The idea of moving cattle to graze higher-quality forages goes back hundreds of years. Long before barbed wire and electric fences, shepherds would move their flocks every day to new areas to graze. Similarly, on the North American prairie, the vast herds of buffalo were continually on the move in search of better grazing.
The early development of grazing management came from André Voisin, a French biochemist/farmer, in the mid-1900s. His ideas on rational grazing were developed by watching his cows graze. Voisin is considered one of the founding fathers of the modern grazing systems and his ideas can be found in his book Grass Productivity, available on the internet. Voisin created a set of grazing rules that are universally applicable to all soil types and climates. He called it rational grazing (not rotational grazing), based on rationing the pasture forage according to the needs of the livestock, similar to feed being rationed out in confinement feeding. In this way, the plants were protected from overgrazing while achieving a high level of forage use.
Four laws for managing grazing
Voisin developed four universal laws for grazing management focused on the grass and the cows’ needs.
His first law was the need for the pasture sward to have a rest period. “Before a sward is sheared with the animal’s teeth, for the sward to achieve its maximum productivity, sufficient interval must have elapsed between two successive shearing to allow the grass to accumulate in its roots the reserves necessary for a vigorous spurt of regrowth and to produce its blaze of growth.”
Voisin’s second law is: Don’t graze the regrowth. “The total occupation period on one paddock should be sufficiently short for a grass sheared on the first day of occupation not to be cut again by the teeth of these animals before they leave the paddock.”
Voisin’s third and fourth laws refer to the nutritional needs of the livestock. “The animals with the greatest nutritional requirements must be helped to harvest the greatest quantity of grass of the best possible quality.
“If a cow is to give regular milk yields, she must not stay any longer than three days on the same paddock. Yields will be at their maximum if the cow stays on one paddock for only one day.”
Voisin lectured extensively on his theories in many parts of the world and his grazing book has been translated into 18 languages and reprinted many times.
By careful observation, Voisin realized that grazing time was critical. He concluded that it wasn’t the number of animals per acre, but the time that plants were exposed to animals that was the chief determinant of overgrazing. If animals were permitted to remain on the pasture too long, a palatable plant will be grazed a second time before it has had time to recover from the first. Also, repeated grazing at short intervals didn’t allow the plants to achieve maximum growth rate, thus limiting the amount of sunlight energy captured and converted to useful feed by the plant.
After understanding and implementing Voisin’s ideas on your grazing operation, there are some additional ideas that can be implemented to go to the next level of grazing management.
Jack Kyle, retired provincial pasture specialist in Ontario, emphasizes the need to develop a forage budget for the season. In other words, how much forage do you need to meet the grazing animals’ needs and how much forage can you reasonably expect to produce on the available pasture acres?
Kyle emphasizes the need to do a forage budget or inventory at the beginning of the grazing season. This will show any deficits and allow time to adjust by having fewer animals, adding acres, adding an annual crop, or buying forage or other feed to supplement.
Pasture conditions need to be monitored on a daily basis in the grazing paddock and weekly in all others. Be aware of any regrowth challenges or early forage maturity and then adjust the program to accommodate those observations.
Realize that as a pasture manager “you have two dynamic life forms: the forages and the animals, and they need to complement each other, not be in competition,” says Kyle.
“When checking cattle, do a serious check of the forages, growth stage, density, species mix, etc.… It is my observation that many times the focus is on the livestock rather than equal between livestock and forage. I have been on more than one pasture walk where all the interest was in the livestock and my pasture story quickly became secondary to that good cow or bull!”
All these factors will likely apply in any situation, although climate and weather may alter the response.
Many years ago, at the Melfort Research Station in Saskatchewan, we were involved with rotational grazing systems. We found that peak above-ground forage production was usually reached during mid- to late-July and management decisions needed to be made at this time to successfully meet the grazing animal’s needs for the remainder of the season.
