Forages

Forage options continue to increase. Producers must continually re-evaluate their forage programs to see if improvements can be made. Harvest maturity recommendations vary by forage type. Forage quality is greatly impacted by maturity of the crop. Methods have been developed to calculate first-cutting date and quality of alfalfa. Ideal length of cut at harvest will depend in part on total ration composition. The goal is to have 15% of the particles greater than 1.5 inches (3.8 cm). Moisture content recommendations for hay crop silage and corn silage partially depend on the storage structure.

It is important to critically assess the types of forages grown on a farm and the specific hybrids or varieties used. Agronomists are continually improving our options. Just because a particular blend of forages has worked well in the past does not mean that it is necessarily the best choice for the future.

Computer programs are now available to assist in looking at all of the factors that impact the question of what to grow. These factors include: climate, soils, labor, equipment, number of cows, production level, manure management and environmental considerations.

The following is a review of some common forages:

Alfalfa is one of the most common forages in North America. It is a perennial legume which makes its own nitrogen, so nitrogen fertilization isn’t necessary. It needs good drainage, a soil pH near 7.0 (neutral), good fertilization (especially with potassium), and pest control. It has a deep root system that helps it to survive in dry conditions. It is harvested as dry hay or silage. The nutrient analysis of alfalfa varies with maturity. If harvested in early bloom, it may have the following analysis (DM Basis): 18% CP, 32% ADF, 42% NDF.

The selection criteria for alfalfa varieties should include yield, winter hardiness, disease resistance (phytophthora, verticillium wilt, bacterial wilt), and quality. There are new varieties that have grazing tolerance and leafhopper resistance.

When Do I Harvest Alfalfa?

Generally, it is recommended that alfalfa be harvested at the mid- to late bud stage. Alfalfa should be harvested when it has 40-45% NDF. Ideally, harvest should begin at 38-40% NDF and end at no higher than 45% NDF. According the Michigan State University research, for every one unit increase in NDF percentage over 40% NDF, there is a 0.69 unit decrease in protein, a 0.84 unit decrease in NDF digestibility, and a 0.83 unit decrease in dry matter digestibility. This has been estimated to have a subsequent cost of $0.05/cow/day in additional concentrate, $0.06/cow/day in lost milk production, and $0.01/cow/day in lowered dry matter intake. This equals $0.12/cow/day or $36.00/cow/year.

Using Growing Degree Days for First-Cutting:

For first-cutting in a year with adequate rainfall, growing degree days (base 41oF), rather than calendar date, should be used to decide when to cut alfalfa. The NDF content of alfalfa has been shown to vary by as much as 10 percentage units from year to year when harvested on the same calendar day. That variation is reduced when growing degree days are used. Start cutting at 750 growing degree days and finish before 970 growing degree days.

The method of calculating growing degree days is different for different crops. To calculate growing degree days for alfalfa, take the average of the minimum and maximum temperature for each day beginning on March 1st. Subtract 41oF from each daily average. Add up all of the growing degree days that are positive numbers. Minimum/maximum thermometers are fairly cheap to purchase, so you can calculate the growing degree days for a specific farm.

Predicting First-Cut Alfalfa Quality in the Field:

Methods have also been developed to determine when to cut alfalfa based on visual inspection.

  • A representative 2 sq. ft area is chosen in the field.
  • The stage of the most mature stem in the area is determined.
  • Late Vegetative – Stem more than 12 inches; no buds or flowers
  • Early Bud – 1-2 nodes with buds; no flowers or seed pods
  • Late Bud- 2+ nodes; no flowers or seed pods Early Flower – 1 node with at least one open flower; no seed pods
  • Late Flower – 2 or more nodes with an open flower; no seed pods
  • Calculate the effective height of the tallest stem by measuring the length of the tallest stem from the soil to the top tip of the stem (not to the tip of the leaf) and subtracting 1.5 inches from that measured height.
  • Use developed tables to determine the NDF content of the forage in the field
  28 29 30 31 32 33 34 35 36 37 38
Late Veg. 36.2 36.7 37.3 37.8 38.4 38.9 39.4 40.0 40.5 41.1 41.6
Early Bud 37.6 38.2 38.7 39.3 39.8 40.3 40.9 41.4 42.0 42.5 43.0
Late Bud 39.1 39.6 40.2 40.7 41.2 41.8 42.3 42.9 43.4 43.9 44.5
Early Flower 40.5 41.1 41.6 42.1 42.7 43.2 43.8 44.3 44.8 45.4 45.9
Late Flower 42.0 42.5 43.0 43.6 44.1 44.7 45.2 45.7 46.3 46.8 47.4

Adapted from M. Rankin, UW Extension Crops and Soils Agent in Fond du Lac County. Procedures and tables used are derived from equations developed by Owens et al. (1995).

