Satellite imagery helps producers to observe, improve cattle weight gain
Researchers at USDA’s Agricultural Research Service have found a new way for farmers to observe and improve their cattle herd’s weight gain. Using images captured from satellites, scientists have been able to monitor the quantity and quality of forage consumed by free-range cattle to determine how foraging patterns relate to weight gain.
The study, “Predicting spatial-temporal patterns of diet quality and large herbivore performance using satellite time series,” aimed to help with the difficulty that many farmers and ranchers face: variability. With temperature and rainfall changing every growing season, it is essential to have a method that measures where the best forage will be to get the most out of grazing.
Focused on observations taken from 40 pastures across 10 summers in the shortgrass steppe of eastern Colorado, the research found cattle that ate high-quality grass consistently gained more weight than cattle that ate more grass. The study also revealed weight gain was affected by the timing of forage green-up and browning down, as high-quality forage tended to green up earlier than lower 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,” says Sean Kearny, postdoctoral research associate in Fort Collins, Colorado. “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 so early in the season. This resulted in cattle feeding on lower quality grass, which reduced their performance.”
As climate patterns shift — and high-quality green-ups happen earlier — researchers emphasize the importance of evaluating the best time to graze cattle. Ultimately, the more time cattle spend on high-quality forage, the more time they have to optimize weight gain. With this satellite imagery, farmers have an approximation of when the highest quality grass will be available.
“We knew forage quality mattered, but we didn’t know to what extent,” says Lauren Porensky, a research ecologist for the Agricultural Research Service. “Now we can estimate diet quality across space and time and have a better idea of what is causing changes in diet quality throughout the season.”
To better understand cattle foraging behavior, scientists are also linking new diet quality and vegetation maps with data from GPS collars. In addition, they are creating a new model to predict diet quality in near-real-time to support adaptive management efforts.