ENERGY REQUIREMENTS

1
ENERGY REQUIREMENTS OF RUMINANTS
2
FEED ENERGY SYSTEMS

• Total digestible nutrients (TDN)
• Traditional system to express digestible energy
  concentration of feedstuffs
• Basis of TDN are physiological fuel values
• TDN, DM DP DCF DNFE (2.25 x DEE)

Nutrient Heat of combustion, kcal/gm Heat of combustion of metabolic products, kcal/gm Nutrient absorption, Physiological fuel value, kcal/gm
Carbohydrates 4.1 - 98 4.0
Fats 9.45 - 95 9.0
Protein 5.65 1.30 92 4.0
3

• Equivalence in energy units
• 1 lb TDN 2000 kcal Digestible Energy
• 1 kg TDN 4400 kcal Digestible Energy
• Limitations of TDN
• Limitations with digestion trials
• Errors in chemical analyses
• Errors in digestibility trials
• Low feed intake increases digestibility
• DMI at 3x maintenance reduces TDN by 8
• Underestimates or does not include all energy
  losses in metabolism
• Underestimates energy loss in urine (5)
• Does not include methane gas
• End product of rumen fermentation
• 3 10 of feed energy
• Does not include
• Work of digestion
• Heat of fermentation
• Heat of nutrient metabolism
• Overestimates the usable energy value of feeds

4
CALORIC SYSTEM

• Energy units
• Calorie (cal)
• Amount of heat required to increase the
  temperature of 1 gm of water from 14.5 to 15.5oC
• Kilocalorie (kcal) 1000 cal
• Megacalorie (Mcal) 1000 kcal 1,000,000 cal
• Caloric system subtracts digestion and metabolic
  losses from the total energy of a feedstuff

5
CALORIC SYSTEM
Gross Energy
Fecal Losses
Digestible Energy
Urine Losses
Gaseous Losses
Metabolizable Energy
Heat Increment Losses
Net Energy
Heat of Nutrient Metabolism
Heat of Fermentation
Retained Energy
Work of Digestion
Maintenance
Lactation
Stored Energy
Growth
6
COMPARISON OF ENERGY FRACTIONS IN DIFFERENT
FEEDSTUFFS
Corn grain kcal/g Alfalfa Hay (midbloom) kcal/g Oat Straw kcal/g
Gross Energy 4.5 4.6 4.7
Digest. Energy 3.92 2.56 2.21
Metab. Energy 3.25 2.10 1.81
NEm 2.24 1.28 0.97
NEg 1.55 0.68 0.42
7
CALCULATION OF ENERGY VALUES IN BEEF NRC
REQUIREMENT PUBLICATION

• DE .04409 x TDN ()
• ME DE x 0.82
• NEm 1.37ME-0.138ME20.0105ME3-1.12
• NEg 1.42ME-0.174ME20.0122ME3-1.65
• where units for DE, ME, and NE are Mcal/kg

8
CALCULATION OF TDN CONCENTRATIONS IN DAIRY NRC
REQUIREMENT PUBLICATION

• Inputs
• tdNFC .98(100-(NDF-NDICP)CPEEash)xPAF
• where PAF .95 for cracked corn
• 1.00 for ground corn
• 1.04 for HM corn
• .94 for normal corn silage
• .87 for mature corn silage
• tdCPf CP x e(-1.2xADICP/CP)
• tdCPc 1 (0.4 x (ADICP/CP)) x CP
• tdFA FA
• tdNDF 0.75 x (NDF-NDICP)-L) x 1
  (L/(NDF-NDICP)).667
• TDN
• TDN1x tdNFC tdCP (2.25 x tdFA) tdNDF 7
• Other specific equations for animal protein
  supplements and fat supplements

9
CALCULATION OF ENERGY CONCENTRATIONS IN DAIRY NRC
REQUIREMENT PUBLICATION

• DE1x (Mcal/kg) (tdNFC/100) x 4.2 (tdNDF/100)
  x 4.2 (tdCP/100) x 5.6 (FA/100) x 9.4 0.3
• Intake discount (TDN1x (0.18 x TDN1x)
  10.3 x Intake) / TDN1x
• where intake is a multiple of maintenance
• MEp (Mcal/kg) 1.01 x DEp 0.45 0.0046 x
  (EE 3)
• NElp
• For feeds with lt 3 EE
• NElp (Mcal/kg) 0.703 x MEp 0.19
• For feeds with gt 3 EE
• NElp (Mcal/kg) 0.703 x MEp 0.19 ((0.097x
  MEp 0.19)/97 x EE 3)