Grass and Alfalfa Mixes

 

Often grasses such as orchardgrass, reed canarygrass or timothy, are seeded with alfalfa (especially areas like the Northeastern U.S.). Grasses have a higher NDF content than alfalfa so, of course, the percent grass in the field will affect the NDF content of the forage that is harvested. The above methods used for predicting alfalfa quality cannot be directly used for alfalfa/grass mixes. It is generally recommended that fields with a lot of grass be harvested first. Grasses should be harvested at the late boot to early head stage.

Grasses

Timothy is a perennial grass grown in cooler climates such as the Northeastern U.S. It is rarely planted as a pure stand but is common as a companion crop with alfalfa or clover. It is recommended that it be cut in the late boot to early head stage. It rapidly matures and decreases in quality after the early head stage. Early bloom timothy may contain 15-17% CP, 32% ADF, and 60% NDF.

Orchardgrass is another perennial grass grown in cooler climates such as the Northeastern U.S. It should be cut in the late boot to early head stage. It also rapidly matures. Early bloom orchardgrass may contain 15-17% CP, 32% ADF, and 60% NDF.

Bromegrass is a cool season perennial grass often grown as a companion crop with alfalfa. It should be cut in the late boot to early head stage. It also matures rapidly. Early bloom bromegrass may contain 15-17% CP, 32% ADF, and 60% NDF.

Red Clover is a perennial legume often grown in soils which are not well-drained enough to grow alfalfa. Red clover should be cut at the first flower to 1/10th bloom stage.

Early bloom red clover may contain 16-18% CP, 35% ADF, and 45% NDF.

At What Moisture Should Hay Crop Silage Be Chopped?

Type of Silo Moisture
Bunker Silo 60-70%
Bagged Silage 60-70%
Upright Stave Silo 50-60%
Oxygen-Limiting Silo 40-50%

What Length Should Hay Crop Silage Be Chopped?

3/8 inch (0.95 cm) Theoretical Length of Cut (TLC) is a common recommendation. But, most importantly, the actual length of the forage coming out of the chopper should be analyzed. More than 15-20% of the particles in hay crop silage should be over 1.5 inches (3.8 cm) in length.

General Recommendations for the Penn State Forage Particle separator:

  Coarse, >0.75 inch Medium Fine, <0.31 inch
Hay Crop Silage 20-25% 30-40% 35-50%

It must be recognized that the ideal length of a particular farm’s hay crop silage will depend in part on the rest of the ration because the goal is to have 15% of the particles in the ration over 1.5 inches (3.8 cm) in length. If the corn silage will be finely chopped and makes up a significant part of the ration, hay crop silage will have to be chopped longer. If long hay makes up a significant part of the ration, one may be able to cut the hay crop silage shorter.

Corn Silage is a popular forage grown in North America primarily as a source of energy for dairy cows. It generally contains about 8% CP, 28% ADF, and 50% NDF. Selection criteria for corn hybrids planted for corn silage includes: maturity, quality, and yield. Longer day hybrids have the advantage of higher tonnage but are riskier in terms of maturation and poorer ensiling conditions later in the fall.

Historically, corn breeders concentrated on improving grain yield, increasing kernel dry down speed, and increasing kernel hardness. Of course, this emphasis was primarily for the purpose of grain production. In the last decade, there has been a focus to specifically produce “silage hybrids” which are planted for silage rather than just having “grain hybrids” which could be used for grain or silage production. The goal for silage hybrids is to have greater starch and NDF digestibility, lower NDF, slower kernel dry down speed, soft kernel texture, and both high grain and forage yield.

Brown Midrib Corn (BMR) is a specific hybrid developed to have high fiber digestibility. It fiber content (ADF and NDF) is only slightly lower than that of traditional hybrids. But, the fiber in this hybrid is digested to a greater extent in the rumen. Therefore, BMR corn has a higher energy content than standard corn hybrids. Part of the reason for the increase in NDF digestibility is the reduced amount of lignin in the BMR corn. Lignin is a woody, indigestible complex that forms linkages with the rest the cellulose in the plant and reduces fiber digestibility.

BMR Corn Silage Study at Michigan State University (Allen et al., 1997)

(%) BMR Corn Silage Normal Corn Silage
DM 31.4 34.4*
NDF 43.8 44.7
ADF 22.6 24*
Lignin 1.7 2.8*
NDF Digestion 49.9 41.5*

* Differences were statistically significant

When normal corn silage is replaced with BMR corn silage in the diet, dry matter intake and milk production usually will increase. With an increase in NDF digestibility, fiber leaves the rumen more quickly, causing the cow to feel hungry more quickly following a meal and eat more.

Michigan State University Study in which Corn Silage Made Up 44.6% of the Ration (Oba and Allen, 1997)

  BMR Corn Silage Normal Corn Silage
Dry Matter Intake (lbs) 56.1 51.7*
Milk (lbs) 91.5 85.6*
3.5% Fat Corrected Milk (lbs) 90.0 84.5*
Body Condition Score Change over 28 days +0.11 +0.02*

* Differences were statistically significant

BMR corn silage does have a lower dry matter yield and problems with its standability in the field have been noted. BMR corn is also more costly to plant. Care should also generally be taken to increase the amount of total NDF (%) in the ration and decrease amount of grain fed in the ration when using BMR corn silage. Otherwise, the risk of rumen acidosis is higher.

