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id. Mode! Evaluation and
tJ Prediction Equations
The evaluation of specific components of the model can
be found in the relevant chapters. This chapter concerns
the evaluation of the overall model relative to energy, pro-
tein, and intake. The model equations are also presented
in this chapter for reference.
METHODOLOGY
Data from experiments published in the Journal of Dairy
Science from 1992 through February 2000 were used to
evaluate the model. Only data from continuous lactation
experiments that lasted at least 6 weeks were used (data
from cross-over type experiments were not used). Twenty-
f~ve papers representing 100 different diets were selected.
The papers were selected so that a wide variety of ingredi-
ents and production levels of cows could be evaluated. The
selection was made prior to diet evaluation; all selected
diets are shown in the plots. Diets varied in:
1. Forage source (corn silage and alfalfa were used in
most experiments)
2. Forage:concentrate ratio
3. Fat supplementation (without and with a wide variety
of fat sources)
4. Nonforage fiber sources (without and with a wide
variety of nonforage fiber sources)
5. Source of starch (mostly corn "rain but sorghum and were used).
barley was also fed in some experiments)
6. Corn grain processing (dry and high moisture, grind
size, steam-treatment)
Cows varied with respect to days in milk, milk yield,
and milk composition. Twenty-three papers used Holstein
cows, two papers used Jersey cows.
Diet composition (ingredients) was entered into the
model. Published nutrient composition of the individual
ingredients was used when available. When nutrient com-
position data were missing, values from the feed com-
position table (Table 15-1) were used. When nutrient
composition of ingredients was not published but nutrient
composition of the total diet was included, nutrient compo-
sition of individual ingredients (usually only the forages)
were changed by no more than one standard deviation so
that composition (NDF and CP) of the diet was the same
as the published composition. Most studies did not include
measured lignin, ash, and neutral and acid detergent insol-
uble crude protein. The protein fraction and digestion rate
data in the composition tables (Tables 15-2a and b) were
used in all evaluations. Few papers published data on min-
eral composition of the ingredients or diets, and because
mean composition data on minerals (Table 15-3) has a
large variance, provision of minerals was not evaluated.
However, the concentration of mineral supplements was
included in the diets.
Mean production data (days in milk, lactation number,
body weighs, and milk yield and composition) were entered
into the model. Day of gestation usually was not published
so a reasonable estimate was entered based on days in
milk. Most papers did not include data on the age of the
cows. Therefore, growth requirements were set to zero for
all cows except those that were exclusively primiparous
(for those cows, model generated growth requirements
1\
EVALUATION
After diet and cow data were entered into the model,
predicted dry matter intake, net energy allowable milk,
and metabolizable protein allowable milk were compared
with actual intake and milk production. Predicted net
315

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316 Nutrient Requirements of Dairy Cattle
energy balance was compared with actual net energy bal-
ance by including net energy provided by or needed for
the measured body weight change. Sources of data used
in the evaluation are shown in Table 16-1.
Dry Matter Intake
Mean observed dry matter intake was 22.3 kg/d and
mean predicted intake was 22.1 kg/d. No evidence of a
linear bias was found (Figure 16-11. Root mean square
error (predicted minus observed) was 2.0 kg/d. Predicted
intake was within + 5 percent of observed intake in 41
percent of the observations and 73 percent of the predicted
intakes were within + 10 percent of observed intake.
Energy
To evaluate the energy portion of the model, intake of
NED (based on actual DMI and model predicted NED
concentration) was compared with NED utilization (model
predicted NED for maintenance, based on actual body
weight, model predicted NED for actual milk produced,
and NED used for measured body weight change). The
data set was as described above except two studies (4
treatment means) could not be used because body weight
change was not reported. If the model is accurate, NED
intake and NED use should be equal with no apparent bias.
Overall, the accuracy of the model was acceptable (Figure
16-21. Intake of NED and NED use were highly correlated
(r2 = 0.61; P<0.011. Energy use was within + 5 percent
of NED intake for 46 percent of the observations and within
10 percent for 76 percent of the observations. Mean NED
intake was 35.4 Mcal/d compared with mean NED use of
34.5, therefore, a small mean bias (0.9 Mcal of NED intake
or 2.5 percent) was present. A linear bias is apparent KNEE
intake = 7.8 + 0.8 x NED Use); however, within the
range of NED used for most lactating cows in the United
States the bias will be small (at 20 Mcal of NED use, esti-
mated mean NED intake is 23.8 Mcal/day; at 30 Mcal/d
NED use, estimated mean NED intake is 31.8 Mcal/day;
and at 45 Mcal of NED use, estimated mean NED intake
is 43.8 Mcal/day).
TABLE 16-1 Sources of Data Used in the Model Evaluation
(see also Figures 16-1 to 16-5)
Aydin et al. (1999)
Bertrand et al. (1998)
Coomer et al. (1993)
Dann et al. (2000)
Dhiman and Satter (1993)
Kalscheur et al. (1999)
Khorasani et al. (1993)
Khorasani et al. (1996)
Kim et al. (1993)
Knowlton et al. (1998)
Kuehn et al. (1999)
Messman et al. (1992)
Mowrey et al. (1999)
Overton et al. (1998)
Pereira et al. (1999)
Santos et al. (1998)
Santos et al. (1999)
Soder and Holden (1999)
Stegeman et al. (1992)
Tackett et al. (1996)
Wattiaux et al. (1994)
Weiss (1995)
Weiss and Shockey (1991)
Weiss and Wyatt (2000)
Wilkerson et al. (1997)
Protein
30
25
,` 20
15
a)
Q
0 10
a)
Q 5
o
1
a) o
-5
-10
O Observed ~ Deviation
0/
10 15 20 25
Predicted DMI ka/d
30 35
FIGURE 16-1 Model predicted vs. actual dry matter intake.
Values from 100 published treatments means from 25 studies.
Evaluation of the protein portion of the model by com-
paring MP allowable milk with actual milk is equivocal.
When MP allowable milk is greater than actual milk, milk
production could be limited by the physiologic state or
genetic potential of the cow or by a nutrient other than
MP. Higher MP allowable milk than actual milk could also
mean that the model underpredicted MP requirements
of the cow. When MP allowable milk was compared with
actual milk, MP allowable milk was less than actual milk
in only 18 (18 percent) observations (Figure 16-31. Of
those 18 observations, MP allowable milk for 5, 8, and 5
observations were within 10 to 17 percent, 5 to 10 percent,
or less than 5 percent of actual milk. Eighty-two percent
of all treatment groups in this data set produced less milk
than the model predicted could be produced from the
amount of MP available. In 67 percent of the observations,
MP allowable milk was more than 10 percent greater than
actual milk. Other than energy, the most likely nutrients

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Mode} Evaluation and Prediction Equations
50i
40
30
20
10
10
7 1
, '0"~
,-"
, /
/
/ 1 1 1 1 1 1 1
20 30 40 50
NEL use, Mcal/d
FIGURE 16-2 NEL intake (estimated from observed dry mat-
ter intake and model estimated NEL concentration) versus NEL
use (estimated from model predicted maintenance and lactation
requirement plus NEL needed to meet observed body weight
change). Values from a data base of 96 published treatment means
from 23 studies. The solid line represents y= x, the dashed line
represents y = 7.8 + 0.8X.
60 .
50
40
30
20
10
o
/
/
/
/
/
/ 1
0 10
o/
0 ~
50 60
1 1 1
20 30 40
MP Allowable Milk, kg/d
FIGURE 16-3 Actual milk production versus model predicted
MP allowable milk production. Values from 100 published treat-
ment means from 25 studies.
limiting milk production and causing MP allowable milk
to be greater than actual milk are specific amino acids.
The difference between MP allowable milk and actual milk
increased as the concentration of lysine decreased from
6.5 percent of MP (Figure 16-4) and as the concentration
of methionine decreased from 1.9 percent of MP (Figure
16-51. This suggests that although supply of total MP was
adequate in many of these experiments, the balance of
absorbable amino acids may have been incorrect and lim-
ited milk production. Experiments specifically designed to
test the MP requirements predicted by the model are
needed.
317
51 , , , , , , , 1
-10 -5 0 5 10 15 20 25 30
MP Allowable Milk, kg/d
FIGURE 16-4 Difference between MP allowable milk and
actual milk versus model predicted lysine concentration of MP.
Values from 100 published treatment means from 25 studies.
Regression line: y = 6.54 - 0.026x.
2.4 r
2.2
2
o
1.8
1.6
1.4
1.2L
-10 -5
· ~
~ it 7~, ~~!v - ,
l
0 5 10 15 20 25 30
MP Allowable Milk, kg/d
FIGURE 16-5 Difference between MP allowable milk and
actual milk versus model predicted methionine concentration of
MP. Values from 100 published treatment means from 25 studies.
Regression line: y = 1.90 - 0.0067x.
MODEL PREDICTION EQUATIONS
Model Structure
The model is divided into two major components: pre-
diction of requirements and supply of nutrients. Within
this structure, there are submodels for young calves, main-
tenance, pregnancy, growth, lactation, dry matter intake,
minerals, reserves, energy and protein supply, amino acids,
and diet evaluation. A glossary of the terms used in the
equations is included at the end ofthe chapter. Background
information explaining the committee's rationale in choos-
ing the approach and coefficients used in the model is
presented in the appropriate chapters. A complete listing
of all of the equations in the model is included in a file
on the compact disk that contains the model itself. Note,
MEng is used to denote metabolizable energy (ME) in the
computer program and in the equations below because
ME can not be used as a variable in the programming
language that we used.
Animal Requirements
The requirements section is divided into four main sec-
tions based on physiological function: maintenance,

