Making Pellets of Forage Sorghum

A. F. Swanson.

As the American pioneers well knew, forage sorghum is a basic feed for livestock in most of the Great Plains.

The forage sorghums, along with barbed-wire fence and windmills, did much to stabilize the livestock industry at the time of the great migration into the territory west of the Missouri River and south of the Kansas-Nebraska line. It was a time of conflict. Cattlemen, who believed in the free range, fought it out with the settlers who, coming to possess the land, brought in fencing, windmills, and stable crops. Forage sorghum was one of the stable crops although, strangely, the earliest settlers used it for molasses. Within a decade, the pioneers discovered its value as cured fodder, as hay to supplement native grasses, and as a winter reserve against bad weather. Sorghum was the cushion that absorbed shocks in the first days of strife and adjustments to the climate, soil, and ways of farming, all different from those in the East.

An expanded use came with the introduction of silos, a movement that gained impetus after 1900. Forage sorghum is a good crop to ensile; sorghum silage, used with a supplement such as cottonseed cake remains today a basic feed in the Sorghum Belt of the United States.

About 10 years ago came the idea of dehydrating the forage sorghums with the equipment that was used for dehydrating alfalfa. Paul Johnson, of Independence, Kans., is said to be one of the first to dehydrate sorghum. He processed 35 acres of Atlas sorgo on his farm in 1940 and fed the product to his dairy herd with apparent success. He mixed the dehydrated sorghum meal experimentally with molasses in proportions of 20, 30, 40, and 60 percent. He reported that the 30-percent mixture seemed to be the best, as it absorbed all of the molasses and produced a dry feed that was neither sticky nor inclined to pack in the bags. He also found that the 40- and 60-percent mixtures were sticky and wet, but the molasses did not seep through the sacks.

John Vanier, of Salina.. Kans., began dehydrating sorghum in 1946. He used dehydrators that he had for processing alfalfa. Besides a milling company, he owned a dairy and ranch, where livestock was available for feeding trials. Chemical analyses were made in the laboratory of his firm.

In the course of the experimentation, he added more proteins, molasses, and other ingredients in proper proportions to the dehydrated meal, which was then made into pellets.

Federal and State research on the use of dehydrated sorghum has been limited. Unpublished data from digestibility trials by the Kansas Agricultural Experiment Station indicate that the nutrient value of dehydrated sorghum meal compares favorably with that of silage or fodder made from the crop.

Sorghum breeders at the several experiment stations in Kansas have cooperated in selecting and testing a number of high-yielding varieties that have a high content of sugar. Some limitations in dehydrating sorghum partly offset-the advantages, and some uncertainty exists as to costs of using prepared feeds in which dehydrated sorghum meal is a base, in comparison with those of feeding sorghums in the form of fodder, silage, and hay, and supplemented with cottonseed cake. Even so, because of the ease and convenience of using it, dehydrated sorghum holds promise as a supplement to the more bulky feeds on farms. It has been favorably received, and the supply has not been equal to the demand.

PROCESSING a growing sorghum crop into pellets is a specialized operation. Field cutters, to reduce the standing crop to green silage, and large trucks, to bring the material to the dehydrator, are required. Up to that point, the operation is the same as for ensiling the crop. When it is to be dehydrated, the green silage is quickly unloaded and passed through huge drums, in which high temperatures and air movement reduce the moisture to 10 percent or less. It takes about 5 minutes from the time of unloading the green silage until the dried product reaches the discharge end of the processing plant, either as a dry, somewhat coarse and bulky meal, or in the form of pellets, if a pelleting machine is used. In a later operation, more protein, molasses, and other ingredients are added to the product, which is repelleted and then sacked. To save one operation, the extra nutrients may be added while the crop is passing through the plant. The pellets can be made in various sizes, but usually they are one-half inch or less in thickness.

One limitation on dehydrating sorghum is the distance from the fields to the processing plant, a factor that limits its general use on farms far from a dehydrating plant. Also, dehydration can hardly be carried out economically unless cheap natural gas is available for fuel. In Kansas, natural gas is readily available from a supply distributed from the western end of the State.

For efficiency, the sorghum should be grown near centers of alfalfa production and dehydrators. The two crops greatly extend the seasonal use of the dehydrating plants. Usually the first alfalfa is ready for processing in late May or early June. The earliest sorghum is ready in August. Growing varieties with a range in maturity makes it possible to extend the season for dehydrating it into October or even later, if the crop is in the shock. The best time, however, to start dehydrating sorghum is when the grain has just entered the hard dough stage, when the stalks are highest in sugar. The whole plant, including the stem, leaves, and head, is dehydrated.

The cost of processing a ton of dehydrated sorghum, from the time the cut fodder leaves the field until it is made into meal or pellets, is only slightly higher than that of making an equivalent amount of sorghum dry matter into silage. A little more than 4 tons of silage is about equal to 1 ton of dehydrated sorghum in dry matter.

When sorghum is dehydrated, nothing is added that the crop did not have while growing. Nearly all the nutrients are retained in the dry product. The process eliminates certain losses that occur when the forage is cured and fed as fodder, or when it is converted into silage. Dehydrated sorghum pellets are easy to handle, store, and transport. The low moisture content makes the product highly resistant to insect damage.

Dehydrated sorghum has a sweet, pleasant taste and odor and an attractive appearance. The pellets are dried down to 8 to 10 percent moisture. They contain 75 to 85 percent total carbohydrates, 3.5 to 6 percent protein, and 2 to 2.5 percent fats. The total sugar content ranges from 25 to 35 percent for dehydrated sorghum, compared to 12 to 20 percent on the basis of green weight in the field.