Forage sorghum and sorghum x sudan hybrids (often referred to as sorghum-sudan) have been around for a long time, but they have been big, stalky and mediocre forage quality, and as a result, beef and dairy cattle feeding on these forages have shown mediocre performance. And for farmers that used sorghum-sudan for hay, the stuff was hard on equipment and hard to dry and. The one advantage of these sorghum products has always been their exceptional drought tolerance.
In recent years, major advances have been made on these products. Specifically, the BMR (brown midrib) trait has been developed, along with dwarf varieties and photoperiod sensitive varieties. Here is an explanation of these advancements.
BMR: “Conventional” sorghum-sudan is high in lignin – the un-digestible part of plants. Forage quality decreases as lignin percentage increases. BMR varieties have lower lignin amounts.
There are three BMR traits sold – 6, 12 and 18 gene. BMR 6-gene and 12-gene hybrids have the lowest lignin content, giving them the highest quality. Daily weight gains for beef cattle feeding on these BMR varieties can often be 1 lb more than conventional varieties. For reference, daily weight gains for conventional sorghum-sudan is often in the 1.5-2.3 lbs. High-quality BMR 6-gene and 12-gene varieties can produce daily weight gains approaching 3 lbs. In a 2010 Tennessee test, two conventional sorghum-sudan products were tested with a BMR photoperiod sensitive hybrid. The BMR photoperiod sensitive product had a 20% higher relative feed value than both the conventional varieties. The BMR trait is the most important advancement is forage sorghum and sorghum-sudan research. Even the stalks on BMR varieties are high quality. Furthermore, BMR varieties can be planted at a lower seeding rate, because a higher population with thinner stalks is no longer necessary.
For the best BMR varieties, yields are usually still as good or better than conventional varieties planted at higher seeding rates.
Dwarf: A new series of forage sorghum and sorghum-sudan varieties are called dwarfs. Some are in a classification call brachytic dwarfs (which is a recessive gene) while others have just been bred to grow shorter than typical hybrids. They are shorter and leafier, which can give them a higher forage quality (more leaves on less stalk). Dwarf varieties or sorghum-sudan are great for grazing because they should grazed at heights of 40 inches or shorter. because they often have thicker stalks, they are not ideal for hay.
Photoperiod Sensitive: Sorghum-sudan hybrids that are photoperiod sensitive will not attempt to go reproductive (make a seed head) until daylight drops below 12 hours and 20 minutes. Therefore, plants stay leafier longer into the season so later grazing cycles or harvests are higher quality. This trait is not beneficial for the southern parts of the of the U.S. where daylight length stays more consistent. However, in the Central and Northern U.S., photoperiod sensitive varieties can extend the vegetative growing season into late September.