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318 Nutrient Requirements of Dairy Cattle
growth, lactation, and pregnancy. Adjustments made for
grazing activity are included in the maintenance section.
There are four classes of animals in this model, lactating
cow, dry cow, replacement heifer, and young calf. If differ-
ent equations are used for heifers, lactating cows, or dry
cows, they will be presented under the appropriate physio-
logic function. The equations used to predict the require-
ments and nutrient supply of the young calves are in a
separate section.
Maintenance
MAINTENANCE ENERGY REQUIREMENTS
Maintenance requirements are computed by adjusting
the NEm requirement for fasting metabolism for the
effects of physiologic state, activity, and, in the case of
heifers, heat and cold stress.
Lactating and Dry Cows The maintenance requirement
for lactating cows is calculated using metabolic body size
(BW0 75), and calculated with the following equation which
includes an adjustment for activity:
NEmaint (Meal/d) = ((BOO— CW)075 X al) +
NEmact
Where al = 0.08 for mature cows based on the require-
ment for NEm (80 kcal/kg BW075) (NRC, 1989), CW
is conceptus weight and NEmact is the variable to calcu-
late the requirement for activity.
NEmact = distance/1000 x Trips) x
(0.00045 x BOO)) + (0.0012 x (BW))
Where Distance is the distance from the pasture to the
milking parlor (km), Trips is the number of times that
animals go to and from the milking parlor daily, and
Pasture is an adjustment for percent of the predicted
dry matter intake supplied by grazing.
NEmact is adjusted for differences in topography for
grazing animals. Topography may be either flat or hilly.
No adjustment is made if the topography is flat.
If Topography = 'Hilly' Then NEmact = NEmact +
(0.006 x BW)
The following equations are used to calculate the net
energy concentration of the diet and the amount of feed
that is required to meet the maintenance requirement.
NEFP = (TotalDMFed— FeedMaint) x
(NEl Total / TotalDMFed) x 0.65
Where NEFP = Net energy for production, TotalD-
MFed = Total dry matter consumed, NEl Total =
total NE (in Meals) and 0.65 is the assumed efficiency
of conversion of metabolizable protein to net protein
Heifers The maintenance requirements for heifers with-
out stress (NEmaintNS) are calculated with the follow-
. .
1ng equation:
NEmaintNS (Meal/d) = (~(SBW— CW)075) X
((al x COMP) + aid) + NEmact
Where:
SEW = shrunk body weight = 0.96 x BW, CW
= conceptus weight (kg),
al = 0.086 (thermoneutral maintenance require-
ment (Meal/day)),
a2 = 0.0007 x (20—PrevTemp) (Adjustment for
previous temperature effect),
COMP = 0.8 + ((CS9 - 1) x 0.05) (Adjustment
for previous plane of nutrition) NEmact = energy
required for activity
In the model, a 1-9 system for body condition scoring
is used so the following equation is used to convert from
the 1-5 system more commonly used in the dairy industry
to the 1-9 system. The conversion to the 9-point condition
score from the 5-point system is:
CS9 = ((CS - 1) x 2) + 1
The following equation is used to calculate the activity
requirement for grazing heifers:
NEmact = (~0.0009 BW) + (0.0016 BOO)) if the heifer
is grazing, otherwise it is 0.
If Topography = 'Hilly' then NEmact = NEmact +
(0.006 x BW)
For heifers, these requirements then are adjusted for
the effects of temperature that are based on surface area,
heat production, tissue and coat insulation, coat condition,
and temperature. First surface area (SA) and heat produc-
tion (HP) (Mcal/m2/day) are calculated:
SA = 0 09 x (SBW067)
HP = (MEI — NEFP)/SA
Where NEFP = Net energy for production which
equals NEGrowthDietNS (Net energy for growth avail-
able in the diet with no stress, Mcal/day), HP = Heat
production (Mcal/m2/day), MEI = Metabolizable
energyintake(Mcal),andNEGrowthDietNS= (Total-
DMFed—FeedMaint) x (NEg Total/TotalDMFed)
The next step is to calculate tissue insulation (TI, Meal/
m2/° C/day). For younger animals, these factors are based
on age alone but, for older animals, body condition score
is also considered. These factors are:
Age (daysJ
' 30
31 to 183
184 to 362
- 363
Tl Factor
2.5
6.5
5.1875 x (0.3125 x CS9)
5.25 x (0.75 x CS9)

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The insulation is further affected by coat condition
(Coat):
Coat condition
Clean/dry
Some mud
Wet/matted
Coated with snow/mud
Factor
1.0
0.8
0.5
0.2
The external insulation value, EI (°C/Mcal/m2/day) is:
EI = ((7.36 - (0.296 X WindSpeed) +
(2.55 X HairDepth)) X Coat) X 0.8
Where WindSpeed (kph) is the average wind speed and
typical HairDepth values for animals in summer are
0.63 cm (0.25 inches) and for winter 1.27 cm (0.5 inches)
and Coat is the coat condition factor.
The total insulation (INS, Mcal/m2/°C/day) is INS =
TI + EI
The effects of heat and cold stress are based on lower
and upper critical temperatures.
The animal's lower critical temperature (LCT, °C) is:
LCT = 39 - (INS X HP X 0.85)
If the LCT ~ ambient temperature (Temp), then
MEcs = SA X (LCT—Temp)/INS
Where MEcs is Metabolizable energy required for cold
stress (Meal/day).
Otherwise, there is no cold stress.
ColdStr= (~(NEDietConc/MEng Total/
TotalDMFed)) X MEcs)
Where NEDietConc is the concentration of net energy
in the diet (kg D M/day), MEng Total is Total ME intake
(Meal/day), and TotalDMFed is total dry matter fed (kg).
To calculate the effects of heat, the HeatStress variable
is used. An index based on visible changes in breathing in
response to heat based on breathing is used:
If HeatStress = 'None' or Temp ~ 30 then HeatStr = 1
If HeatStress = 'Rapid/Shallow' then HeatStr = 1.07
If HeatStress = 'Open Mouth' then HeatStr = 1.18
The final equation to calculate the maintenance require-
ment for replacement heifers is:
NEMaint= ((NEMaintNS + ColdStr) X
HeatStr) + NEmact
Maintenance Protein Requirement
LACTATING AND DRY COWS AND REPLACEMENT HEIFERS
The protein requirements for maintenance for all classes
of cattle except for the young calves are calculated with
the following equation:
Mode} Evaluation and Prediction Equations 319
MPMaint = (0.3 X (BW— CW)06) + (4.1 X
(BW— CW)°~) + (TotalDMFed X 1000 X 0.03
—0.5 X ((MPBact/0.8)—MPBact) + MPEndoReq
Where MPMaint = Metabolizable protein required
for maintenance (g/day)
CW = conceptus weight
Scurf Requirement = (0.3 X (BW— CW) 06);
Urinary Requirement = (4.1 X (BW— CW) °~);
Metabolic Fecal Protein Requirement = (TotalDMFed
X 1000 X 0.03 - 0.5 X ((MPBact / 0.8) —
MPBact));
MP required for Endogenous Protein (MPEndoReq)
= MPEndo/0.67;
MPBact = Metabolizable protein supplied by microbial
protein (g/day);
MPEndo = Endogenous metabolizable protein (g/day)
= 0.4 X EndCP and
EndCP = Endogenous crude protein (g/day) = 11.8
X TotalDMFed.
Growth
ENERGY REQUIREMENTS FOR GROVVTH
Replacement Heifers, Lactating and Dry Cows (1St and
2n~ Lactation only)
In this section of the model, requirements for growth
are calculated from shrunk body weight, SBW (0.96 X
BW) and empty body weight (EBW) (see Chapter 11 for
rationale). The user may choose to enter a desired rate of
gain or may use the model-generated target gains. For
both options, a size-scaling approach is used which requires
information on mature body weight (MBW) and mature
shrunk body weight (MSBW). The user may use data on
mature weights from his/her herd or may rely on default
values generated in the program. Accurate estimates of
mature weight are needed for accurate predictions of
requirements. Representative weights of mature culls cows
with average body condition scores may be used to estimate
mature weights (MW).
MSBW= Mature shrunk body weight= 0.96 X MW
SBW = Shrunk body weighs = 0.96 X BW
EBW = Empty body weight = 0.891 X SBW
EBG = Empty body weight gain = 0.956 X SWG
The following calculation is used to calculate the ratio
of the standard reference weight to mature shrunk body
weight (SRW to MSBW).
SRW to MSBW = 478/ MSBW
EQSBW= (SBW— CW) X SRW to MSBW
Where EQSBW = Equivalent shrunk body weight (kg)
and CW = Conceptus weight (kg).