10
DISCOUNT FACTORS FOR TDN FOR RATIONS WITH
DIFFERENT TDN1X AT INCREASING LEVELS OF DM INTAKE
11
Efficiency of NE
Lactation (64)

Growth (25 45)
Energy balance
0
-
Maintenance (60 70)
73.5 kcal NE/kg.75
Energy intake
12
Implications of differences in efficiency of
energy use for different functions

• When calculating energy needs
• Mature dairy cattle can use one value to express
  the needs for maintenance and lactation (NEl)
• Growing cattle must use separate values to
  express the needs for maintenance (NEm) and gain
  (NEg)

13
Energy requirements

• Maintenance
• of total energy requirement
• 25 70 in dairy cattle
• 70 in beef cattle
• Components
• Basal metabolic rate
• Activity
• Body temperature regulation
• Pregnancy
• Growth
• Lactation

14
CALCULATION OF THE MAINTENANCE REQUIREMENTS FOR
NET ENERGY FOR BEEF AND DAIRY CATTLE

• Beef cattle
• NEm 0.077EBW.75
• Dairy cattle
• NEl for maintenance 0.080BW.75

15
MAINTENANCE MODIFIERS(All except lactation apply
across sexes)

• Breed
• Implications
• Maintenance requirements of breeds with high milk
  potential are 20 higher than those with low milk
  potential
• Maintenance requirements of Bos indicus breeds
  are 10 lower than Bos taurus
• Maintenance represents 70 of total annual ME
  requirement of beef cows
• Match cow breeds to feed resources

Maintenance Maintenance
Breed Kcal ME/BW.75 Mcal/d of total annual ME
Angus x Hereford 130 14 73
Charolais x 129 15 73
Jersey x 145 14.2 71
Simmental x 160 17.9 75
16
RELATIONSHIP OF BIOLOGICAL EFFICIENCY AND FEED
AVAILABILITY

• Maximum DMI at
  Max DMI, kg/yr
• ___Breed__ efficiency efficiency
  3500 7500
• gm calf
  kg/yr gm calf
• weaned/kg DMI/
  weaned/kg DMI/
• cow exposed
  cow exposed
• Red Poll 47.1
  3790 47 24
• Angus 41.3
  4111 39 17
• Hereford 35.1
  4281 30 13
• Pinzgauer 46.9
  5473 38 44
• Gelvieh 44.5
  5475 29 36
• Braunvieh 39.4
  7031 33 42
• Limousin 39.4
  7498 33 42
• Simmental 41.5
  8609 26 42
• Effects of feed availability on biological
  efficiency
• Rebreeding rates
• Weaning weights

17

• Reasons for difference in energy requirements
  between breeds
• Difference in energy expenditure of visceral
  organs
• Difference in protein and fat turnover
• Efficiency of protein accretion 40
• Efficiency of fat accretion 60 to 80

Organ Linear contrast (High milk prod vs low milk prod), g/kg.75
Heart 1.92
Lung 5.52
Kidney 1.86
Liver 5.83 Blood flow 25 of cardiac output O2 consumption 15 of total
GI tract - Blood flow 20 of cardiac output O2 consumption 11 of total
18

• Sex
• Increase NEm requirement by 15 for bulls

19

• Lactation
• Maintenance requirement of lactating cows is 20
  higher than dry cows
• Implications
• Early weaning of beef cows reduces maintenance
  energy requirement
• Reduces feed use
• Stimulates reproduction

Postpartum energy fed Weaning systems cows cycling 60 d post-partum
Low (70 NRC) Early (38 days) 62.5
Normal (7 mo) 26.7
Medium Early 88.9
Normal 13.3
20

• Body condition effects
• Reflects previous nutrition
• NEm 0.077BW.75 x (.8 ((CS-1) x .05)
• Implications
• Can have compensatory gain in growing cattle or
  reduce feed requirements of beef cows by
  restricting nutrition

21

• Activity allowance (Beef)
• Variation
• 10-20 increase in NEm reqt. for good pasture
• 50 increase in NEm reqt on poor hilly pasture.
• Nemact (.006 x DMI x (.9 TDN)) (.05T/(GF
  3)) x w/4.184
• Where DMI is in kg/d
• TDN is a decimal
• T is terrain (1flat, 1.5undulating, 2hilly)
• GF is green forage available in metric ton/ha

22

• Activity allowance (Dairy)
• Walking
• Adjustment .00045 Mcal Nei/kg BW/horizontal km
• Eating
• Adjustment .0012 Mcal Nei/kg BW
• Assumes 60 of diet is pasture
• Walking
• Adjustment .006 Mcal Nei/kg BW
• Assumes a hilly pasture is one in which cattle
  move 200 m of vertical distance/day
• Example

increase in maintenance increase in maintenance
Flat, close to parlor, good pasture Hilly, far from parlor, good pasture
Horizontal movement 2.8 11.4
Eating 7.6 7.6
Terrain - 37.9
Total 10.4 56.9
23
TEMPERATURE EFFECTS

