Energy Systems in Nutrition

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Energy Systems in Nutrition

• AS 233

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Energy

• Feedstuff energy denotes the value of feed for
  its primary functionto furnish energy for body
  processes and to form the nonnitrogenous, organic
  matter of tissues

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Energy

• Energy is needed to make the systems of the body
  function and maintain life
• Animals consume plants and/or organisms to obtain
  the stored energy within the plant and/or
  organisms

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How do we measure energy?

• Calorie Amount of energy required to raise 1 g
  of water, 1? C (14.5? C - 15.5? C)
• Bomb calorimeter allows us to measure the gross
  energy of a substance
• Measures the ? heat when a known amount of sample
  is ignited by monitoring the temperature of the
  surrounding water
• Gross Energy (GE) Energy released as heat when
  an organic substance is completely oxidized to
  CO2 and H2O

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Bomb Calorimeter
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How do we measure the energy requirements of
animals?

• Comparative Slaughter
• Gross energy of feed
• Gross energy of the carcass before feeding period
• Gross energy of the carcass after the feeding
  period
• Calculate the energy requirement by dividing Mcal
  of the difference in tissue energy by the energy
  of the diet

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How do we measure the energy requirements of
animals?

• Animal loses heat to the environment
• SENSIBLE LOSSES Heat lost through convection,
  conduction, or radiation from body
• EVAPORATIVE LOSSES Heat lost via excreta,
  respiratory tract, or skin

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How do we measure the energy requirements of
animals?

• Heat loss can be measured
• Directly
• Indirectly
• Direct Calorimetry
• Determined by the rise in temperature (Sensible
  losses) and humidity (Evaporative losses) of
  absorbing medium

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How do we measure the energy requirements of
animals?

• Respiratory (indirect) Calorimetry
• Based on principle that metabolic heat production
  is the result of oxidation of organic compounds
• Measure the volume of O2 produced, CO2 and CH4
  expired
• CH4 Accounts for microbial activity

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Respiratory Calorimetry
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Measures of Feedstuff Energy

• Total Digestible Nutrients (TDN) a term used to
  express the energy value of a feedstuff or feed
  mixture

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Total Digestible Nutrients

• The chemical analysis values determined on
  feedstuffs are multiplied by their digestion
  coefficients to determine digestible nutrients

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Calculation of TDN for Grass Hay
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Total Digestible Nutrients

• Limitations
• Does not account for other important losses
• Urine
• Combustible losses
• Heat
• Losses are larger for roughages than concentrates
• Thus, lb of roughage has less value for
  productive purposes than for concentrates

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Partitioning of Feedstuff Energy
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Gross Energy (GE)

• Total potential energy of a feedstuff consumed
• Determined by bomb calorimetry

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Fecal Energy (FE)

• During digestion and absorption, GE is broken
  down
• Sources of Fecal Energy
• Dietary GE escaping digestion
• Energy yielding products of metabolism
  originating in the GIT
• Sloughed microbial and mucosal cells
• Digestive enzymes
• Collection of fecal material to determine

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Digestible Energy (DE)

• Computed as GE FE
• 30 - very mature, weathered forage
• 90 - Processed, high-quality cereal grains
• Fails to capture the major energy losses
  associated with digestion metabolism of food
• Overestimates high fiber feeds (hays grasses)
  and underestimates low fiber, highly digestible
  feeds (cereal grains)
• TDN ? DE

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Gaseous Products of Digestion (GPD)

• Include
• Combustible gases that escape the body during
  digestion and absorption
• Methane (CH4) mainly
• Important in herbivore diets (ruminants)
• Not as much a factor in monogastrics
• Measure during direct calorimetry
• Expensive and time consuming

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Urinary Energy (UE)

• Energy released into urine
• Result of intermediary metabolism
• Spent enzymes
• Food losses
• Tissue catabolism

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Metabolizable Energy (ME)

• Sometimes referred to as the useable portion of
  the ingested energy
• Computed as DE UE GPD
• Swine Poultry use ME as their expression of
  energy
• Swine ME is 96 of DE value

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Heat Increment

• Increase in heat production following feed
  consumption
• Consists of 2 components
• Heat of fermentation (HF)-heat produced by
  digestive tract as result of microbial action
• Heat of nutrient metabolism (HNM)-heat produced
  in metabolism as a result of using absorbed
  nutrients
• Wasted in most cases except when being used to
  keep the body warm (part of NEm)

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Net Energy System

• Derived to better evaluate energy utilization and
  partitioning in Ruminants (esp. Beef and Dairy
  cattle, and sheep)
• Swine ME b/c very little HI
• The NE system takes into account heat lost
  through microbial fermentation, digestive
  processes nutrient metabolism
• Computed as ME HI

