Dr. Bill Weiss, Mrs. Dianne Shoemaker, and Dr. Normand St-Pierre, Extension Dairy Specialists, The Ohio State University
Because of growing conditions this year, some corn silage will be made from either drought-stressed corn plants or immature corn plants (or both). Corn silage from either of these types of plants can be an acceptable feed for dairy cows, but they are usually worth less than normal corn silage.
Immature Corn Silage – Nutrient content
The nutrient composition of immature corn silage differs substantially from normal corn silage because the plant contains much less corn grain. As corn plants mature, concentrations of starch increase (because of increased grain) and this dilutes the fiber (measured as neutral detergent fiber, NDF) and crude protein (CP) concentrations. The fiber is also less mature which means it is more digestible than in normal corn silage, but the fiber is still less digestible than starch so energy (as measured by net energy for lactation, NEL) is typically lower in immature corn silage than normal corn silage.
Average nutrient composition (dry basis) of immature corn silage (very early milk stage)
CP 10 to 11% (about 2 or 3 units higher than normal)
NDF 50 to 55% (about 10 units higher than normal)
Starch 15 to 20% (about 15 units lower than normal)
NEL, 0.60 to 0.63 Mcal/lb (90 to 95% of normal)
As the corn silage crop matures, composition approaches normal. For Ohio, normal corn silage averages 8% CP, 42% NDF, 30% starch, and 0.66 Mcal/lb NEL.
Immature Corn Silage – Dry matter concentration
The greatest potential problem with immature corn silage is its moisture concentration. Often, dry matter percentage of the standing crop is 20 to 25%, which is too low for a good fermentation. A nutritious crop WILL BE RUINED by a poor fermentation. If corn plants are immature, delay harvest until it reaches proper dry matter (~30% for bunkers, ~35% for bags and top unloading silos, and ~38% for bottom unloading silos). If the corn is extremely late in the season, you may have to harvest after a frost to obtain proper dry matter concentrations. Frosted corn dries very quickly, so monitor dry matter concentrations often after a frost.
Immature Corn Silage - Other issues
- Kernel processing can actually reduce the energy value of immature corn silage, and because the kernel is poorly developed, processing is not needed.
- Frosted corn silage should benefit from the use of a lactic acid bacteria inoculant because the normal bacterial population on the corn may be low.
Immature Corn Silage – Valuation
Based on the average nutrient composition shown above and using 3 month average nutrient prices generated with SESAMETM1, immature corn silage is worth about 95% as much as normal corn silage. However, because of increased risk associated with immature corn silage (composition could vary greatly from the averages), it should be discounted an additional amount. That amount is difficult to quantify and should be negotiated between buyer and seller, but an additional 5 to 10% discount is probably realistic.
Drought-Stressed Corn Silage – Nutrient content
The composition of drought-stressed corn silage does not follow a consistent pattern such as we see with immature corn silage because drought affects corn plants differently depending on when the drought stress occurs. Therefore, the nutrient composition of drought-stressed corn silage is more variable.
Average nutrient composition of drought-stressed corn silage (extremely variable depending on drought severity, timing of drought, etc.):
CP: Usually higher but highly variable, average is about 10% higher than normal or an actual concentration of 8.8%.
NDF: Usually 5 to 10 units higher than normal (47 to 52%). Fiber digestibility is probably equal to or higher than regular corn silage.
Starch can range from very low (~5%) to 25% (only about 10% units lower than normal), depending on kernel development. If starch is very low, sugars are usually higher than normal. If diets are formulated for starch, additional corn grain will be needed in diets with drought-stressed corn silage.
NEL: Limited data are available, but the best guess is 90% of normal (0.60 Mcal/lb).
Drought-Stressed Corn Silage – Dry matter concentration
In most cases, drought-stressed corn silage will ferment properly if harvested at the correct dry matter concentration. However, dry matter concentrations are more variable within a field (or fields) with drought-stressed corn than with normal corn. This increases the risk of a poor fermentation. As with immature corn silage, drought-stressed corn silage must be made at the correct dry matter; otherwise, it has much less or no value as a feed.
Drought-Stressed Corn Silage - Other issues
- Drought-stressed corn silage could be high in nitrates which could, if severe enough, make the silage virtually worthless. All drought-stressed corn silage should be tested for nitrates prior to feeding.
- Yields are lower for drought-stressed corn silage; therefore, harvesting costs per ton are increased. This means that the cost of the corn plants should be discounted to cover the increased harvesting cost.
Drought-Stressed Corn Silage - Valuation
The nutrient value of drought-stressed corn silage is less than normal corn silage, but without a laboratory analysis of the specific forage, the amount of discount to apply is difficult to determine. A reasonable estimate is that drought-stressed corn silage has a nutritional value of 90 to 95% of normal corn silage.
The relative economic value of the nutrients in drought-stressed corn silage was calculated by using average composition data (8.8% CP, 50% NDF, and 0.59 Mcal/lb NEL) and 3 month average nutrient prices from SESAMETM. Using that approach, “average” drought-stressed corn for silage is worth 93% as much as normal corn silage. However, with drought-stressed corn silage, the buyer is taking on substantial risk (highly variable nutrient composition, nitrates, etc.), and drought-stressed corn silage must be discounted to cover this increased risk. A discount of at least an additional 10% is probably warranted.
Basics of Pricing Corn Silage
This article addresses adjustments to be made to silage pricing to account for differences in nutrient content, harvesting, ensiling, and other risks and issues associated with immature and drought-stressed corn silage. Additional basic corn silage pricing resources are available at https://dairy.osu.edu in issues of the Buckeye Dairy News and under the “Feeding Management” and “Business Resources” links.
THE BOTTOM LINE:
It is absolutely critical that immature or drought-stressed corn silage be made at the correct dry matter. The value of these silages must still be discounted because of increased risks, including variation of nutrient concentrations, harvest challenges, harvest costs, nitrates, fermentation issues, etc. Valuing immature corn silage at 85 to 90% of normal corn silage and drought stressed corn silage at 80 to 85% of normal corn silage would be reasonable. Test drought-stressed corn silage for nitrate levels before feeding.
1SESAME™ is a software program developed at The Ohio State University to price the important nutrients in dairy rations to estimate break-even prices of all major commodities traded in Ohio and to identify feedstuffs that currently are significantly underpriced.