The warm-season annual grasses utilized for pasture, greenchop, silage, or hay are an excellent supplement for perennial cool and warm-season meadows and pastures. Most cool-season grasses become semi-dormant during the hot summer months, and most warm-season perennials provide forage relatively low in protein at this time of the year. The warm-season annuals are most productive during the months of July, August, and September and provide a high quality forage.
Warm soil temperatures (70 to 80 degrees Fahrenheit) are essential for rapid, uniform emergence, growth, and development. Once established, the summer annuals adapt to both hot and dry conditions.
There are several members of the sorghum and millet families utilized as warm-season annuals. The sorghums utilized include: grain sorghums, sorgos, grass sorghums, and sudangrass. The most widely used millets are pearl millet and in more northern areas foxtail millet. The importance and prominence of forage sorghums increased rapidly in the 1960’s with the advent of improved hybrids. Likewise, improvement of pearl millet cultivars and hybrids has led to its increased usage while most other millets are declining.
The warm-season annual grasses are often cut for hay. During a growing season two to five cuttings may be attempted, each with a potential yield of three tons per acre or more. Plants are difficult to cure because of their thick stems; even sudangrass and pearl millet with thinner stems may be difficult to cure because of the large amount of forage to be dried. Sunshine, wind, and the use of a crimper help reduce the time required to dry these products.
Livestock are the most economical harvesters of any forage. However, grazing summer annuals demands considerable management skill. Planting rates and stocking rates must be carefully adjusted to efficiently utilize forage and maximize animal performance. The threat of prussic acid poisoning in the sorghum family and nitrate poisoning in both sorghums and millets are real concerns. Grazing often leads to waste due to trampling or fouling by excreta. All of these issues must be addressed by the producer/manager in order to effectively utilize warm-season annual grasses for pasture.
Utilizing sorghums and pearl millet as silage or greenchop for dairy cows is an increasingly common practice. Management of forage sorghums for silage is similar to that of corn silage. Proper moisture content (65% to 70%), length of cut, packing, and avoidance of air and moisture are critical in the making of good quality silage.
Sorghums become progressively less digestible as they mature. Thus, it’s imperative to harvest when whole plant moisture is in the range of 65% to 70%. Silage inoculant may be necessary as the relatively high moisture of these forages is favorable for butyric acid producing bacteria. These bacteria result in bad smelling, unpalatable feed. Silage inoculant will decrease butyric acid production and speedup fermentation time.
Hi-Gain II is a versatile product utilized for haying, grazing, silage, haylage, or greenchop. Small seeded (approximately 20,000 seeds per pound), Hi-Gain II is a vigorous, fast growing forage with slender, sweet stems and good foliar disease resistance. High in protein (particularly in the first cutting), Hi-Gain II provides rapid weight gain for livestock and high milk production for dairy and beef herds. Widely adapted to varying soil types and climates, Hi-Gain II is productive anywhere in Kansas. As with all the sorghum products, prussic acid accumulation is possible and care must be exercised in the management of Hi-Gain II to minimize the risk.
Seeding Rate: 25 to 40 Lbs. per acre
Planting Date: May (when soil temperature approaches 70o)
Prussic Acid Poisoning: Possible - Manage to avoid
Nitrate Poisoning: Possible - Manage to avoid
Harvest Frequency: 1st cutting 45 to 55 days after emergence,
subsequent cuttings every 30 to 40 days.
Utilization: Haying, Grazing, Silage, Greenchop, Haylage
DO NOT FEED OR ALLOW HORSES TO GRAZE ANY SORGHUM PRODUCT!
The hybrid sorghum/sudans and sorgo/sudans are versatile, high yielding forages. These products are best utilized by haying, silage, or ensilage, or by greenchopping. They produce greater yields of dry matter per acre than other sudan-type crops. However, the forage produced is generally of lesser quality. Daily gains of livestock grazing the sorghum/sudans have been disappointing when compared to the other summer annuals. This is due in large measure to the thick stems, which translate into high crude fiber and low palatability. Large stem diameters can be tempered somewhat by high plant populations.
When managing sorghum/sudan for pasture or hay production, fertilize with 40 to 60 lbs. actual nitrogen preplant. Then apply 20 to 30 lbs. nitrogen after each cutting or grazing. If managing for silage 50 to 70 lbs. nitrogen should be applied preplant. Potash and phosphate materials should be supplied as determined by soil tests.
