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• Feed costs represent over 40 percent of all production costs. Target nutrient needs for all groups of cows.
• Processing corn correctly can maximize microbial growth and milk yield while minimizing acidosis risk.
• Determining milk urea nitrogen levels for groups in a herd can fine tune and adjust nutrient needs.
• Brown mid rib corn silage yields were lower compared to other corn silage hybrids. Rations should be adjusted when feeding brown mid corn silage.

CONTROLLING FEED COST

To optimize profits in the feed cost arena, two key factors must be managed: increase income (milk yield and components) and/or lower feed costs. High milk yield (over 19,000 pounds for Holsteins and Brown Swiss and over 14,000 pounds for Jersey, Guernsey, and Ayrshire) lowers feed costs as it dilutes out maintenance needs andbuilds on a ratio of two pounds of milk (worth 25 to 30 cents) to one pound of dry matter (costs 6 to 8 cents). Meeting feed requirements are essential to optimize profitability (Table 1). Target feed cost to be less than $5.50 per cwt and less than 8 cents per pound of dry matter.

PROCESSING CORN FOR OPTIMAL RUMEN FUNCTION

Depending on the type of starch and grain processing, starch can be rapidly degraded in the rumen, escape from the rumen and be digested in the small intestine (as a source of glucose), or pass through the entire digestive tract appearing in the manure. The site of starch digestion is critical for milk yield, optimal components, and cow health. Dairy farmers and feed companies reported higher milk production when corn was processed finer or feed grade starch was added. Two questions should be evaluated.

1. Can we measure grain particle size in the field?
2. What particle size is optimal?

To answer these questions, three commercial sieves and a pan were used to evaluate corn particle size. These screens are standard sieves and sizes are listed below.

The U.S Standard Sieves can be ordered from Fischer Scientific for $45 (brass) each and a brass pan for $26. Suggested guidelines for dry corn are no corn on the top screen (will come through the digestive tract and appear in manure), 33 to 50 percent on the second screen (fermented slowly in the rumen and some starch is available for digestion in the small intestine), 33 to 50 percent on the third screen (fermented in the rumen), and 10 to 20 percent on the bottom pan (rapid source of rumen fermentable starch and can "jump start" the bacteria). The type of forage (corn silage would favor a coarser particle due to high starch levels in silage) and starch (corn and milo starch are slowly digested in the rumen compared to barley and wheat starch) will impact these guidelines. High moisture particle size corn would be different because the starch is more available due to fermentation in storage. In the field, the following observations may be helpful determine optimal grain particle size when a processing change was made.

1. Measure milk production changes
2. Measure dry matter intake changes
3. Score manure
4. Wash manure or see starch in grain particles
5. Evaluate changes in MUN
6. Watch for signs of rumen acidosis

As grain is processed finer, lower levels of corn (starch) may be needed. High legume-grass forage programs could benefit from more rumen available starch. If a TMR is not fed, finely processed grain may be unpalatable due to dusty feed or the formation of paste in the cows mouth.

MILK UREA NITROGEN (MUN) INTERPRETATION

Measuring rumen ammonia, blood urea nitrogen, and MUN would be a useful management tool to evaluate protein status in dairy cows. If ammonia is not utilized by rumen microbes (converted to microbial protein), it is absorbed across the rumen wall and into the blood. Blood ammonia can shift blood pH and be toxic to the animal. The liver converts ammonia to urea, releasing in the blood as BUN; and excreting it in urine (major route), milk (as MUN), and uterine fluid; or recycling to the rumen by saliva. MUN tests (available through Illinois DHI) measure the portion of nitrogen in milk in the form of urea. As the level of blood urea nitrogen (BUN) increases, the level of milk also increases lagging blood level by 2 hours. High levels of MUN can reflect several nutritional problems.