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320 Nutrient Requirements of Dairy Cattle
The equation is used to compute shrunk weight gain
(SWG):
SWG = 13.91 X (NEGrowthDiet 0 9~6) X
(EQSBw-o 6837)
Where SWG = shrunk weight gain (kg), NEGrowth-
Diet = NEg in the diet (Meal)
If the animal is a replacement heifer, then WG (weight
gain) = SWG (shrunk weight gain),
Otherwise, WG = ADG (Average daily gain)
The following equations are conversions to equivalent
(size-scaled) weights:
EQEBW = Size-scaled empty body weight = 0.891
X EQSBW
EQEBG = Size-scaled empty body weight gain
0.956 X WG
Retained energy (RE) is calculated with the following
equation:
RE = 0.0635 X (EQEBW075) X (EQEBG1097)
Protein Requirements for Growth
REPLACEMENT HEIFERS, LACTATING AND DRY COWS
(lST AND 2ND LACTATION ONLY)
Net protein for growth (NPg) is calculated as follows:
NPg = WG X (268 - (29.4 X (RE /WG)~)
Where WG = weight gain (kg) (always positive) and
RE = retained energy (Mcal).
The efficiency with which net protein is used for gain
(EffMP NPg) is then computed:
If EQSBW ' 478 then EffMP NPg = (83.4 - (0.114
X EQSBW)) / 100
Otherwise EffMP NPg = 0.28908
The next step is to calculate the metabolizable protein
required for growth (MPGrowth) by dividing NPg by the
efficiency with which MP is converted to NP:
MPGrowth = NPg / EffMP NPg
If the animal is a replacement heifer,
D MIAvailGrowth =
— DMIPreg
Otherwise
TotalDMFed— DMIMaint
DMIAvailGrowth = TotalDMFed—DMIMaint-
DMIPreg— DMILact
Where DMIAvailGrowth is the dry matter intake for
growth.
If Age ~ FirstCalf, then ADGwPreg = SWG +
(ADGPreg / 1000)
Otherwise, ADGwPreg = (EQEBG / 0.956) +
(ADGPreg/ 1000)
For replacement heifers only,
If NEfOverMEng ~ O. then ME Growth =
NEGrowth / NEgOverMEng
Calculation of Target Weights and Average Daily Gain
for Replacement Heifers and Animals in 1St and 2
Lactations
The following set of calculations is used to compute the
gain required to achieve specified target weights at first
breeding, calving, and maturity which is assumed to occur
at the beginning of the third lactation. It is important to
ensure that appropriate mature weights, age at first calving,
and calving interval data are entered or the predictions for
target gain will be unrealistic.
The following equations are used to calculate age at
different carvings:
Agelst= FirstCalf
AgeSnd = Agelst + Calflnt
Age3rd = AgeSnd + Calflnt
AgelstBred = Agelst— (280 / 30.4)
It is assumed that heifers will achieve 0.55 of their
mature shrunk body weight at first breeding, 0.82 at first
calving, and 0.92 at 2n~ calving. At the onset of their third
lactation, they are assumed to have reached their mature
weight.
WtlstBred = MSBW X 0.55
Wtlst = MSBW X 0.82
Wt2nd = MSBW X 0.92
Wt3rd= MSBW
ADGlstBred = (Wtlst—WtlstBred) /
((Ageist—AgelstBred) X 30.4)
ADGlst = (Wt2nd—Wtlst) / (CI X 30.4)
ADG2nd = (Wt3rd—Wt2nd) / (CI X 30.4)
If AnimalType = "Replacement Heifer" and
Age ~ AgelstBred Then ADGNonBred = (Wtlst-
Bred— SBW) / ((AgelstBred—Age) X 30.4)
Otherwise, ADGNonBred = 0
If AnimalType ~ "Replacement Heifer", then
ADGNonBred= 0
If AnimalType = "Replacement Heifer" and is preg-
nant then
ADG = ADGlstBred
Otherwise, ADG = ADGNonBred

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Mode} Evaluation and Prediction Equations 321
Pregnancy
PREGNANT REPLACEMENT HEIFERS AND MATURE COWS
Constants used in pregnancy calculations are:
Km = conversion of ME to NE = 0.64
EffMEPreg = The efficiency with which ME is used
for pregnancy = 0.14
EffMPPreg = The efficiency with which MP is used
for pregnancy = 0.33
Until day 190 of pregnancy, no requirements for preg-
nancy are computed in the model. The maximum number
of days that a cow can be pregnant is assumed to be 279.
CBW (calf birth weight) = MW X 0.06275
CW (conceptus weight) = (18 + ((DaysPreg— 190)
X 0.665~) X (CBW / 45)
ADGPreg (AD G of the conceptus) = 665 X (CBW/
45)
MEPreg(ME required forpregnancy) = (~2 X 0.00159
X DaysPreg—0.0352) X (CBW/45~/EffMEPreg
MPPreg (MP required for pregnancy) = (~0.69 X
DaysPreg— 69.2) X (CBW/ 45~) / EffMPPreg
NEPreg = Net energy required for pregnancy =
MEPreg X Km
Lactation
If lactose content of milk is not available,
MilkEn (energy content of milk) = (0.0929 X MilkFat)
+ (0.0547 X MilkTrueProtein / 0.93) + 0.192
If lactose content is known,
MilkEn = (0.0929 X MilkFat) + (0.0547 X Milk-
TrueProtein / 0.93) + (0.0395 X Lactose)
The amounts of energy, protein, and fat in milk then
are computed:
YEn = NElact (energy in milk daily, Mcal/day)
MilkEn X MilkProd
YProtn (daily protein yield in milk, kg/day) = MilkProd
X (MilkTrueProtein /100)
Yfatn (daily fat yield in milk, kg/day) = MilkProd X
(MilkFat / 100)
MPLact (Metabolizable protein required for lactation)
= (Yprotn / 0.67) X 1000
The following equation is used to convert to fat-cor-
rected milk (FCM):
FCM = 0.4 X MilkProd + 15 X (MilkFat / 100)
X MilkProd
Reserves
The factors used to adjust weight at the current CS to
expected weight at CS3.
CS F~ = 0.726
CS F2 = 0.794
CS F3 = 0.863
CS F4= 0.931
CS Fs = 1.000
CS F6= 1.069
CS F7 = 1.137
CS F8 = 1.206
CS Fg = 1.274
CS5EBW = (SBW X 0.851) / ~ CS Fx)
Where CS5EBW = Empty body weight at CS5 using the
1 to 9 scale and CS F = factor to calculate reserves at
CS1 to 9.
EBWX (Empty body weight at CSx) = CS Fx X
CS5EBW
AFX (Proportion of fat at CSx) = 0.037683 X X
TFX (Weight of fat at CSx) = AFX X EBWX
APX (Proportion of protein at CSx) = 0.200886 —
(0.0066762 X X)
TPX (Weight of protein at CSx) = APX X EBWX
ERX (Energy reserves at CSx) = (9.4 X TFX) + (5.55
X TPx)
Where X varies from 1 to 9.
If CS9 ~ 3, then LoselCS = ERcs9— ERCS9-2,
Otherwise, LoselCS = 1000000
If CS9 ~ 3, then NElSub = 0.82 X LoselCS
Otherwise, NElSub = 0.82 X (ERCs9— ER~)
If CS9 ~ 7, then GainlCS = ERcss+2— ERcss
Otherwise, GainlCS = 1000000
If CS9 ~ 7, then NElReq = (0.644 / 0.75) X GainlCS
Otherwise, NElReq = (0.644 / 0.75) X (ERg —
ERcss)
If EnergyBal ~ O. then deltaER = NElReq
Otherwise, deltaER = NElSub
Days to change condition score is calculated only for
cows:
If AnimalType = "Replacement Heifer", then
DaysToChange = 0.
Otherwise, DaysToChange = deltaER / EnergyBal
Energy balance is calculated in the following equations.
For Dry Cows and Lactating Cows:
NEBalance = NEl Total— (NEMaint + NEPreg
+ NELact + NEGrowth)
(These groups of animals use an NE-based system.)
For Replacement Heifers:
MEBalance = (MEng Total — (MEMaint +
MEPreg + MEGrowth))
(Heifers use an ME-based system).

