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Test Cuts Feed Costs
Milk urea nitrogen analyses can help keep you from overfeeding protein.

Overfeeding protein is a common concern when grazing milkers on lush, well-managed pastures. But milk urea nitrogen (MUN) analyses can help you determine if that's the case. If it is, adjusting rations accordingly may reduce your feed costs, increase production, avoid ketosis, improve body condition, boost reproductive performance and help keep nitrates out of surface and groundwater, says Dr. Larry Chase, a dairy nutrition specialist with Cornell Cooperative Extension. Chase is working with NRCS grazing specialist Darrell Emmick and Extension nutritionist Karen Hoffman comparing MUN levels on pasture and during confinement feeding in more than a dozen herds around the state this year.

When cows consume too much protein, they must expend extra energy to convert excess ammonia to urea, explains Chase. Urea levels in their blood, plasma and milk rise. MUN samples are relatively inexpensive and simple to take, and performed correctly can provide a good index of your herd's protein status, he adds.

While MUN research -- especially on pasture -- is still in its infancy, values in the 12 to 16 mg/dl range are considered normal. Readings below that indicate that you should probably increase total and soluble protein in supplemental feeds. Higher values suggest that you should decrease the protein in your rations, or simultaneously feed more high-energy carbohydrate sources, so that the energy is available when rumen microbes need it most.

Don't use MUN tests to try to analyze individual cows, cautions Chase. Sample milk from at least 10 animals grouped by production level, lactation stage or ration. Follow sampling instructions carefully, including prompt refrigeration or the addition of a fermentation inhibitor.

Also, don't base ration changes solely on MUN values, warns Chase. Work with your feed advisory or veterinarian to use MUNs as another tool to fine-tune your feeding program, he suggests. For more information about MUN testing, contact Northeast DHIA at (800) 344-2697.

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