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Use grazing behaviour to manage pastures

Cattle have certain preferences in forage plants and some definite behavioural patterns when grazing.

Dr. Bart Lardner, a research scientist at the Western Beef Development Centre and adjunct professor in the department of animal and poultry science, University of Saskatchewan says ranchers need to be aware of grazing behaviour and use this knowledge to help control animal distribution on pastures. “If you let them do all the selection on their own, you may run into problems with some areas being overgrazed and others undergrazed,” he explains.

“Cattle have patterns of grazing behaviour regarding time of day — preferring to do most of their grazing in the early morning or late in the day when it’s cool. During the heat of the day they rest in a shady area to chew the cud and then head out to graze again in late afternoon,” he says.

Dr. Joseph Stookey, an animal behaviourist at the Western College of Veterinary Medicine in Saskatoon says their natural diurnal grazing pattern, with the largest grazing bout occurring before sunset, matches the plants’ highest nutrient content, after a day of photosynthesis. “In choice tests, ruminants select forage harvested in late afternoon or evening rather than forage harvested in the morning from the same field,” he says.

“A series of USDA studies looked at animals’ ability to choose different forages. The researchers cut hay in the morning and in the evening and used this in the choice tests. They’ve done it with cattle, goats, sheep, and they all select hay that’s cut in the late afternoon and evening. When you analyze the hay in the lab, it has a higher level of carbohydrates because the plants stored more nutrients during photosynthesis through the day.” Carbohydrate level is much higher late in the day. By morning some of the nutrients have moved down into the roots during the night.

“We can’t see any difference with the eye, but the grazing animals can detect the difference in these forages,” Stookey says.

If you notice cattle grazing during the heat of the day, this is usually a clue they are short on feed — having to graze more hours in order to acquire their needed nutrients. It pays to be observant, to notice any changes in their grazing behaviour. If they are eating short grass or seeking out bits of grass amongst the brush, it will take them longer to meet their nutritional needs. “They are also expending more energy with the continual travelling and grazing, and won’t be gaining as much weight as you’d like,” says Lardner.

If cattle are spending too much time in certain areas, we can influence animal distribution with strategic placement of water sources and fencing, or putting salt/mineral up on a ridge instead of down by the creek bottoms where they tend to loaf. “This can help prevent overutilization of pasture near a certain watering area,” Lardner says.

“It’s all too easy to just throw off the salt blocks by the gate, but if a person places the salt and mineral a fair distance away from the creek or other water points, this entices the cattle to move from point A to point B and graze the area in between.” In mountain areas cattle may prefer to be up on a high ridge for their midday lounging where there’s a little breeze and fewer flies. Having the salt/mineral on those high spots encourages them to spend some loafing time up there.

It also helps to establish water points in various areas of the pasture. “Even two water sources are better than one. If they are not more than a mile apart, this helps create better utilization of the pasture between those two points,” says Lardner.

Anything you can do to spread out the cattle will help, so they don’t keep returning to the preferred grazing areas as often. A person needs to be aware of how the cattle are using a pasture. If parts of the pasture are becoming too mature and ungrazed, you need to find a way to make the cattle use those areas.

“When cattle overuse some plants, they keep returning to those plants to eat the new, tender regrowth rather than eat the older, more mature and fibrous plants. This is when we get into the problem of overgrazing,” he says.

“In range management we have three terms: decreaser species, increaser species, and invader species. The decreasers are the ones the cattle prefer the most (often called the ice-cream plants). They will walk a long ways to find those. The increasers are the plants that can withstand some grazing; they are more tolerant to grazing pressure. The third category is the invaders that move into an overgrazed area and the cattle won’t touch them so they tend to take over some areas.”

The readiness of grass in the spring varies from year to year depending on weather and growing conditions. If it’s a late spring, it’s hard for ranchers to keep from turning cattle out too early for the grass, yet it’s best to allow those plants enough time to get to a four- or five-leaf stage so they can withstand grazing. “You can’t just turn out on a calendar date; you have to manage and monitor. Producers may get into problems in the spring by turning out too soon, or in the fall by keeping cattle out too long on certain pastures,” says Lardner.

In some pastures poisonous plants may be a hazard when cattle are turned out too soon or left out too long — after the grass is mostly gone. “Cattle will eat toxic plants when grass is short,” he says. Often these plants come up ahead of the grass and may be the greenest thing out there if you’ve turned cattle out too soon. The same can happen if cattle run short of grass in the fall or during a dry summer.

Every pasture situation and range allotment has different characteristics. “Some have native range pastures that can be used in conjunction with tame seeded pastures for best timing of grazing. We call these complementary grazing systems. There are some tame perennial species we can use for early-spring grazing,” says Lardner.

“This enables us to put cattle out earlier than we could on native range, letting the native pastures have a little more rest and chance to grow more biomass before we use them. Then we can put the cattle out on native range in early summer. We can bring them back in on other tame pastures we call fall-graze species, and perhaps some stockpiled grass as well,” he says. Reducing the need for harvested feed, extending the grazing period, is the best way to reduce a rancher’s costs and have cattle coming into winter in good condition.

“On your tame seeded pastures at home you can maybe increase stocking rates a little more than on a native range. You might rotate the cattle through a pasture quicker (and possibly use mob grazing). The stocking rate can be different between a season-long pasture and a series of pasture rotations. It is usually prudent to do some cross-fencing and create a grazing system,” says Lardner.

“The system itself is not as important as the objectives of that grazing system for the producer.” There has to be a symbiotic relationship between the grass and the grazer for optimum health and production of each. The grass and the grazing animal can benefit one another, with proper grazing management.

“Grazing is a wonderful tool for improving a pasture. It is amazing what grazing can do in terms of plant response and increase in plant growth. Sometimes we also need to remember that rest is part of the grazing cycle. The plants need time to recover from grazing. If you continually use more than 50 per cent of the plant this starts to reduce the root growth biomass,” he says.

You need to monitor the pasture and see which plants are being grazed, and how much. The cattle may be leaving more than 50 per cent of the grass in that pasture, but still overeating some of the preferred plants. “Stocking rate can be a tool to prevent this, by rotating a larger number of animals through a series of pasture segments. With more animals there is less selectivity in their grazing and they utilize more of the available forage — including the plants that are less preferred.” Then you can move them to a new segment of pasture and allow the grazed segment to regrow completely before you allow the cattle to return to it. C

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