Tower Grove Feed Classroom Exercises
The following is an account of how Professor Carl Parsons of the University of Illinois at Urbana-Champaign used Tower Grove Feed in the classroom. This account is not intended as a script to follow, but as a set of examples to spur the imagination.
Tower Grove Feed control levels played a key role in using the software in the classroom. Control levels enable multiple users to change values in a common formula and then solve the formula without affecting each others work. Each client has a main control level with one or more users. Each user can create an indefinite number of subordinate levels, either parallel to each other or in a hierarchy.
Professor Parsons conducted these exercises as a special session in a course taught by his colleague, Tara Felix. Below “Parsons,” his main control level, he created a special control level called “parsons instructor,”. where he set up a sample broiler grower formula. Under “parsons instructor,” he set up a control level and user ID for each of 11 pairs of students, one for Professor Felix, and one for himself called “pars.” During the class, Professor Parsons dropped down to the “pars” level, so that he would be on a level parallel to those of the students and his colleague: one level down from “parsons instructor”.
Everyone in the class could see the sample broiler grower diet and make changes to it without affecting the original on the higher level or anyone else’s changes. While Professor Parsons was explaining the examples on the large classroom screen, he was in the same position as the students and the changes he was demonstrating did not change what each pair of students could see on their own screens. Parsons spent about ten minutes of presenting an overview of the software, which included showing the students how to set up and solve a formula and to view the consolidated results in the Solution Report.
He then began the first exercise. The sample broiler grower formula had a maximum of 8% on corn distillers’ grain with solubles. Parsons instructed the class to eliminate this maximum and re-solve. In his sample formula at the “parsons instructor level”, he had set the ingredient prices to fairly recent values. The result was that because corn and soybean meal currently cost so much, the distillers’ grain came in at 20%. This change illustrated how least cost formulation works, because if cost were the only factor in the formulation decision, much more distillers’ grain would be included in the solution. This example enabled Parsons to emphasize the importance of the restriction to 8%, because a mix with 20% distillers’ grain would make pelleting difficult or impossible. Furthermore, batches of distillers’ grain tend to vary in nutritional quality, so it is risky to include too much.
Next, Parsons had the class restore the 8% maximum on corn distillers' grain and roll back prices for corn, distillers’ grain, soybean meal, and poultry fat to 2007 prices. The result was that the price per ton of the solution dropped from $361 to $180. Corn distillers’ grain appeared in the solution, but at less than the 8% maximum. The purpose of the third exercise was to show the utility of amino acid supplements such as valine, methionine , etc. Five of these were limited with maximums of 0.01%. Prices were restored to current levels and the formula was solved again. The formula cost increased from $361 to $480. What's more, crude protein increased from 19% to a whopping 28%! Parsons explained to the class that the latter increase would likely decrease growth performance, produce wet litter due to increased water intake and increased water excretion to get rid of the excess my nitrogen being consumed, and would be bad for the local environment in many locations.
For the next exercise, the class tested cost sensitivity using the shadow price of ruminant meal and bone, an ingredient which had not yet appeared in the solution. Class members dropped the cost to $1 below the "Low Cost" price of $661 and solved the formula. 3% came into solution where none had appeared before. Parsons then noted that the overall cost of the formula had dropped negligibly and that a nutritionist would have to weigh the cost of storing an extra ingredient for so little savings. Parsons had two more exercises planned, but ran out of time. The first one would have shown the function of the nutrient cost column. The nutrient lleal Digestible Valine had a nutrient cost of -135. This means that if the minimum requirement is reduced by 1%, the cost of the solution would go down by $135. After reducing the minimum by the realistic amount of 0.01% from 0.842 to 0.832, the total solution cost came down by $1.35, as the software predicted.
The other exercise was to show the students how to change nutrient values for an ingredient. The exercise is to click on some ingredient from the Formula Ingredients page (soybean meal without hulls, for example) to get the list of nutrient values, change the value of some important nutrient and show how this change affects the solution.
