Is Sunn Hemp Safe for Grazing?

This article was written by Dr. Jorge A. Mosjidis, Plant Breeder at Auburn University. Many of his plant releases have been extremely valuable to us. Several have been AU Grazer Ceresia Lespedizia and AU Golden Sunn Hemp. He is a good friend and we would like to thank him for his hard work and diligence. His research proved sunn hemp to be safe for grazing. Please see and review his findings.

The Facts about Sunn Hemp Toxicity

Jorge A. Mosjidis ^*a, Joan M. Burke^b and Joseph B. Hess^c

Abstract

Sunn hemp (Crotalaria juncea L.) is an annual plant widely grown in the tropics. The genus Crotalaria includes some species known to be toxic to animals. Development of seed-producing cultivars for the continental United States at Auburn University, AL, has raised the question of whether its seeds and forage are toxic. This review will present the evidence reported in the literature on the presence of toxic compounds in sunn hemp seed and foliage and other Crotalaria species found in the United States and their effect on animals. Results from research on sunn hemp demonstrate it is a valuable source of forage without toxic effects. The seed does not cause acute toxicity to domestic animals because it has only a small amount of the toxic pyrrolizidine alkaloids characteristic of the genus Crotalaria. Therefore, its presence as a feed contaminant does not pose a problem. However, sunn hemp seed should not be incorporated in animal diets because, depending on the amount in the diet and the length of time that the diet is fed, it may cause weight loss and potential death. Conflicting reports found in the literature regarding seed toxicity of C. juncea appear to be caused by the amount of seed included in the diet, length of time the diet was fed, and animal species that consumed it. Statements indicating that sunn hemp forage is toxic seem to be due to misinterpretation of the literature and unwarranted extension of the toxicity problems found in other Crotalaria species to sunn hemp.

Answer: Sunn Hemp is both Safe AND Beneficial!

Sunn Hemp for cattle grazing is quickly spreading across the U.S. To my knowledge, no one had tried this in the U.S. before Petcher (it had proved to work very well for sheep and goats and for wildlife). I allowed my one cow “Mertle” to graze sunn hemp for three years, with zero negative affects. Several friends in the cattle industry decided to try it also. Then, after four years of very successfully grazing cattle on sunn hemp, we decided to move forward.

As a Forage Sunn Hemp leaves are 4 - 5 percent Nitrogen, equal to 25 - 30 percent Protein, 22 - 28 percent NDF, 22 - 27 percent ADF.  Stems are 1.3 - 1.7 percent Nitrogen, equal to 8-10 percent Protein, 74 - 76 percent NDF and 64 - 65 percent ADF. It is a very nutritious forage.

Start grazing when the plants are 32 - 36 inches tall.  Livestock will eat the terminal, the top portion of the plant down to about 18 inches. Only the stem will remain. At this point take the cattle off. With moisture the plants will re-bud and put on new branches. This regrowth provides more leaves and forage than the original plant could produce. This regrowth will take only a week or so. Many cattlemen are on a 10 - 30 day rotation.  

Often cows do not eat it the first day they are turned on to it. However, they quickly learn to enjoy it and by Day 7 they are usually very addicted to it. One hour per day is sufficient for the cattle to receive their protein fix. Allow them to turn into other pastures such as Bahia or Bermuda grass.  

We are using zero fertilizer when planting our sunn hemp pastures. Typically, the winter forage crops planted behind sunn hemp will need little to no fertilizer as well.  

The daily gain of cattle on sunn hemp during the heat of summer has been around three pounds per day. If managed properly the sunn hemp will continue to grow until frost.   

The first on-farm research began on Elias Higdon's Farm in Grand Bay, AL. At that time, very few people in the U.S. had tried grazing cattle on Sunn Hemp.

This Sunn Hemp 10 lb. and Quail Haven Forage Soybean 10 lb./acre seeding rate is 30 days old and 24 inches tall.  His cattle have been grazing earlier planted Sunn Hemp fields for two weeks now. Cattle seem to be a little slicker and healthier. We are taking plant samples of the forage, watching the cattle and documenting as much information as possible. Higdon's knowledge of cattle and desire to pioneer this new crop is a tremendous benefit to all of us. Zero fertilizer was applied to his 275 acres of this mix. Cattle prefer this grazing over their Bermuda and Bahia grass pastures. Higdon’s cattle will enjoy 90 days or more of grazing this high protein feed during the summer months when protein is limited and expensive. In September, the forage will be terminated by mob grazing and then planted with cereal rye and “Lunch” Radish. The winter mix following sunn hemp should need no additional fertilizer. As a Forage Sunn Hemp leaves are 4 - 5 percent Nitrogen, equal to 25 - 30 percent Protein, 22 - 28 percent NDF, 22 - 27 percent ADF.  Stems are 1.3 - 1.7 percent Nitrogen, equal to 8-10 percent Protein, 74 - 76 percent NDF and 64 - 65 percent ADF.  We will keep you posted as this experiment proceeds.

Higdon’s neighbor, Calvin Freeland—who farms 540 acres of soybeans—is very excited about the Sunn Hemp experiment, primarily because the deer have left his soybeans alone and are helping the cattle graze the Sunn Hemp.   

Several mixes are presently being used.  

• Sunn Hemp(15 lbs. per acre) with Red Ripper Cowpeas (10 lbs.) and Apache BMR Pearl Millet (5 lbs.) is a good choice.
• Sunn Hemp(15 lbs. per acre) Red Ripper Cowpeas (10 lbs.) Apache BMR Pearl Millet (5 lbs.) Buckwheat (5 lbs.) Sun Flowers (2 lbs.) is an excellent choice.     

These mixes are dramatically improving herd health over the summer when available forage protein is typically low. The sunn hemp is greatly improving soil health and also providing soil nutrients for the following fall and winter forage crop. Some growers are now on a year round zero fertilizer program. This is a tremendous savings to input costs on these farms. Growers are also reducing the need for hay and grain.

Bottom line, healthier cattle and more money in your billfold. 

Stagger Planting

Our Sunn Hemp grazing mixes, planted in April, May and June, have done very well. Many growers are planting this same mix in July and August. During this time, it usually takes only 35 days to grazing. These later plantings are much stronger going into the fall, allowing us to graze to almost Thanksgiving. The earlier Sunn Hemp plantings tend to fizzle out by early September so we mob graze or terminate those fields and get them quickly planted into our Cosaque Oat Fall mix. If we receive good moisture the Oat plantings are ready to graze by late October. Livestock can be rotated between the Sunn Hemp and the Oat pastures at the same time.  

Stagger planting is another way to ensure nutrient rich forage for your livestock.