Case Studies case studies pdf

(1)

NRC 2012 Models for

Estimating Nutrient

Requirements of Pigs

(2)

1 Introduction and General Overview

These case studies have been prepared to help users understand the use and application of

the NRC (2012) models to estimate nutrient requirements of swine.

A detailed description of the models is provided in Chapter 8 of the 11th revised edition

of Nutrient Requirements of Swine published by the U.S. National Research Council (NRC,

2012). Appendix 1 of that publication also contains a User Guide. A slightly updated version of

the User Guide can be downloaded with the models.

The four models (one for starting pigs, one for growing-finishing pigs, one for gestating

sows, and one for lactating sows) are combined into a Microsoft Excel workbook and stored in

the file NRC swine 2012 v1. The program also includes a database with nutrient profiles of

ingredients and a means to formulate diets and generate feeding programs. The nutrient database

and formulation module allow the amounts of nutrients supplied in specified feeding programs to

be compared with estimated requirements. The program also enables nitrogen, phosphorus, and

carbon losses into the environment to be estimated.

Before operating the model, it is recommended that the original program is saved and a

copy is used. Doing this will protect the settings in the original version of the program. To

operate the models, start Excel and open the file NRC swine 2012 v1.

The program contains macros. Depending on the security settings on your computer you

(5)

When the program opens, the user is asked to agree with the warning about the program’s

use. The user is then directed automatically to the Main Menu, which allows access to the

models and the module Review Feeding Programs. The ingredient database and the feed

formulation system are accessed via the Review Feeding Programs button.

The program allows alternative systems for energy (DE, ME, and DE), amino acids

(standardized ileal digestible [SID], apparent ileal digestible [AID], and total content [applicable

to corn and soybean meal-based diets only]), and phosphorus (standardized total tract digestible

[STTD], apparent total tract digestible [ATTD], and total content [applicable to corn and

soybean meal-based diets only]. Energy and nutrient systems are specified on the Main Menu.

In the models, determinants of nutrient requirements can be entered, and current levels of

performance can be specified. After changing the model inputs and before exploring nutrient

requirements, calculations must be executed by clicking the Calculate button at the top of the

screen. During these calculations nutrient utilization parameters and estimates of nutrient

requirements are generated and stored for individual days.

Once model calculations are executed, estimates of animal performance, key aspects of

nutrient utilization, and nutrient requirements can be explored simply by entering the body

weight range (starting and growing-finishing pigs) or time period (for gestating and lactating

sows) .

Results are presented in graphs and summarized in printable reports.

Notes:

Changes that are made to model inputs, diet compositions, and feeding programs are used

for the current session only. To store changes to inputs for use in future sessions, simply save the

entire file, using a new name.

When using the models to estimate nutrient requirements, there is no need to evaluate

feeding programs. When first using the program it is recommended that No is selected following

(6)

2 Gestating Sows

EFFECTS OF STAGE OF GESTATION AND FEEDING REGIMEN ON NUTRIENT REQUIREMENTS

First, ensure that the appropriate nutrient systems are chosen. To do this, navigate to the

Main Menu and under Step I use the three pull-down menus to select ME for energy, SID for amino acids, and STTD for phosphorus. Under Step II, select No following Do you wish to

evaluate a feeding program?

Under Step III select Gestating Sows. A new window will appear with navigation and

action buttons at the top of the screen. To ensure that the default values are entered for model

inputs, click Enter Default Inputs. The following information should be displayed under

INPUTS:

Diet characteristics that affect nutrient requirements

Metabolizable energy (ME) content, kcal/kg 3300

Fermentable fiber content, % 9.0

Sow performance:

Sow body weight at breeding, kg 165

Parity 2

Gestation length, day 114

Anticipated litter size 13.5

Anticipated birth weight, kg/pig 1.4 Feed intake

Feed intake / (feed intake + feed wastage) 0.95

(7)

Feed intake + feed wastage, kg/day 2.210 2.210 2.210 2.610

Consider housing conditions & environmental temperature?

No

Match observed with predicted performance? No

Now, all necessary information has been entered to generate estimates of nutrient

requirements for the default scenario. To do this, click Calculate at the top of the screen. The

screen has now automatically moved to the results and you may scroll down or to the right of the

screen to display results more fully. Results can be explored for various time periods during

gestation.

Under the headings RESULTS and Range in days for estimating nutrient requirements

first enter 1 for Initial day and 114 for Final day to explore the mean performance and nutrient

requirements for the entire gestation period. Results for this range of days will be calculated

automatically. To return to data-entry fields click Home at the top of the screen.

Enter key result and nutrient requirements in the first column in the table below for

Scenario 1 (default) and day 1 to 114. To explore performance and nutrient requirements during

early (day 1 to 89) and late gestation (day 90 to 114), enter these two combinations of Initial

day, and Final day and record the results in the 2nd and 3rd column under Scenario 1 in the

Table below.

Scenario 1 (default) 2 (constant daily intake) Results

Initial day 1 1 90 1 1 90

Final day 114 89 114 114 89 114

Average feed intake + feed wastage, kg/day

Average total body weight gain, g/day 526 539 481 524 572 354 Average maternal body weight gain, g/day

Avg. maternal body protein deposition, g/day Average protein deposition in conceptus, g/day

Average maternal body lipid deposition, g/day 96 98 90 94 115 19

(8)

How can the large changes in performance and daily Lys and phosphorus requirements

during gestation be explained?

In the model, default feed intake is increased starting on day 90 of gestation. Does this

seem appropriate? What are the potential consequences of low or negative energy and protein

balances in the (maternal) sow’s body?

(In answering these questions you may view the graphs, click Graph at the top of the

screen and scroll across the graphs, if needed. To return to results you can click Home at the top

of the screen.)

The default increase in feed intake starting on day 90 of gestation is a deviation from

using a constant level of feed intake throughout gestation. To evaluate the effect of maintaining a

constant feeding level go to the Feed intake area under INPUTS, and change all four values for

Feed intake + feed wastage to 2.298. Then redo the calculations, click Calculate, and record the results for the three different combinations of Initial day and Final day in the table above and

under Scenario 2 (constant daily intake).

