Understanding and managing forage quality is important for cow-calf and stocker operations that rely on forage as the main component of the diet. The primary factors that affect forage quality include species and cultivar, maturity and temperature.
Energy and crude protein (CP) are the two key components to consider in terms of forage quality. The energy content of forages is affected by digestibility. The more digestible a forage is, the higher the energy content will be. Total digestible nutrients (TDN) is commonly used to describe the energy content of a forage or feed ingredient.
In most situations, the energy content of a forage will have more influence on average daily gain (ADG) or body condition than CP will.
This column will focus on differences in digestibility and thus energy content of forages due to species. In general, cool-season forages are more digestible than warm-season forages. Additionally, annual forages are more digestible than perennial forages.
Typical ADG of replacement heifers or stocker cattle from research studies and field observations are very helpful when comparing different forage species. Below are typical gains for some common forages assuming moderate to low stocking rates and good grazing techniques. Overgrazing will result in much lower animal performance.
Forages that result in higher ADG of replacement heifers and stocker cattle will also result in better performance of cows and higher-quality hay.
- Cool-season annual grasses introduced to the U.S.: 1.5 to 2.85 pounds per day – forages in this group include annual ryegrass, rye, wheat, oats, barley and triticale.
- Cool-season perennial grasses introduced to the U.S.: 1 to 2.25 pounds per day – forages in this group include orchardgrass, perennial ryegrass and fescue.
- Warm-season annual grasses introduced to the U.S.: 2 to 2.75 pounds per day – forages in this group include sudangrass and sorghum-sudangrass hybrids. 1.25 to 2 pounds per day – forages in this group include crabgrass and pearl millet.
- Warm-season perennial grasses introduced to the U.S.: 1 to 1.6 pounds per day – forages in this group include old-world bluestems, Tifton 85 and johnsongrass. 0.7 to 1.3 pounds per day – forages in this group include bermudagrass, kleingrass, bahiagrass and dallisgrass.
- Warm-season perennial grasses native to the U.S.: 1 to 2.25 pounds per day – forages in this group include big bluestem, indiangrass, little bluestem, eastern gamagrass and switchgrass. It is important to be aware that less plant biomass should be removed when grazing forages in this group compared to other forages. Removing less biomass increases ADG.
