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Minimizing moisture is key to winter hay storage

by Wyoming Livestock Roundup

Ranchers need to plan ahead regarding winter forage supplies, and this includes finding ways to store hay to help preserve quality and reduce moisture damage. 

Dr. Emily Glunk Meccage, former forage Extension specialist in the Department of Animal and Range Sciences at Montana State University (MSU) was involved with a research project a couple years ago, which looked at round bale storage outdoors as not everyone has the luxury of hay sheds, and on many ranches, there is a lot of hay stored outside.

“We found how individuals stack hay affects the quality and the moisture retention of those bales over the winter. We want to minimize the amount of moisture and mold in those bales because it can affect cattle health and performance,” says Meccage.  

Danielle Peterson, livestock production specialist for Purina Animal Nutrition, was a graduate student at MSU during this study, and the research was part of her thesis.  She says after processing the data, results were similar to other studies assessing hay stored in various ways.  

These results showed indoor storage is best, but for outdoor storage, single bale high in a long row seems to be the most consistent for retaining quality within bales. The pyramid stack is intermediate.  

Preserving quality

Many people don’t have enough hay yard room to put all their bales in long single rows, so they stack some on top of each other to save space. Even though this might seem more efficient, it can lead to more spoilage.

“We looked at differences between bales stored at the top of the pyramid and the bottom. However, the mushroom stack, where the bottom bale is upright and another is placed on top on its side, had the most variability,” says Meccage. 

“We found top bales had hardly any change in quality, but bottom bales soaked in moisture that had run off of the top bales, as well as moisture from the ground surface,” says Peterson. “Visual quality of the bottom bales from the ground up was much lower than visual quality from the top down.”

The bottom bales were significantly lower in total digestible nutrient (TDN) and energy content and were higher in moisture content than the top bales. 

“This reduction in forage quality can have an impact on animal performance,” says Peterson.

If producers are feeding one group of cattle the top bales and another group the bottom bales, they might be getting completely different nutrient levels, even if the hay was harvested at the same time from the same field.

Minimizing moisture

“We did a two-year study, and at one of our locations we saw a lot more mold growth in between the bales in the pyramid stack than we did the first year,” says Meccage. “Each year is a little different in how much moisture those bales receive and when they receive it.”

Peterson says there are different amounts of precipitation at various locations on any given year, and thus, hay storage results including amount of dry matter and quality loss differ each year.  

“For example, during the second year of our study, our hay storage location at Havre, Mont. had extremely high precipitation compared to other years,” Peterson says. “Moisture that freezes won’t create as much mold as moisture in warm weather.”

“When planning long-term, it’s often a good idea to hold some hay in reserve in case we have a bad year. If we plan to keep some hay over for the next year, it pays to try to stack the hay in a manner that it will keep better and not be ruined by moisture,” says Meccage.

A person could afford to build a hay shed with the money lost in damaged hay over time.

“Hay that’s been stored outside and uncovered may decline in dry matter and quality,” says Peterson. “Feeding this hay can result in lower animal performance including lower average daily gains, poor animal health and possibly even abortion in cows in certain cases with moldy hay.”

Return on investment varies depending on how much hay and what type of hay individuals store, but a hay shed will pay for itself over several years.

“One of the cheaper options that has a beneficial effect fairly quickly is just to decrease the hay-to-soil contact. Having a gravel base to stack hay on will greatly reduce moisture damage. Putting hay on pallets, railroad ties or gravel will allow for drainage and eliminate moisture wicking up into the hay from wet ground. This will help preserve hay quality,” says Meccage.

Putting tarps or black plastic over the hay can also protect it from wet weather and can be economical, especially if producers stack bales on top of each other. The tarp can cover twice as much hay as with a single row. 

 Even though these coverings are expensive, they can often be re-used for several years, which makes them more cost-effective in preserving quality of the hay. The covering also keeps snow and moisture from freezing on the bales, which can make it very challenging to remove the net wrap or twines when feeding them.

Heather Smith Thomas is a corresponding writer for the Wyoming Livestock Roundup. Send comments on this article to

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