These two scenarios result in very similar average feed intake + feed wastage over the

entire gestation period (day 1 and 114).

What scenario is likely to better supports sow performance? Explain why?

Is it appropriate to use the same diet for feeding sows during early and late gestation?

(9)

EFFECTS OF PARITY AND ANTICIPATED LITTER SIZE ON NUTRIENT REQUIREMENTS

Click Enter Default Inputs and ensure that the information in the INPUT area is not

changed from that used for section Effect of Stage of Gestation and Feeding Regimen on Nutrient

Requirements. Again, housing conditions will not be considered and observed and predicted

performance will not be matched.

For each scenario listed in the table below, enter the inputs in the model in areas with the

heading Sow performance and Feed intake. Always use a gestation length of 114 days and an

anticipated birth weight of 1.4 kg/pig. For feed intake, always use two feeding levels; they are

increased automatically by 0.4 kg/day at day 90. After inputs are entered for each scenario, click

Calculate and then record results in the table below. Note that the Enter Default Inputs relates to parity 2. Average maternal body weight gain, g/day

Avg. maternal body protein deposition, g/day Average protein deposition in conceptus, g/day Average maternal body lipid deposition, g/day Average SID Lys requirement, %

Average SID Lys requirement, g/day 10.6 16.7 9.2 15.1 6.7 11.5 6.6 11.9 Avg. SID Thr requirements, ratio to SID Lys x 100

What contributes to the differences in g/day and % of diet requirements for SID lysine

(10)

Why does the required SID Thr to SID Lys ratio change across parity?

Is it appropriate to use the same diets to feed sows of different parity? Why or why not?

Discuss the importance of anticipated litter size when establishing optimum feeding

levels and dietary nutrient levels?

EFFECTS OF HOUSING AND ENVIRONMENTAL CONDITIONS ON NUTRIENT REQUIREMENTS

Click Enter Default Inputs. You can double check the accuracy of the inputs by running

the model after these are entered (click Calculate) to obtain the results presented for Scenario 2

in the table in section Effect of parity and anticipated litter size on nutrient requirements.

To explore the effect of environmental conditions select Yes following Consider housing

conditions & environmental temperature? New data-entry fields will appear; enter or select the

following inputs:

Sow standing, min/day 240

Housing Individual

Effective environmental temperature, oC 20

Now run the program (click Calculate), under RESULTS and Range in days for

(11)

results in the table below under Scenario 1. Then, alter some of the environmental conditions to

generate alternative scenarios; run the program for each scenario and record the results.

Scenario 1 2 3 4 5 6

Inputs Feed intake+wastage on start day 1,

kg/day Average maternal body weight gain, g/day

Avg. maternal body protein deposition, g/day

Average SID Lys requirement, %

Average SID Lys requirement, g/day 10.4 10.4 7.4 10.4 9.4 10.1

What is the effect of increasing the amount of time sows spend standing (Scenario 2 vs.

1) and decreasing environmental temperature (Scenario 3 vs. 1) on sow body weight gain and

lysine requirements in % of diet and g/day? Why do these changes occur?

In a similar manner discuss how and why group housing (Scenario 4 vs. 1),

environmental temperature for group-housed sows (Scenario 5 vs. 1), and floor type (Scenario 6

vs. 5) affect sow body weight gain and lysine requirements in % of diet and g/day. Why is the

response to changes in environmental temperature different for group- vs. individually housed

sows?

Obviously, group-housed sows require more energy to support increased activity, and

when sows are kept on concrete floors in a cool environment extra energy is needed to maintain

(12)

group-housed sows that are kept on concrete flooring and at an environmental temperature of 10oC. To

do this, enter the appropriate inputs and increase Feed intake + wastage, run the program, and

monitor in the Average total sow body weight gain until it is within 5 g/day of Scenario 1.

New Feed intake + feed wastage on start day 1: 2.55 kg/day

Revised SID Lys requirements: 0.45 % of diet, and 11.2 g/day

Based on these considerations, discuss how and why environmental conditions should be

considered when establishing optimum feeding levels and target dietary nutrient levels.

MATCHING OBSERVED WITH PREDICTED PERFORMANCE

When observed sow performance is similar to model-generated predicted performance,

confidence in estimated nutrient requirements is increased. To explore this, make sure to return

to the starting scenario (Section Effect of Stage of Gestation and Feeding Regimen on Nutrient

Requirements; click Enter Default Inputs and ensure No is selected following Consider housing conditions and environmental temperature?).

Now select Yes following Match observed with predicted performance? New data fields

will appear; ensure that the following values are entered:

Observed Model Predicted

Body weight at farrowing, kg 230 -

P2 back fat at breeding, mm 18 -

P2 back fat at farrowing, mm 20.5 -

Adjustment to maintenance energy requirements, % 0.0 Absolute adjustment to maternal body N gaina,

g/extraMcal ME intake 0.00

a

This parameter affects the composition of maternal body weight change (ratio between body protein and body lipid deposition). A higher value reflects a leaner sow genotype and means that sows will preferentially deposit more body protein (or lean body mass) and less body lipid. In the model, the default value is determined by parity only and differences between sow genotypes are not considered.

Now change the two adjustment parameters for the scenarios that are listed in the table

below and record the results. Remember to run the model (click Calculate) after inputs have

(13)

Scenario 1 2 3 4 Inputs

Adjustment to maintenance energy requirements, % 0.0 -5.0 -5.0 -5.0 Abs. adjustm. to maternal body N gain,

g/extra Mcal ME intake 0.00 0.00 0.25 0.50

Results (Initial day: 1; Final day: 114)

Model-predicted body weight at farrowing, kg 225 227.4 228.9 230.4 Model-predicted P2 back fat at farrowing

Avg. total body protein deposition, incl. conceptus, g/day Average maternal body lipid deposition, g/day

Average SID Lys requirement, g/day 10.4 10.4 11.0 11.5

Which of these scenarios most accurately predicts sow body weight and back fat

changes?

