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Evaluating Grazing Forage Electronically!


By Alan Harman


Equipment that allows a livestock producer to know how much nutrition a lamb is getting from the grass it’s grazing on-or even how much weight that lamb will gain if it keeps eating that same grass-is being developed.

This is because of recent developments with spectral reflectance technology.

The Agricultural Research Service’s (ARS) Grazinglands Research Laboratory at El Reno, Oklahoma, has signed a co-operative research and development agreement with two private firms based in Oklahoma for designing, manufacturing and marketing a small, low-cost, hand-held optical remote sensor that can calculate, store and display data on forage’s nutrient quality.

Animal scientist Michael Brown (left), visiting scientist Gao Fengqin (center), and technician Scott Schmidt take weekly weights to estimate the association of weight gain in sheep with forage canopy light absorbance.
Animal scientist Michael Brown (left), visiting scientist Gao Fengqin (center), and technician Scott Schmidt take weekly weights to estimate the association of weight gain in sheep with forage canopy light absorbance.

Under the agreement, the instrument will be developed by Durant Design and Development in Durant and will be manufactured and marketed by TerraVerde Technologies in Stillwater.

They say complete development and commercial use of this technology are at least a few years away.

ARS soil scientist Patrick Starks said the nutritional value of live, standing forages in pastures is essential knowledge for livestock producers. It allows them to make informed management decisions about stocking rates, beginning and ending dates for grazing, and the need for supplements.

Starks and colleagues at the Subtropical Agricultural Research Station at Brooksville, Florida, have shown that spectral reflectance data can almost immediately show quality of forage grasses with an accuracy comparable to much slower conventional lab analysis.

The important difference is that spectral reflectance data can be processed in seconds. Current analysis methods entail clipping, near-infrared spectroscopy, and chemical procedures that, while accurate and site-specific, are laborious and take days to complete.

“There are huge potential benefits to this technology,” Starks said. “In addition to reducing manual sampling, it can lead to nutritional landscape mapping and more efficient pasture management and supplement feeding.”

He said these studies may prove most valuable in tipping growers off as to when or whether forage supplements are needed. “We’re talking about performing precision supplementation,” he said.

The El Reno research also led to an interesting side study in which ARS animal scientist Michael Brown and Redlands Community College undergraduate student Amina Phillips found that spectral technology can help predict weight gains and growth of foraging animals.

The technology could give grazing managers early warning of nutrient deficiencies and could also be used to harvest hay at a desired quality level. Grazing managers could use it to move cattle to various pastures to capture forage at its highest quality.”

The two researchers monitored spring-born lambs for three years to see whether animal weight gains could be predicted using spectral reflectance measurements taken in pastures.

Lambs were randomly assigned to one of four, four-acre pastures so that each pasture was stocked with a dozen lambs. Spectral reflectance of each pasture was measured when initial lamb weights were taken and eight other times.

Brown said the results “suggest that animal gains based on feeding on specific forages can be predicted-using 15 wavelengths of light-with reasonable accuracy.”

But the lamb study also underscored the need for investigations on animal intake and how estimates related to intake can be tied into the reflectance technology. “Once we can develop equations that accurately estimate intake based on spectral reflectance data, we’ll be able to closely formulate forage supplements,” Brown said.

Starks said if it can be determined how much the livestock are eating and the quality of the forage, their expected weight gains can be determined.

“But if gains aren’t acceptable on forage alone, real-time estimates of forage quality and intake will allow us to provide a more exact supplement to the animals,” he said.

Brown said supplementing grazing animals with grain or hay without regard to nutrients they receive from forage is inefficient if they are overfed or underfed.

“But there are times within the grazing season that supplementation is economically efficient,” he said. “So it would be a great advantage for growers to be able to evaluate the need for, and profitability of, supplements in real time.”^





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