The sorgo/sudans are generally sweeter and juicier stalked than the sorghum/sudan crosses. The sorgo/sudans are also smaller seeded and thus are more economical as a given weight of seed will plant a larger area.
Graze-all BMR Brown Mid-Rib
Graze-all BMR is a breakthrough product with exceptional palatability. The brown mid-rib trait results in marked reductions of lignin content in the plant. Lignin is the component of the plant cells that is generally regarded as the primary factor limiting the extent of forage fiber digestion. Graze-all has consistently demonstrated a nearly 19% average increase in feed value when compared to traditional sorghum/sudans. This increased feed value can net the producer an additional $40.00 plus per acre (based upon feed at $60.00 per ton). The brown mid-rib trait is perhaps the biggest technological event of recent forage breeding.
Seeding Rate: 25 to 40 Lbs. Per acre
Planting Date: May (when soil temperature exceeds 65o)
Prussic Acid Poisoning: Possible - Manage to avoid
Nitrate Poisoning: Possible - Manage to avoid
Hybrid Pearl Millet
Hybrid pearl millet is very fine-stemmed when compared to the sorghums. This leafy forage is well-suited to grazing or haying. While hybrid pearl millet generally yields less forage per acre then sorghum crops, it nevertheless has consistently produced more beef per acre than the sorghums in university trials. What hybrid pearl millet lacks in quantity, it makes up for in quality.
Producers like the fact that there is little or no danger of prussic acid accumulation in hybrid pearl millet and that unlike the sorghums; it can be utilized for horses.
Hybrid pearl millet is susceptible to the triazine herbicides where the sorghums are not. Thus, previous cropping and herbicide history should be considered.
When haying hybrid pearl millet, leave 8 to 10 inches of stubble to promote a rapid, leafy regrowth. Cut whenever forage obtains a height of 3 ½ to 4 feet for maximum quality.
Hybrid pearl millet utilized for pasture should be allowed to reach a height of 12 to 18 inches before stocking with livestock. The most efficient utilization of available forage occurs when pearl millet is grazed intensively and then allowed to rest sufficiently long enough for regrowth to occur.
Excel forage sorghum is widely adapted to Kansas. It is a medium maturity forage sorghum with the potential to produce a high quality silage. Grain yield will range from about 35% to 40% of total forage. Plant height will range from 7 to 10 feet and standability is rated as excellent. Low seeding rates (3 to 5 Lbs. per acre) make Excel forage sorghum economical to plant. Excel forage sorghum competes favorably with corn silage from a standpoint of yield and quality, utilizing considerably less water.
Seeding Rate: 3 to 5 Lbs. per acre
Planting Date: Mid-May (soil temp. 70o plus)
Prussic Acid Poisoning: Minimal danger if utilized as silage.
Nitrate Poisoning: Possible - Manage to avoid
Utilization: Silage or haylage
Energy: High (high grain to roughage ratio)
DO NOT FEED OR ALLOW HORSES TO GRAZE ANY SOGHUM PRODUCT!
The forage sorghums are used almost exclusively for the production of silage. These sorghums generally compete very well with corn silage from the standpoint of yield and quality, and they do so with considerably less water.
Forage sorghums should be harvested when seed are in the milk to dough stage, before leaves reach senescence. Earlier or later harvest will effect quality, energy, and/or yield. Length of silage cut at the soft dough stage should be ½ inch, and at medium to hard dough the cut should be 3/8 inch.
Milk production is greater with hybrids having good grain to roughage ratios. The highest quality silage is obtained when grain makes up 25% to 35% of the dry matter yield.
German Strain R
German Strain R Foxtail Millet, selected in Texas by the late J.R. McNeill, is relatively early, fine-stemmed, and leafy with compact cylindrical heads. The spines of the heads tend to be reddish purple in the immature stage but become straw-colored at maturity. The variety has good seedling vigor and is resistant to lodging. It is commonly used for haying and grazing.
Seeding rate: 15-25 lbs per acre
Planting date: Mid-May to July 1 (after soil temperature reaches 70 degrees Fahrenheit)
Maturity: 75-80 days
Fertilize with 50-75 lbs nitrogen and phosphorus and potassium according to soil test.
Members of the sorghum family have been reported to cause “cystitis” syndrome in horses. Cystitis (inflamed urinary bladder) is characterized by uncontrolled urination, abortion or stillbirths in mares, and by the inability to coordinate rear quarters. Cystitis affects only horses and is of no significance in ruminants. Horses are also susceptible to the prussic acid and nitrate poisoning problems more commonly associated with the sorghum family. For these reasons, it is best to avoid sorghum forages in the feeding of horses.