When Do I Harvest Corn Silage?

Generally, corn silage should be harvested when the milkline is ½ of the way down the kernel. But, care should be taken to also harvest corn at the right moisture content. Milkline does not always correlate with moisture content. Use milkline as an indicator of when to start checking moisture. It is recommended that a few plants be chopped and moisture determined starting when kernels are dented and the milkline can be seen. Harvest when the moisture content of the whole chopped plant is between 65 and 70%. The only exception may be to chop corn for upright silos at 60-65% moisture to minimize seepage. Any corn chopped at 60% moisture or less should be chopped finer to try to increase digestibility but it must be recognized that digestibility will still be compromised despite the extra chopping.

What Length Should Corn Silage Be Chopped?

Corn silage should be chopped at 3/8-1/2 inch (0.95 – 1.27 cm) Theoretical Length of Cut (TLC). This should result in 20-25% of the particles being greater than ½ inch (1.27 cm). For a particular theoretical length of cut (TLC) on a chopper, kernel processors can decrease particle size by 15-30%. Processing enhances the packing of silage. If processed corn silage will make up over 40% of the ration dry matter, increase TLC to ¾ inch (1.9 cm) by manipulating the shear bar or by removing knives from the chopper. This will allow one not to rely as much on hay crop silage for ration effective fiber.

For dry (less than 60% moisture), unprocessed corn silage, the TLC must be reduced to ¼ inch (0.64 cm) and a recutter screen may be needed to break the kernels and cobs and avoid the problem of cows sorting at the feed bunk. BMR corn should not be chopped at less than ½-inch TLC.

General Recommendations for Particle Size:

  Coarse,0.75 inch Medium Fine,0.31 inch
Unprocessed Corn silage 10-15% 35-45% 35-45%
Processed Corn Silage 20-25% 30-40% 35-50%

Cereal Grain Forages are cut during the boot to early head stage and the plant contains 55-65% moisture. Digestibility is rapidly reduced after head formation. Cereal grain forages would include barley, oats, wheat, rye and triticale. Nutrient content of these forages may be about 16-17% CP, 36-38% ADF, and 56-59% NDF.

Sorghum Sudangrass is a summer annual grass. It is harvested four to eight weeks after planting with three to five cuttings per season. Harvest at boot stage. This is just before the head emerges and the plant is 3-4 feet tall. Usually it is planted instead of corn when either more drought or flood tolerance is needed. Sorghum Sudangrass may have 7-8% CP, 36% ADF, and 60% NDF. It has about 10-20% less energy than corn silage. BMR Sorghum Sudangrass has recently been introduced and looks promising.

References:

Allen, M. Timing Spring Harvest. In: Managing Forages for More Profit: 1997 Michigan State University Extension Statewide Program for Michigan Dairy Producers and Agribusiness.

Allen, M.S., M. Oba, D. Storck, and J.F. Beck. 1997. Effect of brown midrib 3 gene on forage quality and yield of corn hybrids. J. Dairy Sci. (Suppl. 1) 157.

Cherney, J.H. and R.M. Sulc. 1997. Predicting first cutting alfalfa quality. In: Proceedings from the Silage:Field to Feedbunk North American Conference, Hershey, PA.

Macgregor, C.A. 1994. Directory of Feeds and Feed Ingredients. W.D. Hoard & Sons Company.

Mahanna, B. 1997. Dairy Cow Nutritional Guidelines – Part 1. Pioneer Hi-Bred International, Inc. Website (www.pioneer.com)

Managing Forages for More Profit: 1997 Michigan State University Extension Statewide Program for Michigan Dairy Producers and Agribusiness.

Oba, M. and M.S. Allen. 1997. Effect of NDF digestibility of corn silage on DMI and milk production of high producing dairy cows. J. Dairy Sci. (Suppl. 1) 157.

Owens, V.N., K.A. Albrecht, and R.W. Hintz. 1995. A rapid method for predicting alfalfa quality in the field. J. Prod. Agric. 8:491.

Shaver, R.D. 1995. Look at the bunk when there are feeding problems. Hoard’s Dairyman. December 1995.

Shaver, R. Silage Preservation – The Role of Additives. University of Wisconsin-Cooperative Extension. A3544.

Shaver, R., J. Lauer, and K. Shinners. 1999. Five common questions about making corn silage. Hoard’s Dairyman. July 1999. P. 490.

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Author

Mary Beth de Ondarza

Mary Beth de Ondarza
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Nutritional consultant for the dairy feed industry at Paradox Nutrition, LLC.

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Dr. de Ondarza received her Ph. D. from Michigan State University and her Masters Degree from Cornell University, both in the field of Dairy Nutrition.

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Paradox Nutrition

Paradox Nutrition

Paradox Nutrition, LLC is a nutritional consultation business for the dairy feed industry. Mary Beth de Ondarza, Ph.D. is the sole proprietor.

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