Planning and managing forage inventory on the dairy can sometimes feel like playing Tetris. Like Tetris, we see things begin to pile up or disappear faster than our feed center is prepared for, with consequences more financially weighty than a fistful of quarters at the arcade.
##### Dairy Nutritionist / Standard Dairy Consultants

If there is anything this 1984 classic has taught us, it’s that a little foresight and planning can go a long way in logging a “high score.”

## Develop a plan

The key to successful forage inventory management begins with a plan. In order to project future ingredient usage, we’ve got to have a well-founded estimate of inventories currently sitting on the dairy. There are many methods to measure a drive-over pile or bunker, but when it comes down to it, the math is fairly simple:

Volume (cubit feet) x Density (pounds per cubic feet) = Pounds of feed

Determining volume will require you to harken back to your middle school geometry days – if you are like me, this can be a harrowing experience. Fortunately, there are plenty of good resources available to simplify the process. Your nutritionist likely has access to spreadsheets or other tools that only require a few simple measurements to calculate volume.

On the horizon are several exciting technologies that will aid in estimating volume. One example is photogrammetry, a process where three-dimensional models to scale are derived from thousands of pictures captured via drone – in fact, this technology is already in use to estimate crop yield prior to harvest. Augmented reality technology is available today on your smartphone through the “Measure” app, which utilizes your phone’s camera, accelerometer and gyroscope to overlay measurements of objects on your screen.

The second piece of the equation, density, is often determined by driving a cylinder with a known volume into the bunker face and weighing the feed that was captured, resulting in a ratio of mass to volume, which can be converted to pounds per cubic foot. There are inherent safety concerns with this practice; forcefully driving a rod into what may already be an unstable bunker face can be a little unsettling and is not advisable. A better option is to contact your nutritionist and make him or her do it (just kidding). Your nutritionist likely has access to or knows industry partners who have a special probe designed specifically for this process that can be attached to a skid steer or loader bucket.

With current forage inventories in hand, the next step is to predict usage for the future. This may feel like a shot in the dark, but take a look at how your rations have been designed historically. How much forage-to-concentrate has been fed in the past? Has the ratio of corn silage to hay remained consistent? In addition, you may find you are constrained by current inventories, and rations should be redesigned as soon as possible to ensure that enough remains until next harvest and through a carryover period (three months for corn silage and three weeks for haylage), if possible.

Developing a plan not only means determining how much forage is needed but also requires some spatial reasoning (think Tetris) to make the best use of space of the feeding center. One helpful approach may be to map the current layout to scale using a tool like Excel. Cells may be sized to squares to represent 10 square feet, for example, providing a reasonably accurate representation of available space on the feedpad.

Satellite imagery from “Google Maps” can be a helpful reference. With approximations of feedout rate (feet per day), you may choose to look ahead to harvest with your scale model and begin to determine next year’s layout of feed piles.

When sizing piles, it is important to ensure that size enables adequate feedout rate (6 to 12 inches per day), slope (3-to-1 minimum) and safe total pile height. Also, consider the direction future piles will be fed out; will water run into the exposed face? Will the layout provide a reasonable path for the loader and mixer wagon to access feed? Finally, thinking beyond next year’s layout is critical; the design may work for the next year, but it’s easier than one might think to paint yourself into a corner in year two or three.

## Tracking new inventory at harvest

Getting a hold on initial inventory at harvest can go a long way in keeping accurate forage inventories. The gold standard is running every load across the scale that comes onto the dairy during harvest. Not all of us have that luxury, but that shouldn’t stop us from counting loads if possible. Have those driving trucks take note of each load they dump. If equipped, yield data from the chopper may also provide valuable insight as to how much new inventory was harvested.

With haylage especially, keeping track of dry matter as new inventory comes in can be invaluable; inherently, differences in dry matter affect total dry matter tons harvested. It may be advantageous to mark the bag, bunker or pile where significant dry matter changes have occurred.

## Tracking current feedout

A key to avoiding surprises in inventory management is tracking current feedout and reconciling inventory estimates. Many of us today are fortunate enough to have feeding software to help in this process, which adjusts inventories based on actual scale weights. Feeding software can also tell us, relative to cow numbers and rations, how much of an ingredient is required over a period of time.

In addition to leveraging feed software, several “low-tech” options can be beneficial in tracking feedout. For example, grab a can of your favorite color spray paint and mark a line on the feedpad or bunker wall at the silage face. After a week, measure the distance from your line to the current location of the face to determine feet used per day. This simple technique can give you a solid estimate of days remaining in a pile. The spray paint method may also be employed on bagged feeds – mark a line on the outside of the bag a known distance from the open side and measure distance fed out relative to the line.

Upon initial measurement of the bag, it may be helpful to mark the bag at 10-foot intervals for this purpose. If you are using feeding software, you may check pounds used of that forage in one day relative to depth removed from the pile or bag you measured – with this information, you now know approximate pounds per foot of silage face, which can be extrapolated over the remaining length of the pile or bag. You may be surprised to find that your initial inventory estimate was much different (should have paid more attention in geometry), and it is important to adjust or reconcile inventory on the books. Congruently, once a pile is completely fed out and there is still recorded inventory (or negative inventory), don’t forget to reconcile the difference in your feeding software.

If initial forage inventory was measured at harvest, yet there is still feed “remaining” in the feeding software even after complete feedout, this value represents shrink and may be expressed as a percent of the total initial weight. Knowing your average shrink of a feedstuff is not only valuable for projecting future inventory needs but also in adjusting pricing for that feedstuff. For example, a 15% shrink in corn silage means there were only 1,700 pounds available for every original ton of feed harvested. Because this feed was lost due to shrink, we should account for this in the ingredient cost. If the corn silage was valued at \$40 per ton at the time of harvesting, the result of a 15% shrink is an increase in cost by 15% for a total of \$46 per ton.

\$40 per ton + (\$40 x 0.15) = \$46 per ton

Many managers understand this disappearance in feed, but often the price increase resulting from shrink is overlooked in inventory accounting, resulting in an incomplete calculation of feed cost.