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Basics Of Grazing Behavior

Cattle are grazers and browsers, eating a wide variety of grasses, forbs and leaves/bark from shrubs and trees. Not having upper front teeth, cattle can’t nip off plants as a horse does, but use their flexible tongue to wrap around a “bite” and break it off with a movement of the head. They bite short grass with the lower teeth and hard upper palate, but cannot graze as closely as a horse or sheep.

Domestic cattle are more versatile in diet than wild animals, partly because man has provided a variety of feeds and developed types of cattle that thrive in a variety of environmental conditions. A cow’s selection of plants is partly instinctive and partly learned from experience with various feeds, according to Dr. Clive Phillips (University of Queensland, Australia) who has studied cattle behaviour for more than 25 years.

For instance, a mature cow that’s never been fed grain may refuse to eat it. But a cow that grew up eating grain will readily eat it, even many years later. Young stock learn much of their feed preferences by mimicking other members of the herd, especially their mothers. Calves sample their mothers’ hay when only a few days old and stick their noses in water when mama drinks, following her example. By contrast, a hand-reared calf may not try hay or grain (or water) until several weeks old or older, not having a role model to copy, unless you stick the feed in its mouth a few times. Orphan calves do better if they can live with an older animal to teach them the facts of life about eating.

PLANT PREFERENCE

Cattle have definite preferences when grazing. They prefer new tender regrowth and avoid older, mature plants. As pointed out by Thomas E. Bedell, extension rangeland resources specialist, Oregon State University (now retired), the levels of most nutritive components of a plant decline as it matures, especially protein. “Cattle tend to select plants that are higher in protein and lower in fibre,” he says, so they prefer young, tender plants. A pasture can be most efficiently utilized if stocking rate is such that cattle trim it evenly and then move to new pasture. Rotational grazing works better for many pastures (allowing more cattle per acre and a healthier situation for the plants) than season long grazing.

With season-long grazing, preferred plants are over used. Cattle graze them again and again, because the regrowth is more tender than mature plants that become coarse and dry. Heavily grazed plants may be weakened or killed if this happens year after year. Once a plant becomes coarse and mature, the cow won’t eat it unless there isn’t much else left to eat. Old, rank “wolf plants” are rarely grazed; the plants become choked with dead leaves and stems, not as productive and healthy as a normal plant. For best plant health, grass must be grazed at some point in its growing season. Grazing stimulates new growth. A plant that’s periodically grazed is more vigorous and productive than a plant that’s never grazed. For best pasture health, grasses should be grazed with an adequate number of cattle to trim most of the plants a little, including the less palatable ones, and then the herd moved so plants can regrow. The same principles for growing a healthy lawn apply to pasture, but the periodic mowing is done by cattle.

This type of rotational grazing greatly minimizes the adverse effects of selective grazing by forcing more uniform use of a pasture. Bedell says the animals may not perform quite as well when use is forced but performance “can be better than expected if you can get them to graze the plants available. Unpalatable plants do not necessarily have poor nutritive value; rumen bacteria responsible for a cow’s digestion may not be as fussy as the animal’s taste buds.” They can convert the plant materials into usable nutrients.

SOCIAL FACTORS

Cattle are group grazers. They evolved as herd animals for protection against predators, staying together while grazing, eating plants that can be consumed quickly (minimizing time spent out in the open) then rechewing food later at their leisure in a safe place. They all graze together at certain times of day, moving as a herd over the pasture in a common direction and with a specific inter animal distance between herd members, and often with preferred grazing partners (certain animals in the herd grazing together).

Cattle are gregarious, uneasy and restless if separated from the herd. Yet they also need their individual space. If you put too many cattle in a small area, they become restless and do more walking and trampling of grass. They do best in relatively small groups rather than concentrated in small pastures in large groups. For ideal pasture rotation, you need to discover (usually by trial and error) what makes the most ideal stocking rate for each pasture (and for how long a period), depending on the type of grass, climate and terrain, and type of cattle. Some breeds are more restless when confined in large groups in small areas.

WASTED GRASS

On rangeland, where cattle have a lot of room, manure is dispersed over a wide area and has little effect on grazing patterns. In smaller pastures, fecal deposits may hinder use of some grass. Cattle don’t like to graze plants near their manure. As Dr. Phillips states, rejection of grasses around each fecal deposit will be greater in under grazed pastures because cattle have the choice of other, cleaner areas to graze. They reject grass next to manure at first because they can smell the feces, and later because it has grown tall and too mature.

This rejection of forage next to manure may be nature’s way of limiting parasite infestation; larva that hatch from worm eggs in manure crawl onto adjacent plants, ready to be eaten, to re-infest the grazing animal. Cattle will eat grass around manure of other species such as horses or sheep, whose parasites cannot complete their life cycle in cattle. Cattle and sheep can be grazed together to advantage. They complement one another in plant selection (eating a wider variety of total plants) and few plants will grow too mature and rank and they also graze next to each other’s droppings.

GRAZING TIME

Cattle need adequate grazing time to eat enough forage to meet their needs. If feed is good, they get full quickly and spend more time resting. If feed is scarce, they spend more time grazing. Because of their need to spend part of each 24 hour period chewing the cud, they may not be able to spend enough time grazing if feed is sparse. If cattle are spending part of their normal “resting time” eating, this is a clue they don’t have enough feed.

They may also short-change themselves on grazing time (and lose weight) if conditions are adverse, such as very hot or very cold. In extreme heat, cattle spend more time in the shade than grazing, and do some grazing at night when it’s cooler. In winter, when cattle are cold and days are short, they may stand around waiting for sunshine instead of grazing. Temperature must generally be higher than 20F before cattle get going in the mornings to graze. A little supplement can help, in cold weather.

Dr. Phillips says the high heat of digestion of fibre (in roughages eaten by cattle) enables them to survive very low temperatures without loss of production, provided they have a functional rumen to create that heat. “Pre-ruminant (young) or sick cattle or those that are inadequately fed, have reduced tolerance of cold stress. Feeding time for all cattle increases at low temperatures, but healthy ruminant cattle can easily adjust to subzero temperatures. The major nutritional adjustment is to speed up the rate of reticular contractions (one of the four stomachs) increasing ruminating time and the heat increment of digestion,” according to Phillips.

Stormy weather can cut into grazing time, as will any other conditions that interfere with normal grazing habits and patterns. Heavy rain usually halts grazing; cattle move to sheltered or brushy areas to wait out the storm. But a light rain often encourages them to graze, especially on a hot day.

Heather Smith Thomas ranches with her husband Lynn near Salmon, Idaho. Contact her at 208-756-2841

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