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Tuesday, June 3, 2003
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Nutrient Utilization in the Dairy Cow
by Mike Hutjens
Dairy operations must focus on value-added by marketing their feed and labor thought their dairy business resulting in a favorable return to the owner / investor. This presentation considers optimizing transferring feed nutrients to milk and milk components while minimizing nutrient losses. Nutrient efficiency will be an important. Dairy managers and nutritionists are measuring protein retention, milk yield per unit of dry matter, and energy conversion. Dairy NRC 2001 provides new tools and approaches in nutrient utilization. Veterinarians can review the following table and outline with power points used in the presentations.
Dry matter intake (DMI); optimizing v maximizing
- Maximizing DMI may not be the most efficient point or desirable target.
- Dairy or feed efficiency (pounds of milk per pound of dry matter) should exceed 1.4 (one group TMR) with early lactation groups achieving 1.6 pounds of 3.5% FCM per pound of dry matter or higher.
- Thirteen pounds of dry matter subtracted from total ration dry mater reflect available energy for productive function in Holstein cows.
- Current ration dry matter costs about seven cents per pound in Illinois.
- Cows may consume 1.2 percent of their body weight at total NDF.
- If DMI violates these guidelines, evaluate feed particle size, look for periods of negative energy balance earlier, consider rumen acidosis, and determine if reformulation of the ration is warranted (based on milk price, body condition score, feed costs, stage of lactation, and age of cows).
- Evaluating feed refusals impacts DMI and feed costs. Target 2 to 4 percent of the initial DMI as orts and evaluate particle size using the Penn State Box (less than +/- 10 percent of the initial TMR by box).
Optimizing rumen fermentation
- Maintaining rumen pH levels between 5.9 to 6.2 can optimize microbial yield and VFA production.
- About 60 percent of amino acid needs and 80 percent of energy (via VFA) can be produced by rumen fermentation and microbial growth.
- Penn State Box guidelines for optimal intake and fermentation are 10 to 15 in the top box, 40 to 50 percent in the second box, 30 to 35 percent in the third box, and 10 to 20 percent in the bottom box.
- Dry shelled corn should average 1100 microns with 33 percent above 1100 micron screen , 50 percent from 500 to 11000 micron screen, and less than 10 percent under 500 micron screen (about two thirds of dry shelled corn should passing though a flour sifter).
- Balancing carbohydrate and nitrogen fractions will optimize nitrogen capture of RDP and soluble protein. MUN values from 11 to 16 can rerflect this point.
Balancing and meeting nutrient requirements
- Table 1 contains the recommended nutrient guidelines based on NRC 1989 for protein energy, protein, dry matter intake, and trace minerals guidelines.
- Phosphorous and vitamin E values reflect NRC 2001 values.
- Replacing one quarter to one third of zinc and copper with organic sources is recommended for transition and early lactating cows.
- While nutrient requirements are expressed as percent or parts per million, the cow's needs are needed in pounds, grams, or international units. Actual dry matter intake dictates the nutrient level needed in rations.
Benchmarking cow performance
- Milk components can reflect nutrient form and level.
- Milk production guidelines by stage of lactation and lactation number reflect areas to investigate.
- Milk urea nitrogen values (MUN) are herd specific and should be based on MUN valves from 8 to 10 cows in each group to reflect actual values.
- Manure scores should range from 2.5 to 3.5 depending on the stage of lactation and gestation.
- Blood NEFA and ketone bodies, urine pH, and rumen pH via rumencentesis can be guidelines reflecting nutrient balance and shifts.
Using NRC Dairy 2001 to refine ration formulation
- Accurate dry matter intake adjusted for feed refusal will be critical to fine-tuning rations using the NRC 2001 model. New DMI are 3 to 5 pounds higher than NRC 1989 predictions requiring excellent feed bunk management and feed quality to achieve these higher levels
- Protein levels calculated on metabolizable protein, duodenal amino acid levels, and adjusted RUP based on dry matter intake and intestinal digestibility can improve protein efficiency and avoid excretion of excessive nitrogen.
- Energy values are discounted for level of intake and ration energy density to more accurately predict energy intake. Processing adjustment factor (PAF) allows for changes in feed particle size and treatment of the NFC fraction. Energy adjustments for pasture conditions (topography and distance walked) can be considered.
- Pregnancy requirements reflect days pregnant increasing as the animal approaches calving by increasing nutrient needs (no guidelines for twins).
- Mineral recommendations were corrected for truly available mineral based on source of the mineral. Feed tables list individual mineral average values with a standard deviation and number of samples used in calculating the average value (allows uses to determine confidence in the reported value).
- The model is a user friendly and easy program to run. No balancing or least-cost function can be done with the model. Most users will balance the ration using a current software system and enter this solution in the NRC model to fine tune dry matter intake, amino acid levels, RUP and RDP balance, energy status based on measured dry matter intake, and mineral status based on availability
Table 1. Illinois nutrient recommendations for dairy cows in different stages of lactation and gestation.
0 to 21d
22 to 80d
80 to 200d
|Metabolizable Protein (%)
|*RDP: % of CP (DM)
|RUP: % of CP (DM)
|SIP: % of CP (DM)
|Ether Extract %
*Ratio of NFC to DIP (%of DM) =3.5:1
|Major Minerals in % of DM|
*When anionic salts are used: mineral/anionic salts (%)
|Vitamins in IU per Day|
a Trace minerals: iron (150 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.
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