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Net Energy System

• Energy is partitioned into 3 main categories
• NEm net energy for maintenance
• NEg net energy for gain
• NEl net energy for lactation

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Net Energy System

• Energy is used more efficiently for maintenance
  lactation, compared to growth
• NEg Requirement is dependent on composition of
  gain (fat vs protein)
• NEm requirement - defined as the amount of E
  intake that will result in no loss or gain in
  body energy content
• Measured Amount of E equivalents expended
  during fasting heat production

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Net Energy System

• NEl Energy needed to produce milk
• Can use NEm value due to the similar efficiencies
  of ME use for maintenance and lactation
• NEl is 98.5 efficient compared to NEm
• NEl requirements change according to milk fat

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Net Energy System

• NEm includes Basal Metabolism
• Body Activity
• Thermal Regulation
• NEg includes Pregnancy (fetus) in females
• Semen in males
• Tissue growth
• Fat
• Eggs
• Wool, fur, feathers
• Work

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Net Energy System

• Advantages of this system
• 1. The partitioning of NE into NEm and NEg
  results in a better accountability of E
  efficiency between maintenance and growth

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Net Energy System

• Advantages of this system
• 2. Energy requirements are independent of the
  caloric density of the diet
• 3. Predicts Animal Performance using a wide range
  of feedstuffs

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What can change energy requirements?

• Previous plane of nutrition
• Production scenario and level
• Climate - Thermal Environment
• Pen Conditions - Muddy, frozen, etc.
• Breed

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What can change energy requirements?

• Gender
• Physiological Age
• Body Composition - Fat vs Lean
• Disease
• Stress - Environmental, social, behavioral

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Review of Energy Feeds
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Corn

• Usually the most cost efficient energy source on
  the market
• Basis for most diets
• Poultry Swine Extensively use corn as their
  base diet
• Beef, Dairy Sheep Corn can be replaced w/
  by-products to a certain degree
• DDGS, Gluten feed, etc
• TDN 88 NEm 0.99 Mcal/ NEg 0.68 Mcal/

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Milo (Sorghum)

• Small particle size can be a major problem
• Usually need some processing to break the
  particle down
• Steam-flaking or rolling
• Energy density similar to corn
• 85 on whole-shell basis
• 98 - 100 on flaked basis
• TDN NEm (Mcal/lb) NEg (Mcal/lb)
• Dry 76 .83 .54
• Rolled 82 .91 .61
• Flaked 88 .99 .68

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Barley

• Found mainly in the northern United States
• 2xs the fiber content (NDF) compared to corn
• 2 Fat
• TDN NEm (Mcal/lb) NEg (Mcal/lb)
• Barley 84 0.93 0.63

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Oats

• Found throughout the Midwest
• Used heavily in the horse industry
• Prevention of colic
• Considered a great fiber source - hulls
• 5 Fat
• 42 NDF compared to 45 NDF of Corn Silage
• Starch digestibility 61
• TDN NEm (Mcal/lb) NEg (Mcal/lb)
• Whole 73 .78 .50

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Wheat

• Wheat forage is grazed in N. Texas, Oklahoma S.
  Kansas
• Bloat Acidosis problems
• Highly fermentable (starch digestibility 83)
• Wheat middlings
• By-product of the flour milling industry
• Tremendous binder
• TDN NEm (Mcal/lb) NEg (Mcal/lb)
• Whole Wheat 84 0.93 0.63
• Wheat Midds 83 0.92 0.62

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Corn Silage

• Usually 50 forage 50 grain (DMB)
• Most efficient use of field product
• DM yield/acre
• Excellent roughage source
• highly digestible (75 - 80 digestible)
• Used mainly in ruminant growing programs
• TDN NEm (Mcal/lb) NEg (Mcal/lb)
• 75 0.74 0.47

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Energy Byproduct Feedstuffs

• Corn Gluten Meal Feed
• Distillers Grains w/ solubles
• Ethanol industry
• 4-5 xs higher in fiber vs corn
• Brewers Grains
• Alcohol industry
• Tallow
• Animal fat (Rendering facilities)
• Yellow Grease (Fancy Grease)
• Restaurants, etc.

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Use of fat as energy source in rations

• Ruminants
• lt 5 added dietary fat
• gt 5 Reduce fiber digestion, possible toxic
  effects on microbes, formation of soaps
• Monogastrics
• Questionable in weanling pigs 7 - 28d of age
• Growing-Finishing pigs
• ? intake, ? feed utilization efficiency
• Reduced heat increment
• advantage in heat stress situations b/c fat used
  first for energy over CHOdecreases metabolic
  heat output

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