How do these adjustments to maintenance energy requirements and to maternal body N

gain per unit of extra energy intake affect SID lysine requirements in % of diet and g/day?

Within this context, discuss the importance of accurately predicting sow performance for

(14)

3 Lactating sows

EFFECTS OF PARITY AND LITTER GROWTH RATE ON NUTRIENT REQUIREMENTS

Make sure that the appropriate nutrient systems are chosen. To do this, navigate to the

Main Menu and under Step I use the three pull down menus to select ME for energy, SID for

amino acids, and STTD for phosphorus. Under Step II, select No following Do you wish to

Under Step III select Lactating Sows. A new window will appear with navigation and

action buttons at the top of the screen. To ensure that the default values are entered for model

inputs, click Enter Default Inputs. The following information should be displayed under the

heading INPUTS:

Sow body weight after farrowing, kg 210

Lactation length, days 21

Average number of pigs nursed 11.5

Daily piglet weight gain, g; mean over entire lactationa 230 Feed intake:

Feed intake / (feed intake + feed wastage) 0.95 Use model predicted feed intakes Yes

(15)

Consider environmental temperature? No Match observed with predicted performance?: No

a

The user may choose to use mean piglet weight at weaning as an alternative means to estimate milk production.

Now all relevant information has been entered to generate estimates of nutrient

requirements for the default scenario. To do this, click Calculate. The screen has now

automatically moved to the results. Results can be explored for various time periods during

lactation. To return to data-entry fields click Home at the top of the screen.

Under the headings RESULTS and Range in days for estimating nutrient requirements

enter 1 for Initial day and 21 for Final day to explore average daily performance and average

nutrient requirements during the entire lactation period. Enter key result and nutrient

requirements in the first column in the table below (Scenario 1; Parity 2 and higher).

To explore nutrient requirements of Parity 1 lactating sows enter the values shown in the

table above and for Scenario 2 (Parity 1) in the appropriate fields under INPUTS and either

Sow performance or Feed intake, run the model (click Calculate) and enter the results in the

(16)

Scenario 1 (Parity 2+) 2 (Parity 1) Inputs

Sow body weight at farrowing, kg 210 175

Lactation length, days 21 21

Average number of pigs nursed 11.5 11

Daily piglet weight gain, g; mean over entire lactation 230 230

Parity number 2 and higher 1

Results (Initial day: 1; Final day: 21) Average feed intake + feed wastage, kg/day

Average sow body weight gain, g/day -276 -368

Average sow whole body protein deposition, g/day Average sow whole body lipid deposition, g/day Average milk production, kg/day

Average SID Lys requirement, g/day 48.9 45.7

Average STTD phosphorus requirement, % Average STTD phosphorus requirement, g/day

What contributes to the difference in dietary SID Lys requirements (% of diet) between

Parity 1 and Parity 2+ sows? (There is no need to rerun the model to explore the effects of each

input individually; these differences will be explored in more detail in subsequent sections.)

EFFECTS OF SOW BODY WEIGHT AND LITTER GROWTH RATE ON NUTRIENT REQUIREMENTS

Increase either sow body weight at farrowing or the number of pigs nursed and daily

piglet weight gain in similar proportions and assess the effects of these changes on Lys and

phosphorus requirements.

Return to the default input parameters (click Enter Default Inputs). The results for

Scenario 1 should be identical to those presented for Scenario 1 in section Effects of parity and

(17)

Scenario 1 2 3 4 5 Inputs

Sow body weight at farrowing, kg 210 246 210 210 210

Lactation length, days 21 21 21 21 21

Average number of pigs nursed 11.5 11.5 13.5 11.5 13.5

Daily piglet weight gain, g; mean over entire lactation 230 230 230 270 270

Parity 2+ 2+ 2+ 2+ 2+

Results (Initial day: 1; Final day: 21) Average feed intake + feed wastage, kg/day

Average sow body weight gain, g/day -276 -379 -717 -755 -1280 Average sow whole body protein deposition, g/day

Average sow whole body lipid deposition, g/day Average milk production, kg/day

Average SID Lys requirement, % 0.78 0.76 0.85 0.84 0.92

Average STTD phosphorus requirement, %

Which of these factors has the smallest and largest effect on nutrient requirements:

increases in sow body weight, the number of pigs nursed, or daily piglet weight gain? Explain

why.

Obviously sows under Scenario 5 loose a considerable amount of body weight during

lactation. Discuss the potential effect of these body weight losses on subsequent reproductive

losses.

(18)

EFFECT OF ENVIRONMENTAL TEMPERATURE ON FEED INTAKE AND SOW PERFORMANCE

Feed intake in nursing sows is known to vary between sow units and influenced by

various factors associated with the sow genotype and the environment. For example, in section

Effects of parity and litter growth rate on nutrient requirements parity was shown to affect feed intake. When the model is used to predict feed intake, it is assumed that feed intake is lower in

Parity 1 lactating sows than in Parity 2+ lactating sows.

To explore the effect of environmental temperature with the lactating sow model, click

Enter Default Inputs and in the section with the heading Feed intake, select Yes for Consider environmental temperature? Then, vary environmental temperature using the values presented in the table below and record its effect on feed intake, sow body weight gain, and milk

production after running the model (click Calculate after inputs have changed).

Scenario 1 2 3

Sow body weight at farrowing, kg 210 210 210

Lactation length, day 21 21 21

Average number of pigs nursed 11.5 11.5 11.5

Daily piglet weight gain, g; mean over entire lactation 230 230 230

Parity 2+ 2+ 2+

Environmental temperature, oC 18 22 26

Results (Initial day: 1; Final day: 21)

Average feed intake + feed wastage, kg/day 6.613 6.190 5.629

Average sow body weight gain, g/day -276 -473 -733

Average sow whole body protein deposition, g/day Average sow whole body lipid deposition, g/day Average milk production, kg/day

What is the effect of environmental temperature on sow feed intake, milk production and

sow body weight losses?

