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Producing Emergency or Supplemental Forage for Livestock

Fred D. Kramer and Keith D. Johnson
Agronomy Department, Purdue University
Purdue University
Cooperative Extension Service
West Lafayette, IN 47907

When winter injury impairs forage crop stands, drought decreases forage crop yields, or additional livestock immediately increase forage needs, some nontraditional crops or nontraditional uses of commonly grown crops should be considered. The selection and management of emergency or supplemental forage crops require special consideration.

Summer-annual grasses provide excellent forage during the summer. Small grains can be mechanically harvested as silage or hay and can ease fall or spring shortages when grazing is possible. Brassica crops such as rape, kale, and turnips make good late-summer and fall pasture, but require advanced planning in order to have a sufficient growing season. Corn silage, crop residues, and soybeans can also be utilized by the livestock producer to help meet forage needs.


Summer-Annual Grasses

Shortages of forage most often occur during the summer. Commonly grown perennial cool-season grasses such as tall fescue and orchardgrass become semi-dormant during the hot summer months. During this period, cool-season grasses produce very little growth and shortages can quickly occur if moisture is inadequate.

Maintaining proper herd size, renovating pastures with a legume, fertilizing according to soil test, and utilizing a rotational grazing system can aid in reducing summer-forage shortages. However, during years of below-average rainfall, there can still be the risk of having a short supply of feed. Planting a summer-annual forage crop may then be justified. Since the need for extra forage usually becomes obvious after row crops have been planted in the early spring, summer-annual grasses are a good double-crop option when planted after a small grain has been removed as forage (late May-early June) or grain (late June-early July).

Productive summer-annual grasses are characterized by rapid growth in late spring and summer; they are used for pasture, green chop, silage, and hay. Use in Indiana is more common in, but not limited to, the southern sections of the state. These grasses include forage sorghums, sudangrass, sorghum-sudangrass hybrids (commonly referred to as "Sudax®"), and pearl millet. They can be valuable in the development of a year-round forage system.

With the exception of pearl millet, the summer-annual grasses previously mentioned are members of the sorghum family. The sorghum family is very large and includes several weeds such as shattercane and Johnsongrass. The crossing of johnsongrass and the cultivated crops will occur at a very low frequency. The result of this cross will be a plant that may or may not have rhizomes. These rhizomes would not be expected to over-winter in Indiana. Shattercane on the other hand, will readily cross with the cultivated crops to produce an annual "hybrid weed."

Utilizing the crop at an immature growth stage helps because the grass will not flower and, therefore, cannot cross with shattercane or johnsongrass. While male-sterile summer-annual grasses (pollen is nonfunctional but the female parts are intact) have been developed, these plants can be fertilized with pollen from other relatives in the sorghum family. Again, proper-cutting management will eliminate the risk of damaging populations of "hybrid weeds."

Weed problems with the summer-annual grasses more often arise from the seed source itself. Most summer-annual grass seed production occurs in the high plains of Texas. Several different wild sorghums exist in this area of the U.S.; and as a result, unwanted seed can be found in our seed supplies. By paying attention to the "percent-purity" figure on the seed tag and purchasing quality seed from a reputable dealer, many of these problems can be eliminated.

Summer-annual grasses to consider include the following:

Sudangrass is a rapid growing warm-season grass which can produce a good quality forage if managed properly. It usually contains lower levels of prussic acid than sorghum-sudangrass hybrids, but is also lower yielding.

Sorghum-Sudangrass Hybrids resembles sudangrass in growth, but the hybrids are taller, have larger stems and leaves, and generally produce higher yields. They are more likely to contain toxic levels of prussic acid than are other summer-annual grasses. This grass can become coarse and unpalatable if not utilized properly.

Pearl Millet is another annual grass that could be grown for supplemental forage. It tends to have smaller stems and is more leafy than the other grasses previously mentioned; it does not produce prussic acid. Slow growth and poor regrowth has caused the limited use of this grass in Indiana. It is more adapted to the warmer, more humid climates of the southeastern United States.



