Milk Urea Nitrogen, an Easy Monitoring Tool

Is there too much protein in a dairy cow utilizing? Milk urea nitrogen (MUN) is a simple test that is routinely measured when milk is picked up at the farm. Milk urea nitrogen is a byproduct of protein breakdown in the cow. When there is more protein in the ration, and therefore in the rumen (the first stomcah compartment,) than the microbial population in the rumen can use that protein gets broken down to ammonia, and the ammonia is absorbed into the bloodstream. Ammonia floating around in the blood is toxic to the cow so she converts ammonia to urea, which is then excreted in urine and milk. Most of the urea ends up in the urine contributing to the majority of nitrogen found in manure, which can lead to air and water quality concerns.

The higher the concentration of MUN the less efficiently the cow is using the nitrogen in her feed, which means more is being excreted in urine. This represents not only a waste of ration protein (nitrogen), but also a waste of energy that could be going to milk production because it takes energy to convert excess protein to urea.

So, what should the concentration of MUN be in milk? Assuming the ration is balanced well in other areas a concentration as low as 8-10 mg/dl can be okay, but 10-14 mg/dl is still considered normal. Any values consistently above are a red flag that the protein concentration of the ration is too high. Generally, a ration crude protein concentration of 16% would be associated with normal MUN levels, and should be sufficient to meet the protein demands of a lactating cow.

Try to Avoid "Juicing" Silos

Corn is soon to be chopped for silage and with the wet weather this summer many farmers will experience "juicing" of new silage. Juicing, or leachate, is worse when silage is put up too wet and with the wet summer it will take a long time for corn to dry down. Regardless of the amount of leachate, it needs to be managed to avoid negative environmental impacts. Silage leachate is a serious threat to surface and ground water quality due to its high concentration of nutrients. One gallon of leachate can lower the oxygen content of 10,000 gallons of river water to a level that is difficult for fish to survive. Also, the high ammonia and nitrate concentrations in silage leachate can lead to algae blooms, which can further reduce the oxygen concentration in lakes and streams. Silage leachate is also very acidic and can burn the grass in the surrounding area, increase the acidity of bodies of water, and corrode concrete and metal structures. All farms, regardless of size, are regulated under the water quality laws, which means all farms need to control pollutants (i.e. silage leachate) that runs off their farm into streams and other surface waterways.

Since some silage leachate will occur, it is important that there be a system to divert it away from surface water and well heads. Leachate and any contaminated rain water should be captured and diverted into a lagoon or a filter strip. Leachate that has been collected can be treated to make it less caustic to water resources by dilution with clean water or manure, neutralization with hydrated lime, aeration, and simply storing the material will help to reduce the potency of the leachate. Field application is the best method to dispose of leachate, but care should be taken about when, where, and how it is spread so that damage is not done to the plants in the field or to surrounding environment.

Management practices that help reduce silage leachate also result in better quality corn silage for your cows because leachate contains nutrients like water-soluble carbohydrates, proteins, and vitamins that could be going into your cows instead of the stream. With corn silage being the major component in many rations it is important that care be taken to produce a good quality feed and in the process prevent the potentially negative environmental impact of silage leachate.

Phosphorus in Byproduct Feeds

Byproduct feeds are becoming a more temping purchase as corn and soybean prices increase, but phosphorus (P) levels of rations need to be monitored is byproducts are in the ration. The 2001 National Research Council, Nutrient Requirements for Dairy Cattle, recommends 0.29% to 0.40% P in rations to support milk production, but generally 0.38% is enough to meet most dietary needs. This value already contains a fudge factor so there is no need to feed above these recommendations.

Unlike nitrogen, which moves down through the soil, P tends to build up in the top layers of soil, and in areas of historic intensive farm the P levels in the soil can be quite high. Up to 90% of P is bound to the sediment so the main way to prevent P from getting into water sources is to reduce erosion. Once P gets into streams, lakes, and other waterways it causes algae blooms, which remove oxygen from the water essentially making the water unlivable for aquatic organisms. This tends to make the news when “dead zones” develop in the Chesapeake Bay, but the smaller streams running through your property also supports aquatic life that can be detrimentally impacted by P runoff.