If grazing begins too early in the spring, herbage production is greatly reduced. The phenological growth stage of the grass is the best indicator for the starting date for grazing. Grazing plants before the third new leaf stage causes negative effects in grass growth. Starting grazing after the third new leaf stimulates tiller production and leads to more above-ground herbage biomass.
With our rotational grazing work, we alternated each year which brome alfalfa/blue grass paddock was grazed first. This really helped sustain our pasture production. In addition, we seeded and grazed crested wheat grass for early spring grazing, before grazing any of the brome/alfalfa paddocks. We also fertilized half of these paddocks on alternate years.
The promotion of tillering in spring is very important. Grant Lastiwka is a former provincial forage specialist and is now with Union Forage in Alberta. Lastiwka starts grazing his cattle after the three-new-leaf stage on tame pastures and after the 3.5-leaf stage on his native pastures. He grazes tame pastures first and gets over all his pastures based on monitoring all paddocks, the plant growth stage and weather patterns.
“Keep records of the number of cattle grazing each paddock and for how long. Use this information in the future to plan your grazing actions, and continue monitoring your results and adjust accordingly. Remember, it is a perennial and one year begets the next,” says Lastiwka.
“Second time over is varied as extended grazing is needed or not. You can take more, maybe 50 to 70 per cent depending on landscape, longer-term plan, year growth environment, growth present, and economics. In addition to forages and animals complementing each other, the third dynamic life form — soil organisms — need to be considered,” says Lastiwka.
Dr. Mike Schellenberg, retired forage scientist at Swift Current, recommends moving cattle to pastures with the best or highest nutritional value. “This requires pastures being seeded to a species nutritionally peaking at different times throughout the grazing season.”
This can be accomplished by seeding a single species with a specific nutritional peak, says Schellenberg. Alternately, producers can seed a mix of different species with different nutritional peaks.
“Mixtures will also diversify the soil microbes, potentially improving soil health. Legumes in the stand will improve the forage nutritional quality and provide biological N to the soil. When using mixtures, one must be aware of what is in the stand to avoid potential animal health issues such as overaccumulation of nitrates in fall or concentration of other undesirable compounds in non-legume or grasses. The ideal mix is dependent on individual requirements and objectives. They can be annuals, perennials or mixtures of both,” says Schellenberg.
Figuring out a forage inventory
Both Kyle and Lastiwka emphasize the need to know how much forage you have available for grazing and how long it will last. You need to estimate the pounds per acre of available forage. One way to do this is to cut a measured area for hay and then weigh the bales. Another is to hand-cut a few square metres or square-yard samples and weigh on a kitchen scale. You could estimate dry matter content at 20 per cent for green growing grass, 15 per cent for really lush grass, and 25 per cent for mature grass. A more accurate dry matter reading could be obtained using a designated microwave and following internet directions.
“Both these methods are time-consuming but the idea is to get a baseline understanding of what amount of standing forage is required each day to meet the individual cow’s requirements. From the estimate of animal needs, how quickly do they graze the pasture down to a suitable residual, and use that estimate of yield,” says Kyle.
To estimate the animal needs, Kyle uses three per cent of body weight, which allows for some tramping and waste.
“I used a grazing stick sometimes but they didn’t seem to give a wide variation. Our mix of species in Ontario doesn’t work well for either the stick or the plate meter. I found that people thought they couldn’t do this, but the good pasture managers didn’t take long to have a good idea of how much forage they had available,” says Kyle.
Lastiwka uses a grazing stick and gets a reasonable yield guestimate when several sites are checked. He starts with a daily move and modifies for correct paddock size the following day, as it is a small area affected. When one starts grazing after the third-leaf stage, leaving too little residual can be a mistake, but is not as damaging, as the plants have recovered the lost winter nutrient stores.
“Proper management of growth in spring is critical as it sets the stage for how quickly and how much regrowth occurs over all the shorter growing season. Mistakes now are magnified,” he says.