the nutrient content

Energy content can be too high

NSH oxalates bind Ca, altered Ca:P BigHead

PRG may have low fibre and high sugar during rapidgrowth that not all horses do well on GI disturbances, behaviour

Overgrazing, lawns and troughs, faecal contaminationand parasites

Ryegrass staggers

Lolitrem B in high endophyte grasses Yes, affects horses too

Over-react to external stimuli Muscles tremors, uncoordinated gait

Usually late summer after drought when grazingvery low

Remove from pasture, hay Low or no endophyte pasture? Horse friendly

pasture?

Blood tests Mycotoxin binders

Feeding the equine athleteWhy not pasture alone?

As energy requirements increase

the ration needs to become moreenergy dense

Maintenance: eats about 2% BWper day as DM

Can consume up to max 3% BW perday as DM

Pasture has low energy density

BUT must consume at least 1.5%BW as forage each day for GI health


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What other energy sources are there?

Grains (oats, barley, maize)

Premixed feeds (grains, chaff, minerals and

vitamins often)

Fats and oils

Superfibres

(Protein)

Meeting energy requirements:

carbohydrates

Oats

Barley Maize

Palatable

Energy varies

Starch digested in small

intestine

-amylase limiting: no more

than 2.5kg per meal!

GI disturbances common

Meeting energy requirements:

carbohydrates

Processed grains

Loose

Pelleted

Extruded

Sweetfeeds

Added sugar

Complete and premixed

feeds

Must be fed as directed

Same for balancers

Are grains bad?

No!

Energy dense, variable protein, often low in

minerals and vitamins

Quality variable

Affordable

Problems with too much grain

Rapid fermentation of undigested grain in hindgut Behaviour

Problems with grain: grain overload

Undigested soluble CHO in hindgut

Proliferation of lactic acid producing bacteria

Change pH

Death of gram negative bacteria

Endotoxin in cell wall

Any disruption in mucosa allows endotoxin to be absorbed

Laminitis and endotoxaemia

How much grain to feed?

Limit of 2.5kg per

meal/500kg


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Grain meals

Sugar high after meal

Linked with

Hot and excitable behaviour

Stereotypies

Muscle problems in susceptible horses

Development orthopaedic disease in

youngsters

What if grains make the horse too hot?

Try other energy sources

Fermented forages

Other sources of highly digestible fibre

Sugar beet pulp

Soya hulls

Fat-fortified feeds and fat supplements

Vegetable oil

Stabilised rice bran

Alternative energy sourcesFats and Oils

Incorporated in many prepared feeds

Up to 10% DE (even up to 25% of total MJ)

Energy dense so smaller volume required

Vegetable oils more palatable, introduceslowly

Performance benefits?

Calmer

Improved fat oxidation; glycogen sparing

Fats and Oils

Incorporated in many prepared feeds

Up to 10% DE (even up to 25% of total MJ)

Energy dense so smaller volume required

Vegetable oils more palatable, introduceslowly

Performance benefits?

Calmer

Improved fat oxidation; glycogen sparing

Protein Supplements

Often overdone!

Usually as the energy content increases the

protein also increases

Most protein supplements 20-25%CP

Quality of protein in important

lysine for young horses

Usually expensive


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Minerals and vitamins

Often overdone!

Complete, premixed and balancer feeds

Ca:P ratio (NB grains)

Iron not required

Selenium important

Toxicity: acute and chronic

Other supplements

Often not much information

Overdone?

Creatine, carnitine, branch chain amino acids

Antioxidants

Evaluating the diet of a horse

Diet evaluation

Check energy content

Usually too much (fat, fizzy horse), or too little

(thin, lethargic horse)

Check forage content and quality of feedstuffs

At least 1.5% BW as forage DM each day

Check protein content

Minerals and vitamins

Basic rules

50 to 100% diet as forage

Horses eat between 1.5 and 3% of their bodyweight as drymatter each day

Small stomach

Important hindgut bacteria

No more than 2.5kg grain at any time

Small feeds often

Feed by weight not volume

Change feeds slowly (hindgut bacteria)

Feed as individuals

Optimal nutrition

May optimise performance

Wont improve genetic potential

Wont make up for poor training


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Dietary problems in the equineathlete

Feeding behaviour issues

Horses are not nutritionally wise!

Feed shortage = abnormal behaviour

High concentrate:roughage / low roughage availability

= abnormal behaviour Stabling w. ad-lib hay = similar behaviour to grazing

pasture

Feeding time budget constant despite herbageavailability

Herbage shortage, horse needs to extend feedingbudget but doesnt = undernutrition

Herbage excess, horse needs to restrict feedingbudget but doesnt = overnutrition

Effect of feed type on time spent behaving

abnormally in horses(Cuddeford,1996)

nFeed Feed

level% of time

spent

feeding

% time inabnormal

activities

Pasture 6 Grass Ad-lib. 58 0

Stable 5 Hay Ad-lib. 55 2

Tie-stall 5 Hay Ad-lib. 64


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Typical diets

12 year old pony 450kg (430-480. Prone to beingoverweight when not in work.)

Currently: hunts twice weekly. 3kg red clover/ryegrass hay

Balancer pellets for mineralsand vitamins

Sugarbeet if pasturequality/quantity decreases

Oats if reqd

Summer: Jenny Craigpaddock Balancer pellets for minerals

and vitamins

Grass hay (stalky)

Typical diets

5yo Standardbred gelding, full training 480kg

Paddock trained

Approx 6kg premixed feed

1-2kg fermented forage

1-1.5kg lucerne/oaten chaff

Electrolytes

Mineral mix

Apple cider vinegar

Garlic

Summary

Optimal nutrition for optimal performance

Each horse is an individual and needs to be

fed as such

Forage is more than a filler

Grains arent always bad but there are

alternatives

Aim for a balanced dietthere can be toomuch of a good thing

Questions?

feeding horses student version 2013

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