• Previous temperature
• Adjustment
• NEm (.0007 x (20-Tempprevious) 0.077)
  Mcal/BW.75

24
Body temperature regulation
High Heat Production Low
Wet/poor insulated conditions
Normal LCT (Cattle) Fasted 18-20C Fed
7C
normal conditions
LCT
UCT
HI
LCT
UCT
Well insulated conditions
Activity
LCT
UCT
Basal Metabolic Rate
39 C
Low Temperature High
25
Effects in applied nutrition

• Mature dairy cows
• Cold stress
• Not considered by NRC
• Reasons
• High heat production
• Maintained in confinement
• Heat stress
• Increase maintenance NE requirement by 25

26

• Beef cattle (and dairy heifers)
• Cold stress may have major effects on NEm
  requirement
• Components
• Surface area SA .09BW.67
• External insulation EI (7.36 0.296 Wind
  2.55 Hair) x Hide x Mud
• Determined by
• Wind
• Coat length
• Hide thickness
• Mud or snow Effects on
  EI
• Some mud
  -20
• Wet matted
  -50
• Snow covered
  -80
• Internal insulation II 5.25 (.75 x CS)
• Adult cattle
• Total insulation TI EI II
• Diet heat increment HI (MEI-NEI)/SA

27

• Calculations
• Lower Critical Temp LCT 39 (TI X HI x 0.85)
• NEcold stress SA (LCT-Current temp)/TI x Diet
  NEm
• 
  Diet ME
• Add to NEm requirement for total Nem requirement

28
Example 600 kg cow (BCS 5) with a dry coat at
-5C temp.
29
Example 600 kg cow (BCS 5) with a snow-covered
coat at -5C temp.
30

• Heat stress in beef cattle
• Shallow panting Increases NEm reqt by 7
• Open mouth panting Increase NEm reqt by 18

31

• Effects of excess protein on NEm requirement
• Needed for synthesis of urea above requirements
• Calculation
• NEm, Mcal/d ((rumen N balance, gm recycle N,
  gm)
• excess N from MP,
  gm x .0113) x NEm/MEdiet
  
  
• Not included in NRC beef or dairy requirements
• Included in BRANDS and CNCPS program

32
Pregnancy

• Very inefficient utilization of energy (14 to
  16)
• Increase energy requirement drastically during
  last trimester of gestation
• Energy
  reqt in last trimester
• 
  of maintenance
• Cattle
  180
• Calculations
• Beef
• NEm, kcal/d 0.576 birth wt (0.4504
  0.000766t)e(.03233-.0000275t)t
• Dairy
• NEl, Mcal/d (.00318 x t -.0352) x (birth
  wt/45)/.218

33
Bodyweight gain

• Less efficient than maintenance
• Calculations
• NEg intake, Mcal/day DMI, kg x NEg conc.,
  Mcal/kg
• After maintenance requirement is met
• Shrunk BW, kg SBW .96 x Full BW
• Standard reference BW SRW (base medium-frame
  steer)
• 478 kg for small marbling
• 462 kg for slight marbling
• 435 kg for trace marbling
• Equivalent shrunk BW, kg SBW x SRW/Final SBW
• EBW .891 x EqSBW
• EBWG .956 x SBWG
• Retained energy, Mcal/day .0635 x EBW.75 x
  EBWG1.097
• Equals NEg intake if known in predicting gain
• SBWG, kg 13.91 x RE.9116 x EqSBW-o.6837

34

• Adjustments for FSBW
• Reduce FSBW by 35 kg if no implant used
• Increase FSBW by 35 kg in Trenbolone acetate is
  used with an estrogen implant
• Increase FSBW by 35 kg if extended periods of
  slow rates of grain
• Reduce FSBW by 35 kg if fed high energy from
  weaning to finish

35
ExamplePredict the rate of gain of a 700 lb (318
kg) Angus steer (BCS 5) fed 1.5 kg corn silage,
5 kg corn grain, and 1 kg soybean meal (DM basis)
that will finish at 1250 lb (568 kg) at small
marbling with no environmental stress.