Does it seem reasonable to assume that environmental temperature does not affect milk

(19)

represent relationships between environmental temperature, feed intake, and milk production is

described on pages 142 to 144 in Nutrient Requirements of Swine.)

EFFECT OF FEED INTAKE ON SOW PERFORMANCE AND NUTRIENT REQUIREMENTS

To explore the effect of feed intake on nutrient requirements, first enter the default values

(click Enter Default Inputs) and in the section with the heading Feed intake select No for Use

model predicted feed intakes? New data-entry fields will appear; ensure that the following information is entered:

Intake specification Mean Mean daily feed intake + feed wastage, kg/day 5.000 Mean diet ME content, kcal/kg 3300

Then vary Mean daily feed intake + feed wastage using the values presented in the table

below and record its effect on sow body weight gain and nutrient requirements, after you have

run the model (click Calculate).

Scenario 1 2 3 4 Average sow whole body protein deposition, g/day

Average sow whole body lipid deposition, g/day Average milk production, kg/day

(20)

Average SID Lys requirement, g/day 41.8 46.2 50.6 55.2

How does feed intake relate to milk production, sow body weight changes, and average

sow whole body protein and lipid deposition?

How does mean daily feed intake+ feed wastage affect nutrient requirements, expressed

(21)

4 Growing-Finishing Pigs

EFFECT OF BODY WEIGHT ON NUTRIENT REQUIREMENTS

Main Menu and under Step I use the three pull down menus to select ME for energy, SID for amino acids, and STTD for phosphorus. Under Step II, select No following Do you wish to

Under Step III select Growing-finishing pigs. A new window will appear with navigation

and action buttons at the top of the screen. To ensure that the default values are entered for

model inputs, click Enter Default Inputs. The following information should be displayed under

the heading INPUTS:

Gender

Gilts & Barrows Feed intake

Feed intake / (feed intake + feed wastage) 0.95 Options

Use predicted intake as model input

Gender Gilts & barrows

Consider environmental temperature? No

(22)

Immunized against GnRH? No

Feed Ractopamine? No

Whole body protein deposition (Pd) pattern

Options Use default Pd pattern for each gender

Gender Gilts & barrows

Present observed growth performance?

Options Do not consider

Now all relevant information has been entered to generate estimates of nutrient

requirements. To do this, click Calculate at the top of the screen. The screen has now

automatically moved to the results and you may scroll to the right of the screen to more fully

display results. Results can be explored for various body weight ranges, that are defined under

RESULTS and Range in body weight for estimating nutrient requirements. Results for this range in body weight will be calculated automatically. To return to data-entry fields click Home

at the top of the screen.

Body weight range 1 2 3 4

Specified in RESULTS and section Range in body weight for estimating nutrient requirements:

Initial body weight, kg 25 50 75 100

Final body weight, kg 50 75 100 135

Results

Average feed intake + wastage , kg/day 1.583 2.230 2.637 2.933 Average body weight gain, g/day

Avg. whole body protein deposition, g/day Average whole body lipid deposition, g/day Average SID Lys requirement, %

Average SID Lys requirement, g/day 14.8 17.9 18.3 16.9 Avg. SID Thr requirement, Ratio to Lys × 100

How do feed intake, whole body protein deposition, and nutrient requirements expressed

as % and g/day and Thr as a ratio to Lys change with increasing body weight? Discuss the

(23)

EFFECTS OF GENDER, IMMUNIZATION AGAINST GNRH, AND FEEDING RACTOPAMINE ON NUTRIENT REQUIREMENTS OF FINISHING PIGS

Click Enter Default Inputs to return to initial values.

To explore the effect of gender (selected following Gender under INPUTS), feeding

Ractopamine (select Yes following Feed Ractopamine? under INPUTS), or immunizing entire

male pigs against GnRH to control boar taint (select Entire males following Gender and Yes

following Immunized against GnRH? under INPUTS) on nutrient requirements, run the

scenarios described in the table below. Simply enter the inputs that are specified below and in the

footnotes.

In the section RESULTS and Range in body weight for estimating nutrient

requirements, enter 100 for Initial body weight, kg and 130 for Final body weight, kg. For each scenario, run the model (click Calculate) and record the results.

Viewing the graphs (click Graphs and then on Home to return to inputs and results) may

help in the interpretation of the results and answering the following questions.

Scenario Gilts Barrows Barrows

fed

Gender Gilts Barrows Barrows Entire

males

Entire males

Immunized against GnRH? No No No No Yesb

Feed Ractopamine? No No Yes* No No

Specified in RESULTS and section Range in body weight for estimating nutrient requirements:

Initial body weight: 100 kg; Final body weight: 130kg Results

Probe back fat at slaughter body weight, mm

Average feed intake + wastage, kg/day 2.822 3.013 2.991 2.733 3.076 Average body weight gain, g/day

Avg. whole body protein deposition, g/day Average whole body lipid deposition, g/day Average SID Lys requirement, %

Average SID Lys requirement, g/day 17.4 16.8 19.4 19.3 18.9 Avg. SID Thr requirem., Ratio to Lys × 100

a

When selecting Yes for Feed Ractopamine? new data-entry fields will appear. For Initial body weight (i.e., when Ractopamine is first fed) enter 115; for Number of levels (in step-up program) enter 1; for Diet level 1

enter 5.

b

(24)

How do nutrient requirements differ among gilts, barrows, and entire males? How is this

related to feed intake and whole-body protein deposition? Based on nutrient requirements,

discuss the value of split-gender feeding.

How does feeding Ractopamine to barrows influence growth performance, feed intake,

and nutrient requirements?

How does immunizing entire male pigs against GnRH influence growth performance,

feed intake, and nutrient requirements?

