Harvesting sunflowers for silage requires careful consideration

North Dakota State University Extension
Sunflower silage can make a suitable feed for beef cows after considering several factors.

Many producers are wondering if their crops will make it to grain harvest or if they should they salvage the crop and harvest it as forage.

"Sunflowers may be no exception to this question — the decision to harvest sunflowers as forage, particularly silage, requires careful consideration of several factors," says Zac Carlson, North Dakota State University Extension beef cattle specialist.

“Sunflower silage can make a suitable feed for beef cows,” says Carlson. “Generally speaking, sunflower silage is about 80% of the feeding value of corn silage. Still, the challenge is getting it put up, because sunflowers typically don’t dry down well.”

Consequently, dry feed must be added to the silage pile to reduce the moisture level to a point where seepage is not a major problem.

The moisture problem in sunflower silage can be corrected by several means. Former NDSU animal science specialist, LaDon Johnson, suggested blending corn and sunflower silages when packing as one method. Johnson advised a blending ratio of one load of sunflower silage to three to four loads of corn silage. He also suggested waiting seven to 10 days following a killing frost to facilitate dry down. Some varieties may take longer, and waiting longer also increases the risk of wind damage to the crop and greater dry matter losses.

Johnson also advised blending dry forage into the silage pile to reduce the moisture content. 

Optimal moisture content in sunflower silage appears to be 60% to 72% or 28% to 40% dry matter. To minimize effluent seepage problems, the moisture level will likely need to be below 65%. Silage that is too wet will also result in undesirable clostridial fermentation, reducing the forage quality and may limit voluntary intake due to palatability. Keep in mind the target moisture of 60% to 72%; harvesting immature sunflowers can produce silage with lower fiber, lignin and fat content, possibly improving the forage quality.

Sunflower silage is lower in energy at 61% to 66% total digestible nutrients (TDN), variety dependent, than corn silage at 68% TDN. The lower energy of sunflower silage is mainly due to the greater fiber content of sunflower silage, which is approximately one-third more than corn silage and three times the amount of lignin, the indigestible portion of the fiber.

However, confectionery and oil-type sunflowers can make silages that contain more protein (11.1% to 12.5% versus 8.2% crude protein, respectively), fat (7.1% to 10.7% versus 3.3%, respectively), calcium (0.8% to 1.5% versus 0.24%, respectively) than corn silage at 100% dry matter.

“Due to the fat content of sunflower silage, the forage should be limited to one-half or less of the diet dry matter basis,” says Carlson. “In forage-based diets, dietary fat content exceeding 3% will reduce the intake and digestibility of forages. Likewise, the high fiber content of sunflower silage may reduce intake by slowing down the rate of passage in the rumen.”

As with making any silage, allow 28 days for the ensiling process to occur before feeding or exposing the forage to oxygen.

Pricing silages can be complex. Factors that may influence the value of sunflower silage include substitute feed costs, fertilizer costs, harvesting costs, removal of residue and nutrients from the field, storage costs, harvest and storage losses or shrink, and energy, protein and fiber content of the sunflower silage. Analyze the sunflower for nutrient content, use these values to better understand the forage quality, and determine the pricing based on forages with similar nutritive value, such as medium quality hay.

“For crops covered by insurance, be sure to contact your crop insurance agent before harvesting for silage,” says Hans Kandel, NDSU Extension agronomist. “Likewise, check any herbicide and insecticide labels applied to the crop and follow the pre-harvest time restrictions before harvesting.”

“Many drought-stressed plants accumulate nitrates,” says Miranda Meehan, NDSU Extension livestock environmental stewardship specialist. “Before feeding, test your drought-stress sunflower silage for nitrates. Although proper ensiling will reduce nitrates, it does not guarantee the forage will contain ‘safe’ levels of nitrates.”

See the NDSU Extension publication “Nitrate Poisoning of Livestock,” https://www.ag.ndsu.edu/publications/livestock/nitrate-poisoning-of-livestock, for more information about elevated concentrations of nitrates in feedstuffs.

For more information on harvesting sunflowers for silage, contact your local NDSU Extension agent.