• Step 1. Calculate NEm and NEg concentrations of
  diet
• If fed an ionophore, increase NEm conc by 12

36

• Step 2. Calculate feed required for maintenance

No adjustments for breed or temperature stress
needed in this problem
37

• Step 3. Calculate NEg remaining for gain

38

• Step 4. Calculate the Equivalent Shrunk BW

39

• Step 5. Calculate Shrunk BW gain

40
Lactation(Dairy)

• Equal efficiency to maintenance
• NEl reqt for lactation, Mcal/day kg milk/day x
• (.0929 x milk fat) (.0547 x milk
  protein/.93) (.0395 x lactose)
• Simply add to NEl needed for maintenance
• Energy from body tissue loss (5-point BCS scale)
• Body condition score Mcal
  NEl/kg BW loss
• 2
  3.83
• 2.5
  4.29
• 3
  4.68
• 3.5
  5.10
• 4
  5.57

41
ExampleHow much milk with a composition of 3.5
fat, 3.3 protein, and 5 lactose should a 1450
lb (659 kg) Holstein cow produce if she is
consuming a diet containing 2 kg alfalfa hay, 5
kg alfalfa haylage, 5 kg corn silage, 10 kg corn
grain, and 2 kg soybean meal (DM basis)?

• Step 1. Calculate the NEl intake

42

• Step 2. Calculate the amount of NEl remaining
  after meeting the maintenance requirement

43

• Step 3. Calculate energy concentration in milk
• Step 4. Calculate milk production

44
Dairy example 2If previous cow was producing 50
kg/day of milk with the given composition, how
much tissue would she need to mobilize at a BCS
of 3.5?

• Step 1. Calculate total NEl reqt.

45

• Step 2. Calculate the energy deficit
• Step 3. Calculate the amount of tissue needed to
  fill deficit

46
Lactation (Beef)

• Equations
• k 1/T
• T week of peak lactation
• a 1/(Peakyld x k x exp)
• Peakyld peak yield, kg/day
• Milk prod, kg/d Yn n/(a x expkn)
• n current week
• E .092 x MF .049 x SNF - .0509
• E Milk energy, Mcal/kg
• MF Milk fat,
• SNF Solids not fat,
• NEm, Mcal/day Yn x E

47
FEEDING TO MAINTAIN REPRODUCTION

• Maintaining reproductive performance requires
  given levels of body fat
• No less than 15.8 carcass lipid or 13.5 empty
  body fat at parturition
• Can be as low as 12.4 empty body fat at
  parturition if fed at 130 of NRC energy
  requirement for 60 days post-partum
• Empty body fat at breeding should be 15 for
  optimal pregnancy rates
• Cows should not exceed 20 carcass lipid or 17.8
  empty body fat
• Body weight
• Although NRC publications prior to 1996 used body
  weight, most producers dont weigh cows
• Body weights of pregnant cows can be confounded
  with conceptus

48
USE OF CONDITION SCORING FOR BEEF COWS

• Systems
• 9-point visual system (NRC/Oklahoma)
• 9-point palpation system (Tennessee)
• 5-point visual system (Purdue)
• Limitations
• All systems are subjective
• Different systems make it difficult to
  standardize relative to nutrient requirements
• Advantages
• Dont require weighing of cows
• Less confounded by pregnancy than body weights
• Related to body weight
• Relationship with BW change
• Purdue 1 BCS unit change 68 kg (5-point
  system)
• NRC 1 BCS unit change 50 kg (9-point
  system)
• Relationship varies with age
• Mature cows 1 BCS unit change 34 kg (9-point
  system)
• Primiparous heifers 1 BCS unit change 68 kg (9
  point system)

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51

• Relationship of body condition score to body
  composition
• Component BCS
  Change/BCS (5-point) BCS BW
• r
  
  r
• Carcass lipid .63
  
  .70
• Carcass protein .36
  
  .59
• Empty body lipid .48
  5.5-66 units .74
• Empty body protein .26
  .2-1 units .47
• Hot carcass weight
  
  .95
• Backfat
  .075-.29 cm
  .62
• Relationship of BCS from different systems to
  body lipid
• BCS
  System
• 9-pt 5-pt NRC, 9-pt.
  Texas, 9-pt. Purdue, 5-pt
• 
  Empty body lipid,
• 1 1
  3.77 0
  3.1
• 2
  7.54 4
• 3 2
  11.30 8
  8.7
• 4 15.07
  12
• 5 3
  18.89 16
  14.9
• 6
  22.61 20
  

