Grazing

Overview

Grazing by cattle, sheep, and goats can be used as a technique for controlling weeds. There are differences in effectiveness among grazers depending on weed species and environments being targeted, but in general, grazing (herbivory) for weed control varies more by the plants being grazed than the animals grazing them. While grazing can be a useful tool in an integrated management practice, there are many different things to consider, including toxicity, stage of growth of the plant, palatability, etc. If you are interested in how grazing can be a successful part of your integrated management, please contact your local University of California Cooperative Extension Livestock Advisor (https://ucanr.edu/sites/UCANR/County_Offices/), Natural Resource Conservation Service (https://www.nrcs.usda.gov/wps/portal/nrcs/main/ca/contact/local/), or a Certified Rangeland Manager (https://bof.fire.ca.gov/projects-and-programs/professional-foresters-registration/rpf-crm-rosters/) to help you develop a successful control plan.

In recent years, land managers have begun to consider grazing and browsing not just in terms of livestock production for food and fiber, but as a means of managing for the sustainability and healthy function of California’s ecosystems. Livestock can control the mass, height, and cover of herbaceous vegetation and reduce the encroachment of shrubs into grassland. In addition to covering the use of grazers for targeted weed control, we discuss their use as ecosystem engineers, altering and improving habitat by herbivory, trampling weeds, reducing fuel load, altering soil compaction, or providing other byproducts of animal behavior. Grazing and browsing (collectively called grazing here) are not effective as a single-event solution to a weed problem and only work to remove target vegetation when managers can attract and constrain animals to the target area. Grazing can successfully slow the spread or suppress populations of weeds but is very unlikely to eradicate large populations without potentially damaging desired vegetation. It should be viewed as a supporting practice for long-term management or slowing spread while other control methods are being brought to bear.

Livestock are effective at reducing biomass, height and cover of non-native annuals and preventing shrub encroachment on California’s annual grasslands and woodlands. They can be used to target specific weeds by managing the time, frequency and intensity of grazing or browsing. This is best accomplished with fencing, attractants and selecting the appropriate species based on class (sex and age) and experience.

In general, cattle prefer to graze on palatable plants that provide the most bulk (biomass) - usually, grasses. Sheep and goats are less able to process lots of cellulose, so they typically pick plants and plant parts that have higher amounts of easily digested sugars and are lower in complex fibers – this means leaves, seeds, and cambium (inner bark). Sheep often prefer broadleaved herbaceous plants (forbs), but will use grasses, especially leaf material and fine stems. Goats prefer leaves and immature leader twigs of shrubs and trees, and the cambium layer of trees that have soft outer bark. Cattle and sheep are commonly described as “grazers” and goats (like deer) as “browsers”. Cattle have wide mouths and will use their tongue to rake in mouthfuls of vegetation (low selectivity). Sheep and goats have narrower mouths, which allows them to selectively nibble off parts of plants. There is a fair amount of “plasticity” in these animals, however. Individual animals, and even whole herds, can develop skills for utilizing plants in ways that do not entirely follow these generalizations.

Each situation and opportunity for weed control is unique to the area and the species being targeted. Cost can range from providing an income, if you are using livestock that are already on-site and you are being paid to graze, to being more costly than other management methods if you have complex grazing needs, no infrastructure and no animals on-site. On an area basis, it is more expensive to graze small acreages than large acreages because of the economy of scale. It is easier for an animal owner to move livestock to a larger area where they will be longer than moving them between smaller sites frequently.

How to Use

Grazing and browsing can alter the structure and vigor of plants. Experienced and observant managers can selectively use animal species, densities, and previous foraging experiences together with specific timing and frequency of grazing events in order to control particular plants. Different scales of weed invasion and different species require different approaches to grazing. Small weed patches are challenging because it is hard to focus animals on them. Large target areas, in contrast, typically will require more animals than feasible. Techniques to concentrate animals such as temporary electric fencing, supplementation (feed hay on top of target plants, place supplement tub in area, or the application of molasses) may work to target areas in large pastures.

Livestock can be “trained” to eat some weed species they do not initially show an interest in. This does not mean that animals will ever exclusively eat these weeds; however, they are more likely to eat them along with the forage they encounter. Several training methods have been developed, including placing hay or molasses on top of the target plant. Kathy Voth’s method (https://extension.sdstate.edu/cows-eat-weeds) is the most common training practice currently used by targeted browsing experts.

