Silage harvest and storage management can dramatically impact silage quality and nutrient digestibility. Dr. Limin Kung, professor at the University of Delaware, shares recommended best management practices.
Keys to Silage Success:
- Start with high-quality forage
- Harvest at correct moisture and dry matter (DM) content, with a quick wilt (for grasses and alfalfa)
- Chop to an adequate particle size
- Treat with a microbial inoculant
- Pack quickly and tightly to eliminate air and start fermentation
- Keep air out during storage and feed out
Maturity and Dry Matter (DM)
“Harvesting forages at optimum maturity sets the stage for the rest of the year. High forage quality drives intake and, in turn, drives milk production,” Kung said. “Not even the best nutritionists in the world can make cows maximize their milk production if they are working with poor-quality forages.”
Corn silage harvest should occur when the whole plant is at 35% ± 2% DM. Corn plants dry down at a rate of about 0.5 percentage units per day, but expect a faster dry-down in dry, hot weather.
Managing the period of wilting can be a challenge. The goal is to result in maximum conservation of fermentable sugars and obtain an adequate DM level to prevent the growth of clostridia, he said.
“Wet grass and alfalfa silages are highly prone to undergo clostridial fermentations when the dry matter is less than 30[%] to 35%. Wilting these crops above this level of DM makes it harder for clostridia to dominate the ensiling process,” said Dr. Kung.
Forage Particle Size
Avoid chopping corn silage too finely because it reduces the effective fiber. However, coarsely chopped silage does not pack well and often leads to sorting of the total mixed ration (TMR).
“Recommendations for theoretical chop size usually run between 3/8" to 1/2" for unprocessed corn silage and about 3/4" for processed silage,” he noted. “However, in diets where corn silage makes up the majority of the forage, 15% to 20% of the particles should be greater than 1.5" long. Try to achieve a physically effective [neutral detergent fiber (NDF)] of the TMR of about 22%.”
Whole plant processing crushes the entire plant through rollers and can be accomplished in the field during harvesting; at the silo but prior to storage; or after ensiling just prior to feeding. Processing corn silage improves starch digestibility and allows for good packing in silos, even with a longer length of particle chop.
“Generally, adequate processing is occurring if more than 90[%] to 95% of the kernels are crushed or cracked; … kernels are broken into at least 4 pieces; and cobs are more than quartered,” he said.
The keys to making quality silage are to:
- Rapidly exclude air from the forage mass, which will result in a rapid production of lactic acid and reduction in silage pH, and
- Prevent the penetration of air into the silage mass during storage.
- Packing fast but densely
- Distributing forage evenly in the storage structure
- Chopping to a correct length
- Ensiling at recommended DM levels for specific storage structures
- Sealing quickly and tightly
“Bunk and pile silos should be filled as a progressive wedge to minimize exposure to air and packed in 6" to 8" layers,” he said. “The recommended optimal bulk packing density for bunk and pile silos is a minimum of 44 lb. to 45 lb. of wet forage per cu. ft.”
For more information on bunker silo filling, click here.
Forages can be inoculated with various microorganisms to alter the resulting pattern of fermentation in the silo. Inoculation can help in three general areas:
- The prevention of clostridial fermentation
- The enhancement of aerobic stability
- The capability of making a good fermentation even better
Sealing the Silos
After filling, silage should be covered with plastic immediately and weighted down with tires or gravel bags to exclude air. Split tires can be easier to handle and do not accumulate water.
Cover with either:
- Two layers of normal plastic
- A thin layer of oxygen barrier plastic and then a layer of white plastic
“Use of plastic to line the side walls of bunker silos has also grown in popularity to prevent the seepage of water into the silo mass,” Kung said.
Photo courtesy of Dr. Limin Kung
Allow Forages Time to “Cure”
A “fall slump” in milk production is common on dairy farms, resulting from feeding corn silage that has not had adequate time to complete the fermentation process. Most silages require 3 to 6 weeks before the fermentation process is complete. In addition, Kung suggests that, if possible, producers should transition to new silage over a week to 10 days.
“Starch availability of corn silages and high moisture corn increases with prolonged storage,” said Dr. Kung.
For more details on Kung’s recommendations on Silage Management 101 – The Basics, click here.