Driving cars and sampling forages

The author is a dairy nutrition consultant with GPS Dairy Consulting LLC and is based in Malone, Wis.

Frequent and accurate forage testing is necessary for ration balancing. Forage moisture needs to be assessed on the farm routinely.

Even if I yell at you, I still love you. Not exactly the definition of modern parenting, but it is my opening line when I teach my daughters to drive. As I sit next to them for the first time in the parking lot, a bit of fear races through me. I know that none of that academic training they’ve received so far — the Department of Motor Vehicles book, the test, and their driving class — has trained them enough to know how hard to push the gas pedal to make the car go forward. Or more importantly, which pedal is the brake.

When I worked as an extension agent, I put a nice concise table and description together on the frequency and technique for sampling forages. As I now work full time as a nutritionist in the field, I realize training feeders in the real world requires recommendations that don’t fit in a table. There is no yelling, but a bit of fear does exist. If we don’t get a good sample, it doesn’t make sense to waste time balancing to two decimal places on a computer. How do I mitigate risk with a weekend feeder? Can our feeders sample easily and accurately every time, knowing when and where to hit the brake and turn the wheel?

Some practical considerations

Dry matter matters. For a total mixed ration (TMR), we know that the most important factor for accuracy starts with correct dry matter measures. A few feeders will mix a load of forage in the mixer and then subsample. Many others, especially those with large bunkers and wide or tall faces, might push the forage together, mix it with a payloader, and then subsample.

Giving the right tools and instructions to feeders is critical. If they use a dehydrator, I’d rather see 15 hours than nine hours, just in case the humidity is high and the sample dries slowly. If using a Koster tester, it needs a clean area that is free of dust (uncommon in feed rooms) to prevent fire damage. Or better yet, install an electrical autotimer that can shut down at one hour.

On-farm dry matters should be used instead of lab values that might come back once a week. Corn silage that is sampled two times per week and haylage sampled three times a week should help the feeder see trends. If the corn silage is within a point of yesterday (in a bunker), don’t adjust the software. If it changes more than one point, retest before you make a change. For haylage, I prefer to be slightly more aggressive. Haylage will change as you move from one end of the bunker to the other. If it changes 1%, then adjust the value in the software.

Rain events are difficult to manage. Did it rain one-half inch or 3 inches? Did it rain hard right after facing? Was it raining with a south wind pelting the face of the bunker or pile? Or what about snow? Rules of thumb need to be developed for feeders to address these issues. Put it in a nice table if you want, but these issues are more accurately driven home by experience on each farm.

Frequency can vary

How often should samples be sent to a lab and how do I use those results?

Corn silage piles and bunkers have a true starch and neutral detergent fiber digestibility (NDFD) value that is pretty constant if the feed is faced, mixed, and subsampled correctly. The academic research indicates that you should sample every four days. Practically, most large dairies should sample weekly (maybe two times a week at the start of the bunker).

When I get these samples back from the lab, I will average the last five to 10 samples and weigh those samples evenly. Even with the best intentions and techniques, we can get outliers. If the dairy only samples every other week, we will have just four samples in two months; if there is one outlier on the fourth sample, the average can be deceptive.

Haylage piles and bunkers need to be handled differently. We know that the first 50% of the pile will be different than the second 50%, depending on field and intraday changes. We just don’t always know when and where that change will happen. Weekly samples are again the preferred sampling method. When haylage samples come back from the lab, I will weigh them more heavily (exponentially) to the last samples. This gives a foundational average with a definite lean to the last sample.

Hay or straw can be simple or difficult. Do you receive new loads weekly or have a year-long inventory? Develop a strategy that is appropriate for your feeding. If straw is fed at one-half of a pound in your lactating TMR, sampling is less important. If you are feeding 5 pounds of hay to your lactating cows, you need a system of sampling at the time of delivery.

Good luck on getting a good sample of baleage. Baleage is a car wreck for many hay probes as they don’t probe easily. While you can do the probe and tape method with baleage, it leaves you open to ruining a good bale if the hole isn’t sealed with an appropriate tape and remains as such. Drive carefully.

In smaller silage bags, the forage can change every day as the feed is segmented by incoming loads during the harvest season. Larger bags with less segmentation are slightly more consistent. Just managing dry matters on a daily basis requires a separate training program, like driving a semitruck through New York City.

The advice for driving cars and sampling forages is similar — stay safe, be practical, and stay on the road.

This article appeared in the February 2023 issue of Hay & Forage Grower on page 21.

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