Graziers are quick to tear up pastures, plant the latest “wondergrass,” dump truckloads of fertilizer onto their paddocks or install irrigation in the name of boosting pasture productivity.
But many overlook the one strategy they can implement to boost their productivity at little or no cost, says Jim Gerrish, an independent grazing lands consultant from Idaho.
“Does anybody believe that changing the residual height that we’re grazing, say from two inches to four inches, allows you to grow more grass?” he asked, in a presentation on management intensive grazing at the recent Manitoba Grazing School.
According to Gerrish, if the pastures are already divided up into grazing units with a watering system set up and ready to go, just making a simple management decision to move the cattle when the grass is four inches tall instead of two inches will increase forage productivity by at least 50 per cent in the North American environment.
“To make a decision doesn’t cost anything,” Gerrish said. “But the response to that decision is huge.”
That’s because a pasture is like a giant solar panel, with plants converting sunlight, carbon dioxide, water and minerals into meat via livestock. More leaf area means plants can support more growth, and managing those flows and cycles is the key to profitable ranching, said Gerrish.
There’s no shortage of CO2, solar energy is free, and how efficiently water and minerals are used depends on grazing management. Not overgrazing reduces bare soil and compaction problems, so water soaks in more quickly instead of evaporating, and moving livestock in high densities distributes manure nutrients more effectively.
“Genetics and nutrition are critically important, but they are way overrated as single solutions to your problems,” said Gerrish.
If the stocking rate is too low, forage quality suffers because plants are underutilized. Too high, and productivity declines as the pasture is grazed too hard, soil becomes compacted, and water infiltration reduced. Gerrish said cows are like unionized workers – they only graze from eight to 10 hours per day due to their need to ruminate and rest.
“We can’t really affect that except by making it easier for them to graze,” he said.
Grazing too short is the greatest cause of poor animal performance.
Studies have shown that on “perfect” pasture, a cow will take 15,000 to 18,000 bites per day.
On pastures with shorter grass, that number could rise to 45,000 bites per day, as the animals lose the ability to wrap their long tongue around the grass stalks – their most efficient method of harvesting grass – and start nibbling like sheep or horses.
“But 45,000 of those little bites will never match 18,000 of those big, pull-’em-in tongue wads,” said Gerrish.
“The only thing we control in this whole equation is bite size. We control bite size by how much grass we keep in front of them.”
A beautiful pasture, knee-high and filled with forbs and legumes, can make a rancher feel like a “rock star” of grazing management, but pasture quality only accounts for 27 per cent of productivity. The rest, or 73 per cent, depends on the residual grass, or how much is left over, to restart growth.
COST OF OVERGRAZING
Postponing pasture moves not only affects bite size, but pasture regrowth, because the leaf biomass – the “solar panel” – is reduced. Even the soil is injured in subtle ways because the amount of organic matter left over to sustain nutrient cycling is cut back.
“And by taking some of that trash cover away, we make the soil hotter, so nitrogen fixation slows down,” said Gerrish. “We’ve also diminished biological activity near the surface, so manure doesn’t break down as quickly,” he said.
“We’ve just wrecked the whole system in our arrogance by saying, ‘Oh, she can stay another day.’”
Optimizing forage intake is important, too.
With stockers, if 2.3 per cent of bodyweight roughly translates into a pound per day of gain; many ranchers think doubling that is necessary to double the rate of daily gain. In fact, it’s only necessary to increase intake above the marginal amount needed to keep the animal alive.
Leaving a taller residual is the easiest way to increase daily intake, because the bulk of a grass plant’s feed value is in the top half.
“The deeper you make them feed into that canopy, not only are you lowering their intake potential by making them take smaller bites, but each of those smaller bites is lower quality,” said Gerrish.
“There is no such thing as wasting grass; leave some of that stuff behind. It helps the animal, the plants, the soil, and your bottom line.”
Better grazing management is a win-win not just for the rancher, he added, because increased plant growth and residuals that go back into the soil store organic carbon.
“If 20 per cent of the world’s grasslands were managed to leave one to two inches more residual for 10 years, it would take CO2 levels in the Earth to pre-industrial revolution levels,” said Gerrish. “That is how simple the carbon dioxide problem is.”
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– JIM GERRISH