Byproduct feeds are at least twice as high in P as corn grain, and soybean meal is also fairly high in P. Therefore adding a lot of these byproducts can rapidly increase the overall P content of rations, and like nitrogen, excess dietary P ends up in the manure. That manure then needs to be spread on ground that already has high P concentrations limiting the options for where it can be spread without increasing the P content of the soil. Therefore decreasing the P content of the ration along with decreasing soil erosion will result in the greatest reduction of P runoff into water sources.

What is Dry Matter and Why is it Important?

Knowing the dry matter concentration of any wet feed is something every producer should know.

Determining the dry matter concentration of wet forages is one of the most basic, and arguably the most important things to measure in wet forages and can be easily done on the farm. The Benefit to measuring the dry matter concentration on farm is that it is quicker than sending it to a lab, and the quicker the ration is adjusted to the new dry matter concentration the more accurate the ration.

Once the dry matter is determined, the ration needs to reflect any changes in the value. For example, if corn silage dry matter changes from 35% dry matter one week to 30% dry matter the next week, but the ration is not adjusted to reflect that change, crude protein concentration of the diet will increase from 15.8% to 16.3%. In this example, the cow will be getting more protein and nitrogen than she needs, and the excess nitrogen will end up in the urine potentially leading to air and water pollution.

Excess nitrogen and phosphorus are major contributors to water quality concerns of the Chesapeake Bay. Conversely, if the dry matter of the corn silage increased from 30% to 35% and the ration is not adjusted the cows will be getting less energy and protein than they should be because increasing the corn silage will dilute out the rest of the ration. This could lead to a decrease in milk production, which is never a good thing.

Formulating rations to the cow’s requirement and then mixing that ration as close as possible to what is on paper is necessary in order to reduce nutrient losses to the environment and maintain a consistent high level of production. This becomes very difficult to do when the dry matter of a large portion of the ration is not known accurately. So get out there and start weekly testing of your feeds!

Good Feed Management Pays

In times of narrow margins it becomes increasingly important that producers focus on increasing feed efficiency to save money on feed costs. The Natural Resources Conservation Service (NRCS) has implemented a new program that will provide EQIP (Environmental Quality Incentive Program) money to producers to help them improve feed management. When cows utilize nutrients more efficiently for milk production they excrete less manure, and specifically, less nitrogen and phosphorus.

The Feed Management Program was adopted by NRCS in 2003 with two main purposes; 1) improve net farm income by feeding nutrients more efficiently and 2) reduce the excretion of nitrogen, phosphorus, and other nutrients by minimizing over-feeding of nutrients. The Mid-Atlantic region has been at the forefront of implementing this program, which will help Pennsylvania reach its goal of reducing nitrogen excretion to the Chesapeake Bay by 37 million pounds per year and phosphorus by 1.3 million pounds per year by 2010.

There are five basic steps to getting started with a Feed Management Plan.

1. Determine the purpose of the plan, which is done by the producer and a Technical Service Provider (TSP).

2. The TSP and producer determine if a Feed Management Plan is the best way to address the resource concern.

3. The TSP, producer, and nutritionist (certified to write plans) do an economic evaluation to determine the cost of making feed or manure hauling changes.

4. Nutritionist and producer develop the Feed Management Plan.

5. Nutritionist and producer implement and monitor the plan.

This is an exciting new program that can likely increase profitability through improved income over feed costs, better nutrient efficiency, and reduced nutrient excretion. Specific rules for receiving EQIP funding are different in each state so contact your state NRCS representative for information Questions about the program should be directed to Jana Malot, State Grassland Specialist with NRCS or Virginia Ishler, Nutrient Management Specialist with Penn State University.

Begin by Beginning...

The beginning is always the hardest part, so please be patient. The purpose of this blog is to highlight the intersection of agriculture and the environment. One of the goals is to inform the environmental side of the conversation about what agriculture is doing to improve the environment and let the agriculture side understand the concerns of the environmental groups. Too often there is a lack of constructive communication between these two groups and hopefully is some way this little blog will help to bridge that gap.