52

• Relationship of body condition score to
  reproduction
• Body condition score at calving is the primary
  factor related to reestablishment of cyclic
  activity in beef cows
• Cows that calve at BCS gt 5 (9-point system) will
  exhibit estrus regardless of post-partum
  nutrition regime
• Feeding extra energy post-partum to cows that
  calve at BCS lt 4 will increase the percentage of
  cows exhibiting estrus in a finite breeding
  season
• Richards (1986)
• Days to first estrus
  Days to conception 1st service conception
• Post-partum
  Calving BCS
• nutrition lt 4 gt 5
  lt 4 gt5 lt 4
  gt 5
• High (.45kg/d) 60 51
  91 84 67
  59
• Mod. ( 0 kg/d) 60 46
  91 85 65
  67
• Low (-.68 kg/d) 56 50
  88 82 54
  70
• L/H (5 kg corn/d 67 49 91
  87 75
  70
• 14-d before
• and through
• breeding)

53
BODY CONDITION SCORE EFFECTS ON ENERGY RESERVES

• Energy in body condition
• Body condition score (5-point system)
  Mcal/kg BW change
• 1
  2.57
• 2
  3.82
• 3
  5.06
• 4
  6.32
• 5
  7.57
• The reason for this difference is that weight
  change at condition score 1 is 17 fat, but is
  77 fat at condition score 5
• Implications
• It takes more energy to increase condition score
  at a higher condition score than a lower
  condition score
• Loss of body condition at a high body condition
  provides more energy than loss of body condition
  at a low body condition score
  

54

• Calculation of energy from body reserves
• Body composition from BCS
• Proportion of empty body fat AF .037683CS
• Proportion of empty body protein AP .200886 -
  .0066762CS
• Proportion of empty body water AW .766637 -
  .034506CS
• Proportion of empty body ash AA .078982 -
  .00438CS
• Empty body weight, kg EBW .851SBW
• Total ash, kg TA AA x EBW
• Calculation of total fat and protein reserves
• AA1 .074602
• AF1 .037683
• AP1 .194208
• EBW1, kg TA/ AA1
• Total fat, kg TF AF x EBW
• Total protein, kg TP AP x EBW
• Total fat1, kg TF1 EBW1 x AF1
• Total protein1, kg TP1 EBW1 x AP1
• Calculation of mobilizable energy
• Mobilizable fat FM TF - TF1

55
Example 1

• If a beef cow with a shrunk BW of 485 kg at a BCS
  4 has a NEm requirement of 10.46 Mcal/day is
  consuming alfalfa hay with a NEm conc of 1.43
  Mcal/day at 10.9 kg/d, how long will it take for
  this cow to increase to a condition score of 5?
• NEm requirement, Mcal/day
  
  10.46
• NEm fed, Mcal/day
  1.43 x 10.9
  15.59
• NEm excess or deficient, Mcal/day
  fed-reqt
  5.13
• AF at CS4
  .037683 x 4
  0.1507
• AP at CS4
  .200886-.0066762 x 4
  0.1742
• AA at CS4
  .078982-.00438 x 4
  0.0615
• EBW at CS4
  .851x485
  412.74
• Total ash at any BCS
  EBW x AA
  25.3675
• AF at CS5
  .037683 x 5
  0.1884
• AP at CS5
  .200886-.0066762 x 5
  0.1675
• AA at CS5
  .078982-.00438 x 5
  0.0571
• EBW at CS5
  25.3675/.0571
  444.26
• Total fat at CS4, kg
  412.74 x .1507
  62.2000
• Total protein at CS4, kg
  412.74 x .1742
  71.8993
• Total fat at CS5, kg
  444.26 x .1884
  83.6986

56
Example 2

• If a beef cow with a shrunk BW of 485 kg at a BCS
  4 has a NEm requirement of 10.46 Mcal/day is
  consuming mature bromegrass hay with a NEm conc
  of 0.94 Mcal/day at 9.7 kg/d, how long will it
  take for this cow to decrease to a condition
  score of 3?
• NEm requirement, Mcal/day
  
  10.46
• NEm fed, Mcal/day
  0.94 x 9.7
  9.12
• NEm excess or deficient, Mcal/day
  fed-reqt
  -1.34
• AF at CS4
  .037683 x 4
  0.1507
• AP at CS4
  .200886-.0066762 x 4
  0.1742
• AA at CS4
  .078982-.00438 x 4
  0.0615
• EBW at CS4
  .851x485
  412.74
• Total ash at any BCS
  EBW x AA
  25.3675
• AF at CS3
  .037683 x 3
  0.1130
• AP at CS3
  .200886-.0066762 x 3
  0.1809
• AA at CS3
  .078982-.00438 x 3
  0.0658
• EBW at CS3
  25.3675/.0658
  385.52
• Total fat at CS4, kg
  412.74 x .1507
  62.2000
• Total protein at CS4, kg
  412.74 x .1742
  71.8993
• Total fat at CS3, kg
  385.52 x .1130
  43.5638