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The Workbench is where you work directly on a diet (or formula). Normally, you spend most of the time in the Workbench while using Tower Grove Feed. There are main three pages in the Workbench: Formula Nutrients, Formula Ingredients, and Formula Ratios. There is is also a page for each of the formula reports: Solution Report, Batch Report, and Parametrics
In Formula Nutrients, you define the requirements of the diet.
In Formula Ingredients, you indicate which ingredients are available to formulate the diet. You can also place minimum or maximum restrictions on the ingredient. You can change an ingredient's cost or the nutrient quantity it provides.
In Formula Ratios, you can observe the ratio between nutrients, ingredients, or both that results from solving the formula. You can also specify a minimum or maximum restriction on a ratio.
Formula header fields
The formula name drop down allows you to change the Workbench formula without having to return to the formula list in the Workshop. If you restricted the formula list in the Workshop to a single species, only formulas for that species will appear in the drop down.
The name is the primary way to identify objects in Tower Grove Feed. No two objects of the same type in the same hierarchy can have the same name, no matter what the language. The same object can have different names in different languages. The name can be changed only by the owner of the object, but any user can make the first translation of a name into another language. Objects of different types may have the same name. For example, 'salt' can be the name of both a nutrient and an ingredient. (This is only an example, and, as this is not usually a good practice, Tower Grove Feed has not used the name 'salt' this way at the system level.)
An arbitrary short name, abbreviation, or other ID that can be used as an alternative identifier of objects. The code can be used to group objects. By default, ingredients are sorted by code. For formulas and ingredients supplied by the system, Tower Grove Feed provides a systematic coding.
Batch Weight is the weight the least-cost solution targets. Typically, it is a standard size of 1000 for metric system users and 2000 for English system users. Batch Weight is required.
It also could be the size of the batch mixer (say 5000) or even an individual daily intake size for an animal (say 30).
Its interpretation is affected by Dry Matter.
The unit of measure indicates the type of measurement to record weights. The choice is almost always between 'pounds - lb' and 'kilograms - kg'. The unit of measure applies to the batch weight, the weights of ingredients in the formula solution, and to ingredient cost units. You could also select 'tons' or 'metric tons' but these are not typically used. Pound (lb) usually refers to an avoirdupois pound.
Currently the unit of measure designation is for information only. If you change the unit of measure, Tower Grove Feed does not recalculate ingredient costs or reset batch weight or costs automatically. If, for example, you change from kilograms to pounds, the most common thing to do is to set change the Formula defaults batch weight to 2000 and also set the Control level defaults cost units to 2000.
The Dry Matter field is a check box that determines whether the solution nutrients and the Batch Weight are to be considered as 100% dry matter. Solution ingredients will be shown “as is.”
If checked, solution nutrients and Batch Weight are shown as 100% dry matter.
If unchecked (default) solution Nutrients and Batch Weight are shown “as is.”
A common tendency for the novice is to put restrictions on everything in sight, the tighter the better, compounding the mistake with the thought that every minimum needs a maximum, and vice versa!
The maxim "Less is More" should be followed in setting up restrictions. Unnecessary restrictions not only limit the trade-offs available to the least-cost algorithm, thereby resulting in a solution that is more costly, but also can cause infeasibilites.
If you have no clues in "debugging" an infeasible solution, remove half the constraints and solve again, repeating until you have a feasible solution.
Then add back half of the constraints that you most recently discarded, repeating until you have isolated the culprit(s).
The log field enables you to display linear program (LP) solution statistics on the screen and in debug mode to produce a spreadsheet showing various stages of the calculation of the result.
There are three possible specifications:
- None (default) - Do not Log LP statistics or produce a spreadsheet.
- Statistics - Log LP statistics to the screen.
- Debug - Log LP statistics to the screen and produce a spreadsheet showing the calculations.
You should almost always solve a formula with "Log: None" specified. The other settings are used by the software developers to isolate problems. They can also be used by an analyst to determine why the solution to a particular formulation is #Infeasible.
Optimum Density specifies whether or not the solution calculations should find the optimum yield for the diet without having to produce the exact batch weight specified for the formula. If there is a least cost diet that meets the formula's requirements but with a yield lower or higher than the batch weight, then that diet will be the solution regardless of its final yield.
Optimum Density allows the solve algorithm to increase (or decrease) yield in order to find the optimum nutrient density, resulting in a lower cost than solving with the formula's batch weight. Nutrient density is an important tool in feeding animals under conditions of heat or stress.
Two fields control the use of Optimum Density: the optimum density code and the range percentage.
The Optimum Density codes are:
- "Y - Yes" to find the optimum yield
- "N - No" to use the fixed batch weight (the default)
- "W - WeightLimits" to find the optimum yield within specific limits
If you specify "W-weight limits" you should also specify a range percentage. This is the range within which the solution may vary from the specified batch weight. For example if the batch weight is 1000 and the range percentage is 10%, then the solution yield may be anywhere from 900 to 1100.
