AVS466 Dairy Cattle Nutrition Introduction

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AVS466 - Dairy Cattle NutritionIntroduction

• David Marcinkowski
• Extension Dairy Specialist

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Class Website www.umaine.edu/animlvet/AVS466/ind
ex.htm

• It can also be reached from my staff page on the
  AVS website

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Nutrition Affects Everything

• Production
• Economics
• Health
• Reproduction
• Growth
• Labor
• Genetic Expression
• Agronomic Systems
• Impact on nutrient cycles
• NPK

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Farm Nutrient Cycle
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Nutrient Cycles

• More nutrients (N, P, K) enter the farm in the
  form of feed than fertilizer
• Can create build up that leads to problems
• Maine dairy producers buy a lot of grain off farm
  
• Nutrients tend to build up in the soil over time.
  It takes 1 - 2.5 acres of land just to get rid of
  the nutrients from one cow. 
• Pollution potential.
• N run off into water supplies, ammonia into the
  air
• P and K build up in soils
• P runs off with erosion - Eutrophication
• Much research interest in decreasing excretion of
  these nutrients by gaining better digestion with
  erosion

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Blame the Nutritionist!

• Nutrition is so important, blame everything on
  nutrition. 
• Some problems on the farm are caused by
  nutrition, but many more are caused by
  management, reproduction, genetics, etc.

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Feeding is Costly

• Feed represents
• 40-60 of the total operating costs on dairy
  farms.
• 70-80 of the cost of raising heifers.
• Costs include feed that is purchased from other
  sources., but also seed, fertilizer, lime,
  fencing, gas, oil, equipment, repairs, chemicals,
  labor and building (silos etc.)
• Witter Center feed costs
• 5.61 per lactating cow per day
• 1683 per cow per year
• 7.48 per cwt of milk produced
• about 67,000 per year for the milking herd

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High Milk Production With Low Feed Costs

• Dairy producers always striving for more
  production with less costs
• Shouldnt they be striving for greater profit?

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High Production Benefits

• More milk means more income
• More milk means more costs
• More milk means more profit
• Spreading out maintenance costs over more lbs of
  milk
• Spreading out fixed/overhead costs over more lbs.
  of milk.
• Marginal costs go down
• High production doesnt cause stress

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Marginal Costs

• Marginal cost to produce and additional lb of
  milk
• More production means dilution of the maintenance
  requirement so marginal cost goes down
• Maintenance costs 1/day
• Milk production variable costs 10 cents/lb
• Marginal cost goes down
• 1 lb/day - 1 1(0.10) 1.10
• 2 lb/day - 1 2(0.10) 1.20 (0.60)
• 10 lb/day - 1 10(0.10) 2.00 (0.20)
• 11 lb/day - 1 11(0.10) 2.10 (0.191)
• 100 lb/day - 1 100(0.10) 11.00 (0.11)
• 101 lb/day - 1 101(0.10) 11.10 (0.1099)
• Milk sells for 15 cents / lb
• Never want to do anything that reduces milk
  production!

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High Production Problems

• Generally increased production is the animals
  response to a reduction in stress
• Better housing More milk
• Production increases the risk of problems
• As production goes up the tightrope gets narrower
• But if management is there we dont have to see
  more problems
• Greater chance of metabolic problems such as
  acidosis, ketosis, milk fever, laminitis etc.
• Greater chance of other health problems-
  mastitis, reproduction, culling etc.
• When put on a per unit of milk basis the
  incidence of many of these health problems is
  actually less

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Law of Diminishing Returns

• As production increases
• Ration becomes more sophisticated and expensive
• More difficult to squeeze all nutrients into a
  volume the cow can consume
• At some point the law of diminishing returns
  kicks in
• Point exists when an increase in feed cost for an
  additional pound of milk is greater than the
  return form the pond of milk

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Nutrient

• Definition
• A dietary essential for one or more species of
  animal
• All animals do not require the same nutrients
• Laboratory analyses determines the nutrients we
  feed
• Fiber vs ADF
• Ruminants have simpler dietary nutrient
  requirements because many are supplied by the
  rumen bugs

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Nutrient Categories

• Protein
• Carbohydrates
• Lipids/Fats
• Minerals
• Vitamins
• Water

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Chemical Analysis Scheme
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Protein is Required to

• Principle component of body tissues
• Enhance feed intake and energy use
• Enzymes
• Supply N to the rumen microbes
• Ammonia, Amino acids, Peptides
• Supply amino acids for synthesis of
• Milk protein
• Tissue protein
• Enzymes, hormones etc.
• What are proteins and amino acids?