Plant secondary chemicals (for example, tannins) can affect livestock digestion and health. Protein supplementation may reduce the effects of secondary chemicals somewhat. Animals fed low-nutrient dead or dormant vegetation, like late season annual grasses, will likely need energy and protein supplements to meet nutritional requirements. Land managers should expect this and plan for suitable locations to place the supplemental feed sites. Areas might include dense weedy sites or other areas away from sites that need more protection.

High-intensity grazing of grasses and forbs must occur as the target plants are leaving the vegetative growth stage and beginning to flower, but prior to seed set in order to prevent regrowth. Woody species can be controlled at a wider range of phenological stages but are generally most palatable to browsers when producing new growth. Seeds are not always damaged by passing through the digestive tract of animals. This is especially true of grass seeds. Grazing and browsing timing will vary from year to year with temperature and soil moisture, requiring frequent site visits. The longer the target plant can propagate, the more challenging the control.

Timing and frequency. Livestock grazing is most effective at suppressing invasive weeds when it prevents seed production of annual plants, or others that similarly rely mainly on seeds for reproduction. Generally, a plant has the most difficulty recovering if it is grazed between the time when the flower head is ready to emerge (boot or bud stage) and full bloom. For grasses, this means the boot stage. This is a short period of time just before flowering. Timing will vary year to year with precipitation and temperature, but usually, there will be roughly a two-week window for grass species. To control forbs, the best time to graze is during the bud stage, when plants are “bolting” (sending up a flowering stalk). In Central California, the bud stage of many forbs occurs as annual rangelands are entering the dry season. Timed properly, grazed grasses and forbs will not have enough water and nutrients for regrowth and seed production.

Any grazing done prior to this window may not reduce targeted plants since there may be enough water and nutrients for plants to regrow. In some cases, using repeated grazing may be necessary, but care should be taken if there are susceptible desired plants. In some instances, the period when weeds are most susceptible also coincides with desired plants. Monitoring desired and targeted species is necessary, and grazing should stop if desired plants receive too much pressure. On California’s annual rangelands, the dominant species are typically introduced annual grasses such as soft chess (Bromus hordeaceus), wild oats (Avena fatua), foxtails (Hordeum sp.) and/or Italian rye grass (Festuca perennis) which may still provide the desired ecosystem services. In comparison, Medusahead (Elymus caput-medusae) and barbed goatgrass (Aegilops triuncialis) are invading annual rangelands and reducing ecosystem services. These invasive annual grasses mature later than other annual grasses with the exception of annual rye grass, typically maturing in late May to early June. This difference in maturity can be used as an advantage to control these species when grazing is delayed until after seed set of desirable species. Native perennial grasses are most susceptible to grazing when flowering (spring and summer depending on species). If there are native perennial grasses in the area, care should be taken to ensure natives are not overgrazed. This may mean moving animals out of the area before goals are met for targeted species.

All livestock species will browse on shrubs and trees. Cattle and sheep will preferentially select seedlings and resprouts, whereas goats will reach up to browse growing ends of mature shrubs. Livestock can be introduced into areas recently cleared of shrubs (e.g., following shrub removal or after a wildfire) to browse on the palatable young shrubs and trees. Browsing after shrub control treatments can extend the results of the original shrub removal. In the case of a wildfire, livestock can help suppress shrubs, increasing grasses. Livestock may preferentially browse some shrub species, but usually target new growth regardless of species. Browsing 50-60% of axillary and apical buds of shrubs in the dormant season (winter) can hinder spring regrowth. Defoliation is generally more detrimental to shrubs than it is to grasses. Successful shrub management may periodically require higher stock densities and ongoing grazing to prevent shrub encroachment and establishment. Note that although livestock can browse and impact shrub species, they may eat grasses and forbs first, particularly in the green season. It is important to keep monitoring the situation. Practitioners should be aware that removing the native shrub canopy will increase non-native plant cover in virtually every plant community in California.

