KNOWLEDGE OF GRAZING BEHAVIOR CAN AID MANAGEMENT

by: Heather Smith Thomas

As ruminants, cattle can eat a lot of forage in a short time. Then they chew the cud and process the feed more thoroughly. They tend to graze in the early mornings and again in the late afternoon—into the evening—resting during the middle of the day. In really hot weather cattle graze at night. They have preferences in forage plants, and certain behavioral patterns when grazing. Understanding and taking grazing behavior into account can help stockmen optimize production when managing cattle on pastures.

Plant selection when grazing is partly instinctive and partly learned. Social factors also affect where and when cattle graze; they travel in groups and defer to the lead or dominant animal to make decisions about where and when they graze.

Dr. Bart Lardner (Research Scientist, Western Beef Development Center, University of Saskatchewan) says ranchers need to be aware of grazing behavior 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 over-grazed and others under-grazed,” he explains.

If cattle have season-long use in a mountain area, for instance, they may go too high, too soon, and overuse immature higher grasses, leaving the lower elevation grasses to become overly mature. It would be advantageous to keep the cattle in lower elevations pastures first—with fences or herding—to make them use the lower elevations while that grass is still green and palatable, allowing the higher elevation grasses more time to grow.

“Cattle have patterns of grazing behavior 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 (Western College of Veterinary Medicine, Saskatoon, Saskatchewan) says cattle have some interesting aspects of grazing behavior that some producers may not be aware of. “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 a choice test, ruminants prefer/select forage harvested in the late afternoon/evening rather than forage harvested in the morning from the same field,” he says.

Since cattle tend to graze in the early morning and again in the evening, these are probably the times of day they would eat more feed if we are feeding them. “I don't think people pay much attention to feeding times, in relationship to what the animals would do naturally. There has been some study looking at this in the feedlot industry, regarding when is the most optimum time to feed,” says Stookey. Cattle don't like to eat as much during the heat of the day in the summer. If the biggest feeding is in the late afternoon or evening they clean it up better.

“If you look at the amount of intake when cattle are grazing, they actually eat more in the evening than they do in the morning. Logically we'd say this is probably because it helps them get through the night, but you could also say that they'd need a big meal after they get up again in the morning to graze, since they are relatively empty. You could justify either time, but we now realize that the reason they graze more in the evening is because of the nutrition level of the plants at that time of day,” he says.

“A series of USDA studies (results published in 1999, 2002 and 2005) looked at animals' ability to choose different forages. The researchers cut some hay in the morning and some in the evening and used this in these choice tests. They've done it now with cattle, goats, sheep, and they all prefer and are able to select the hay that's cut in the late afternoon and evening. When you analyze that hay in the lab, it shows that it has a higher level of carbohydrates because that plant stored more nutrients during photosynthesis through the whole 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. After thousands of years of evolution, the grazing animals are well tuned in to the differences in the forage plants, and have a keen sense of what is most palatable and nutritious.

In winter during cold weather, cattle tend to graze after the sun comes up and stop grazing soon after the sun goes down. They don't like to stir from their warm beds until sunup, and usually try to seek a good bedding area before the temperature drops after sundown. “During sunlight hours they also tend to avoid shade (even the shadows of their herdmates) and they prefer to stand perpendicular to the sun, to soak in as much warmth as possible. They absorb a lot of heat from direct sunlight,” he says. At sunup they generally get up from their beds and hike to the spot in their pasture where the sun will hit first.

When feeding cows supplementary forage or protein during winter, knowing their grazing habits may enable the producer to feed at the best time of day to aid rather than hinder their total intake. If the cattle are grazing a winter pasture, you want them to graze as much as possible even though you are giving them a supplement. It might be best to time it so you don't disrupt their morning or late afternoon grazing period. If the weather is really cold and the cattle are slow to get going in the morning, however, it may pay to feed them early in the morning to stimulate them to get started eating sooner.

During summer in a rotational grazing or mob grazing program, knowing the natural grazing habits of cattle may help you decide when the best time(s) of day might be to move them to the new pasture.







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