New way to predict weight gain in grazing cattle on rangelands from satellite imagery: USDA ARS

New way to predict weight gain in grazing cattle on rangelands from satellite images

Contact: Maribel Alonso
Email: [email protected]

WASHINGTON, December 15, 2021 – USDA’s Agricultural Research Service (ARS) has developed a unique approach to use satellite imagery to predict weight gain in cattle on rangelands. By merging multiple images over a period of time, scientists were able to monitor how forage quality changes spatially and over time in short-grass steppe rangelands, and how this relates to weight gain in livestock. free throughout the summer grazing season.

Managing the grazing season in rangelands can be difficult due to the high variability in temperature and precipitation over time. From a manager’s perspective, knowing when and where forage production and quality change is essential to optimize weight gain in outdoor livestock and meet other environmental goals. It is not just a question of determining the quantity of fodder (total quantity of plant biomass); it also means looking for the highest quality forage throughout the season.

“This study is possibly the first time that high-quality data sets have been used to predict cattle weight gain directly from satellite images,” said Sean Kearney, Post Doc research associate in Fort Collins, CO. .

In the study published in Ecological applications, the scientists used satellite images, along with field observations of 40 different pastures grazed over a 10-year period, to predict the performance of cattle grazing in eastern Colorado throughout the summer season. The study site, the Central Plains Experimental Range, is a location of the Long-Term Agroecosystem Research Network (LTAR).

These three images show a progression (left to right) from lower biomass / higher quality forage to higher biomass / lower quality forage. Weight gain in free-range cattle tended to be lower under the right conditions, when feed quality was low, although forage biomass remained high. Photos by Dr Edward Raynor, USDA-ARS.

Predictions of cattle performance – in particular, weight gain – were made from satellite estimates of forage quantity and quality. Satellite forage quality predictions were a first for the region, and they proved particularly important. In particular, weight gain was affected by the timing of greening and senescence (browning) of the forage.

We observed that in years when satellite imagery showed forage greening earlier, before livestock began to graze, feed quality declined more rapidly and livestock weight gain was lower, especially around the end of the grazing season, ”Kearney said. in some years a large amount of biomass was still available late in the season, but much of the high quality forage was missed because it peaked (reached the best quality) so early in the season. This led the cattle to feed on inferior grass which reduced their performance.

With recent climate models of early spring greening, higher temperatures, and drier weather during the summer months, it is critical to determine the right time to start and stop livestock grazing, in order to match the timing of the pasture with high quality forage.

We knew the quality of the forage mattered, but we didn’t know how much, ”said Lauren Porensky, research ecologist. season.

What is the next? Scientists are combining these new maps of diet and vegetation quality with data from GPS collars to better understand what drives foraging behavior in livestock, as well as to work on a new model to predict the quality of animal feed. near real-time diet to support adaptive management efforts by pastoralists and other range managers.

The Agricultural Research Service is the principal in-house scientific research organization of the United States Department of Agriculture. On a daily basis, the ARS focuses on solutions to agricultural problems affecting America. Every dollar invested in agricultural research has an economic impact of $ 17.

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