Grazing Intensity or Stocking Rate. Stocking rates (animal units per unit of grazable forage) must be adjusted to maintain effective grazing intensity as site productivity varies. Well-defined goals for the condition of the site must be established. For example, targets for residual dry matter (RDM – the amount of dry forage measured in September that will be present to protect soils from winter erosion and create a microclimate to germinate new seedlings), habitat structure and/or composition, and sensitive species impacts should guide management decisions and adjustment of stocking rates, as well as duration of grazing in any given year. This is the art of grazing: monitoring the land and watching for signs to increase or decrease livestock for the desired effect. It will take time to develop a relationship with an operator to meet target plant control goals. During this time, the grazing project will require frequent monitoring and communication with the operator. It may be necessary to feed supplements or use temporary fencing to achieve the stocking rate for a specific area. When determining the stocking rate, the size of the area, percent of target species in the area, amount of palatable vegetation, and slope should all be considered. The local manager’s experience with their livestock, and supplemental tools to encourage targeted grazing should also inform stocking rate and appropriate stock density. A higher number of animals for a short period of time will reduce selectivity by increasing grazing competition, resulting in more uniform grazing. If the target species is very palatable, lower numbers for longer periods of time are possible, though control of the target species may be patchy as a result. Constantly monitoring the progress of the livestock in relation to goals is key. See Supplemental Information for more on stocking rates and developing grazing prescriptions.

Target weed species should be monitored for the correct stage of growth to be susceptible to grazing impacts. Early season drought will cause all species to mature earlier than usual. While grazing during the dry season may help reduce biomass, it will not typically stop the return of invasive weeds that have already set seed. Additionally, sources of dry-season water and protein supplementation may be required to allow livestock to graze dry plants without losing too much weight. During wet periods, managers should consider the risk of increasing soil compaction if high animal densities or prolonged periods of grazing are used.

Cattle. Classes of cattle include cow-calf pairs, dry cows, stockers, and bulls. See Supplemental Information for a definition of each class. Each class will exhibit different grazing behaviors. Stockers and dry cows will travel farther from water than cow-calf pairs. Experience can play a big part on how willing an animal will be to graze a weed species. If the animal has grazed the plant in the past, they are more likely to do so again. If dry cows or cow-calf pairs are brought to a novel area, they will be less likely to try new species of plants they encounter, and typically will not travel as much of the new pasture compared to stockers.

Sheep. Sheep will often have a guardian animal with them to protect from predators, typically a guardian dog, but potentially a llama or a donkey. Some flocks will also be overseen by a fulltime herder. If sheep are used to control weeds, there is a greater chance that the project will have adult ewes (equivalent to dry cows). If ewes with lambs are being used to graze, there may be more concern for predators and weather conditions that may affect young lambs. Solar powered woven wire electric fence is often used with sheep to keep them in a small, defined area for grazing. See Supplemental Information for definitions of sheep classes and reproduction.

Goats. Goats tend to be more willing to explore and test fencing and equipment, may be more curious, and sometimes more aggressive than sheep. This means they can require more experience and better equipment to maintain and manage successfully. Fencing is similar to sheep fencing, with solar powered woven wire electric fence commonly used. If goats are being used to control more herbaceous and less woody plants, a secure fence is needed so they do not escape the grazing area to search for “greener pastures”. Properly selected, experienced, and conditioned goat herds are likely to make better use of difficult terrain and vegetation (especially brush) than other domestic livestock species. However, those environments are also among the most difficult to construct and maintain effective temporary fences in. Goats can also climb on woody plants to some extent, so fencing should be carefully placed so that shrubs and trees don’t provide goats with a ladder out of the intended grazing or browsing area. See Supplemental Information for descriptions of goat classes, reproductive cycle and common breeds.

Special Tips

While the information presented here is provided to help aid you in selecting grazing and/or browsing, there are many more variables in designing a successful grazing management plan than we can address here. For the best end product, please consult with a professional range manager – a Certified Rangeland Manager, local UCCE Livestock Advisor or local Natural Resource Conservation Service Range Conservationist. A site visit will also be necessary to ensure a well thought out plan is created for your situation.

An inventory of plant species should be done prior to beginning weed control. The inventory should include location and density of weeds as well as locations of sensitive plants that should be protected from animals and toxic plants that could harm livestock. Knowing your starting point will help aid you in determining the success or failure of any control measure as well as help aid you in selecting the appropriate tool(s) and method(s) for control.

Use photo monitoring to establish a visual record of control efforts. Permanent markers (fence posts) can be installed or used and direction described to repeat the photo in subsequent year using either a digital camera, smart phone or tablet. In addition, apps are available to help manage photos over time.

Some treated sites may appear “overgrazed” for weeks to months following initial treatments. Done properly, however, the site will recover in the next growing season, and dramatic changes in appearance will not be common in the future. If the property is public, or easily seen by the public, some educational outreach will be important to explain the restoration process. Signage with before and after pictures may suffice to communicate the undesirable “before” state, the intermediate state after grazing, and the desired “after” state with reduced undesirable species allowing for more ecosystem services such as habitats for native wildlife and plants, water quality, reduced wildfire risk, and viewshed quality, to name a few.