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322 Nutrient Requirements of Dairy CattIe
Weight change in cows due to energy balance is com-
puted in the following equations:
For Lactating Cows:
If NEBalance ~ O. Then kg weight change — CALCIUM (~d)
NEBalance /4.92
If NEBalance ~ O. Then kg weight change
NEBalance /5.12
For Dry Cows:
If NEBalance ~ O. Then kg weight change
NEBalance /4.92
If NEBalance ~ O. Then kg weight change
NEBalance /6.40
If the animal is gaining weight, the protein requirement
for this gain must be computed.
If NEBalance ~ 0 Then
MPReqReserves = (Reserves WG X
ProteinInGain) / 0.492
MPProvReserves = 0
RUPReqReserves = MPReqReserves /
DietRUPDigest
If NEBalance ~ 0 Then
MPReqReserves = 0
If the animal is losing weight, the protein provided by
catabolism is computed.
MPProvReserves = ~—1 X Reserves WG) X
ProteinInGain X 0.67
RUPReqReserves = MPProvReserves /DietRUPDigest
Where MPReqReserves = metabolizable protein
required for reserves, MPProvReserves = metabolizable
protein provided by mobilization of reserves, RUPReqRes-
erves = RUP required for repletion of reserves and RUP-
ProvReserves = RUP provided by mobilization of reserves.
Mineral Requirements
In most cases, the requirements for minerals are deter-
mined for each physiologic function, maintenance, growth,
lactation, and pregnancy, but for some minerals this
approach has not been followed. The maintenance compo-
nent of the mineral requirement includes fecal, urinary,
sweat, and miscellaneous losses. Because the bioavailability
of minerals from various sources differs, the amount of the
total mineral in the diet that is absorbable is determined.
Growth requirements for minerals are calculated for heif-
ers during their first lactation, but not during their first
dry period or during the second lactation.
All calculations for milk mineral requirements are done
on a 4 percent fat corrected milk basis (FCM). The equa-
tion to convert to FCM is:
FCM = (0.4 X MilkProd) + (15 X ~ MilkFat / 100)
X MilkProd)
Fecal
If DaysInMilk ~ O. then Fecal = 3.1 X (BOO/ 100)
If DaysInMilk = O. then Fecal = 1.54 X (BOO/ 100)
Urinary
Urine = 0.08 X (BOO/ 100)
Sweat
Sweat = 0
Pregnancy
If DaysPreg ~ l9O, then
Fetal = 0.02456 X Exp(~0.05581 - (0.00007 X
DaysPreg)) X DaysPreg) — 0.02456
X Exp(~0.05581 - (0.00007 X (DaysPreg — 1~)
X (DaysPreg— 1~)
If DaysPreg c l9O, then Fetal = 0
Lactation
If DaysInMilk ~ O. then
If breed = Holstein or Milking Shorthorn, then
Milk = 1.22 X Milk Prod
If breed = Jersey, then
Milk = 1.45 X Milk Prod
Otherwise, Milk = 1.37 X Milk Prod
Growth
If BW ~ 0 and WG ~ O. Then
Growth = (9 83 X (MW022) X (BW-022~) X
(WG/0.96)
PHOSPHORUS (id)
Fecal
IfAnimalType = Cow,then Fecal = 1 X TotalDMFed
Otherwise, Fecal = 0.8 X TotalDMFed
Urine
Urine = 0.002 x BW
Miscellaneous
Misc= 0
Sweat
Sweat = 0
Pregnancy
If DaysPreg—190 Then
Fetal = 0.02743 x Exp(~0.05527— (0.000075 x
DaysPreg)) X DaysPreg)) — 0.02743 x

OCR for page 315

Mode} Evaluation and Prediction Equations 323
Exp(~0.05527— (0.000075 X (DaysPreg— 1~) X POTASSIUM (g/day)
(DaysPreg— 1~)
Otherwise, Fetal = 0
Lactation
If DaysInMilk ~ O. then Milk phosphorus = 0.9 X
MilkProd
Growth
If BW ~ 0 and WG ~ O. then
Growth = (1.2 + (4.635 X (MW022) X (BW-022~) X
(WG / 0.96)
MAGNESIUM (g/day)
Fecal
Fecal = 0.003 X BW
Urine
Urine = 0
Miscellaneous
Misc = 0
Sweat
Sweat = 0
Pregnancy
If DaysPreg ~ 190 Then Fetal = 0.33 g/day
Otherwise, Fetal = 0
Lactation
If DaysInMilk ~ O. Then Milk = 0.15 X MilkProd SODIUM (g/day)
Growth
Growth = 0.45 X (WG / 0.96)
CHLORINE (g/day)
Fecal
Fecal = 2.25 X (BOO/ 100)
Urine
Urine = 0
Miscellaneous
Misc = 0
Sweat
Sweat = 0
Pregnancy
If DaysPreg ~ 190 Then Fetal = 1
Otherwise, Fetal = 0
Lactation
Milk= 1.15 X MilkProd
Growth
Growth = 1 X (WG / 0.96)
Fecal
If AnimalType = Lactating cow
Fecal = 6.1 X TotalDMFed
Otherwise Fecal = 2.6 X TotalDMFed
Urine
Urine = 0.038 X BW
Sweat
If Temp ~ 25, then Sweat = 0
If Temp 25 to SO, then Sweat = 0.04 X (BW / 100)
If Temp ~ SO, then Sweat = 0.4 X (BW / 100)
Miscellaneous
Misc = 0
Pregnancy
If DaysPreg ~ 190 Then Fetal = 1.027
Otherwise, Fetal = 0
Lactation
Milk= 1.5 X MilkProd
Growth
Growth = 1.6 X (WG / 0.96)
Fecal
For lactating cows, Fecal = 0.038 X BW
Otherwise, Fecal = 0.015 X BW
Urine
Urine = 0
Miscellaneous
Misc = 0
Sweat
If Temp ~ 25, then Sweat = 0
If Temp 25 to SO, then Sweat = 0.1 X (BW / 100)
If Temp ~ SO, then Sweat = 0.5 X (BW / 100)
Pregnancy
If DaysPreg ~ l9O, then Fetal = 1.39
If DaysPreg ' l9O, then Fetal = 0
Lactation
Milk= 0.63 X MilkProd
Growth
Growth = 1.4 X (WG /0.96)