INTERACTIVE EFFECT OF PIG GENOTYPE AND FEEDING LEVEL ON NUTRIENT REQUIREMENTS DURING THE EARLY FINISHER PHASE

Restore the original inputs (click Enter Default Inputs) and run the scenarios described

in the table below. Simply enter the inputs that are specified below, run the model (click

Calculate) and record the results.

To enter values for Actual mean feed intake + waste, under INPUTS, in the section Feed

intake and following Options select Use observed intake as model input. New data-entry fields will appear. For Actual mean intake or intake curve select Mean, for Actual mean feed intake

(25)

To enter values for User defined mean Pd, under INPUTS,in the section Whole body

protein deposition (Pd) pattern and following Options select Specify mean Pd and Gender. For gender, Gilts & barrows will then be displayed, as specified in the section Gender. For User

defined mean Pd potential enter the value specified in the table (e.g., 120 for Scenario 1). In the section RESULTS and Range in body weight for estimating nutrient

requirements, enter 100 for Initial body weight, kg and 125 for Final body weight, kg.

Scenario 1 2 3 4 5

Inputs

Actual mean feed intake + wastage, kg/day 2.300 2.100 1.950 2.300 2.100 1.950

User defined mean Pd, g/day 120 120 120 160 160 160

Initial body weight: 100 kg; Final body weight: 125kg Results

Probe back fat at slaughter body weight, mm Avg. whole body protein deposition, g/day Average whole body lipid deposition, g/day Average feed intake + wastage , kg/day Average body weight gain, g/day Average SID Lys requirement, %

Average SID Lys requirement, g/day 16.3 16.1 15.8 18.8 18.7 17.5 Avg. SID Thr requirem., ratio to Lys × 100

At the highest level of feed intake how and why do lysine requirements differ between

the two pig genotypes?

How do Lys requirements expressed as g/day and % of diet change with reductions in

feed intake for the two genotypes of pigs (e.g., low and high mean Pd)?

How can you explain the differences in response to energy intake for these two types of

(26)

How and why do Thr requirements, expressed as a ratio to Lys × 100, change with

feeding level and type of pig?

MATCHING OBSERVED WITH PREDICTED PERFORMANCE – BASED ON MEAN

INTAKES, DAYS TO SLAUGHTER, AND PROBE BACK FAT THICKNESS

When observed growing-finishing pig performance is similar to model-predicted

performance, confidence in estimated nutrient requirements is increased. To explore this, be sure

to return to the starting scenario (click Enter Default Inputs).

Under the header Feed intake and Options select Use observed intake as model input,

and ensure that Mean is entered following Actual mean intake or intake curve , and that the

values 2.300, 3300, 25.0, and 125.0 are entered in the data-entry fields for Actual mean intake +

wastage, Mean diet ME content, Initial body weight, and Final body weight, respectively. Under the header Whole body protein deposition (Pd) pattern and Options select Specify

mean Pd and gender, and ensure that Gilts & barrows is displayed following Gender and the value 120 is entered following User defined mean Pd potential.

Following Match observed with predicted performance? select Yes and ensure that the

values 0 and 1 are entered for Adjustment to maintenance energy requirements and Adjustment

to slope of Pd versus E intake, respectively.

Following Present observed growth performance? and Options select Specify days from

starting to slaughter body weight and ensure that the values 25, 125, 16.5, and 119, are entered in the data-entry fields for Starting body weight, Slaughter body weight, Probe back fat at

slaughter body weight, and Days from starting to slaughter body weight.

Now vary User defined mean Pd potential and Adjustment to maintenance energy

(27)

For each of the scenarios, also record Lys requirements, as % and g/day, for pigs between

100 and 125 kg body weight. In the section RESULTS and Range in body weight for estimating nutrient requirements, enter 100 for Initial body weight, kg and 125 for Final body weight, kg to evaluate Lys requirements.

Performance

RESULTS, section: Overall performance; between starting and slaughter body weight

Starting body weight, kg 25

Slaughter body weight, kg 125

Probe back fat at slaughter body weight, mm 16.5 Average body weight gain, g/day 840

Average overall lean tissue gain,a g/day 318 278 302 326 318

Initial body weight: 100 kg; Final body weight: 125kg

RESULTS, section: Average SID AA, calcium and phosphorus requirements

Average SID Lys requirement, % -

Average SID Lys requirement, g/day -

a

Lean gain is calculated from estimated carcass lean yield that is calculated from probe back fat. The equations that are used to estimate carcass lean yield from carcass weight and probe back fat thickness vary among packing plants and can be adjusted. To make adjustments, click the Carcass evaluation under Inputs and section Match observed with predicted performance?

How are average body weight gain and back fat thickness affected by changes in mean

Pd potential and maintenance energy requirements? How can this be explained?

How and why does overall lean tissue gain change when maintenance energy

(28)

125 kg body weight? (HINT: use the Whole body protein deposition (Pd) graph to better

understand how maintenance energy requirements affect whole body protein deposition at the

various stages of growth; you may also evaluate the effect of maintenance energy requirements

on Whole body protein deposition in RESULTS section Performance and diet characteristics

for 25 to 50 vs. 100 to 125 kg body weight).

MATCHING OBSERVED WITH PREDICTED PERFORMANCE – BASED ON

OBSERVED FEED INTAKE AND GROWTH CURVES (FOR ADVANCED USERS ONLY)

A limitation of the approach used in section Matching observed with predicted

performance – based on mean intakes, days to slaughter, and probe back fat thickness is that

observed and model-predicted performance is matched based on mean intakes and days to

slaughter and probe back fat. It is thus possible that observed feed intake or growth rates could

be higher at lower body weights and lower at higher body weights, or vice versa, without

affecting mean values. This can have implications for estimated nutrient requirements. It is more

accurate to match performance based on feed intake and growth curves (i.e., to characterize

performance at various stages of growth).

To explore matching performance based on curves, make sure to return to the starting

scenario (click Enter Default Inputs).

Under the header Feed intake and Options select Use observed intake as model input,

and ensure that Curve is selected following Actual mean intake or intake curve, and that

Polynomial is selected following Curve Type. The values 310.4, 173.41, -1.1024, and 0.00002664 should already be entered in the data-entry fields for a, b, c, and d, respectively.

