Packing, preserving and properly feeding from the bunk silo relies on feeder knowledge of the chemistry behind the crop. That was the basic premise behind the two-day “Feeder Schools” held by Cornell Cooperative Extension last fall and hosted by dairy farms in different regions of New York.

“I think the primary take-home lesson for the feeders is to get them to understand how important their role on the dairy is and how everything they do can impact so many other areas on the dairy,” Betsy Hicks, extension dairy specialist, said of the purpose of the classes.

Bunk basics

A lot can happen to crops from field to rumen. By starting out with the best quality forage and maintaining that quality in every step of the process, ensiled feed can retain the maximum amount of nutrition and digestibility for the herd.

Harvesting silage at the proper moisture content is the crucial first step. Corn silage is best at 65 to 68 percent moisture, while the moisture content of haylage should be between 45 and 55 percent. The dry matter content at ensiling affects fermentation, which in turn impacts the nutritional content available to the cows.

When the moisture content is too high at ensiling, fermentation is less efficient. This causes the production of acetic acid, rather than lactic acid. Acetic acid utilizes sugars, reducing the amount available for rumen digestion. Wet piles also increase butyric acid fermentation, a definite problem for the cows.

“Even if the forage is packed at the correct moisture content, rain can cause that to change,” Hicks said. “When a feed pile gets wet, the dry matter goes down.”

A dry pile inhibits fermentation and produces a lot of heat, burning up sugars. Protein content suffers too. And low moisture content means the pile won’t pack well, so the pile will be less dense, letting air in and quality out.

Perfecting packing

Air in the pile will decrease fermentation and increase loss of nutrients. Even forages packed at the correct moisture content can lose quality due to poor bunk management. Best management practices involve filling the bunk with thin layers, packing them well and filling it quickly. These strategies will keep air out. Poorly packed feed will undergo more shrink or loss.

“If we pack better, we get higher densities,” Hicks said. “If we get higher densities, we can minimize dry matter losses and have an overall higher quality product that will remain more stable at feedout.”

Filled bunks should be sealed and covered immediately with a clear layer of plastic to prevent air infiltration, and again with a second tarp layer. Finally, tires or gravel-filled bags to hold coverings in place, weigh down the pile and keep air out are needed. Lining the sides of the bunk with plastic, to prevent water infiltration, is recommended.

Bunk sides should not be too steep. A slope of 1 foot in height for every 3 feet in length is the goal. This is not only a safety issue; proper packing is less likely to occur in piles packed at greater angles. The height of the pile should not exceed the walls surrounding it.

Understanding how well a pile is or isn’t ensiled requires checking its temperature and taking a few core samples (using forage probes) to measure dry matter density. Realizing that piles are not uniform in density or dry matter content allows feeders to better prepare consistent rations and more accurately perform sampling to calculate dry matter content.

Knowing the density will help keep track of inventory, as density affects dry matter loss over time. Less dense piles won’t retain their feed value as long as well-packed ones do. Prioritizing which piles get fed first to maximize nutrition at feedout can be a cost saver.

Feeding frenzy

“Feeders should be checking dry matter on some sort of schedule – I would say at least weekly or when they know they're getting into a different part in the bunk,” Hicks said. “A sample to dry down should be obtained after removing from the face what they plan to feed and mixing it with the loader bucket.”

Dry matter content can be readily calculated by collecting a sample from the pile. The sample is then dried, using a Koster tester, microwave, food dehydrator or other similar method. The difference between the wet sample weight and the dry sample weight, divided by the wet sample weight, then multiplied by 100 calculates the moisture percentage. Subtracting this from 100 provides the percentage of dry matter in the feed sample.

Correcting for changes in the dry matter content due to rain, or due to utilizing feed from different sections of the pile, requires a feeder to do a bit of thinking. While simple math calculations can be done each time conditions change, there are also procedures that can help to mitigate moisture content concerns.

Some farms have calculated a standard adjustment for precipitation events. For example, a mere 1/4 inch of rain might signal a 1 percent drop in dry matter content if forage is wet, while 1 inch of rain would be expected to do the same if the feed has not yet been defaced. The feeder can alter the amount of silage needed based on the farm’s standard.

Feeders should avoid defacing all of the silage for the day. Instead, deface only what you need for immediate use. Silage that is faced but not used, no matter the weather, can spoil readily. Faced silage should be mixed in the windrow, making the feed more consistent in moisture content.

“Having feeders understand this concept will hopefully get them to understand why a bunk may need to be fed out more quickly, and understand why we need to maintain a clean face with little leftover feed knocked down,” Hicks explained.

Educated feeders can minimize waste and keep feed quality optimal, keeping the herd healthy, milk production up and feed costs down.  

Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food system topics.