Rangeland cattle producers strive to graze their livestock in ways that are economically, socially, and environmentally sustainable. A major challenge facing many producers is to better manage cattle grazing in concert with clean water, fish and wildlife habitat, and recreational activities in riparian zones — for example, stream sides and shorelines. Attainment of these goals rests largely in a producer's ability to cost effectively control when and where cattle graze.
Opportunities exist for applying animal behavior principles to control cattle distribution and limit cattle grazing impacts in riparian areas. Adjusting the timing of grazing, supplemental feeding, herding, and selective culling are four strategies that producers can use to help ensure the sustainability of riparian cattle grazing. All four practices are more effective when ranchers capitalize on their knowledge of cattle grazing behavior.
Understanding and manipulating cattle behavior provides numerous opportunities for ranchers and scientists to develop cost-effective ways to limit grazing impacts in riparian zones. Failure to seize these opportunities will inhibit the economic, social, and environmental sustainability of riparian cattle grazing.
The timing of riparian grazing is important for good management. Cattle typically avoid grazing on wet soils. This explains why cattle usually spend more time feeding in upland sites during spring and early summer, and wait to graze riparian zones in mid and late summer. Therefore, allowing cattle to graze early in the season may limit utilization of streamside plants and streambank trampling if the ground surface is sufficiently wet.
Cattle browsing of riparian shrubs can be avoided by closely monitoring the abundance and palatability of the herbaceous forage. Cattle browsing of riparian shrubs increases with decreased palatability and availability of herbaceous vegetation. As long as the herbaceous component in the riparian zone is succulent and plentiful, cattle will not utilize shrubs much, even late in the growing season. Cattle, however, tend to shift their diet selection to riparian shrubs if the herbaceous component has been largely consumed or has reached seasonal maturity. Accordingly cattle consume more riparian browse in a dry year than in a wetter year. Some evidence indicates that increased browsing of willows in late summer may be related to a change in the chemical makeup of willows. For example, increased cattle browsing of planeleaf willow (Salix planifolia) coincides with decreased concentrations of ampelopsin in its foliage. Ampelopsin is a flavonoid, a specific plant metabolite that is believed to be unpalatable to browsing animals.
In mountain meadows, shrub utilization by livestock is usually slight as long as a herbaceous stubble height of 10 cm (4 inches) or greater remains. A definite shift in preference typically occurs when the herbaceous vegetation is utilized beyond this level. The shift is increasingly apparent when stubble height is reduced below 5 cm ( 2 inches). Cattle use should be closely monitored when stubble height for the most palatable herbaceous species reaches 7-8 cm (3 inches). At stubble heights below 7 cm (3 inches) cattle browsing of shrubs can quickly become excessive. Cattle behavior sometimes becomes visibly more unsettled when their diets shift from herbs to browse, and astute observers can use this behavioral cue to indicate when cattle may need to be relocated.
Cattle may disperse out of a riparian zone before the herbaceous stubble height is reduced below 10 cm (4 inches). Cattle often leave valley and canyon bottoms late in the season when cold air accumulates in the riparian zone, and when late-summer or early-fall rains improve the palatability of the herbaceous forage on adjacent slopes. Thus, late-summer or early fall may be an opportune time to allow cattle access to some riparian areas. However, cold-air drainage in flat, broad valleys is not prohibitive to cattle, and late in the season cattle are often drawn to these riparian areas because they contain the only remaining succulent vegetation. Understanding site-specific animal behavior is critically important for developing riparian grazing plans.
Supplemental feed can help disperse cattle away from riparian zones. Cattle tend to disperse farther from supplemental feeding sites when hand-fed supplement is not provided every day. Protein can readily be fed at two- or three-day intervals, even weekly, which can reduce feeding costs significantly. Grain supplements for energy, however, must be fed daily to avoid reducing fiber digestion. Hand-fed supplement should be provided when it least disrupts normal grazing activity patterns. Early afternoon is generally best. Animals supplemented in the morning expend more energy foraging and traveling compared with animals supplemented in the afternoon or un-supplemented animals.
Self-fed supplements should be placed no more than two miles apart if in level or gently rolling topography; supplements are usually placed one mile apart or closer if the topography is rough. Supplements should not be located less than one-third to one-fifth miles from surface water to limit animal impacts in riparian areas. However, it is important to remember that animals consuming supplements with high salt content need access to an ample supply of water so that animals are able to excrete the salt via urine. Livestock consuming salt-mix supplements often increase their water intake 50 to 75%. Salt-mix supplements will not effectively change animal distribution when there are many natural salt licks or alkali spots in the area.
Cattle tend to consume supplemental salt only when it is convenient during their normal foraging pattern, but they are not apt to appreciably alter their behavior to obtain salt. Consequently, salt placement is generally incapable of overriding the attraction of water, shade, and palatable forage often found in riparian zones.
Supplements should be placed in accessible sites. Moving the locations from year to year can help limit impacts to soils and vegetation from congregated animals, but moving the locations annually may prevent cattle from learning where to locate the supplement. Unfortunately, permanent locations for supplementing discourage animals from foraging far away from the feeding site and may encourage substitution feeding. Inclement weather may reduce supplement consumption from self-feeders because animals avoid traveling to the feeders. Consumption during inclement weather is more easily maintained when supplement is provided near shelter cover.
Movements between pastures are made easier by withholding supplement just prior to turning cattle onto a new grazing area. Upon entering the new area, the cattle are then trailed to the new supplementation site(s) and greeted with a familiar reward. Gathering animals very early in the morning, prior to their morning grazing bout, and then herding them to new supplementation sites works well. Supplemented animals are easier to handle and easier to gather and herd than un-supplemented animals.