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324 Nutrient Requirements of Dairy Cattle
SULFUR (g/day)
A non-factorial approach is used to determine the sulfur
requirement.
Total = 2 X TotalDMFed
COBALT (mg/day)
A non-factorial anoroach is used to determine the cobalt
requirement.
1 1
Total = 0.11 X TotalDMFed
COPPER (mayday)
Fecal
Fecal = (0.0071 X BW)
Urine
Urine = 0
Sweat
Sweat= 0
Miscellaneous
Misc = 0
Pregnancy
If DaysPreg ~ 10O, then Fetal = 0.5 mg/day
If 100 c DaysPreg c 225, then Fetal = 1.5 mg/day
If DaysPreg ~ 225, then Fetal = 2 mg/day
Lactation
Milk= 0.15 X MilkProd
Growth
Growth = 1.15 X (WG / 0.96)
IODINE (mg/day)
= 0
= 0
= 0
Miscellaneous
Misc = 0
Fetal
Fetal = 0
Lactation
If DaysInMilk ~ O. then Milk =
If DaysInMilk = O. then Misc
Growth
Growth= 0
.
.5 X (BW / 100)
0.6X (BW/100)
IRON (mg/day)
= 0
= 0
= 0
Miscellaneous
Misc= 0
Pregnancy
If DaysPreg ~ l9O, then Fetal = 18
Otherwise, Fetal = 0
Lactation
Milk= 1 X MilkProd
Growth
Growth = 34 X (WG / 0.96)
MANGANESE (mg/day)
Fecal
Fecal = 0.002 X BW
= 0
Sweat
Sweat = 0
Miscellaneous
Misc= 0
Pregnancy
If DaysPreg ~ l9O, then Fetal = 0.3
Otherwise, Fetal = 0
Lactation
If DaysInMilk ~ O. then Milk = 0.03 X MilkProd
Growth
Growth = 0.7X (WG/0.96)
SELENIUM (mid)
A non-factorial approach is used to determine the selenium
requirement.
Total = 0.3 X TotalDMFed
ZINC (mg/day)
Fecal
Fecal = 0.033 X BW
Urine
Urine = 0.012 X BW

OCR for page 315

Sweat
Sweat = 0
Miscellaneous
Misc = 0
Pregnancy
If DaysPreg ~ l9O, then Fetal = 12
Otherwise, Fetal = 0
Lactation
Milk= 4 X MilkProd
Growth
Growth = 24 X (WG / 0.96)
VITAMIN A (1000 IU/kg)
A non-factorial approach is used to determine the Vitamin
A requirement.
If AnimalType = Lactating Cow, Dry Cow, or Replace-
ment Heifer with DaysPreg ~ 259, then Total =
O.llXBW
If AnimalType = Replacement Heifer with DaysPreg
c 259, then Total = 0.08 X BW
VITAMIN D (1000 IU/kg)
A non-factorial approach is used to determine the Vitamin
D requirement.
The requirement is 0.03 XBW.
VITAMIN E (IU/kg)
A non-factorial approach is used to determine the Vitamin
E requirement.
If the animal is grazing and the AnimalType =
Dry Cow, then Vit E required = 0.5 X BW
If the animal is grazing and the AnimalType =
Lactating Cow or Replacement Heifer,
Then Vit E required = 0.26 X BW
If the animal is not grazing and the AnimalType
Dry Cow, then Total = 1.6 X BW
If the animal is not grazing and the AnimalType
Lactating Cow or Replacement Heifer, then
Vit E required = 0.8 X BW
Dry Matter Intake Predictions
LACTATING AND DRY COWS
, =
The equation to predict intake for lactating cows (DMI-
Lact) is:
DMILact = (((BW075)X 0.0968) + (0.372 X FCM)
— 0.293) X Lag
Mode} Evaluation and Prediction Equations 325
Low intake in early lactation is adjusted using the Lag
variable for lactating cows:
Lag= 1 — e`-ixo.is2xtwo~+367~y
The equation for predicting the dry matter intake of dry
cows (DMIDry) in the last 21 days of pregnancy is:
DMIDry = ((1.97 - (0.75 X e`0~6X`DaYsPreg-28011))
lOO)XBW
REPLACEMENT HEIFERS
Heifer intakes are adjusted for environmental tempera-
ture and conditions using the coat condition (CoatCond)
variable to calculate CCFact, the adjustment factor. In
the following section, we describe how the environmental
adjustments are made and then provide the equation for
heifer intake (DMI RH).
If CoatCond = Clean/Dry, then CCFact = 1
If CoatCond = Some Mud, then CCFact = 1
If CoatCond = Wet/Matted, then CCFact = 0.85
If CoatCond = Covered with Snow/Mud,
then CCFact = 0.7
Heifer intake also is adjusted for temperature effects
(TempFact). At temperatures ~ 35, night cooling also
affects intake:
If Temp ~ -15, then TempFact = 1.16
If-15 ' Temp c 5, then TempFact = 1.07
If-5 c Temp c 5, then TempFact = 1.05
If 5 c Temp c 15, then TempFact = 1.03
If 15 c Temp c 25, then TempFact = 1.00
If 25 c Temp c 35, then TempFact = 0.9
If Temp ~ 35 without night cooling,
then TempFact = 0.65
If Temp ~ 35 with night cooling, then TempFact = 0.9
Predicted intake also is adjusted for the effects of age
with the SubFact variable:
If Age c 12, Then SubFact = 0.1128
If Age ~ 12, Then SubFact = 0.0869
The energy concentration of the diet affects intake using
the DivFact variable. For lactating and dry cows, net energy
diet concentration is calculated as follows:
NEDietConc = NEl Total / Total DMFed
For replacement heifers, the equation is: NEDietConc
= NEm Total /Total DMFed
If NEDietConc ~ 1, then DivFact = 0.95
Otherwise DivFact = NEDietConc
Because intake decreases immediately prior to calving,
an adjustment to intake is made in this period as well.

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326 Nutrient Requirements of Dairy Cattle
If DaysPreg ~ 210 and if DivFact ~ O. then
DMI RH = ((BW075) X (((0.2435 X NEDietConc) —
(0.0466 X (NEDietConc2)) — SubFact) / DivFact)) X
TempFact X CCFact
If DaysPreg ~ 210 and ~ 259, then an intake adjustment
factor (DMIRH Factor) is used to adjust the intake of
heifers. This DMIRH Factor is multipled by DMI RH
to obtain the predicted DMI for heifers. The DMIRH-
Factor is calculated as follows:
DMIRH Factor = (1 + ((210—DaysPreg) X 0.0025))
if DaysPreg ~ 210 and ~ 259
Otherwise DMIRH Factor = 1
If DaysPreg ~ 259, then DMI RH = ((1.71 —
(o 69e`0.35XDa~Preg—2801))) / 100 X BW
SUPPLY CALCULATIONS
Energy
The percent concentrate in the ration is calculated based
on the amounts of feeds designated as "Concentrate" that
are fed.
PercentConc = (ConcSum / TotalDMFed) X 100
For feeds that are not classified as Vitamin/Mineral sup-
plements, TDN at 1X maintenance (TANS) and at the
actual increment above maintenance is calculated.
TDNX = (Feedx.TDN / 100) X (DMFed X 1000)
TDN ACtx = (Feedx.TDN ACtx / 100) X (DMFed
X 1000)
The following calculations are used to determine the
energy value of all feeds that are not classified as Calf Feeds
or as Vitamins/Minerals. A different set of calculations is
used to calculate the energy value of the milk-based calf
feeds, and vitamin and mineral supplements are assumed
not to contain energy.
Non-fiber Carbohudrate (NFC) amounts and
It is assumed that nonmember carbohydrate digestibility,
NFCDigest= 0.98
The total digestible NFC = tdNFC = NFCDigest X
(100—NDF—CP—Fat—Ash + NDFIP) X PAF
Where NFCDigestibility = non-fiber carbohydrate
digestibility, NDF = neutral detergent fiber, CP = crude
protein, Fat = Fat, NDFIP = neutral detergent insoluble
protein, and PAF = processing adjustment factor.
The tdNFC is calculated for each feed and the amounts
from the individual ration components are added together.
Crude Protein Contribution to Energy
The contribution of protein to the energy supply is com-
puted in the next set of calculations. Different routines are
used to calculate protein digestibility depending on how
the feed is classified using the energy equation class (Ener-
gyEqClass) that divides feeds into forages, concentrates,
or feeds of animal origin also is used.
Protein digestibility of forages is calculated with the
following equation:
tdCP = Exp((-1.2 X (ADFIP / CP))) X CP
Where tdCP = total digestible Crude Protein, ADFIP =
Acid detergent insoluble protein, and CP = crude protein.
Below is the equation to calculate protein digestibility
of feeds (tdCP) containing proteins from animal sources:
tdCP = (CPDigest X CP)
For all other classes of feeds, tdCP = (1 - (0.4 X
(ADFIP / CP))) X CP
Contribution of Fat to the Energy Supply
If Fat ~ 1, then tdFat = 0
Otherwise, tdFat = (Fat— 1) X 2.25
If Category = Fat and EnergyEqClass = Fatty Acid,
TDN = Fat X FatDigest X 2.25
DE = 0.094 X FatDigest X Fat
If Category = Fat and EnergyEqClass = Fat,
TDN = 10 + ((Fat— 10) X FatDigest X 2.25)
DE = (FatDigest X (Fat— 10) X 0.094) + 0.43
TDN Calculations
Adjustments are made based on feed type in the calcula-
tions of TDN. TDN and DE are computed with the follow-
ing equations if the feed is an Animal Protein:
TDN = (CPDigest X CP) + ((Fat— 1) X 2.25) +
((NFCDigest X (100 — CP—Ash— Fat)) - 7)
DE = (tdNFC X 0.042) + (tdCP X 0.056) + (0.094
X (tdFat/2.25)) - 0.3
For feeds that are not Animal Proteins or Fats and
that do contain some NDF (forages, many by-products,
concentrates), the following equations are used:
TDN = tdNFC + tdCP + tdFat + dNDF — 7
DE = (tdNFC X 0.042) + (dNDF X 0.042) +
(tdCP X 0.056) + (0.094 X (tdFat /2.25)) - 0.3
The equation below is used for feeds that do not contain
NDF, that are not primarily fat and that are not derived
from animals (molasses, for example):