Under the header Whole body protein deposition (Pd) pattern and Options select Specify

(29)

Following Match observed with predicted performance? select Yes and ensure that the

values 0 and 1 are entered for Adjustment to maintenance energy requirements and Adjustment

to slope of Pd versus E intake, respectively.

Following Present observed growth performance? and options select Specify growth

curve; Polynomial function and ensure that the values 25.0, 125, and 19.5 are presented in the data-entry fields for Starting body weight, Slaughter body weight, and Probe back fat at

slaughter, respectively. NOTE that for Probe back fat at slaughter the value 19.5 has to be entered manually.

For the polynomial growth function the values 24.5, 0.57, 0.0044, and -0.000018 should

already be entered in the data-entry fields for a, b, c, and d, respectively.

Now vary PdMax, Body weight at start PdMax decline, and Adjustment to slope of Pd

versus E intake as indicated under inputs in the table below, run the model (click Calculate) and

record the results for overall performance (RESULTS section Overall performance; between

starting and slaughter body weight) .

In the section RESULTS and Range in body weight for estimating nutrient

requirements, enter 25 for Initial body weight, kg and 50 for Final body weight, kg to evaluate lysine requirements (RESULTS section Average SID AA, calcium and phosphorus

requirements).

Also, after each change view the Body weight gain graph to monitor how changes to the

model inputs improve the match between observed and model-predicted body weight gains at the

different stages of growth (e.g., at the low, intermediate, and high body weight).

Performance

RESULTS, section: Overall performance; between starting and slaughter body weight

Starting body weight, kg 24.5

Slaughter body weight, kg 125.2

Probe back fat at slaughter body weight, mm 19.5 Average body weight gain, g/day 839

(30)

Initial body weight: 25 kg; Final body weight: 50kg

RESULTS, section: Average SID AA, calcium and phosphorus requirements

Average SID Lys requirement, % - 0.95 0.98 0.98 0.89

Average SID Lys requirement, g/day -

Consider how PdMax, Body weight at start PdMax decline and Adjustm. to slope of

Pd versus E intake can be adjusted to more closely match observed and model-predicted body

weight gains at the various stages of growth and nutrient requirements, especially at the lower

(31)

5 Diet Formulation and Feeding Programs

USE OF THE FEEDING PROGRAM & DIET FORMULATION MODULE

Feeding programs must be specified in order to compare levels of nutrients that are

supplied with the diets with model-generated estimates of nutrient requirements. Specified

feeding programs are also required to estimate losses of nitrogen, phosphorus, and carbon into

the environment.

Feeding programs provide information on dietary nutrient levels and the order in which

diets are fed. The diet formulation program can be used to calculate dietary nutrient levels from

feed ingredient compositions. Within feeding programs, diet changes are identified by either day

(gestating sows, lactating sows, and growing-finishing pigs) or body weight (growing-finishing

pigs only). Feeding levels are specified elsewhere, as inputs for the different models.

To illustrate the use of the diet formulation system and the approach for developing

feeding programs, make sure that the appropriate nutrient systems are chosen. To do this,

navigate to Main Menu and under Step I use the three pull down menus to select ME for energy,

SID for amino acids, and STTD for phosphorus.

Under Step II, select Yes following Do you wish to evaluate a feeding program? and

then click the button Review Feeding Programs. A new window will appear with navigation

(32)

Click 1. Select Ingredients at the top of the screen to move to a new window, where a list

of ingredients is provided. The first ingredient (e.g., Corn, Yellow Dent) should be chosen with

care as it will be included in all diets that are formulated. To add a new ingredient, click the

blank data-entry box following ingredient no. 10, and from the pull-down menu select Peas, field

Peas.

To review the nutrient contents in this ingredients scroll to the right. The headings

present the nutrients according to nutrients that are selected according to nutrient systems

(columns F to T), nutrient that are independent of nutrient systems (columns U to AA), and

nutrients based on each of the three nutrient systems for energy (columns AB to AD), crude

protein and amino acids (columns AE to BQ), and phosphorus (columns BR to BT). If headings

for columns and rows are not displayed, then click View in the Windows Menu, and check

Headings in the area Show. Values in white cells can be changed. In columns U to BT, values

with blue font are those that are relevant to the nutrient system that are selected (e.g., ME, SID

amino acids, and STTD phosphorus), and these values are duplicated in columns F to T.

For Peas, field Peas change the Total crude protein content (in column V) from 22.17 to

24.0. Note that the cell color has changed to yellow, to identify that the original value has been altered.

Now remove Peas, field Peas from the list, by clicking on its name (under the heading

Ingredient and scroll to the bottom of the list in the pull-down menu and select Clear (Force all

nutrient levels to 0)

The nutrient levels that are displayed here are taken directly from the Ingredient Library,

which represents the values presented in NRC (2012). To review these, click Ingredient Library

at the left of the screen and underneath the heading Ingredient Data Base. Note that for some of

the ingredients values are missing for some of the nutrients. After reviewing the Ingredient

Library you can return to the Feeding program & Diet formulation module by clicking on

Ingredient Data Base.

In the screen 1. Select Ingredients new ingredients can be added. To do this, click the

blank data-entry box following ingredient no. 11, and type in Custom premix and hit enter. This

new ingredient name is now highlighted in yellow and you can enter nutrient levels in white cells

(33)

the heading Ingredient and scroll to the bottom of the list in the pull-down menu and select Clear

(Force all nutrient levels to 0).

You may review nutrient profiles in 1. Corn, Yellow Dent, 2. Soybean Meal, Dehull, Sol

Extr, 8 Fat, A/V blend and 9. Premix 3% incl. Contents of key nutrient should be:

ME

To access the feed formulation system, click the 2. Formulate Diet button at the top of

the screen.

