Sweet Sorghum for Commercial Animal Feeds

Slowly the vehicles snaked into the furthest side of his farm. In the mudDy sticky black cotton soils, only the 4x4 wheel drive vehicles could manage. Out of the vehicles, one of my coleagues shouted, if you do not have 4x4 shoes, please remain in the vehicle. On sight is hactares of sorghum and immediately ask “ what do you do to the bords.” Let them eat i need the stems more, i plant for animal feed,” says Stuart Barden

Sweet sorghum, because of its high yields and high sugar content, has attracted great attention as feedstuff and energy crop. Of all usages, sweet sorghum stalks are mainly ensiled or directly used as animal feed. Ensiling is a process of solid state fermentation by mixed bacteria of nature; however, the silage obtained has low protein content (4-8%) with poor palatability. Great attempts on microbial fermentation have been made to enhance protein content in agricultural straw for poultry feed.

Sorghum (Sorghum bicolor L. Moench) lends itself to a variety of uses. Its uses for feed and fodder are now overtaking that for food in many parts of the world. Recent developments in enhancing sorghum digestibility make it a strong competitor to maize in view of its relative advantage as low input demanding crop that can thrive better under harsh conditions. The forage stuff included grass, sweet and hybrid types and their production under green chop, grazing, hay or silage making systems. As feed stuff, the potential of utilizing sorghum grains in diary, beef and poultry nutrition is great. Recently advances have been made in quality enhancement of sorghum and the role of processing to improve the relative efficiency of sorghum as feed-grain.

Sorghum has recently witnessed an increasing importance as feed crop in the semi arid tropics and drier parts of the world where livestock constitutes a major component of the production system. Such importance is further accentuated by global warming, increasing water shortages, and growing demand for high quality forage resources. Although the crop has great genetic diversity enabling selection for most economic traits, yet improvement efforts are mostly grain oriented with little attention being given to non-grain attributes. The fodder’s contribution to the total value of sorghum production has increased considerably. They reported that the grain/ straw price ratio of sorghum has dropped from 6:1 in 1970 to 3:1 currently and is likely to decline further.

Feed use was relatively minor until the mid- 1960’s when there was a rapid expansion. Currently, about 48% of world sorghum production is fed to livestock. Sorghum has great potential for fodder production under limited resource conditions. Compared to other cereals, especially maize, sorghum is more droughts tolerant, less input demanding and thrive better under harsh conditions. The advent of hybrid sorghum in the l950’s represents a turning point contributing to expanded use and higher yields of the crop.

Animal Feed
Fodder sorghums are usually classified into three major categories. These sorghums have little value as directly marketable seed crops, but their value becomes apparent as they are marketed through livestock and industrial utilization.

Sweet sorghum varieties and hybrids are good for animal feed. They are tall plants (2 to 4 m) with sweet thick stems. Unlike traditional sorghum, forage sorghum has poor regrowth ability following harvest, so is best adapted to a single-cut system. It is best utilized as a silage crop, although it can be grazed or cut for hay if managed appropriately. Its silage is usually slightly lower in energy than that of corn but similar in protein. Sorghum is an important silage crop for beef and dairy producers. The general shortcomings of sorghum silage in comparison to that of corn include lower nutritive value and threats of prussic acid and nitrate poisoning. Forage and grain sorghums types are the best suited for silage production.

If silage is made perfectly, anaerobic bacteria (lactic acid bacteria) will convert carbohydrates to lactic acid, the pH is rapidly lowered and the silage is preserved. Yet, some DM is lost during lactic acid production in even the best of circumstances. Whenever oxygen is present, carbohydrates are converted to carbon dioxide and water, accompanied by the generation of considerable heat resulting in serious losses in DM ranging from 5% - 15% in very good silage to 25% - 50% in very bad one. Losses are quantified as the amount of forage DM fed-in minus that fedout of a silo. These losses are the result of effluent, respiration, primary and secondary fermentation, and aerobic activity during the storage and feed-out process.

The use of silage has long been an integral component of temperate feeding systems worldwide, as a means to ensure year round feed supply for high production animals. However, its use in the tropics has been restricted to isolated cases, usually involving higher-return enterprises, and particularly the dairy industry. This technology requires high investment in facilities, accurate timing in the several stages of the ensiling process, and better understanding of the whole process than hay making demands.

In addition to these demands, silage making and management in tropical conditions needs special attention and care with regard to three key points:

In warm areas: It is more difficult to control the correct stage for harvesting due to very rabid phasing of growth stages. This is especially crucial with cereal crops in the last stages of maturity.

Dry Matter Content: The correct dry matter (DM) content in the plant before ensiling is an important factor for the fermentation success. Unexpected weather (dry, wet or hot) can damage the crop and increase losses.

Aerobic stability: Rapid deterioration of silage, especially during the feeding-out process is a real problem in a hot climate. It reduces quality and results in losses. Aerobic stability should become a routine test in hot areas.

Stem (lignin) ratio to the whole plant: Reducing the proportion of stem in the plant will increase its digestibility, so, in practice, shorter hybrids are preferable.

Some of the important properties determining the value of sorghum silage include:

High energy
Structural carbohydrates and starch are the main energy resources in cereal crops. Starch is mainly accumulated in the grain, the amount of which greatly affects the total energy content. The higher the proportion of grain in the plant, the more the total energy. The positive effect of the presence of starch is especially important for dairy cows. Therefore, a high-grain sorghum hybrid is better.

DM content
Ensiling technology requires at least 30% of DM in the forage. With less than 30% DM, undesirable fermentation takes place and increases losses. To increase the DM content, the recommended stage for harvesting should be between milk and dough stages. Harvesting at late-dough maturity or later will increase the undigested amount of the grains and reduce the nutritional value.

Tannins
As pointed earlier, tannins have a negative effect on the digestibility rate of the protein in the diet.