To prevent accidental introduction of weeds to new locations, animals should be fed weed-free forage for 24-48 hours after grazing an infestation and kept in a holding area where weeds germinating from seeds that have passed through animals can easily be detected and controlled.

Optimal Conditions for Use

Graze a target weed just before flowering to maximize effectiveness. Its stage of growth (phenology) should be regularly monitored leading up to grazing. An early dry season will result in plant species maturing earlier. Additional water sources and supplementation may be necessary to encourage or sustain grazing in an area long enough to meet control goals. While this will take extra monitoring, it can be an optimal time to control species since drought conditions may not allow for regrowth, and therefore reduce seed production. Optimal site conditions include low cover of sensitive or other desirable species that are vulnerable to grazing.

Caveats

Some native grasses are most susceptible to damage from grazing during flowering (late spring and summer, depending on species). This often coincides with the flowering periods of some invasive species. If there are native perennial plants in the area, care should be taken to ensure they are not being grazed very heavily in that critical window or if necessary, the treatment is not repeated in the same location season after season.

Grazing and browsing, even at high intensity, are seldom effective at eradicating weed populations, and rather should be part of an integrated pest management (IPM) plan. Even after targeted plants are reduced to desired levels, grazing and browsing may be continued, perhaps at altered frequency and intensity, to maintain the ecosystem in the desired condition.

Although livestock production is compatible with habitat enhancement, there may be a production cost associated with targeted grazing. A land manager can usually expect to pay for a targeted grazing service. In contrast, when grazing supports livestock production, the rancher typically pays to graze.

Access and infrastructure (roads, fencing, gates and water) may limit the ability to use grazing on a given site. Truck and trailer access for example may be required to transport animals. A legal perimeter fence must have five strands of barbed wire, while a single strand of temporary electric fence may suffice for an interior fence. The grazing operator can determine if the fences in the area are sufficient. The ability of grazing and browsing to control vegetation is not hindered by distance from roads as much as it is limited by logistics related to grazing. Facilities for handling livestock are another consideration. At a minimum a loading chute is required. This could be a small pen with panels to funnel animals into and out of a trailer. In general, larger livestock require more infrastructure than smaller livestock. In every grazing area fresh water from either a stock pond, trough, or stream must be accessible to the livestock. Water, salt, or other supplements may be used to attract livestock to target plants.

Grazing and subsequent digestion by animals will not kill all seeds. Seeds can remain viable and can be spread to other areas or distributed further in the control area if sufficient care is not taken in animal management. Thus, grazing must be done prior to seed set, preferably right as the plant is leaving the vegetative stage and entering the reproductive stage (full emergence of seedhead). Timing varies for each plant and can vary year to year depending on precipitation and temperatures. Grazing at this time capitalizes on higher plant palatability compared to later reproductive stages when seeds are developed, while occurring late enough in the year for annual plants to be moisture limited and not able to regrow. Grazing before this time may allow the plants to recover and flower before the season ends.

Moist soils are more susceptible to compaction than dry soils, so high-density grazing may compact soils more during wet conditions. Managers should consider the risks of compacting soils on desirable species when considering using high animal densities or prolonged periods of grazing during wet periods.

Livestock grazing has been used in recreational use areas. Even when managers educate park users on the use of livestock in the park, common management practices, and how to share the trails (such as no dogs off leash), ranchers in these areas must deal with open gates, trash around the trails, and other nuisances. While these may seem minor, gates are important in targeted grazing, keeping animals in or out of a specific area to remove weeds. Livestock may try to consume trash found along trails creating an animal health concern.

If there are bighorn sheep in the area, care should be taken when planning sheep or goat grazing. Domestic sheep have been found to carry respiratory diseases that have a higher mortality rate in bighorn sheep. Results are mixed in regard to goats also being carriers and may depend on whether the goats have been mixed with domestic sheep or not (Pils, 2018).

Potential Hazards to Humans, Environment, and Cultural Resources

Human safety. Low risk. Human hazards and conflicts are rare with livestock grazing. If using animals in an area where there is recreation, there can be perceived potential hazards from the public, especially if visitors have off-leash dogs. Dogs off leash around cows with calves create a potential issue since the cow will protect her calf from her perceived threat of the dog or even the person if they are too close. Sheep and goats will not seem as threatening to people because of their smaller size but will still protect their young as will the guardian animal with them. University of California Cooperative Extension efforts to educate users on natural animal behaviors and how to share space (such as restricting dog use or enforcing leashed dogs only) have reduced conflicts (fact sheets are available: https://ucanr.edu/sites/BayAreaRangeland/). Grazing and recreation co-exist in East Bay Regional Parks in the San Francisco Bay area, Sonoma County Open Space, East Bay Municipal Utility District lands and San Diego County Parks, and other areas.

