Dairy Nutrition
• Considerations
– Nutrient requirements
– Nutrient content of feeds
• Sampling for accuracy
– Processing of feeds
– Cost of feed
• Availability
• Contracting
– Management style
– Data evaluation
Understanding Dairy Nutrition
• Nutrients
• Dietary formulation
– Sampling feed ingredients
• Feeding management
• Cow observation
Early Mid lactation Late
Dry Matter Intake
Milk
Production
Body Weight
0 1 3 9-11 12 13 14
Month
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Nutrient Requirements
(NRC)
Nutrient needs of animal
•Based on body weight, milk
production, milk fat content,
pregnancy and growth
Feed tables with “book” values
•Nutrient content of feeds
http://www.nap.edu/catalog.php?record_id=9825#toc
Milk Rules of Thumb
• Peak
– 30 to 70 days postpartum
• Second month on DHI test
– Heifers (1st lactation) possibly later
– Peak times 200 equals lactation total potential
• Example: 100 # X 200 = 20,000#
• Persistency
– 1st lactation cows drop 6% per month after peak
– Older cows drop 9% per month after peak
Nutrition Based on Dry Matter
Dry matter = as fed x % dry matter
Dry matter % = dry matter x 100%
as fed
Dry matter intake is always less than as fed
intake!
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Dry Matter Intake Guides
Dry Cows: (B.W. x .0185)
23 pounds of DM for maintenance (1250#)
Milk Cows:
(.0185 x B.W.) + (.305 x lb 4% FCM)
4% FCM = (0.4 X lb Milk) + (15 X lb Fat)
1 lb of DM milk yield 2 - 2.5 lb
NRC Dry Matter Intake
lb DMI per day
4% FCM
Milk Yield
(lb) 880 lb BW 1,100 lb BW 1,320 lb BW 1,540 lb BW
44 32 35 38 40
66 39 43 46 49
88 48 51 53 55
110 NA 59 62 63
132 NA NA 71 74
Changes in Nutrient Requirements
Body Wt + NEL CP Ca
Milk (3.5%) (Mcal) (lb) (lb)
1400 lb BW 10.12 0.932 0.057
1400 lb BW + 10.12 + 0.932 + 0.057 +
60 lb/d 18.6 = 5.04 = 0.18 =
28.72 5.972 0.237
1400 lb BW + 10.12 + 0.932 + 0.057 +
150 lb/d 46.5 = 12.6 = 0.45 =
56.62 13.532 0.507
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Dilution of Maintenance Costs
(% of nutrient for milk)
Body Wt + NEL CP Ca
Milk (3.5%) (Mcal) (lb) (lb)
1400 lb BW 10.12 0.932 0.057
1400 lb BW + 28.72 5.972 0.237
60 lb/d (64.8%) (84.4%) (75.9%)
1400 lb BW + 56.62 13.532 0.507
150 lb/d (82.1% (93.1%) (88.8%)
Energy Sources
• Carbohydrates (Fermentable)
– Fiber (Cell wall)
• Cellulose, hemicellulose
– Non-Fiber (Cell contents)
• Starch, sugars
• Fats and Oils (Not fermentable)
Diagram of a plant cell showing cell wall structure
Cell Content
Protein
Sugar
Primary
Fats Wall
Starch
Pectins Secondary
Wall
Hemicellulose
Cell NDF
Wall Lignin
ADF
Cellulose
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ADF
(Acid Detergent Fiber)
* Lignin and cellulose
* Cell wall of the plant
* Digestibility is lower
* Increases as plant matures
* Predicts energy level
NDF
(Neutral Detergent Fiber)
* Total cell wall
* ADF + hemicellulose
* Modest digestibility
* Dry matter intake control
* Increases as plant matures
Total Digestible Nutrients
(TDN)
Expressed as % or lb
• Older system; moving to each “nutrient” needs
• Digestible Protein (70%)
• Digestible Crude Fiber (30 - 40%)
• Digestible Nitrogen Free Extract (80%)
• Digestible Ether Extract (60 - 80%) X 2.25
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Net Energy Basis
Expressed as Mcal/lb
• Net Energy Maintenance NEM
• Net Energy Lactation NEL
• Net Energy Growth NEG
Partitioning of ration (60% Alfalfa & 40% Corn) energy and losses in a
lactating cow
Net Energy (40%)
Metabolizable NE
Energy (60%)
Digestible ME
Energy (70%) Losses as heat (20%)
1. Fermentation
DE 2. Nutrient metabolism
Gross Energy
in feed (100%)
GE Losses in urine (5%)
and in gas (5%)
Loss in feces
(30%)
Net energy system
Forage Analysis
Proteins, Ether Extract (Lipids), Ash (Minerals)
Cell Contents
Sugars, Starches, Pectins
Nitrogen-Free
Extract Hemicellulose
Alkali-Soluble
NDF
Alkali-Insoluble Cell
ADF Wall
Crude Fiber
Cellulose
Forage analysis showing Crude Fiber
(Green) versus Van Soest (Yellow)
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Protein
Total Crude Protein
• CP = Nitrogen (N) x 6.25
• 100 lb CP = 16 lb N
• 100 / 16 = 6.25
• Example: Alfalfa hay =
3% N x 6.25 = 18.75% CP
Available Protein
• Protein available for digestion
• Should be 90% or more of CP
• Less than 90% CP available indicates:
– Heat damage
– Excessive maturity at harvest
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Unavailable Protein
• Protein unavailable for digestion
• Should be less than 10% of CP
• If greater than 10% of CP indicates:
– Heat damage
• Malliard Reaction
• Carmelized protein
– Pay attention to distillers grains and other
heated protein sources
– Bound protein
– ADF-N (ADIN)
Avoid Heating & Carmelization in Silages
• Proper stage of maturity
• Correct moisture content
– Oxygen-limiting (45 - 50%)
– Conventional (55 - 60%)
– Bunkers & bags (65 - 70%)
• Length of chop
• A tight silo or pack well
• Fill rapidly
• Seal if needed
Crude Protein (CP) = Nitrogen x 6.25
Contains Protein & NPN
Unavailable CP
• Bound or ADF-CP (ADIN)
Available CP • when protein is overheated
• Mostly undigestible & excreted in feces
Rumen Degradable CP Rumen Undegradable CP
May be soluble or insoluble Largely insoluble and
• Used by microbes passes to small intestine
Digestible CP in intestines & Undigestible CP in intestines
supplies amino acids to cow & excreted in feces
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Nonprotein Nitrogen (NPN)
• N not in a protein
• True protein is N in a long chain of
amino acids
• NPN must be incorporated into
microbial protein to be beneficial
• Examples of NPN
– Urea
– Monoammonium phosphate
– Free amino acids
Sources
• Some slides adapted from Dairy
Nutrition & Management (ANSCI
200/492), University of Illinois at
Urbana-Champaign, Dr. Mike Hutjens
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