Ag Connection

Your link to the Universities for ag extension and research information


Volume 4, Number 1
January 1998
 
This Month in Ag Connection
Before You Throw Another Log on the Fire
Definitions of Forage Quality — Their Importance to Ruminant Performance
Forage Test Terminology
Barry Steevens' Tips for Winterizing Dairy Cows

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Before You Throw Another Log on the Fire

Many area landowners harvest timber as firewood, lumber or veneer logs. For better or worse, conditions created by timber harvest last a long time. Proper forestry management can increase the value of the timber, prevent erosion, and improve wildlife habitat.

Timber stand improvement will increase the woodland's value for timber products. Woodcutters can improve the timber stand by following these forestry practices developed by forestry professionals:

Thinning is cutting trees from an immature stand to increase the growth and improve the form of the remaining trees.
Release is the removal of damaged and diseased trees or inferior species to encourage fast growth and better quality of vigorous young desirable trees and lessen the spread of disease. Den trees are important to several species of wildlife and some should be left in the woodlot.
Pruning is removing limbs to produce the maximum merchantable length in the butt log. This is primarily recommended for potentially high-value younger trees.

Best management practices (BMP's) include practices that can prevent erosion and reduce non-point source pollution. Because of their extensive root systems, trees are very effective for keeping soil where it belongs - on the ground and out of waterways. Leaves, on the trees and on the ground, help break the force of rain, minimize soil erosion and increase water absorption.

Consider the following best management practices when harvesting timber:

Do not cut all trees along streams unless they appear ready to fall into the stream. The riparian zone (area along the stream composed of trees, shrubs and grass) reduces runoff, traps sediment, reduces the water's velocity, and stabilizes the stream bank. Riparian zones also provide excellent wildlife habitat.
Locate logging trails out of stream channels and away from stream banks. If it is necessary to cross a stream, cross at right angles where the stream is narrow.
Logging trails should follow the contours. Avoid steep or long slopes and soft ground. If necessary, travel those areas when the ground is either dry or frozen.
Avoid hauling wood under wet conditions that could result in excessive rutting.
Pile brush and debris in gullies and depressions where possible.
Stabilize disturbed open areas by fertilizing and seeding.
Remove and properly dispose of all trash, oil containers and other refuse.

You can maintain the balance between profitable timber harvest and a healthy environment by following these best management practices. For professional assistance in developing timber improvement plans, contact the Missouri Department of Conservation.

Author: Cindy DeOrnellis, Associate Farm Management Specialist


 

While color is easy to see and describe, it has little to do with animal performance.


Other University Outreach and Extension resources on forage testing and results:

Forage Test Terminology

G03150: Forages for Cattle: New Methods of Determining
Energy Content and Evaluating Heat Damage

G03151: Using a Microwave Oven to Determine Moisture in Forages

G03160: Understanding and Interpreting Feed Analysis Reports

G03161: Using NDF and ADF To Balance Diets

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Definitions of Forage Quality — Their Importance to Ruminant Performance

How do you determine your forage quality? A common way to estimate hay quality is color. While color is easy to see and describe, it has little to do with animal performance. We have encouraged producers to get a hay analysis done so that they may accurately determine the needs for supplements. However, it defeats the purpose of the test if you find yourself staring at a page full of acronyms in utter confusion.

Cell Diagram
Figure 1. Components of a forage plant divided into cell wall and cell contents.

Before we get into the terminology of forage quality, it is important to understand what is being measured within a forage plant and why. All biological systems start with the basic building block of a cell. Forages are made up of cells which can be divided into two parts - cell contents and cell wall (Figure 1).

Cell contents contain soluble carbohydrates (glucose, fructose, sucrose, fructosan, and amylose starches), organic acids, protein, pectin, starch, triglycerides and glycolipids. The availability of these components to ruminants is more than 90%. However, utilization is limited by intake and rate of passage of the forage through the digestive system.

These limits are due to the fibrous contents of the cell wall: cellulose, hemicellulose and lignin. Cell walls become thicker as the plant matures. This thickening of plant cell walls increases the fiber content of the total plant, and decreases the cell content portion of the plant. It is this relationship, the amount of cell content vs. the amount of cell wall content present, that is measured by a forage test.