OCR for page 315

Mode} Evaluation and Prediction Equations 327
TDN = ((0.98 X PAF) X (100—CP—Fat—Ash))
+ (CP X (1 - (0.4 X (ADFIP / CP)))) + ((2.25 X
(Fat— 1) - 7))
DE = (0.98 X PAF) X (0.042 X (100— CP— Fat
— Ash)) + (CP X (0.056 X (1 - (0.4 X (ADFIP /
CP))))) + (0.094 X (Fat— 1)) - 0.3
The equations for feeds with fat and ash are:
TDN = ((0.98 X PAF) X (100 — Fat—Ash)) +
((2.25 X (Fat— 1) - 7))
DE = (0.98 X PAF) X (0.042 X (100 — Fat—Ash))
+ (0.094 X (Fat— 1)) - 0.3
No energy values are calculated for Vitamins or Minerals.
Energy Caloulations and Conversions
For animals other than young calves, the ratio of total
dry matter intake to intake used to meet the maintenance
requirement (DMI to DMIMaint) is calculated with the
following equations.
For replacement heifers
DMI to DMIMaint = TotalTDN / (0.035 X (SBW075))
Where DMI to DMIMaint is the amount of
intake needed to meet the maintenance requirement,
TotalTDN = Total dietary TDN, and SEW = shrunk
body weight.
For lactating and mature cows
DMI to DMIMaint = TotalTDN / (0.035 X (BW075))
For young calves
DMI to DMIMaint = TotalTDN / (0.035 X
(CalfBW075))
Fat Adjustment
After the total amount of fat in the diet has been deter-
mined (code not shown), it is necessary to make an adjust-
ment to the TDN value if the diet contains more than 3
percent fat. Fat digestibility is calculated differently for
feeds classified as fatty acids than for other fats. The equa-
tions below show how fat digestibility is calculated for The equation for heifers is
1) fat supplements classified as fats, 2) fat supplements MEng = 0.82 X DE
classified as fatty acids, and 3) for other feeds:
1). DigestibleFat= 10 + ((Fat— 10) X FatDigest)
2). DigestibleFat = Fat X FatDigest
3). DigestibleFat= Fat— 1
If (Fat Total / TotalRegDMFed) ~ 0.03 Then
Adj TDN = TDNConc — (((TotalFat) - 3) X
(TotalDigestibleFat / TotalFat) X 2.25)
TDNConc = Adj TDN / ((100 - (TotalFat -
3)) / 100)
Discount Variable
This variable is used to discount TDN to account for
depressed digestibility of feeds above maintenance levels.
It used to calculate energy availability for all classes of
animals except young calves.
If a feed is not a milk-based calf feed and contains
energy, then
DiscountVariable = ((0.18 X TDNConc) - 10.3) X
(DMI to DMIMaint— 1)
Where DiscountVariable = Factor used to discount
TDN, TDNConc = TDN concentration in the ration,
and DMI to DMIMaint is the amount of the speci-
fied ration needed to meet the maintenance
requirement.
The discount variable cannot be ~ 0 and, if the TDN of
a feed is ~ GO, then the DiscountVariable = 1. Otherwise
Discount= (TDNConc—DiscountVariable)/TDNConc
For feeds other than milk-based calf feeds and if TDN-
Conc ~ O. then
TDN ActX= TDN X Discount
Different discounts are applied depending on the fat
content of the ration. These discounts apply to all classes
of animals except young calves.
If Fat ' 3 and if the animal is a dry cow or a lactating
cow, then
MEng = (1.01 X DiscDE) - 0.45 + (0.0046 X
(Fat— 3))
If Fat ~ 3 and the animal is a heifer, then
MEng= 0.82 X DE
Net energy for lactation for feeds having more than 3%
fat is computed.
NEl = (0.703 X MEng) - 0.19 + ((((0.097 X
MEng) + 0.19) / 97) X (Fat— 3))
If the feeds have ~ 3% fat, the equation to compute
ME for lactating and dry cows is
MEng= (1.01 X DiscDE) - 0.45
The equation to compute the NEl of low fat feeds is:
NEl = (0.703 X MEng) - 0.19
For feeds that are not classified as fats
MEforNEg= 0.82 X DE
NEg = 1.42 X MEforNEg — 0.174 X MEforNEg2
+ 0.0122 X MEforNEg 3 - 1.65
NEm = 1.37 X MEforNEg — 0.138 X MEforNEg2
+ 0.0105 X MEforNEg 3 - 1.12

