Research carried out in the US has found that rotational grazing actually reduces the performance of beef cattle on range-based systems.
This is in total contrast to the results found on Irish livestock farms, where rotational grazing is concerned.
The US work was carried out by the United States Agricultural Research Service (ARS).
It compared rotational with continuous grazing options, asking the fundamental question – which system allows for more sustainable and profitable free-range livestock production?
Rotational grazing
Ranchers often rotate cattle seasonally among different pastures on their operations. But many also allow cattle to graze season-long in a single pasture.
Implementing a more intensive rotational system within the growing season had been thought to offer a greater chance for more sustainable grazing management.
A team of researchers at ARS has just completed a 10-year study on how grazing practices used in these two systems affect cattle foraging behaviour.
The work also looked at diet quality, and yearly weight gain in semi-arid, extensive rangelands.
The team started by exploring the efficiency of using cattle GPS tracking collars, combined with activity sensors, to monitor the animals’ grazing activities.
“The primary objective of the study was using the sensors to measure the steers’ foraging behaviour, and relate this to how they are gaining weight,” said David Augustine, a research ecologist with the ARS Rangeland Resources and Systems Research in Colorado.
“The collars collected precise data based on the animals’ feeding habits per day.”
The use of the technology specifically informed ranch managers about animal distribution and foraging behaviours of free-ranging cattle in extensive rangelands.
Experiment
The ARS researchers then applied the same technology in a range-scale experiment where steers were either divided into smaller herds in the paddocks of a non-rotational grazing system, or managed as a single large herd in a multi-paddock rotational system.
Significantly, the first five years of data showed that the rotationally managed cattle gained, on average, 14% less weight than cattle in the season-long management system.
“Cattle did not have as much freedom to roam and be more selective on what to eat, so they ended up eating what was available in front of them, which was lower quality forages with less protein, and they gained less weight as a result,” Augustine explained.
“These behaviours were directly correlated to the average of 14% reduction in steer weight gain in the multi-paddock rotating system compared to the non-rotational continuous system.”
The study showed herds in the multi-paddock rotating system feeding in more linear pathways instead of moving around looking for greener grass and selecting bites of more digestible vegetation.
They also fed slower, spent more time on the same patch of grass, and didn’t turn their heads around much while feeding, compared with steers in the continuous grazing system.
These behaviours of less selective foraging resulted in a lower diet quality, which led to reduced weight gain during the growing season.