U.S. Department of Agriculture researchers have "developed a unique approach" to use satellite images in predictions about cattle weight gain on rangelands, a news release earlier this week said.
That unique approach, developed by the USDA's Agricultural Research Service, might be the first of its kind, Sean Kearney, a post doc researcher with USDA's Rangeland Resources & Systems Research, said in the Wednesday, Dec. 15 news release.
"This study is probably the first-time high-quality datasets have been used to predict cattle weight gain directly from satellite imagery," Kearney, based in Fort Collins, Colorado, said.
The approach fuses multiple images over a given period and allows scientists to monitor how forage quality changes over that period in a particular piece of rangeland within the shortgrass steppe between the Rocky Mountains and the continent's mixed-grass prairie. The steppe ranges from central Alberta in the north to central Texas in the south, and passes through southeast Wyoming and eastern Colorado and into Nebraska's panhandle and all of west Kansas, and also into the high plains of Texas, Oklahoma and northern New Mexico.
The new approach monitors and predicts weight gain of free-ranging cattle through the summer grazing season.
"Managing the grazing season in rangelands can be challenging due to high variability in temperature and rainfall over time," the news release said. "From a manager's perspective, it is essential to know when and where forage production and quality are changing to optimize free-range livestock weight gain and meet other environmental objectives. This is not just about chasing forage quantity (total amount of vegetation biomass). It is also about looking for the highest-quality forage throughout the season."
The news release included three images that showed a progression from lower-biomass/higher-quality forage to higher-biomass/lower-quality forage with free-range grazing cattles' weight gains that tended to be lower in the latter's foraging areas.
The new approach was developed in response to difficulties managing the rangelands' grazing season, always a challenge given the area's volatile weather patterns. The USDA researchers found that the best grazing areas are those not with high quantities of forage, but those with high-quality forage.
"We observed that in years when satellite images showed forage greening up earlier, before cattle began to graze, the quality of the diet declined more rapidly and cattle weight gain was lower, especially toward the end of the grazing season," Kearney said. "In some years, plenty of biomass was still available late in the season, but a large portion of the high-quality forage was missed because it peaked (reached top quality) so early in the season. This resulted in cattle feeding on lower-quality grass, which reduced their performance."
