Anyone with an entry-level working knowledge of electronic spreadsheets can adapt the spreadsheet I designed for assisting with feed formulation. I have reduced the spreadsheet as presented here to its essentials for the sake of simplicity. In actual practice, I have several additional columns (for example, to calculate feed costs as I plug in different weight values for ingredients). You can add more columns as well, populating them with appropriate formulas to calculate whatever values you wish to track (perhaps fats and carbohydrates in addition to protein). In this simplified version, however, we will calculate only the percent of protein in the mix, and the amounts of premix and individual ingredients to use as we make up single 25-pound batches.

The basic feed formulation spreadsheet. Formulas to enter into cells requiring them. (Note: Actual syntax of the formulas might be different for your spreadsheet program.) Sample winter layer mix. Sample mix for chicks on pasture.

Note first of all that the ingredients are divided into "Premix" and "Grind/Whole Portion." It would be extremely inefficient to measure out the supplements, which are added in relatively small amounts, into the mix when making up individual batches. Therefore, we mix together the premix ingredients for, say, 500 pounds, then weigh out into individual plastic bags the appropriate amount for a 25-pound batch, then store the bags until needed.

The actual list of ingredients on your spreadsheet will likely differ from that of mine, of course. I like to note in the list, in parentheses, the percent protein of each ingredient. (I do this just as a reminder to myself-it has nothing to do with the calculations of the formulas.) Note that I've also added a reminder to myself never to add more than 2-1/2 pounds of crab meal in any formulation (since its selenium, a necessary trace mineral, can actually have a toxic effect in large amounts).

I have used colored backgrounds to highlight the two key types of cells in the spreadsheet. (The colored shading is for illustration only-there is no need to use colored backgrounds in your spreadsheet.) Cells with a light yellow background are cells into which you will enter data. That is, you will enter weights for individual ingredients you are considering. Cells with a light green background are cells into which you will enter formulas. (See "The basic feed formulation spreadsheet.")

In the second spreadsheet (See "Formulas to enter into cells requiring them."), I have printed the formulas to be entered into the requisite cells. In an actual electronic spreadsheet, of course, the formula itself is not displayed in the cell-only the numerical result of the formula's calculation is displayed. Please note that the exact syntax for formulas in your spreadsheet program may differ from that in the formulas given here. (I use Gnumeric, an open source spreadsheet program.) Use the Help section of your spreadsheet program to determine the exact syntax required-otherwise, your formulas will not function.

The first formula to enter is in Cell B18, which simply sums all the values in the cells above it [=sum(B3:B16)], to give a total of all the individual weights you enter for the ingredients. (Note that as I enter values in Column B, I always ensure that this total comes out to 100 pounds, since that makes it easier to think in terms of percentages.)

Next we add formulas in Column C to calculate the amount of protein added by each ingredient, based on the weight of the ingredient added multiplied by its percent protein. Thus in Cell C6 (for fish meal), the formula is =B6*0.6-that is, the weight of fish meal entered in Cell B6 multiplied by 60 percent protein.

Having added a formula for every ingredient contributing protein (and note that there are no formulas entered for ingredients like kelp meal or Nutri-Balancer which do not), we now add a formula in Cell C18 to total all the individual amounts of protein calculated by those formulas, then divide by 100, to express the percent protein in the mix as a decimal: =sum(C3:C16)/100

At this point we are able to enter experimental values in Column B for any or all the ingredients, and the formulas entered thus far will automagically recalculate the amount of protein contributed by individual ingredients, and the percent protein for the mix. Now we add formulas in Column D to divide the amounts of all the ingredients figured on a hundredweight basis by four, to calculate the amounts of each to use when making up a 25-pound batch, a more practical amount to work with if mixing by hand.

The first formula entered in Column D (Cell D10) is a bit special, in that it first totals the amounts of ingredients per hundredweight to make the premix, then divides by four, in order to define the amount of premix to measure out per 25-pound batch, that is: =sum(B3:B9)/4

The other formulas in Column D are more straightforward-they simply divide the amount of the ingredient entered in Column B by four, to define the amount of that ingredient to measure out when making a 25-pound batch of feed. Thus in Cell D12, the amount of alfalfa meal to use per 25-pound batch is: =B12/4

Finally (basically as a check), we add a formula in Cell D18 to total the entries in Column D: =sum(D10:D16) (If we have a total in B18 of 100 pounds, the amount returned in D18 will always be 25 pounds.)

To see how the spreadsheet works, let's imagine we want to formulate a winter layer feed with a target protein value of 15 percent. We simply insert reasonable values for the individual ingredients (for a total of 100 pounds at Cell B18), and the spreadsheet recalculates the percent protein for the total mix at Cell C18, and the amounts of each ingredient needed to make a 25-pound batch. (Note that we can make any amount of premix at a time we wish, but Cell D10 tells us how much premix to weigh out and set aside for 25-pound batches.)

I said we enter "reasonable" amounts for ingredients. I cannot tell you what amounts to use in your own formulations-you still have a lot of homework to do on your own in formulating your feeds. For example, our amount for Nutri-Balancer will be based on Fertrell's recommendation for this supplement, and on the fact that our winter flock is confined to the poultry house on deep organic litter. In this case, two pounds of Nutri-Balancer per hundredweight is appropriate.

In the case of our winter layer feed, we enter the values shown in "Sample winter layer mix." Note how, as we enter values in Column B, the sheet automatically recalculates new values in Columns C and D.

Suppose we want to formulate a starter feed for heritage breed chicks on pasture with mother hens. (See "Sample mix for chicks on pasture.") Since growing chicks do not need nearly as much calcium as adult layers, we greatly reduce the aragonite. We boost the fish meal to just over 5 percent of the total (which is the maximum we want to add for this ingredient), since growing chicks have higher protein needs than adult layers. Since the chicks will be eating plenty of fresh green grass, clovers, and weeds, we omit the alfalfa meal entirely. Note that the percent protein for this mix is 17.6 percent, well below the 22 percent that would be recommended for fast-growing meat hybrids such as Cornish Cross. However, heritage breed chicks have not been bred for such high-protein input. Also, the mother hens will certainly be supplying additional protein to the chicks in the form of insects and worms. Thus a protein percentage that is low by industry standards is perfectly appropriate for this home-mixed feed.