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Chemical Structure of Amino Acid
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Protein
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Amino Acids

• Essential and Nonessential
• Nonessential - synthesized by body
• Essential - 10 Essential AAs
• Necessary for the animal
• Must come from diet
• Not a concern in most ruminant diets because
  essential AAs are synthesized by rumen bugs
• However in higher producing animals we see a
  response to adding certain AAs

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Protein Terminology

• Intake protein IP - What the cow eats
• Crude Protein Calculated from Nitrogen content
  of feed
• Proteins are 16 N
• Multiply N content of feed by 6.25 (100/16)
• Soluble and Insoluble - refer to breakdown in
  water or rumen fluid
• SIP Quickly available to rumen bugs

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Protein Terminology

• Degradable and Undegradable - refers to whether
  it breaks down in the rumen or not
• Degradable - Broken down in rumen and used by the
  rumen bugs
• DIP or RDP
• Undegradable protein is also referred to as
  bypass protein
• UIP or RUP

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Protein Terminology

• Microbial protein - refers to protein produced by
  the bugs in the rumen
• Calculated from the ration NSC and degradable
  protein available to the bugs
• If you have a balance of these two you maximize
  rumen microbial activity

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Two Proteins Available to Cattle

• True protein - AAs
• Non-protein nitrogen NPN
• Any form of available nitrogen
• Rumen microbes use both sources for the
  production of microbial protein
• Microbial protein supplies 50 of cows protein
  requirement
• Microbial protein is much higher quality protein
  than the feed components from which it was
  produced
• As a result you don't have to worry too much
  about the amino acid (AA) content of the diet or
  providing the essential AA in diet.

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Essential AA Profiles
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Proteins in Rumen

• Proteins hydrolyzed to AAs and peptides
• Protein degradability
• Not all bypass protein is equal
• of dietary protein that is broken down
• Amino acids have one of two fates
• Incorporation into microbial protein
• Deamination to ammonia and VFA
• Important because some microbes need ammonia
• Ammonia is used to make other AAs
• But this process wastes energy because VFA used
  for energy

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NPN Non Protein Nitrogen

• Utilized by rumen microbes to make AAs
• Produces ammonia in the ruminant
• Several forms
• Ammonia
• Urea Most common
• Rumen has high urease activity Broken down
  Quickly
• 45 Nitrogen
• 281 protein
• Other nitrogenous compounds - Nitrates etc.
• Use questionable in high producing cows

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Rumen Ammonia

• Two Fates
• Used to form AAs and proteins
• Process needs carbon skeleton to form AA
• Carbon comes from sugar or VFA
• Energy needed
• Balance of P and CHO important
• Imbalance causes more ammonia to be absorbed
• Absorbed by rumen into blood
• Liver converts to urea
• Recycled or excreted in urine
• Conversion requires energy

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Limitations of Microbial Protein Synthesis

• Two most likely limitations
• Energy available
• NH3 available
• These need to be synchronized
• For diets containing urea, may also need
• Sulfur (for S-containing AA)
• Branched-chain C-skeletons
• MO cannot make branched-chain C-chains
• These normally not a problem

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Matching Protein and Energy Sources
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Energy

• Not a nutrient
• Obtained from several sources
• Carbohydrates - CHO
• Fats - 2.25 times the energy
• Proteins Via deamination

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Carbohydrates

• Major source of energy for cattle
• Makes up more than 65 of DM in feeds
• Broken down in rumen to VFAs, methane, carbon
  dioxide and water
• Two types
• Structural and Nonstructural
• Tremendous differences in the speed with which
  structural and nonstructural breakdown in the
  rumen.
• Structural Slow Nonstructural - Rapid
• Compatible combination important for good rumen
  digestion

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Volatile Fatty Acids VFAs

• Acetic acid 2 Carbons
• Absorbed by the rumen wall
• Oxidized throughout the body to generate ATP.
• Proprionic acid 3 Carbons
• Removed from portal blood by the liver.
• In the liver, proprionate used for
  gluconeogenesis
• Butyric acid 4 Carbons
• Rumen as ketone beta-hydroxybutyric acid
• Most used by the rumen wall

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Carbohydrate Forms

• Sugars
• Starches
• Pectins
• Hemicellulose
• Cellulose
• Lignin
• 1-3 Nonstructural
• 4-6 Structural

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Sugars

• Glucose, Fructose, Sucrose, Galactose etc.
• Most easy form to digest
• Quickly utilized by rumen bacteria within minutes
  
• Little to none bypasses the rumen
• Water soluble
• Located mainly in the plant cell cytoplasm
• Present in whole grains and forages