1. Protein imbalance with high levels of total protein, excessive degradable intake protein (DIP), high or low undegradable intake protein (UIP), amino acid imbalances, and/or excess soluble intake protein (SIP)
2. A shortage of rumen fermentable carbohydrate (CHO) including starch, sugar, or fiber to capture available rumen ammonia
3. Poor rumen microbial environment reducing microbial growth

Low levels of MUN can reflect inadequate ammonia in the rumen for optimal microbial growth leading to a protein shortage in the cow.

Herd or group levels less than 12 and over 18 mg/100 ml can reflect losses of nutrients, higher feed costs, health effects, and/or reduced milk production. Individual cows MUN can vary greatly. Summarizing 10 or more individual cow MUN values is recommended (statistically reflects MUN within 2 units of the group value). If group MUN values are over 18, several losses can be occurring.

• Significant energy losses occur when a cow must convert ammonia to urea and excrete it in urine.
• If you are purchasing protein (nitrogen) that is excreted as urea, the financial loss could be $0.20 per cow per day.
• High levels of BUN can reduce conception rate due to energy loss in early lactation (negative energy balance), change of pH in the uterus, and/or mineral shifts in the uterus.
• High levels of protein can affect cow health and the immune system, especially in cows with metabolic problems.
• High BUN levels have an environmental impact as excessive nitrogen is excreted in manure with odor and water quality.

MUN tests should be run to establish a base line value to compare when a ration change has occurred or a protein related concern may be occurring. Review milk production and feeding groups to evaluate if MUN patterns exist. MUN values in cows fresh less than 35 days are variable and difficult to interpret.

BROWN MID RIB (BMR) CORN SILAGE UPDATE

Michigan State researchers reported that BMR corn silage is lower in lignin content (about half of normal corn silage), 6 to 8 percentage units higher in total plant digestibility, 5 pounds higher feed intake, and 5.5 pounds more milk per cow per day. Higher forage digestibility and dry matter intake are advantages when feeding high producing cows. Farmers questioned high seed prices last winter ($240 per bag) and lower corn silage yields.

One observation in the fall of 1997 with BMR corn silage was higher moisture content. Dairy producers delayed chopping one to two weeks waiting for it to dry down. In northern regions, dairy managers were anxious as cold weather and poor harvest conditions could develop. The height of BMR corn silage was shorter than normal corn silage. A windy day (Sept 29th) caused damage to corn with the BMR experiencing more damage. Seven Illinois dairy farmers volunteer last winter to collect data on their farms comparing BMR to their best corn silage hybrids (control corn silage). Preliminary data is summarized in a research report. The following strategies can be considered with BMR corn silage.

1. New York DHI can determine the in vitro dry matter ($19 per sample) and NDF plus dry matter ($23 per sample) digestibility for forages. Samples are incubated in rumen fluid for 30 hours to simulate rumen retention time. Because BMR corn silage is more digestible, traditional ADF and NDF values will not reflect higher energy values. A digestibility test of BMR corn silage would be a good investment along with traditional corn silage varieties.
2. Assign an additional 3 to 5 energy units (TDN or net energy-lactation) for higher digestibility in BMR silage. If your normal corn silage has 0.70 Mcal of net energy-lactation per pound of dry matter, plug in .74 or .75 for BMR in your computer. This shift will lower the amount of grain energy and increase forage levels.
3. Because the fiber is higher in digestibility, monitor total ration ADF and NDF levels. Higher levels of fiber may be needed to maintain optimal rumen function and pH.

Table 1. Illinois nutrient recommendations for dairy cows in different stages of lactation and gestation.

^a. Trace minerals: iron (100 ppm), cobalt (0.1 ppm), copper (15 ppm), manganese (60 ppm), zinc (60 ppm), iodine (0.6 ppm), and selenium (0.3 ppm).

^b. Ratio of Minerals in Total Ration: zinc to copper 4:1, iron to copper 40:1, potassium to Mg 1:1, copper to molybdenum 6:1, potassium to sodium 3:1, nitrogen to sulfur 11:1