Cell contents are measured as protein and energy. The cell wall is measured as fiber, which can be further divided into acid and neutral detergent fiber. A working definition of quality is a plant that contains a high percentage of cell contents and a low percentage of cell walls (i.e., high protein and energy and low fiber).

Ruminants adjust their intake in response to their energy requirements.Therefore, quality is very important because cell wall contents (fiber) will limit the intake and digestibility of a forage. When ruminate diets contain large portions of indigestible fiber, the quantity of feed consumed may be limited by rumen capacity. In some instances rumen capacity is reached before an animal has consumed enough forage to meet energy demands.

This phenomenon can be seen when a high fiber hay is fed to cows with high energy demands such as cows nursing calves.

While the cow's energy requirement increases her potential intake, her intake becomes limited due to the low digestibility and rate of passage of the hay. The rumen becomes full of hay before enough hay has been consumed to meet energy demands. The result is full cows that lose body condition.

Forages are good sources of vitamins A and E and minerals.

Should you test for all of the components listed? Depends on what your needs are. Dairymen require more precise measurements than a beef cow-calf producer. For many, testing for NDF, ADF, protein, calcium and phosphorus will be adequate, provided that you can calculate energy from ADF. For the majority adding TDN will be beneficial. Table 1 should help you further understand the quality of your hay once tested.

Table 1. Quality standards for legume, grass, or grass legume hay. Hay Market Task Force, American Forage and Grassland Council.
Quality
Standard
CP ADF NDF DDM DMI RFV
Prime >19 <31 <40 >65 >3.0 >151
1 17-19 31-35 40-46 62-65 3.0-2.6 151-125
2 14-16 36-40 47-53 58-61 2.5-2.3 124-103
3 11-13 41-42 54-60 56-57 2.2-2.0 102-87
4 8-10 43-45 61-65 53-55 1.9-1.8 86-75
5 <8 >45 >65 <53 <1.8 <75

Notes:  This does not include warm season grass hay or by-products. CP = crude protein, ADF = acid detergent fiber, NDF = neutral detergent fiber, DDM = digestible dry matter, DMI = dry matter intake, RFV = relative feed value.

 


Author: James Rogers, Livestock Specialist


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Forage Test Terminology

Neutral Detergent Fiber (NDF) is a measure of the total cell wall contents (cellulose, hemicellulose, and lignin). NDF is the portion of a forage sample left after extraction with a neutral detergent solution. It is expressed as a percentage and is directly related to intake, the higher the NDF value the lower the predicted intake. Research has shown that NDF intake will be limited to 1.1-1.2% of body weight.

For example: with a 1000 pound cow, 12 pounds of her intake may be in the form of NDF (1000 x 1.2% = 12). If the forage contains 65% NDF then her predicted intake of that forage per day would be 18 pounds (12/.65 = 18.5).

NOTE!  This equation is valid only for cool season grass hays and legumes. It is not a valid prediction equation for intake of warm-season grass hays or fibrous by-products. There is little relationship between NDF and digestibility and therefore indigestibility in these feeds. Use of this equation to predict intake will under-estimate actual intake of these feedstuffs.

A "prime" forage will have an NDF value of less than 40% while a "poor quality" forage would have and NDF value of greater than 65%.

Acid Detergent Fiber (ADF) is an estimate of all cell wall contents except hemicellulose. It is the portion of a forage sample left after extraction with an acidified detergent solution. ADF can be used as an estimate of the digestibility of a forage. Prime forages will have ADF values of less than 31% while low quality forages will have and ADF values of greater than 45%.

Crude Fiber is useful only to classify feeds as either a roughage or a concentrate. Roughages generally are classified as feeds with greater than 18% crude fiber. Concentrates would contain less than 18% crude fiber.

Crude Protein (CP) is the total amount of protein in a forage. It is calculated by measuring the total nitrogen content of a forage and multiplying by 6.25. CP is an indicator of forage quality; however, it is not a reliable predictor of animal performance due to the concept of the first limiting nutrient. If an animal's performance is limited due to low energy in the diet, excess protein will do little to increase performance. While excess protein can be converted to an energy source by the animal, it is an expensive way to meet energy requirements.