Prussic Acid Poisoning
Prussic acid (HCN) or hydrogen cyanide has long been recognized as a potentially devastating problem in the pasturing of livestock on sorghum forage. Symptoms of prussic acid poisoning include: nervousness, increased rate of respiration, trembling, blue coloration of mucous membranes, spasms, convulsions, and death. Prussic acid is concentrated in new growth of leaves and shoots. As the plants mature, prussic acid content declines due to the relative increase in stem, leaf, sheath, and midrib. The regrowth after cutting, intensive grazing, or after a mild frost can be very high in prussic acid because it is essentially all new leaves and shoots. Likewise, the growth that occurs immediately after a period of drought may have dangerously high levels of prussic acid. Generally, as long as growth is continuous the danger of prussic acid poisoning is relatively slight, however, should growth be interrupted and then begin again, extreme caution must be exercised.
The risk of prussic acid poisoning can be reduced by sound management practices. Do not begin grazing of these products until 18 to 20 inches of forage accumulation has occurred. If the crop is stunted by drought or frost do not graze or chop until the crop has recovered (several days after first flush of growth). Do not pasture following a closely cut hay or greenchop harvest until 18 to 20 inches of regrowth has occurred. Avoid pasturing these crops after a killing frost for three to five days or until all growth has turned down. Apply phosphorous and potassium fertilizers according to soil tests and avoid excessive application of nitrogen fertilizer. High rates of nitrogen fertilizer combined with low soil levels of phosphorous can double the prussic acid content of young leaves. If in doubt, harvest the crop as hay or silage. Prussic acid dissipates as the forage lies in the windrow and studies have shown that the ensiling process reduces the prussic acid level by 50% to 80%.
While all sorghum forages have the potential to produce dangerously high levels of prussic acid, there are differences among species and cultivars. A ranking of these products from lowest potential to greatest is as follows; (1) varietal sudangrass, (2) hybrid sudangrass, (3) hybrid sorghum/sudangrass and (4) forage sorghums.
The nitrate content of sorghum and pearl millet forages can be high, depending upon growing conditions and the source and amount of nitrogen fertilizer. Excessive rates of nitrogen fertilizer from any source can result in a problem, however, nitrate accumulation by these forage crops is usually greater when nitrate fertilizers are used rather than ammonium sulfate or urea. Low light intensity, frost, hail, low temperature, disease infection, insect feeding, etc., can result in high nitrate content in these forages.
High nitrate forage consumed by livestock results in poor growth, reproduction problems and poor milk production. If nitrate content of forage is very high, rapid death can and does occur. Nitrate is converted by the animal into nitrite. Nitrite absorbed into the blood converts normal hemoglobin into methemoglobin, which is incapable of transporting oxygen to body tissues.
Treatment for animals suffering from nitrate toxicity usually consists of an intravenous injection of methylene blue solution, which brings about the reconversion of methemoglobin to hemoglobin. If nitrate problems are suspected, a representative sample of the forage should be sent to a laboratory for analysis. If the suspect forage is confirmed to be dangerously high in nitrate, it should be mixed with other roughage before feeding or discarded.
The risk of nitrate poisoning can be substantially reduced by sound management practices. Avoid grazing or harvesting these crops immediately after periods of drought, hail or frost. Do not make excessive nitrogen fertilizer applications. It is best to apply a portion of nitrogen fertilizer preplant (40 to 50 lbs.) and then after each grazing period or harvest make relatively small applications (20 to 30 lbs.). Avoid grazing these products after harvest as hay or greenchop until sufficient regrowth has occurred (nitrate accumulates in lower parts of the stalk). Harvest in the afternoon or evening, after the crop has been exposed to several hours of sunlight (avoid harvesting on cloudy, overcast days). If forage is suspect, harvest as silage. The ensiling process reduces nitrate concentration by 40% to 60%. Finally, never allow hungry animals to pasture potentially high nitrate crops without first feeding roughage to reduce initial intake.
While it is difficult to define the level of nitrate that will produce toxicity symptoms or adversely affect animal performance, when the line is crossed the results may be devastating. Generally, the sorghum sudangrass hybrids and pearl millet accumulate higher levels of nitrate than does sudangrass.