Feed Shrink – Part 1. How much are you losing in the field and on the way to the bunk?

If you are in the Northeastern U.S., you are done harvesting corn silage for 2014. So, do you know how much you have? Do you know how to find that number?

There are a few ways that this may have been recorded during your corn silage harvest: yield monitors, truck weights, or bunk measurements will all give you a yield number, but which is the correct number? Data from yield monitors will give you the best information about what was in the field, since it measures as you harvest. However, it may not be the best number to use for calculating your inventory. Why? There are losses of feed as soon as it leaves the chopper spout. You can miss a truck, overfill a wagon, have blow-off or spill from trucks, and/or have problems when it is delivered to the bunk.

rd side corn 1

This doesn’t look like a lot of corn, but during chopping season, it’s not unusual to see roadsides littered with corn silage. If you are traveling a long way with uncovered trucks, this can add up. Having yield monitor measures of production in the field and a measure of feed at or in the bunk is very useful to determine where you can tighten up your harvest practices. Remember: every pound of feed that is lost during harvest is a pound of feed you will not have available to feed. The only way to know what you are losing is to measure.

Calculating Harvest Losses

A good place to start with measuring loss is from the field to the full bunk. In an ideal situation, you will have yield monitor information and truck weights at the bunk to calculate this difference. If you have yield monitor information and not truck weights, you can get at this difference by measuring what is in the bunk.

Bunk Calculations

Use the following steps to determine the tonnage of forage in your bunker silos:

1. Determine cubic feet of forage

Average height x width x length (measured in feet) = ft3

                  X                     X                      =                         ft3

2. Multiply cubic feet times the density of feed. Density can be determined by using a penetrometer or  a forage sampler and measuring the volume and weight of the sample removed. The Master Forage Probe available from Dairy One was designed for this purpose.  Visit our website for more information:  https://dairyone.com/analytical-services/feed-and-forage/master-forage-probe/.

3. Multiply #1 x #2 for total pounds of forage in the bunk

4. Divide by 2000 to calculate tonnage

For more information on calculating volume in other storage types, take a look at: https://cdp.wisc.edu/pdf/Feed%20charts.pdf

Cost Calculations

The next step in evaluating loss is the cost. This can be looked at as the dollars lost or the lost opportunity to feed cows. To calculate dollars lost, subtract the bunk inventory from the field level yield and multiply by the current value of corn silage in your area. Crop insurance providers or feed dealers should be able to help you come up with that number. The lost opportunity to feed cows is found by subtracting the bunk inventory from the field level yield and then dividing by the pounds of feed per cow per day. Knowing this information can tell you 1) how long will truck covers take to pay for themselves, 2) are there areas of our harvest we should tighten up for next year, and/or 3) if we were to store more of what we harvested, could we add cows or reduce input costs?

As with most management or purchase decisions, having good data available will simplify and clarify the decision making process.

In the next blog post, I will talk about how and when to measure losses from fermentation, storage, and feed out.


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