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328 Nutrient Requirements of Dairy Cattle
Otherwise,
MEng= DiscDE
NEl = 0.8 X DiscDE
NEm = 0.8 X MEng
NEg= 0.55 X MEng
Computation of the total energy values for the diet.
MEng Total = TotalMEConc X TotalRegDMFed
NEUTotal = TotalNElConc X TotalRegDMFed
NEg Total = TotalNEgConc X TotalRegDMFed
NEm Total = TotalNEmConc X TotalRegDMFed
If AnimalType is not "Replacement Heifer", then
NEDietConc = NE Total / TotalRegDMFed
If AnimalType is "Replacement Heifer", then
NEDietConc = NEm Total / TotalRegDMFed
Protein Supply and Requirements
Microbial yield (MCP Total) is calculated as a percent-
age of discounted TDN (TDN Act Total):
MCP Total = 0.13 X TDN Act Total
The following equation is used to calculate the amount
of crude protein from each feed.
CPX = (FeedxCP /100) X (DMFed X 1000)
To calculate the site of digestion of protein, both passage
(kp) and digestion (kc) rates are needed. Separate passage
equations are used for concentrates, dry forages, and
wet forages.
Concentrate
Kp = 2.904 + (1.375 X BW DMI) — (0.02 X
PercentConc)
Dry Forage
Kp = 3.362 + (0.479 X BW DMI) — (0.017 X
FeedxNDF) — (0.007 X PercentConc)
Wet Forage
Kp = 3.054 + (0.614 X BW DMI)
The amount of RDP in a specific feed is calculated using
the following equation. It is assumed that all of Protein A
is ruminally available and that none of Protein C is
degraded in the rumen. Thus, only Protein B is affected
by digestion and passage rates.
If (Feedx.Kd + Kp) ~ 0 Then
RDPX = ((Feedx.Kd / (Feedx.Kd + Kp)) X
(~(Feedx.PrtB / 100) X (FeedxCP /100~) X
FeedxDMFed)~) + (~(FeedxPrtA / 100) X
(FeedxCP / 100~) X FeedxDMFed)
Otherwise, RDPX = 0
The amount of ruminally-undegraded protein is
obtained by subtraction:
RUPX = (CPX— (RDPX X 1000~) / 1000
If RUP Total ~ O. then DietRUPDigest =
TotalDigestedRUP / RUP Total
Otherwise, DietRUPDigest = 0.
The requirement for RDP is calculated in the follow-
. .
sing equation.
RDPReq = 0.15294 X TDN Act Total
RDPSup = TotalDMFed X 1000 X DietCP X CP RDP
RDPBal = RDPSup — RDPReq
RUPSup = CP Total — RDPSup
RUPReq = TotalCPReq — (MPBact + MPEndo)) /
DietRUPDigest
The efficiency of microbial crude protein synthesis can-
not exceed 0.85.
If MCP Total ~ (0.85 X (RDP Total X 1000~), then
MCP Total = (0.85 X (RDP Total X 1000~)
CP required = RUPreq + RDPReq
MPBalance = (~(MPFeed X 1000) + MPBact +
MPEndo) — (MPMaint + MPPreg + MPLact +
MPGrowth))
Amino Acids
The amino acid supply is calculated using the following
equation with arginine (Arg) as an example. The structure
of this equation is similar for all of the amino acids that
are considered in the model.
TArg = TArg + (~(DMFed / TotalDMFed) X
(CP / 100) x ((RUPx X 1000) / CPX)
X (Arg/ 100) X TotalDMFed) X 1000)
Where TArg = Total arginine, DMFed = quantity of
feed X fed, TotalDMFed = Total dry matter fed,
CP = % Crude Protein, RUPX = RUP in feed X,
CPX = crude protein in feed X.
The next step is to calculate the total digestible supply
of each amino acid. Below is the equation for Dig TArg.
The equations for the other amino acids have the same
format.
Dig TArg = Dig TArg + (~(DMFed/ TotalDMFed)
X (CP / 100) X ((RUPX X 1000) /
CPx) X (FeedxRUPDigest /100) X (Arg/ 100) X
TotalDMFed) X 1000)

OCR for page 315

Where Dig TArg = Total digestible arginine,
RUPDigest = RUP digestibility of feed X
The total essential amino acid supply before the contri-
bution of the microbial protein has been added (EAATotal-
BeforeMP) is calculated.
EAATotalBeforeMP = (TArg + THis + TIle + TLeu
+ TLys + TMet + TPhe + TThr + TTrp + TVal)
The variables xl and x2 are used in the following sets
of calculations of the total amount of each amino acid
supplied. The equations to calculate the total amounts of
each amino acid follow. In all equations, it is assumed that:
If EAATotalBeforeMP ~ 0 then
xl = ((TArg (or other amino acid) / EAATotalBefore-
MPP X 100)
Otherwise xl = 0
If ((RUP Total X 1000) + EndCP + MCP Total)
0 then
x2 = ((RUP Total X 1000) / ((RUP Total X 1000)
+ EndCP + MCP Total)) X 100
Otherwise, x2 = 0
TotalArg = 7.31 + (0.251 X xl)
TotalHis = 2.07 + (0.393 X xl) + (0.0122 X x2)
TotalIle = 7.59 + (0.391 X xl) — (0.0123 X x2)
TotalLeu = 8.53 + (0.41 X xl) + (0.0746 X x2)
TotalLys = 13.66 + (0.3276 X xl)— (0.07497 X x2)
TotalMet = 2.9 + (0.391 X xl) — (0.00742 X x2)
TotalPhe = 7.32 + (0.244 X xl) + (0.029 X x2)
TotalThr= 7.55 + (0.45 X xl) — (0.0212 X x2)
TotalVal = 8.68 + (0.314 X xl)
The total essential amino acid supply is calculated below:
TotalEAA = 30.9 + (0.863 X EAATotalBeforeMP)
+ (0.433 X MCP Total)
Total flows of RUP of specific amino acids are calcu-
lated below:
TotalRUPArgFlow= 0.863 X TArg
TotalRUPHisFlow= 0.863 X THis
TotalRUPIleFlow= 0.863 X TIle
TotalRUPLeuFlow= 0.863 X TLeu
TotalRUPLysFlow= 0.863 X TLys
TotalRUPMetFlow= 0.863 X TMet
TotalRUPPheFlow= 0.863 X TPhe
TotalRUPThrFlow= 0.863 X TThr
TotalRUPTrpFlow= 0.863 X TTrp
TotalRUPValFlow= 0.863 X TVal
Duodenal flow (g/day) is calculated using an equation
of the form below for each amino acid. Arginine is given
as an example.
Arg Flow = (TotalArg / 100) X TotalEAA
Mode} Evaluation and Prediction Equations 329
The contribution of microbial crude protein and endoge-
nous protein to the amino acid supply is calculated as
follows. The form of this equation is similar for all
· ~
am~no ac~us.
TotalMCPEndArgFlow= Arg Flow-
TotalRUPArgFlow
The next step is to calculate the supply of each amino
acid in RUP that is digestible. The form of the equation for
each amino acid is similar to that given for arginine below:
If TArg ~ O. then dTotalRUPArg = TotalRUPArgFlow
X (Dig TArg / TArg)
Otherwise, dTotalRUPArg = 0
The amount of a specif~c amino acid that is digestible
and is of microbial or endogenous origin then is calculated.
Arginine is used as the example but similar calculations
are made for all amino acids.
dTotalMCPEndArg = 0.8 X TotalMCPEndArgFlow
The flow of digestible arginine, or other amino acids)
then is calculated.
Dig Arg Flow = dTotalRUPArg +
dTotalMCPEndArg
The protein in the duodenum must be converted from
crude protein to a metabolizable protein basis. Microbial
crude protein is converted to metabolizable protein with
an eff~ciency of 0.64:
MPBact= 0.64 X MCP Total
MPFeed= TotalDigestedRUP
MPEndo = 0.4 X EndCP
The next computation is to determine the percent of a
specific amino acid of metabolizable protein. The arginine
equation is similar to those of the other amino acids.
If (MPBact + (MPFeed X 1000) + MPEndo) ~ O. then
ArgPctMP = 100 X (Dig Arg Flow/ (MPBact +
(MPFeed X 1000) + MPEndo))
Otherwise, ArgPctMP = 0
Minerals
Two sets of equations for the calculation of the supply
of minerals are presented here for all classes of animals
except for young calves. Both the amount of mineral sup-
plied and the amount of the mineral that is absorbable are
calculated. The f~rst equations are for the macrominerals
using calcium as an example. In the mineral equations, d
is used for mineral supplements instead of x to denote
the feed.

