Forage producers who want the best silage, hay or grazing should remember that quality and nutritive value are related, but not necessarily the same thing, said a Texas Cooperative Extension specialist.

"Nutritive value is what we read in the lab analysis," said Dr. Larry Redmon, Extension forage program leader, at recent workshop in Plainview.

"Forage quality encompasses nutritive value, but goes a step further to include the livestock component.
"Do they prefer it over other feed? Is their intake good? Do they gain well on this feed? These three things are the livestock component of forage quality."

The "official" nutritive value from a lab analysis can affect market value and livestock performance, he said. As managers, forage producers have more control over nutritive value than overall quality.

"There are three ways we can affect nutritive value," Redmon said. "We can choose a different forage. We can change our soil nutrient status. Or we can harvest our chosen forage at a different growth stage.

Annual forages are more nutritious than perennial forages. Cool-season forages rate higher than warm-season forages, and legumes rate higher than grasses.

"If we rate them for digestibility, from top to bottom, legumes are No. 1, cool-season annuals are second, cool-season perennials are third, warm-season annuals are fourth, and warm-season perennials come in fifth,"
Redmon said.

Nitrogen is the No. 1 soil nutrient in the forage nutrition equation, he said. It enables plant growth and production of amino acids that help determine crude protein.

When deciding when to harvest, producers should remember that "maturity is the eternal enemy of forage nutritive value," Redmon said.

"Harvesting when the forage is young yields the highest nutritive value. Wait until a later growth stage and it has less nutritive value. As a forage matures, the good 'tasty' components in the plant cells shrink because the cell walls thicken to support the plant as it grows."

If the weather looks "iffy" at harvest time, it's best to postpone cutting until better curing weather is forecast, Redmon advised. Rain will leach carbohydrates out of cut forage lying on the ground, reducing its total energy content.

"The most important thing we can do to preserve quality and nutritive value after cutting and curing is put it in the barn," he said. "A good hay barn will pay for itself in three to five years by protecting your forage from the elements."

A laboratory analysis that confirms nutritive value is also a good marketing tool, he said. Labs typically analyze forages for crude protein, net energy, fiber digestibility and vitamin/mineral content.

Net energy is often expressed as total digestible nutrients or in vitro true digestibility. Fiber digestibility, which affects total digestibility and energy, is expressed as acid detergent fiber and neutral detergent fiber.

"Neutral detergent fiber is associated with dry matter intake...how much they eat," Redmon said. "Acid detergent fiber is associated with dry matter digestibility. Both are valuable ratings, but in-vitro true digestibility is probably the best value/rating for comparing total nutritive value.

"It is a better measure of both digestibility and energy," he said.

More information on forage selection, production, harvesting and quality is available online at http://forages.tamu.edu.

Writer: Tim W. McAlavy