Helpful hint: The two optimum density codes use a different model for solving than the fixed batch weight model. A code of "W-weight limits" and a range percentage of zero specifies the same batch weight as "N - No", but uses the optimum density model in the solve. This can be useful for cases where the solve has difficulties with "N - No".
Previous Cost is the total ingredient cost of the formula solution from the previous solve.
Round Code is a one character field that determines how the solution will be rounded.
Enter one of the following:
- N (default) does NOT round the ingredients.
- Y rounds the ingredients without regard to the batch weight.
- R rounds the ingredients exactly to the batch weight (the largest ingredient will have any leftover amounts from rounding the other ingredients).
- U rounds the ingredients UP without regard to the batch weight.
Show changed items only
In the list of items, show only those that have been changed at the the current level. Do not show items that have inherited values only.
The species is the type of animal that the formula is designed for. The species of a formula can be changed only by a user at the level of the formula's owner. The ability to change the species is provided to allow you to copy a diet (formula) from one species to another,
The following Species Codes are pre-loaded:
Total ingredient cost of the formula after clicking solve.
It is the cost of the yield.
Formula Type consists of two one-character fields which the user can assign freely.
For example, some users put the initial of the owner of a particular formula here so that other users do not modify it without permission from the owner.
There is one specialized use of these codes for medication interlock codes used by the 3000 series of Wisconsin Electric Manufacturing Co. batch mixers:
Type 1 2 Function U N Unmedicated - may not follow medicated feed U Y Unmedicated - may follow medicated feed M N Medicated - may not follow medicated feed M Y Medicated – may follow medicated feed
The actual weight of the least-cost solution. The solve button creates the yield. It should be the same or very nearly the same as the batch weight (unless optimum density is specified). If not, the least-cost solution may be infeasible.
The Formula reports enable you to quickly display, print, extract, or send a variety of information about a formula. The default is to display as HTML; that is, to show the report results on the screen. You can also select PDF and XLS. PDF creates a file that you can print or email to someone. XLS creates a spreadsheet, which you can open in Microsoft Excel, Open Office, or other programs so that you can make new calculations on the results of the reports.
The Solution report shows the results of solving formula.
The Batch report lists the ingredients in the solution in the order that they are to be mixed.
The Parametrics report helps you investigate what would happen if one or more of your formula specifications were to change.
Formula Nutrient Fields
If you key a restriction (minimum or maximum amount) for a nutrient and click #Save, it will be selected automatically and the box in the Sel column will be checked. If you uncheck a nutrient with a restriction, the amount fields will have gray backgrounds and the restrictions will not be used in solving the formula. If the nutrient is on the species short list, it will still appear when in the result you run the Solution Report with short nutrient list checked.
Actual is the amount of the nutrient that is actually in the formula solution after Solve.
Formula Nutrient Cost is the savings to the TotalCost that can be realized if the nutrient constraint is changed by one unit.
If cost is positive, then if the maximum is increased by one unit, the TotalCost will decrease by approximately the cost. Also, if the maximum is increased by one tenth of a unit, the total cost will decrease by approximately one tenth of the cost. If the cost is a large number compared to the maximum, then the amount that the total cost will decrease is less than the number shown. If cost is negative, then if the minimum is decreased by one unit, the TotalCost will decrease by approximately the cost (ignoring the sign). Also, if the minimum is decreased by one tenth of a unit, the total cost will decrease by approximately one tenth of the cost (ignoring the sign). If the cost is a large number compared to the minimum, then the amount that the total cost will decrease is less than the number shown.
Max is the maximum units of the nutrient that is desired in the formula solution.
Min is the minimum units of the nutrient that is desired in the formula solution.
The units in which the quantity of the nutrient is specified. The unit is usually a ratio consisting of one fundamental or a derived unit divided by another. Examples of compound units are: mg/kg or mcal/kg. Percentage, which is the ratio of the specified nutrient to the whole result is the most commonly used unit.
Specifying a nutrient's value as a percentage, however, does not mean the the nutrient's percentage of the whole is ever calculated. The solution is reached by combining the quantities found in each ingredient in the solution. So if corn has 10% protein and the formula calls for at least 20%, then corn (if it is to end up in the solution) must be combined with other ingredients having more than 20% protein, so that the average percentage of protein in the solution is at least 20%.
Nutrients that have their units specified as a percentage can easily total more than 100% in the solution, because nutrients (unlike ingredients) can overlap each other. Protein, for example, overlaps the individual amino acids.
The units of one nutrient have nothing to do with the units of another nutrient (as far as the program is concerned). The units of the nutrients in the solution do not have to add up to anything. In contrast, the percentages of the ingredients minimums in the formula cannot exceed 100% and, when the status of the solution is Optimal Solution Reached, the actual percentages always add up to 100%.
A nutrient minimum of, say, 1800 mg/kg of choline, can be thought of as order for that much choline. A feasible solution must provide at 1800 mg/kg choline, regardless of what other nutrients are specified.
Some units specify kilogram (kg) as the denominator (e.g., mcal/kg). To allow you to use pound based units, Tower Grove Feed provides alternative set of nutrients (with "- lb" as a suffix) that use pound-based rather than kilogram-based units.