A well-prepared, firm, moist seedbed is best, though these grasses can be established in grass sods or stubble if no-till equipment is available. Two or more seedings may be desired to make rotational-grazing management easier or to spread out hay-harvesting time. However, yields of later plantings will be reduced due to hot, dry conditions in August and cooler fall temperatures. The seed should be broadcast and harrowed, lightly disked, or seeded with a grain drill. The seed should only be lightly covered by soil, 1/4 to 1 inch deep. More complete information on establishment, such as seeding rates and seeding dates can be found in Table 3.


Table 1. Nitrogen Recommendations for the Production of Summer-Annual Grasses.

                                    Yield Goal (tons dry matter/acre)
Previous Crop                        3-4                      5-6                6+
                                             lb. N per acre
Good legume stand (more               40                      90                120
than 4 plants/sq. ft.)

Average legume stand                  70                     120                150
(2 plants/sq. ft.)

Soybeans, corn, small                100                     170                200
grain, sorghum, grass

Table 2. Phosphorus (P205) and Potassium (K20) Recommendations for the Production of Summer-Annual Grasses.

   Soil Test Range     Soil Test              Yield Goal (tons Dry Matter/a.)
Bray P1     Exch. K      Level          3-4               5-6               6+
(lb./a.)   (lb./a.)
                                                       pounds per acre
                                     P2O5     K20      P2O5      K2O     P2O5      K2O
 0-10         0-80     Very Low     100     100       120      150      130      180
11-20       81-150     Low           70      70        90      120      100      140
21-30      151-210     Medium        50      50        60       70       70       90
31-50      211-300     High          30      30        40       50       50       60
  51+        301+      Very High     20       0        20        0       20        0

Table 3. Establishment Information for Emergency and Supplemental Forages.

Crop           Comments            Planting  Seeding  Emergence  First grazing     Hay         Palatability
                                     date      rate       time      (week)        yield
                                           (lb pure live (day)                 (ton/acre)
Sudangrass Rapid growth; medium     May 1 -    25         10          4             3-4          High
               prussic acid         July 15
             potential; used for
              pasture, silage,
             green chop, hay

Sorghum x   Rapid growth; high      May 1 -    20         10          4             4-5          Medium to
sudangrass   yield; high prussic    July 15                                                      high
hybrids     acid potential; best
            for pasture, silage,
               green chop

Pearl       Slower growth and       May 1-15-  20          7         4-5              3           High
millet      regrowth; no prussic    July 15
           acid; use as pasture,
           silage, green chop, hay

Winter        High yield; best     *Aug 15 -   120         7          4             2-4           High
wheat         as hay, pasture,       Sept 1;
            silage, green chop      Sept 15 -
                                     Oct 31

Winter      High yield; lower       *Aug15  -  112         7          4              -4          Medium
 rye        quality than wheat;      Sept 1;
           use as hay, pasture,      Sept 15 -
           silage, green chop        Oct 31

Winter     Lower yield; medium      *Aug15  -   96          7         4             2-3          Medium to
barley      quality; southern        Sept 1;                                                       high
           1/3 of Indiana only;      Sept 15  -
           best for hay, pasture,    Oct 15
           silage, green chop

Winter      High yield; lower       *Aug15  -  100          7         4              3-4          Medium
triticale  quality than wheat;       Sept 1;
           No market for grain;      Sept 15 -
           best as hay, pasture,     Oct 31
           silage, green chop

Spring     Lower yield; spring       Mar 1 -   96         10          4               2-3          High
oats         or fall grazing;        Apr 1 5
              use as hay,       or  *Aug 1  -
             pasture, silage,        Sept 1
              green chop

Brassica      High quality;          May 1 -   1 1/2,      10        10              4-6           High
crops         used for late-         July 1    turnips &
             summer or fall               swedes; 3 1/2,
                grazing                      kale & rape
*Seeding dates are for fall pasture usage. Other seeding dates listed
are for spring forage and grain.


