Richard Taylor, Extension Agronomist; rtaylor@udel.edu
With the very hot weather upon us and many areas of the state very short of available soil water, it is time to think about possible emergency forages for those producers with livestock. The traditional cool-season pasture and hay grasses such as orchardgrass, timothy, and tall fescue are not very productive during the summer months when high temperatures and drought limit their productivity and quality. On the other hand, the warm-season grasses do not reach their maximum growth rates until daytime temperatures rise into the 90°F. Summer annual grasses such as forage sorghum, sudangrass, sorghum-sudangrass hybrids, pearl millet, and teff can provide high quality summer grazing and sometimes emergency hay for livestock in our region. Many of these species even germinate when soil moisture conditions seem to be too dry for successful establishment although it often is difficult to know for certain if they will germinate and establish in a given situation. Although late planting limits their yield potential, many of these grasses can be planted up until late July and still produce valuable and needed animal feed although the cost of production will make the feed expensive.
The term “millet” is loosely used to refer to a variety of grass crops whose seeds can be harvested for human or animal feed. The term is used differently depending on local customs and sometimes continental influences. For example in many parts of Asia and Africa, sorghums are called millet whereas in Australia the species called broomcorn in the U.S. is called broom millet. When compared with the more commonly grown cereal grains such as corn, wheat, barley, and milo (grain sorghum), the millets are generally suited to less fertile soils and areas of drought or excess heat.
Foxtail, Italian, or German Millet
Foxtail millet can be planted when it is too late in the season to make most other crops. It takes about 65 to 70 days to mature with summer temperatures and enough moisture to establish the crop. The crop requires warm to hot weather and matures quickly under warm conditions. It has a low water requirement although it can’t stand severe drought since it is characterized by a shallow root system. This annual grass forms slender, erect but leafy stems that vary in height from 1 to 5 feet. Foxtail millet usually won’t regrow following a harvest, unlike pearl millet. It’s been used in our region for a single harvest hay crop. Millets should be planted about two weeks after ideal corn planting time. Millets also have smaller stems and tend to be leafier than the forage sorghums, sudangrass, and sorghum-sudangrass crosses.
The primary use for foxtail millet hay is for sheep and cattle. This grass can cause problems if used as a major part of a horse’s diet so as hay it should not be sold as horse hay. Problems include a laxative effect, excessive urination (cystitis), and kidney and bone or joint problems. The chemical, glucoside setaria, is found in foxtail and proso millet and is reported to cause illness and even death in horses. Foxtail or German millet also can cause oral mechanical lesions.
Pearl Millet
Pearl millet is considered the most suitable millet species for horse grazing or hay. It has moderate to good nutritional quality if kept short (about 2.5 feet or less). Pearl millet is leafy, with an upright growth habit, and grows from 4 to 8 feet tall. There are dwarf or semidwarf types such as Tifleaf I, II, and III that are leafier and have less stem than the taller types. Although the taller types produce more dry matter than the dwarf types, the stems make hay making more difficult. Although still requiring a mower-conditioner to crush the stems to hasten drying, the newer and leafier pearl millets are far superior to the older tall-type pearl millets. Pearl millet is more tolerant of lower pH and low fertility than the sorghum species.
Pearl millet does not contain glucoside setaria as does foxtail or proso millet and unlike the sorghums does not have the potential to cause prussic-acid (HCN) poisoning in animals. If raising pearl millet to feed horses, do not allow it to go to seed since a fungus can infect the seed and causes an accumulation of a toxic alkaloid (similar to alfatoxins in corn). Since pearl millet should not be harvested for hay when seeds are present (due to the very low quality of the forage), alkaloid toxicity should not be of concern to horse hay buyers.
Japanese Millet
Also called barnyard millet or billion dollar grass, Japanese millet is grown principally as a forage grass. It resembles barnyardgrass and probably originated from that species. It makes the most rapid growth of all the millets when conditions are favorable and can ripen grain in as little as 45 days. It should be cut for hay before heading to be palatable and to make curing easier since the plant can have thick stems. Usually it is from 2 to 4 feet tall and does best on the better soils.
Teff
Teff is the common name for an annual lovegrass that is primarily used for grain in Africa and Europe but is also used for hay in South Africa and parts of Europe. It has excellent seedling vigor and good production and quality traits although it is somewhat shallow rooted so there is concern about grazing animals (especially horses) pulling it out of the soil. A couple of reports from this region suggest that it can be successfully grazed by horses if seeded in an existing pasture.
It has been grown as a summer annual on Delmarva and has been sold here as grass horse hay. Teff’s palatability and quality vary greatly perhaps due to our lack of experience as to when to harvest the crop. As a hay crop, it can be cut and windrowed at early head (flower or seed head) emergence but you should not wait until the head is completely emerged and flowering has occurred since quality and palatability will be very much reduced.
Sorghum, Sudangrass, Sorghum-Sudangrass Crosses
For sorghum, sudangrass, sorghum-sudangrass crosses, hybrid sorghums, and other sorghum species, horses should not be allowed to graze and should not be fed hay from these species. Forage cystitis, an inflammation of the bladder can result. Sorghum species also contain prussic acid that can be metabolized or converted into cyanide. Cyanide poisoning can cause muscle weakness, urinary tract failure, neural degeneration, and death. This generally happens if the sorghum is grazed when young immature growth is present (plant height under 18 to 24 inches or regrowth occurs following a period of stress conditions or regrowth occurs during a grazing cycle) or the crop is damaged by frost or freezing weather. After a frost or freeze and until the foliage dries out (about 1 week), it should not be grazed. Regrowth after a frost or non-killing freeze should not be grazed.
It is very important to consider not only the expected yield potential from the many species and varieties of sorghum but also the digestibility of the varieties. Some BMR (brown mid-rib) sorghum varieties are now available and these have been shown to differ in daily average gains by as much as 0.75 lb/day. This difference in quality can translate to huge differences in the cost of producing a pound of beef. Many companies tout the high yield potential for the various sorghums and millets and may show yields in the 6 to 7 tons/acre range. In excellent production years (plenty of heat and rainfall), these yields can be achieved but in drought years a more realistic yield expectation of 2 to 3 tons/acre (using the entire summer growing season) should be the basis of your decision. Dr. Chris Teutsch at Virginia Tech’s Southern Piedmont AREC has conducted yield trials on many of these varieties so when making decisions refer to his results.
Kleingrass is also not recommended for horse since it produces a condition known as photosensitization. This is similar to that seen with alsike clover where sensitive horses can become severely sunburned.
Other Potential Problems
Nitrate toxicity following heavy nitrogen applications can occur especially during periods of summer drought. If urea or ammonium-based fertilizers are applied to the crop, it is only a matter of time before the nitrogen fertilizer is converted by soil bacteria into the nitrate form. After nitrate is taken up by the plant, stress conditions such as dry weather can lead to the accumulation of nitrate in the lower stems of grass plants. Stress conditions include not only drought but also cloudy, cool weather following the rapid uptake of nitrates since both situations prevent the plant from transforming the accumulated nitrate into amines, amino acids, and proteins. This is generally slightly less of a concern with horses than with ruminants but nitrate levels can be in high enough concentrations that a potential toxicity problems can occur in horses.
Some species of millet can cause problems when grazed as lush pastures because they can contain significant levels of oxalates. The oxalates interfere with calcium absorption and horses can develop bone malformation and lameness. To date, this problem has primarily been seen in Australia and not in the U.S.