Nutrition: Forage Strategies with Expensive Corn

March 1, 2011 10:13 PM

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Evaluating Corn Silage Quality for Dairy Cattle

The price of shelled corn continues to raise forage, cereal grain and by-product prices. One strategy for dairy managers to position their feed costs for 2011 is to raise the optimal quality and type of forage on the farm. Consider these ideas for lowering feed costs and providing feed flexibilities while optimizing profit potential.

Forage quality is an old story, but it’s key in feeding higher forage rations with less corn or barley. Guidelines to target forage quality indexes for 2011 are as follows.

Corn silage: 32% to 36% dry matter; more than 30% starch; and NDFD (neutral detergent fiber digestibility) more than 60% (30-hour analysis).

Legume-grass forage: RFQ (relative forage quality)index more than 170; crude protein more than 20%; and NDFD more than 50% (30-hour analysis).

Forage ratios and types require more planning. Using Midwest forage yields (5 tons per acre of alfalfa dry matter and 8 tons per acre of corn silage dry matter) with optimal quality, Randy Shaver of the University of Wisconsin calculated milk per ton and milk per acre using the MILK2006 equation. The results for corn silage were 3,220 lb. of milk per ton and 26,000 lb. of milk per acre; for alfalfa, 2,863 lb. of milk per ton and 14,314 lb. of milk per acre. Are you optimizing the type of forage that you can raise on your farm considering soil limitations, degree days and erosion control?

Silage storage should optimally capture and preserve the forage nutrients raised. Conduct a silage fermentation profile to determine if your forage harvesting and storage system allows for the following targets:

Silage pH less than 4.5 for legume-grass silage and less than 4 for corn silage; lactic acid levels more than 4%; acetic acid less than 2%; butyric acid less than 0.25%; and lactic acid more than 70% of total volatile fatty acid (VFA) produced in storage.

DT 020 D11034Forage variation reflects the impact of harvest window (days to harvest the crop), number of cuttings (three to eight for legume-grass forage) and forage harvesting equipment. The table above shows variation in corn silage and alfalfa-grass forages. Standard deviation is the range in feed nutrients tested (one standard deviation means 67% of forage samples fit in this range). Corn silage has lower standard deviation with more consistent nutrient levels when building
rations. As a result, fewer "safety" nutrient margins are needed. For example, an extra 1% crude protein in the total ration dry matter may be needed with legume-based forage rations.

Rumen "friendly" forage is forage that provides an adequate rumen fermentation environment for microbes, stimulates cud chewing for bicar-bonate production and maintains an optimal rumen pH between 6 and 6.2 with an acetate-to-propionate VFA ratio greater than 2.5.

March is an excellent time to plan your 2011 forage production system and ration building program. Looking back at your 2010 forages can show opportunities for reducing the challenge of higher corn prices.

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