Soil tests will provide the best information as to crop fertilization needs. In an emergency situation and when soil test levels for phosphorus (P) and potassium (K) are medium or higher, a good summer-annual forage crop can be grown without the addition of P and K fertilizers. If P and K soil-test levels are not known, fertilization will be similar to rates used to grow 100 to 150 bushels/acre corn. These nutrients should be incorporated prior to seeding.

Nitrogen (N) fertilization is critical to achieve high production. Split applications of nitrogen should be made. Half of the N should be applied and incorporated prior to seeding, and the remainder divided equally and applied after each cutting or grazing period to achieve the most efficient use of the nutrient. If the soil is dry, ammonium nitrate is the preferred topdress material. Urea may be used, but it needs to be applied just prior to rainfall or the rates need to be increased 10-20% to compensate for volatilization losses. Be realistic with yield goals; yields will be reduced if the full-growing season is not utilized. Tables 1 and 2 outline fertilizer recommendations for summer-annual grasses.



Summer-annual grasses respond best to rotational-grazing systems. Millet, sudangrass, and sorghum-sudangrass hybrids may also be harvested and fed as green chop, silage, or hay. During a feed-shortage year, green chopping is an efficient way to stretch feed supply, but it is time consuming and somewhat weather dependent. When making hay, a mower-conditioner should be used to increase the drying rate. Even when a mower-conditioner is used, haymaking can be difficult because of the high moisture content and large stems. Table 4 gives more information on harvesting summer-annual grasses. blke


Table 4. Harvest Information for Summer-Annual Grasses and Brassica Crops.

                                           Desired Use

            Silage and           Fall Pasture                 Summer Pasture
                            When to      When to      When to   Height after Interval
                            graze        terminate    graze       grazing    between
                                         grazing                  (inches)   grazings
Crop                                                                         (weeks)
Sudangrass    Prior to                  Frost (may                              2-3
             boot stage                resume 5 days
Sorghum X     or when                   after killing
sudangrass   36 in. tall    18-30 in.      frost)       18-30        6-8
----------			      ---------------		            ---------
Pearl                                     When                                  3-4
millet                                    utilized
Brassica                     10 wk.    When roots       10 wk.
crops        Not recom-   after summer  and tops        after
              mended        seeding    are utilized     spring         5         3

Potential Animal Health Hazards

The two most frequently reported animal health problems associated with summer-annual grasses are prussic acid poisoning and/or nitrate poisoning.

Prussic-Acid Poisoning occurs in sudangrass and sorghum-sudangrass hybrids. In general, ruminants are more susceptible to prussic-acid poisoning than swine or horses. Toxic levels of prussic acid occur most commonly after a killing frost or drought. For more information on prussic acid poisoning, refer to Extension Publication AY-196 Minimizing the Prussic-Acid Poisoning Hazard in Forages.


Nitrate Poisoning usually occurs when high rates of nitrogen fertilizer are used in one application and then a drought or sudden weather changes occur. High-nitrate levels are especially found in the lower stems. The nitrate in plants harvested for hay does not dissipate as it cures, so problems can occur when the hay is fed. There can also be problems in grazing the stubble in the fall and winter after the leaves and upper parts of the plants are consumed and livestock begin eating the lower parts of the stalk. Nitrate poisoning can occur in pearl millet as well as in the sorghum-sudangrass hybrids and sudangrass.

Sorghum Poisoning of Horses occurs as an infection of the urinary tract, called cystitis, when horses graze on sorghum. The concern is reduced when the forage is harvested as hay.


Utilization and Animal Performance

When summer-annual grasses are harvested at the proper growth stage, digestibility will be moderate to high and animal performance will be good. As these plants mature, they will be higher in fiber which reduces the feeding value.

Performance of livestock fed summer-annual grasses should be similar to those fed low-endophyte tall fescue or orchardgrass. If these summer-annual grasses are maintained at an immature growth stage, crude protein and digestibility values could be slightly higher than those of tall fescue and orchardgrass.


Small Grains

Some of the more traditional crops that can be used for emergency or supplemental forage include small grains such as wheat, rye, barley, and spring oats. Triticale, a nontraditional small grain, can also be used for these purposes.