To review diets that have already been stored in the system, click the white cell following

Diet Name and review the list in the pull-down menu, and select CoSBM Early Gest. The following information should be displayed:

Inclusion level, %

Ingredient

86.74 Corn, Yellow Dent

10.00 Soybean meal, Dehull, Solv Extr

0.26 Fat, A/V blend

3.00 Premix, 3% incl.

Please note that the inclusion level of the first ingredient is calculated automatically and

to bring the sum of inclusion levels of all ingredients to 100%. The first ingredient (e.g., Corn,

Yellow Dent) is specified as ingredient no. 1 in section 1. Select ingredients.

What are the contents of Metabolizable energy (ME, kcal/kg) and SID Lys (%) in the

diet?

To create and save a new diet for gestating sows, type in a new diet name (1 phase

gestation) in the white cell following Diet Name, press the Enter key and then click Yes when prompted. Then click the first white data-entry field, below Ingredient, access the pull-down

(34)

Inclusion level. In the same manner select Fat, A/V blend and Premix, 3% incl. and specify the inclusion levels presented in the table below.

The contents of Metabolizable energy (ME) and SID Lys in the diet should be 3300

kcal/kg and 0.62%, respectively.

To save the diet click Save Diet.

Diet Name 1 Phase gestation

Inclusion level (%) Ingredient

- Corn, Yellow Dent

15.00 Soybean meal, Dehull, Solv Extr

0.36 Fat, A/V blend

3.00 Premix, 3% incl.

You can review the nutrient levels in the stored diets by clicking the 3. Diet Data Base

button at the top of the screen. Up to 25 diets can be stored that have been generated with the

feed formulation system. In addition, diet nutrient levels can be entered directly for another 25

diets (diets 26 to 50), bypassing the feed formulation system. For diets 26 to 50 nutrient levels

can be added in columns U to BT in a manner that is identical to that used for ingredients.

You may check the levels of key nutrients in the Typical gestation diet as well as an

alternative Low protein gestation diet:

ME

If the CoSBM Late Gest diet is not stored in the diet data base, then it can be added: click 2. Formulate Diet, enter following Diet Name CoSBM Late Gest, and under ingredients add 16.00% Soybean meal, Dehull, Solv Extr 0.38% Fat A/V blend and 3.00% Premix 3% incl. as ingredients. Nutrient levels should be identical to the values in this table.

To review and create feeding programs click 4. Create Feeding Program at the top of the

(35)

Click the white cell following Feeding program Name and using the pull-down menu

select Gest CoSBM. The following information should now be displayed:

Feeding program name GestCoSBM Category of swine Gestating Number of phases 2

To create and save a new feeding program for gestating sows, type in a new feeding

program name (1 phase) in the white cell following Feeding program name. Then select

Gestating following Category of swine and enter 1 following Number of phases. Then select 1 Phase gestation under Diet name. Finally, click Save Program to add it to the database.

Now that feeding programs have been reviewed, the models can be used to compare the

supply of dietary nutrients according to the feeding program with model-generated estimates of

nutrient requirements, and to estimate nutrient losses into the environment. These aspects will be

explored in subsequent case studies (sections Evaluate the environmental impact of alternative

feeding programs and Evaluate the effect of using high-fiber coproducts on threonine requirements and energy utilization in finishing pigs).

EVALUATE THE ENVIRONMENTAL IMPACT OF ALTERNATIVE FEEDING PROGRAMS

In pork production it is becoming increasingly important to reduce nutrient losses into the

environment. To explore N losses in gestating sows, a simple one-phase feeding program will be

compared to an alternative two-phase feeding program.

Main Menu and under Step I use the three pull down menus to select ME for energy, SID for amino acids, and STTD for phosphorus.

Under Step II, select Yes following Do you wish to evaluate a feeding program? Under

Step III select Gestating sows. Ensure that the following information is now displayed, and

(36)

following Select feeding program will need to be used to select the 1Phase feeding program (see

section Use of the Feeding Program & Diet Formulation module). You may be prompted to

click OK to confirm start day in the Feed intake section

Select feeding program 1Phase

Sow body weight at breeding, kg 165

Parity 2

Gestation length, day 114

Anticipated litter size 13.5

Anticipated birth weight, kg/pig 1.4 Feed intake

Feed intake / (feed intake + feed wastage) 0.95

Start day 1 30 60 90

Feed intake + feed wastage, kg/day 2.210 2.210 2.210 2.610

Consider housing conditions & environmental temperature?

No

Now run the model (click Calculate) before entering results in the table below. The

values for Initial day and Final day should be entered under RESULTS in the section Range in

days for estimating nutrient requirements. To access under RESULTS the section Nutrient balance over the entire gestation period scroll to the right. To return to data-entry fields click Home at the top of the screen. For Scenario 2 simply select Gest CoSBM following Select feeding Program under INPUTS, run the model and enter the results.

Scenario 1 2

Inputs

Feeding program 1 Phase Gest CoSBM

Results

Initial day 1 1 90 1 1 90

Final day 114 89 114 114 89 114

Avge feed intake + wastage, kg/day

(37)

Avge SID Lys requirement, % SID Lys level in diet on final day, %

Nitrogen intake & waste, kg/sow - - - -

Nitrogen excretion, kg/sow 4.61 - - 4.03 - -

How does the change from a one-phase feeding program to a two-phase feeding program

affect sow performance and nitrogen excretion? Discuss advantages and disadvantages of

moving from a one-phase to a two-phase feeding program.

EVALUATE THE EFFECT OF USING HIGH-FIBER COPRODUCTS ON THREONINE REQUIREMENTS AND ENERGY UTILIZATION IN FINISHING PIGS

To assess the effect of dietary fiber level on energy and nutrient utilization in growing

pigs, evaluate the ingredient composition and nutrient levels in a standard corn and soybean

meal-based diet, generate an alternative diet that contains Corn DDGS and wheat shorts, and

then evaluate the effect of these diets on performance and nutrient requirements.

