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