Soft Red Winter Wheat is an excellent fall and spring pasture which is high in digestibility. Because of it its excellent winterhardiness, wheat can be sown later in the fall and withstands wetter soils than barley can tolerate. Wheat can produce more tonnage than barley and is of higher quality than rye. After proper fall or early-spring grazing, it can be harvested for grain, silage, or hay.

Winter Rye is the most winterhardy of the small grains. Quick growth in both fall and spring make it the most productive of the small grains for pasture. Rye is of poorer quality than the other small grains and can become unpalatable if allowed to mature past the boot stage.

Winter Barley can supply good quality grazing in the fall if seeded early, and it should not be grazed as close or as late in the fall as wheat or rye. Spring-grazing period. will be similar to rye. Good quality silage can be obtained from barley, but the awns make it less desirable than the other small grains for hay. Because barley lacks winterhardiness, it should only be grown in the southern third of Indiana.

Winter Triticale can be used for late fall and early-spring pasture, silage, or hay. It is managed similarly to wheat and has a higher forage yield but lower quality as compared to wheat. It is not commonly harvested for grain as no cash markets currently exist.

Spring Oats is commonly used as a companion crop for seeding legumes; it may be used as hay, silage, or pasture in spring and early summer when sown in the early spring. Spring oats may be sown in August for fall pasture, but it will be killed by frost and will not produce spring growth. It is better adapted to northern than to southern Indiana.


Establishment and Fertilization

Seeding small grains for forage should be done in the same manner as for grain. As a general rule, a firm, fairly smooth, shallow seedbed is desired. A drill is the preferred seeding method, although broadcasting followed by a harrowing or disking can be an acceptable seeding method. Aerial seeding into standing crops can also be made, but seeding rates should be increased by about 20%.

Fertilization of small grains for forage should be heavier than for grain production. Increase N, P2O5, K2O fertilization by a third if the crop will be harvested as both pasture and grain. High nitrogen rates on small grains can increase lodging and the likelihood of nitrate poisoning. Split nitrogen applications will help reduce these problems.

Soil tests should be taken and fertilizer applied according to the soil-analysis results. Table 3 of this publication gives establishment information.



Grazing small grains is difficult in most of Indiana because of delayed planting dates and wet fields during the prime grazing season. Sandy fields in southwestern Indiana, however, are commonly grazed. Heavy-fall grazing increases the danger of winter kill, except when excessive fall growth exists. Heavy or late-spring grazing can greatly reduce grain yields. Remove livestock from small-grain pastures to be harvested for grain when "jointing" of the crop is first observed. Rye will begin to joint two weeks ahead of wheat and five weeks ahead of oats.

Small grains are more commonly harvested for forage as silage or hay. The stage of harvest is critical in determining feeding value. Recent Purdue research data indicates dry matter yields increased from 2.3 to 5.0 tons per acre as small grain harvest was delayed from boot to soft-dough maturity stages. Associated with the increased yield was reduced forage quality. Crude protein content declined from 9.9 to 4.6%, and digestibility declined from 68.3 to 54.8% as the small grains matured. It is apparent the livestock species and the class of livestock (e.g., gestating or lactating) as well as the effect of planting date upon the succeeding crop's yield are critical factors in determining when the small grain should be harvested. Regardless of the growth stage at which the small grain is cut, a mower-conditioner should be used to increase the drying rate. Table 5 has specific harvest information.


Table 5. Harvest Information for Small Grains.

                                     Desired Use
Silage or hay1      Fall Pasture2,3                     Spring Pasture4
               When to     Height after    When to       Height after  Interval between
                 graze      grazing          graze        grazing         grazings5
Boot to early    6 in.      2-3 in.        When growth    3-4 in.         2-4 wk.
heading stage                              begins until
                                           jointing if grain
                                           is desired
1 Harvest later for more tonnage but lower quality.
2 Do not graze when small grain is dormant or when the ground is frozen.
3 Fall pasture only early-seeded small grains. Spring oats can be grazed until utilized.
4 Ground should be firm (not wet).
5 It a grain crop is desired small grains can only be grazed one time during the spring.