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330 Nutrient Requirements of Dairy Cattle
Supplied = Supplied + ((Feed,Ca / 100) X
Feed DMFed)
Absorbable = Absorbable + (~(Feed`Ca/100) X
Feed, DMFed) X (Feed, CaBio))
The second set of equations represents those used for
trace minerals using zinc as an example.
Supplied = Supplied + (Feed,Zn X Feed,DMFed)
Absorbable = Absorbable + ((Feed`Zn X
Feed, DMFed) X (Feed, ZnBio))
Ration density (RD) = Supplied / TotalDMFed
YOUNG CALF SUB-MODEL
Both the requirements and supply portions of the young
calf sub-model are in this section.
Requirements
ENERGY REQUIREMENTS
For young calves, the efficiencies with which feeds are
used for maintenance and gain, Km and Kg, for milk-based
and other feeds are fixed.
Milk-fed
CalfKm = 0.8 for milk-based feeds
CalfKg = 0.69 for milk-based feeds
Fed Milk and Starter
CalfKm = 0.75 if the feed is not milk-based
CalfKg = 0.57 if the feed is not milk-based
The equation to calculate the basal maintenance require-
ment of a calf without stress is:
NEmCalf= 0.086 X (CalfBW075)
The next step is to calculate the CalfKm and CalfKg for
the proposed ration using the fixed efficiencies of conver-
sion of ME to NEm and NEg.
CalfKg = CalfKg + (0.57 X (FeedxDMFed X
FeedxMEng))
NonMineralFeeds = NonMineralFeeds +
(FeedxDMFed X FeedxMEng)
If NonMineralFeeds ~ 0 Then
CalfKm = CalfKm / NonMineralFeeds
CalfKg = CalfKg / NonMineralFeeds
LOWER TEMPERATURE ADJUSTMENTS TO CALF
MAINTENANCE REQUIREMENT
The maintenance requirement for young calves is
adjusted to account for cold stress as follows:
Temperature Calves > Temperature Calves <
(° C) 2 months (° C) 2 months
>5 0 ~ 15 0
0 to 5 0.13 10 to 15 0.13
-5 to 0 0.27 5 to 10 0.27
- 10 to - 5 0.40 0 to 5 0.40
- 15 to - 10 0.54 - 5 to 0 0.54
-20to-15 0.68 -lOto-5 0.68
-25to-20 0.81 -15to-10 0.86
- 30 to - 25 0.94 - 20 to - 15 0.94
<-30 1.07 -25 to -20 1.08
-25 to -30 1.21
~ - 30 1.34
The resulting equation for the maintenance requirement
of young calves with the temperature adjustment is:
NEmCalf = (NEmCalf X (l+TempFactor))
The next step is to recalculate ME required for mainte-
nance with the NEm that has been adjusted for tempera-
ture effects.
If CalfKm ~ 0 Then
MEMaint = NEmCalf / CalfKm
Otherwise MEMaint = 0
The following equation is used to calculate the amount of
intake devoted to meeting the maintenance requirement:
If the feed is classified as a calf feed (milk-based) and
if cMEng ~ O. Then If DietNEmCalf ~ 0 Then
CalfKm = CalfKm + (0.86 X (FeedxDMFed X
FeedxcMEng))
CalfKg = CalfKg + (0.69 X (FeedxDMFed X
FeedxcMEng))
An adjustment is made to ensure that no energy values
are computed from mineral supplements:
NonMineralFeeds = NonMineralFeeds +
(FeedxDMFed X FeedxcMEng)
For all other classes of feeds if MEng ~ 0
CalfKm = CalfKm + (0.75 X (FeedxDMFed X
FeedxMEng))
DMIForNEmCalf= NEmCalf/DietNEmCalf
Else DMIForNEmCalf = 0
A similar calculation is used to calculate the dry matter
intake available for growth and the net energy available
for growth:
DMIForGrowth= (TotalDMFed—
DMIForNEmCalf)
NEFGCalf= DMIForGrowth X DietNEmCalf
If CalfKg ~ 0 Then MEFGCalf = NEFGCalf/ CalfKg
Else MEFGCalf = 0

OCR for page 315

If NEFGCalf ~ O Then
EnergyADGCalf= Exp(~0.8333 X (Log(~1.19 X
NEFGCalf) / (0.69 X (CalfBW0355))))))
CALF PROTEIN REQUIREMENTS
Caltprotein requirements are computed with the follow-
ing equation:
ProteinReqCalf = CalfADG X 0.188 (30 g N/kg gain
= 187.5 g Net Protein / kg gain)
Total apparently digested protein (TotalADP) is calcu-
lated as follows where 0.93 and 0.75 are the assumed digest-
ibilities of milk-based feeds and starter feeds respectively:
TotalADP + ((TotalMilkCP X 0.93) + (TotalStart-
erCP X 0.75)) X 1000
The ratio of ADP to CP is calculated as follows:
ADP to CP = TotalADP / ((TotalMilkCP +
TotalStarterCP) X 1000)
Calf Protein Maintenance Requirements
EUN = Endogenous urinary N losses = 0.2 X
(CalfBW075)
MFN = Metabolic fecal N = (MilkDMI X 1.9) +
(StarterDMI X 3.3))
BV = Biological value = (0.8 X (TotalMilkCP /
TotalCP)) + (0.7 X (TotalStarterCP / TotalCP))
ADPmaint = 6.25 X (((1 / BV) X (EUN + MFN))
— MFN)
CPmCalf = ADPMaint / ADP to CP if
ADP to CP>O
ADPgrowth = (ProteinReqCalf X 1000) / BV
Mode} Evaluation and Prediction Equations 331
TABLE 16-2 Ration Densities of Required Minerals
for Three Categories of Feeds for Calves
Mineral Milk-Replacer Starter Grower
1.0
0.7
0.07
0.4
0.65
0.25
0.29
100
40
40
10
0.5
0.11
0.3
9
0.6
50
0.7
0.45
0.1
0.15
0.65
0.2
0.2
40
10
0.25
0.1
0.3
4
0.6
25
0.6
0.4
0.1
0.14
0.65
0.2
0.2
50
40
40
10
0.25
0.1
0.3
4
0.6
25
If TotalDMFed>O Then
RDReq = ((MilkFeeds X m) + (CalfStarter X n)
+ (RegFeeds X o)) / TotalDMFed
Where m = concentration of mineral X in MilkFeeds,
n = concentration of mineral X in calf starter, and
o = concentration of mineral X in regular feeds.
Calf Supply and Diet Evaluation
In the calf submodel, milk-based feeds are in a separate
category in the feed library because the energy values for
these feeds are calculated differently from feeds that may
be used as starter feeds. Any feed in the library except for
the milk-based calf feeds may be used as a starter feed.
The information for the starter feeds is taken from the
appropriate category of the main feed library.
ADPAllowGain = ((TotalADP — ADPmaint) X Calf Energy and Protein
BV) / 0.188
CALF MINERAL REQUIREMENTS
A factorial approach is not used to estimate mineral
requirements for young calves. The requirements for calves
are based on the amounts of milk-based feed, starter, and
grower that are offered. It is assumed that the values pre-
sented in Table 10 = 6 for milk replacers, calf starter, and
grower meet the mineral requirements of the young calf.
Table 16-2 indicates the desired ration densities for each
of the three categories of feeds (milk-based calf feeds, calf
starter, and calf grower). The densities for calf grower are
used as the standard for all feeds in the Feed Library
except milk-based feeds and calf starter.
To calculate the desired concentrations of each mineral,
the following equation is used:
The energy calculations to obtain TDN, DE, and ME
are included in the main energy computation section. To
get the appropriate energy and protein values, the totals
from the calf feeds are calculated and then the totals from
the other feeds are obtained. Finally, the contributions
from the two groups of feeds are added together.
In the following sets of calculations, it is assumed that
the initial value of the variable is 0.
TotalNEm = TotalNEm + (DMFed X cNEm)
TotalNEg = TotalNEg + (DMFed X cNEg)
TotalME = TotalME + (DMFed X cMEng)
TotalCP = TotalCP + (DMFed X (cCP / 100~)
TotalDCP = TotalDCP + (DMFed X (cDCP/ 100~)
If Category = "Calf Feed— Milk" Then
MilkDMI = MilkDMI + DMFed
MilkME = MilkME + (DMFed X cMEng)

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332 Nutrient Requirements of Dairy Cattle
TotalMilkADP = TotalMilkADP + (DMFed X
(cDCP / 100~)
TotalMilkCP = TotalMilkCP + (DMFed
(cCP / 100))
Otherwise
StarterDMI = StarterDMI + DMFed
StarterME = StarterME + (DMFed X cMEng)
TotalStarterADP = TotalStarterADP + (DMFed X
(cDCP / 100))
TotalStarterCP = TotalStarterCP + (DMFed X
(cCP / 100))
To convert starter/regular feeds from CP to cDCP:
cDCP = 0.75 X CP
Here are the equations to obtain the total values:
TotalNEm = TotalNEm + NEm Total
TotalNEg = TotalNEg + NEg Total
TotalME = TotalME + MEng Total
DietNEmCalf = TotalNEm / TotalDMFed
DietNEgCalf = TotalNEg / TotalDMFed
DietMECalf = TotalME / TotalDMFed
Mature Weights
Mature weight is used both to estimate the target growth
rates of replacement heifers and to predict calf birth
weights. The user has the option of entering the mature
weight based on herd observations or of using default
values.
The default weights for various breeds are:
A~yshire
Brown Swiss
Guernsey
Holstein
Jersey
Milldng Shorthorn
545 kg
682 kg
500 kg
682 kg
454 kg
568 kg
Calf birth weight is calculated from mature weight using
the following equation:
CBW From MW= 0.06275 X MW
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