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Sugars

• Many byproducts are low in sugars and starches
  because these are removed in the processing of 
  flour, alcohol and sweeteners.
• Beet Pulp
• Corn Gluten Feed
• Brewers grain
• Distillers Grains
• Sugars are higher in forages and whole grains
• Molasses is a good feed to increase sugar content
  of ration

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Chemical Structure of Glucose
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Starches

• Sugar polymers
• alpha bonds
• Readily digested in the rumen
• Breakdown less efficient than SI - Methane
• Second best energy source for most rumen bugs
• Hydrolysis to sugars by amylolytic bacteria
• 50 may bypass rumen Rate of passage
• Sugars and starches make up NSC
• Feeds
• Whole grains highest
• Forages next
• Most byproducts are low

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Chemical Structure of Starch
                                                 
                                                  
     
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Sugar and Starch Measures

• Non-structural Carbohydrate
• Determined Enzymatically with amylase 
• Non Fiberous Carbohydrate
• Determined by subtraction
• NFC DM-NDF-CP-Fat-Ash
• Includes pectins
• Expressed as percent of DM
• NSC and NFC often used interchangeably but they
  are different, because of pectin level.
• These values will be similar in feeds that have
  little pectin.
• way off on feeds like beet pulp that have a lot
  of pectin.

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Pectins

• Structural carbohydrate?
• Intercellular glue
• Linear and branched chains galacturonic acid
  molecules
• High digestibility in rumen
• Present in forages and some by products
• Beet pulp, Citrus Pulp and Soy Hulls

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Structure of Pectins
Linear and branched chains galacturonic acid
molecules
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Cellulose and Hemicellulose

• Cell wall components
• Structural CHOs
• Long branched chain polysaccharides
• Hemicellulose contains pentose sugars (mainly
  xylan) and other compounds
• Insoluble in water
• Digestion requires cellulolytic bacteria
• Slowly digested
• Digestibility affected by lignin
• NDF - both
• ADF - just cellulose

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Structure of Cellulose
Beta bonding
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Plant cell wall
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Lignin

• Structural carbohydrate - Wood
• Cell wall component
• Indigestible by ruminants
• Fungi
• Slows digestibility of all other components
• Present in ADF and NDF
• Polymer of aromatic alcohols
• Heavily crosslinked polymer of aromatic/phenolic
  alcohols
• Forms a net like structure around other cell wall
  components

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Structure of Lignin
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Fiber Measures

• Acid Detergent Fiber
• Lignin and Cellulose
• Cell wall of the plant
• Digestibility is lower
• Increases as the plant matures
• Predicts energy level
• Neutral Detergent Fiber
• Total cell wall
• ADF hemicellulose
• Moderate digestibility
• Dry matter intake control
• Increases as plant matures
• Both expressed as percent of the DM

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Net Energy Measures

• Energy level in a feed or ration can be expressed
  in a variety of ways.
• TDN Total digestible nutrients
• NFE Nitrogen free extract
• Net Energy Basis
• NEM
• NEL
• NEG
• Expressed as Megacalories of Energy - Mcals

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Net Energy

• Different types of livestock get different
  amounts of energy from a feed. Depending on
  whether the energy is used for
• Maintenance
• Production
• Growth

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How are they calculated?

• The NEM is calculated by determining the amount
  of the feed required to keep an animal at a
  constant weight. 
• The NEG value of a feed is calculated by
  determining the energy deposited as fat and
  protein in body tissue from feed consumed above
  that needed for maintenance. 
• The NEL value of a feed is calculated by
  determining the energy utilized to produce milk
  from feed consumed above that needed for
  maintenance. 

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Net Energy Regressions

• The NEL content of a feed is difficult to
  determine experimentally, so NEL is not measured,
  but calculated. Usually as a function of
  something that can be measured such as TDN or
  ADF.
• NEL of Grass 1.085-(0.0150 X ADF) 
• In this case NEL is a function of ADF!

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Source of Energy is Important

• Ground Corn vs Corn Gluten Feed
• Both have NEL of .89 Mcals/lb
• GC 9 NDF CGF 45 NDF
• Which is best?

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Source of Energy is Important
Which is better?
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Lipids
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Fats

• Also known as Ether Extract
• Highest energy per lb
• Chemical structure
• Fatty acids - Hydrocarbon chains
• Glycerol
• Majority absorbed in small intestines
• Few converted to VFAs
• Too much fat in the diet inhibits rumen digestion
  of cellulose
• Fatty Acids inhibit bacteria
• Coats fiber to prevent breakdown

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Chemical Structures of Fats
Fatty Acid                                   
Triglyceride
Palmitic Acid 16 Carbons Stearic Acid 18
Carbons Oleic Acid 181 Linoleic Acid 182