Animal Performance and Utilization

Small-grain forages will be similar to orchardgrass and low-endophyte tall fescue in feed value. Properly harvested cereal-grain forage will range from 8.5 to 12.5% crude protein and 52 to 66% total digestible nutrients (TDN). These factors indicate that as far as animal feeding is concerned, small-grain forage can be substituted for orchardgrass or low-endophyte tall fescue on a one to one basis.

Animal health concerns are not as prevalent with the small grains as they are in the summer-annual grasses. General rules include:

  • 1. When turning lactating animals out on lush spring pasture, supplement with high-magnesium mineral blocks or mineral-salt mixtures to reduce the incidence of grass tetany.
  • 2. If seed is treated with a fungicide or other type of treatment, be sure to follow harvest restrictions on the label. In some cases, the forage may not be grazed for 6 weeks after planting.
  • 3. Remove dairy animals from small-grain pasture 2 hours before milking to reduce the problem of off-flavored milk.
  • 4. Split nitrogen applications to avoid nitrate poisoning.


Other Crops

Brassica Crops (turnips, kale, and rape) can be described as high-yielding, high-quality, and fast-growing biennial crops. The crop is utilized the seeding year only. The most common usage is for late-summer or fall grazing.

The crops are about 85 to 95% digestible by farm animals. Leaf crops (kale and rape) contain up to 25% protein in the leaves and about 10% protein in the stems. Root crops (turnips) have about 13% protein in the leaves and approximately 8% protein in the roots.

Brassica crops can be sown with no-till equipment, a forage-crop drill on a conventional seedbed, or broadcast and followed by cultipacking.

Soil fertility is very important for good yields. Seventy-five pounds of N per acre is recommended. If soil tests are medium in P and K, 60 pounds of P2O5 and K2O should be applied. If soil tests are lower, additional amounts of P & K should be used.

More information on brassica crops can be found in Tables 3 and 4.

Soybeans can be used for hay or silage, should the need arise. They will make high-quality feed if the plants are cut when the seed pods are still green. To reduce the selective grazing of livestock consuming leaves and not stems, the soybeans are best utilized as silage instead of as hay. Mid-season, tall-growing varieties will provide the highest yields.

Soybeans will require more curing time than other hays. The use of a mower-conditioner is recommended. Feed value will be similar to good red-clover hay.

Corn Silage can be used as green chop or made into silage. Silage should be made when the "black layer" forms. This is an indication of maturity and will result in the highest attainable yield and quality.


Crop Residues

Crop residues are a very economical source of feed to supplement pastures. Corn, grain sorghum, small grains, and soybeans are the major crop residues grazed. Corn fodder will average between 3 to 4% protein and yield about 1 ton per acre of usable feed. With proper management, salt, mineral, and vitamin A are the only supplemental feed required for mature beef-cows grazing corn residue during the first third of gestation.

Some residues can also be baled for bedding or feed. A stalk chopper and hay rake should be used before baling. The packaged feed will be of similar quality to the residues in the field, but the baling process is hard on equipment because of an excessive amount of soil contamination.


Other Considerations

When emergency or supplemental forage crops are needed, the economics of production should be considered. The variable, or direct costs,. of producing pasture or hay may be higher than that of purchased forage. Generally, it is assumed that when weather dictates the need for "emergency" forage, local hay prices will also be high. This is an assumption many people make, but if the time is taken to price and compare these costs with the production costs of supplemental forage, buying hay may prove to be the most economical alternative. The availability of machinery and forage handling equipment will also play an important role in determining the economics of producing emergency and supplemental forage.


RR 7/88

Cooperative Extension work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture cooperating: H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Cooperative Extension Service of Purdue University is an equal opportunity/equal access institution.



For more forage information contact Dr. Keith Johnson: johnsonk@purdue.edu

Copyright © 2007, Purdue University, all rights reserved.
An equal access/opportunity university.

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