Main Menu and under Step I use the three pull down menus to select ME for energy, SID for amino acids, and STTD for phosphorus. Under step II, select Yes following Do you wish to

evaluate a feeding program?, and then click Review Feeding Programs

Under 1. Select ingredients, ensure that the following ingredients are included in the list

below the heading Ingredients: Corn, Yellow Dent; Soybean meal Dehull, Sol Extr.; Barley;

Wheat, Hard Red; Wheat Shorts, Corn DDGS, >6% and < 9% Oil; Canola meal, Solvent

Extracted; Fat, A/V blend; Premix 3% incl. If not, add at least Corn, Yellow Dent; Soybean meal

Dehull, Sol Extr.; Wheat Shorts, Corn DDGS, >6% and < 9% Oil; Fat, A/V blend; Premix 3%

incl. to the list, using the drop-down menus in the white data-entry fields.

Under 2. Formulate Diet ensure that the diet CoSBM 50-75 kg BW is included, by

selecting it using the pull-down menu, following Diet Name. The ingredient composition and

contents of key nutrient should be identical to the values presented in the table below.

Generate a new high-fiber diet based on the ingredient composition shown in the table

(38)

ingredient list, select the ingredients below the heading Ingredients and enter the inclusion levels

that are specified in the table below. Then click Save Diet to add the new diet to the data base.

To calculate the NE contents of these diets, return to the Main Menu, under Step I select

Net energy (NE) for energy system, return to Review Feeding Program and 2. Formulate Diet, select the appropriate diet and record the results.

Diet Name

72.04 Corn, Yellow Dent 30.55 Corn, Yellow Dent

24.40 Soybean meal, Dehull, Solv Extr 16.45 Soybean meal, Dehull, Solv Extr 0.56 Fat, A/V blend 30.00 Corn DDGS, >6 and <9% Oil

3.00 Premix, 3% incl. 20.00 Wheat Shorts

3.00 Premix

Metabolizable energy (ME) 3300 kcal/kg Metabolizable energy (ME) 3177 kcal/kg

Net energy (NE) 2478 kcal/kg Net energy (NE) 2281 kcal/kg

SID Lys 0.85 % SID Lys 0.82 %

SID Thr 0.54 % SID Thr 0.61 %

SID Lys to ME ratio 2.588 g/Mcal SID Lys to ME ratio 2.588 g/Mcal

Under 4. Create Feeding Program, ensure that the feeding program named GFCoSBMwt

is included. The list of feeding programs can be accessed using the pull-down menu in the white

cell following Feeding program name. For this feeding program, the following information

should be displayed:

Feeding program name GFCoSBMwt Category of swine Grow+Finish

(39)

Create an alternative feeding program by entering GF co-prod following Feeding

program name. Then enter the information that is presented in the table below and click Save Program.

Feeding program name GF co-prod Category of swine Grow+Finsh

Number of phases 4

To evaluate these feeding programs, click Main Menu, make sure for energy systems

ME is chosen, and Yes is selected following Do you wish to evaluate a feeding program? Then select the model for Growing-Finishing Pigs.

Ensure the following information is provided under INPUTSa:

Select feeding program GFCoSBMwt

Gender

Gilts & Barrows Feed intake

Feed intake / (feed intake + feed wastage) 0.95 Options

Use predicted intake as model input

Gender: Gilts & barrows

Consider environmental temperature? No

Consider pig space? No

Immunized against GnRH? No

Feed Ractopamine? No

Whole body protein deposition (Pd) pattern

Options Use default Pd pattern for each gender

Gender Gilts & barrows

(40)

Present observed growth performance?

Options Do not consider

a

These inputs can be reloaded quickly by clicking on Enter Defaults Inputs. In that case, inputs on the Main Menu are changed as well; return to Main Menu and select Yes following Do you wish to evaluate a feeding program?

Click Calculate at the top of the screen. The screen has now automatically moved to the

results and you may scroll to the right of the screen to display results more fully. Record results

observed between 50 and 75 kg body weight (under RESULTS and in the section Range in body

weight for estimating nutrient requirements enter 50 and 75 for Initial body weight and Final body weight, respectively). To return to data-entry fields click Home at the top of the screen.

First enter results for the current ME system, and change to the Co-product feeding

program, using the pull-down menu in the white cell following Select feeding program under

INPUTS, and click on Calculate at the top of the screen after each change.

To change to the NE system, go to the Main Menu and under Step I select Net energy

(NE) following Energy and then choose the model for Growing-finishing pigs to run the model again for the two feeding programs.

ME system NE system

Feeding program CoSBM Coproduct CoSBM Coproduct

Specified in RESULTS and section Range in body weight for estimating nutrient requirements: Initial body weight: 50 kg; Final body weight: 75kg

Results

Average diet ME content, kcal/kg 3300 3182 - -

Average ME intake, kcal/day 6992 6992 - -

Average diet NE content, kcal/kg - - 2477 2294

Average NE intake, kcal/day - -

Average feed intake + wastage, kg/day Average body weight gain, g/day Average gain:(feed intake + wastage) Avg. whole body protein deposition, g/day Avg. whole body lipid deposition, g/day Average SID Lys requirement, % Average SID Lys requirement, g/day Average SID Thr requirements,ratio to Lys

× 100

(41)

How and why are feed intakes (average feed intakes + wastage) different among feeding

programs and energy systems?

When using the ME system, how does feed efficiency [gain/(feed intake + wastage)]

differ between the CoSBM and the coproduct feeding programs? Is this consistent with

differences in diet ME content?

Calculate the ratio between NE an ME content for the two diets. Why is this ratio lower

for the coproduct feeding program than for the CoSBM feeding program?

When using the NE system, how does feed efficiency [gain/feed intake + wastage)] differ

between the CoSBM and the coproduct feeding programs? Is this consistent with differences in

diet NE content? Based on these considerations, are diets better formulated using the NE system

than the ME system?

When using the ME system, how do Lys and Thr requirements differ between the two

feeding programs? Why?

Why is the increase in the optimum Thr to Lys ratio slightly higher in the NE system than