BROOKINGS, S.D. - There are several reasons livestock producers should consider fall grazing their alfalfa fields."Standing alfalfa can serve as an excellent protein supplement for livestock grazing adjacent crop residues such as cornstalks," explained Tracey Erickson, SDSU Extension Dairy Field Specialist. She added that grazing alfalfa in late fall or winter can also reduce alfalfa weevil infestations by removing stems and plant parts that serve as a wintering site or spring laying site for weevil eggs. For producers considering fall grazing alfalfa, Erickson said bloat and crop injury should be considered. "If dealt with correctly, both issues are manageable, allowing producers to take advantage of this high quality forage resource."
Minimize winter injury & prevent bloatAccording to research in the north central U.S., grazing may not interfere with the alfalfa going dormant. However, Erickson said producers need to manage the grazing, so that 6-8 inches of alfalfa regrowth remain, to minimize winter injury and ensure adequate regrowth in the spring. To prevent bloat, Erickson said producers never turn hungry livestock into an alfalfa pasture and should wait to turn their cattle out onto a field until 50 to 70 percent of the alfalfa top growth has been frozen and dried by a killing frost. "Ruminants are most susceptible to alfalfa bloat 3 to 5 days after a freeze," Erickson said.Erickson added that frost may increase the incidence of bloat by rupturing plant cell walls, leading to a high initial rate of digestion. "This causes gases to become trapped in the stable foam in the rumen which is produced from the digestion of the alfalfa instead of being released through the normal belching process of ruminant digestion," she explained. Additional ways to minimize risk of bloat:
- Never turn hungry livestock into an alfalfa field
- Avoid dramatic changes in forage quality;
- Delay grazing alfalfa for 3 to 5 days after freeze damage, or until 50-70% of the top growth has dried;
- Observe livestock closely the first few days and remove any "chronic-bloating" animals;
- Allow livestock free-choice access to grass hay or corn stalk bales while grazing lush alfalfa;
- Consider providing a bloat preventative to livestock several days prior to and while grazing alfalfa;
- Feed bloat-reducing compounds such as poloxalene at least 2 to 5 days before turnout and for a short period of time/days after the livestock ruminant cattle have been turned out, and they have adjusted to the new diet;
- Provide a supplement containing bloat-reducing compounds such as an ionophore;
- Provide a mineral supplement with adequate salt and avoid excessive potassium, calcium and magnesium; and
- Make sure there is adequate access to fresh drinking water.
