Submitted to: Cow Country News
Publication Type: Popular Publication
Publication Acceptance Date: 12/12/2015
Publication Date: 1/1/2016
Citation: Aiken, G.E. 2016. From the Lab Bench: Differences in annual and perennial grasses in meeting cattle production goals. Cow Country News. Pgs 44-45.
Interpretive Summary: There are advantages and disadvantages with planting annual warm-season grasses, and should only be utilized if they meet a specific purpose. They are useful in increasing the supply and quality of forage during the middle to late summer when there is a slump in the growth of cool-season perennial grasses. They can also serve as an alternative to toxic endophyte-infected tall fescue during the summer months to avoid the severe heat stress that is common for cattle grazing toxic tall fescue during the summer. Because of their high yield and quality potentials, warm-season annual grasses can provide high yields of good quality hay. Some disadvantages of warm-season grasses, particularly the sorghums, are that excessive nitrogen fertilization can cause them to accumulate nitrates to toxic concentrations, and prussic acid can be produced and cause cyanide poisoning when the grasses are subjected to early frost or drought conditions. Cattle producers must balance between the advantages and disadvantages of warm-season grasses before deciding to plant these grasses to meet a specific purpose.
Technical Abstract: A column was written that provided the advantages and disadvantages of annual warm- and cool-season grasses. Warm-season annual grasses can increase the supply of forage during the summer slump in cool-season perennial grass growth. Utilization of toxic endophyte-infected tall fescue pastures can be considered a special case, with cattle being moved to a warm-season annual or perennial pasture to avoid grazing toxic fescue during the season when the cattle are most vulnerable to fescue endophyte-induced heat stress. Depending on the stocking rate for the farm, larger acreages of annual grasses will be needed, which can be challenging. Warm-season annual grasses can certainly serve the purpose of needing higher yields and quality of hay. Warm-season annuals, particularly the sorghums, require good nitrogen fertility, but can accumulate nitrate to toxic concentrations if excessive N is applied, or if there are a few weeks of overcast skies or cool temperatures. Prussic acid (cyanide poisoning) can also be a problem with the sorghums in the presence of an early freeze or drought conditions. Planting these grasses annually and managing them should be factors in deciding to utilize annual grasses for the purpose of meeting a special need.