Beware Early Grazing of Stressed Plants

Thursday, March 21, 2024

'You have to get down on your hands and knees and assess the actual grass plants.'

By Richard Kamchen

Prairie beef farmers beset by drought conditions in 2023 ought to be cautious about letting their cattle graze too soon this spring.

"The rule of thumb generally is if it's one day too early, it sets you back three days in the fall," says Pamela Iwanchysko, a livestock and forage extension specialist with Manitoba Agriculture.

Grant Lastiwka, a beef farmer and forage specialist with Union Forage in Calgary, explains that plants start building for the following year in the latter part of a season.

"What they're experiencing determines how many tillers per grass plant they're going to build for next year. And in many cases of stress, it is never as much as it will be normally."

Plants also undergo stress during winter in areas experiencing a combination of cold temperatures and inadequate snow cover.

The stress in both instances can result in less potential yield in the spring, and it's then when plants need to get off to the right start to express more tillers.

"It is a plant within a plant, so one plant will sprout several plants. And it sprouts fewer when life isn't very good," Lastiwka says.

Agrologist Karin Lindquist, founder of Praise the Ruminant, further adds that when plants come out of dormancy in the spring, their root and crown reserves are being drained just to grow their first leaf and start the second. When those young plants are eaten, they're set back at a point when their reserves are already depleted.

"Plus, they've started photosynthesizing, putting their energy into growing new shoots and new roots. The eaten young plant must find some way to restore those lost shoots with the remaining leaf material left behind and regrow new roots," Lindquist says.

It's generally safe to graze when grass plants reach three fully developed leaves on the stem, says Iwanchysko.

"You have to really get down on your hands and knees and assess the actual grass plants," she says.

This stage, however, is very short, and the window can easily be missed, notes Lindquist.

"Move animals so they graze the pasture as lightly as possible – optimum is taking only one bite per plant – so they can move on to the next pasture before the grasses get too far ahead of them," she says.

Overgrazing

Not only will grazing too soon severely set a pasture back, but it will also allow animals to overgraze.

"Overgrazing is a function of time, where returning too soon hampers a plant's ability to regrow enough leaves and maintain enough root biomass to store more energy, exchange nutrients with soil microbes, and reach water beyond just the first few inches at the surface," Lindquist says.

Overgrazing also "eats the roots," she adds, where each time a grass's leaves are eaten before it has time to replenish them, more roots die off.

"Therefore, when starting grazing too soon affects new spring plants by removing the first third or half by reducing their photosynthesizing ability, allowing animals to return before they can recover with what leaf material they have left further reduces that capability," Lindquist says.

Those plants must be left to recover much longer than previously thought and it means that a pasture, depending on both soil moisture and the amount of precipitation received, may not be ready to graze until late spring or early summer, she says. Alternatively, it will have to be left until fall or for stockpile grazing.

Lastiwka also cautions against having too many cattle competing for available grass.

"If the number of animals and your need for grazing days is not in balance with forage yield, plant biological needs in recovery time after grazing cannot be met," he says. "Overgrazing will occur and plant health declines. Best production plants are lost and invaders replace them. Future pasture productivity is declining."

To get time for plant recovery when drought conditions stymie growth, Lastiwka recommends grouping your herds, and, for a short period, allowing them to graze a pasture more uniformly and severely before moving them.

"Don't come back to that pasture until the plants have recovered. We graze that once a year. We move those cattle to a new piece every one to three days and backfence so they can't go back."

Feed options

As farmers balance feed shortages with protecting recovering plants this spring, there are options for them to get by until pastures are ready.

Cattle need a balanced ration of straw and grain with the right mineral mix that balances their calcium, phosphorus, magnesium, and other essential minerals needs, Lindquist says. Cows close to calving will need more protein compared to when they are in their first or second trimester, she notes.

"Hay must be saved for after-calving cows and younger calves simply because straw acts as a gut fill as opposed to necessary, available nutrients that are easier for the post-calving cow to digest and turn into milk for her calf," Lindquist says.

What straw to use can be tricky. Straw from cereals like barley, wheat, and oats is lower in calcium than pea straw, while canola straw, which has decent protein content, carries a risk of too much sulphur, which can cause polio, she points out.

"The high fibre content and low digestibility of straw can hamper nutrient absorption and availability, so it's very important to have feed tested and to work with a ruminant nutritionist to know what best options are available to keep animals in good condition and good health until it's the right time to put them out to pasture," Lindquist says.

Lastiwka notes cattle resist eating straw in the spring: "It's very bulky and they know the grass is greener on the other side of the fence, even if there's hardly anything there."

In cold weather, however, they will eat straw, and he'll take advantage of that, and keep the better-quality feedstuffs for when spring arrives. On a high straw diet, however, he significantly increases the grain in the ration: 10-plus pounds per head per day of 20 per cent crude protein and 80 per cent total digestible nutrients in the form of mill-run pellets or wheat midds. He also has his straw feed tested.

Producers who stockpiled forages last fall will be able to take advantage of that when the snow melts.

Manitoba Agriculture's Iwanchysko explains these paddocks contain specific species that maintain their quality late in the fall and throughout the winter.

"Typically, a lot of producers are moving toward the practice of putting cattle out on pastures that are stockpiled in the spring while they're calving so they have lots of forage available to those cows when their nutritional needs are at their highest," Iwanchysko says.

Farmers can also supplement if necessary. BF