ADF-nitrogen (ADF-N) is heat damaged protein. Excessive heating after baling can cause some protein to become bound to the indigestible fiber portion. If an ADF-N value of 10% or greater is noted excessive heating has occurred. This portion is also included in crude protein.

Available protein is crude protein minus nondegradable portions such as heat damaged protein.

Total Digestible Nutrients (TDN) describes the energy value of a forage. It includes the sum total of the digestible portions of crude protein, crude fiber, nitrogen free extract and fat. It is expressed as a percentage. Prime hay will be 65% or greater TDN while poor quality hay will contain less than 53% TDN. TDN does not account for any energy losses that occur during digestion. Because of this, TDN values tend to overestimate energy values in forages.

Net Energy (NE) is a more exact measure of energy as it accounts for energy losses that occur in digestion. NE values are commonly expressed as megacalories per pound (Mcal/lb). NE can be further broken down to Net Energy lactation (NEl), Net Energy maintenance (NEm), and Net Energy gain (NEg). NEm refers to net energy for maintenance in beef cattle and NEl refers to net energy for lactation in dairy cattle. They are the same value and differ only in name and species application. Any energy excess above NEm in beef cattle is put toward NEg or net energy for weight gain.

Dry Matter Intake (DMI) provides an estimate in percent body weight of the intake of a forage. It is calculated by dividing 120 by forage NDF. Prime forages will have a DMI of greater than 3.0% while poor quality forages will be less than 1.8% of body weight. For example, a 1000 pound cow should consume 30 pounds of forage dry matter of a forage with a DMI estimate of 3%.

Digestible Dry Matter (DDM) is a measurement of energy. It may be calculated chemically or mathematically by using the ADF value. The higher the ADF the lower the DDM.

Relative Feed Value (RFV) is an index that combines the digestibility estimates of ADF and the intake estimates of NDF. A reference value of 100 is used, based on full bloom alfalfa. As it is an energy term, a hay with an RFV of 110 would have 10% more energy than full bloom alfalfa. Prime hay will have an RFV of greater than 151 while poor hays will have an RFV of less than 75. Comparing RFV values between cool season and warm season forages is not a valid comparison.

As-Fed Basis lists forage nutrient contents including water as you would normally feed it.

Moisture is the water content of the feed.

Dry matter (DM) is forage nutrient content minus water. These values will always be higher than As- Fed values as water acts to dilute nutrient content. For comparing feeds always use the dry matter basis.

Author: James Rogers, Livestock Specialist


 

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Barry Steevens' Tips for Winterizing Dairy Cows:

Windbreaks. Use old round bales or hang secured nylon shade cloth vertically. Cows should be protected from the wind for 30 minutes after milking to allow teats time to dry off and blood circulation to reestablish.

To be most effective, a windbreak should be 80% solid. If a windbreak is made with large round bales, spaces should be left between them that will amount to 20% of the length of the windbreak. For example, if a bale is 5 feet in diameter, a one-foot distance should be left between bales for the windbreak to be effective.

Feed. Increase daily hay and grain feeding by three to six pounds. Feed intake goes up 10 to 20 percent in cold weather. The extra feed maintains good body temperature.

Water. Make sure plenty is available. Caution: Electric heated waterers are notorious for stray voltage. If you see cows lapping at the water, that's a sure sign they are getting shocked.

Bedding. Give the cows straw or hay to lie on, not mud.

Teats and udders. Use a teat dip that has a skin conditioner (lanolin is good). Dry teats and udders before cows go outside. Fresh cows suffer from edema - swollen udders and teats that are subject to freezing - and they need treatment with teat dip containing a skin conditioner. Chapped teats can lead to mastitis.

Walking areas. Do what you can so cows don't have to walk through frozen mud. The sharp edges and holes can bruise or cut cows' feet.

Author: Barry J. Steevens, State Dairy Specialist, UMC

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University Outreach and ExtensionAg Connection - January 1998
http://outreach.missouri.edu/agconnection/newsletters/is-98-01.htm -- Revised: September 30, 2002
daydr@missouri.edu