Cultural resources. Low risk. Livestock grazing typically is not a concern regarding cultural resources. If there is concern about potential trampling or soil erosion at cultural resources sites, the site can be fenced off with temporary electric fence.

Sensitive species. Low risk. Livestock grazing typically is not a threat for most sensitive species. Grazing in vernal pools, once thought to be detrimental, has since been shown to be beneficial to vernal pool flora and fauna. Many threatened and endangered species live on rangelands, some of the last habitat available to them due to surrounding development of natural areas for housing, vineyards and orchards. In many cases, invasive species are more detrimental to habitat than grazing. Woody species in grazing areas may be a concern, but grazing can and should be controlled to balance weed management with browsing on woody species and soil moisture. Win-win situations are possible, and monitoring should be done to ensure goals are met.

Erosion risk. Low (with proper management). Erosion risk is minimal for most habitat types when grazing is properly managed. Established residual dry matter (RDM) guidelines related to rangeland type and topography are available athttps://anrcatalog.ucanr.edu/pdf/8092.pdf. Although the RDM publication focuses on productivity, the guidelines also help protect soil from erosion and nutrient loss. Riparian or wetland areas grazed in the wet season would be at the biggest risk of erosion. Time grazing, if possible, to the dry season when there is less soil moisture.

Consider Combining with the Following Non-Chemical Methods

Grazing is compatible with other methods in an Integrated Pest Management (IPM) plan. Grazing may be followed-up with other methods of control when control is incomplete and it may also supplement other control options. It can be included in any plan to remove woody species since young growth is very palatable and grazing can lengthen the lifespan of the results of mechanical removal or a controlled burn. Grazing can be a viable alternative to mowing as well. Multispecies grazing, using cattle, sheep, and/or goats at the same time, should also be considered where appropriate.

Don’t Use This Technique When/For

Do not allow grazers to feed on toxic plants. Many plants can be toxic to animals. Below is a table of common plants found on rangelands that are known to be toxic to livestock. It is not comprehensive. While some of the plants listed are often grazed successfully (ryegrass, starthistle), often there is a timing or amount of the vegetation that provides a safer grazing window. The list below is from Livestock-Poisoning Plants of California, 2011 (see References). An “X” means the plant does have toxic characteristics for that species. Note that this is not a comprehensive list of toxic plants.

Plant (common name)	Cattle	Sheep	Goats
Arrowgrass	X	X	X
Avocado			X
Chokecherry	X	X	X
Cocklebur	X	X	X
Curly Dock	X	X
Deathcamas	X	X	X
Dogbane/Indian Hemp	X	X	X
Fiddleneck	X	X	X
Foxtails	X	X	X
Greasewood	X	X	X
Groundsel	X	X
Horsetail	X	X
Klamathweed	X	X	X
Tall Larkspur	X	X
Locoweed	X	X	X
Lupine	X	X	X
Milkweed	X	X	X
Nightshades	X	X	X
Oak	X	X	X
Oleander	X	X	X
Poison Hemlock	X	X	X
Ponderosa Pine	X	X
Ryegrass	X	X	X
Starthistle		X
Summer Pheasant’s eye	X	X
Tobacco	X	X
Toyon	X	X	X
Veratrum	X	X
Water Hemlock	X	X	X
Western Bracken fern	X

The importance of timing and stocking rate are critical when managing species with lower palatability. Both yellow starthistle and medusahead can be reduced with properly timed grazing at appropriate stocking rates but can increase if too few animals are used and they are able to selectively graze more palatable species or if implemented at the wrong time.

Supplementary Information

History

Grazing and browsing animals have roamed California’s landscapes for millions of years. Although the large grazing herds of bison found in the Midwest never occurred here, large herbivores did populate the grasslands, shrublands, and woodlands during the Pleistocene. The arrival of the first humans at least 20,000 years ago coincided with the mass extinction of many species of megafauna. However, it was the arrival of Europeans and domestic livestock in the 18^th century that began the transformation of California’s landscape. Non-native grasses and forbs spread throughout California’s coastal prairies, valleys, deserts and foothills.

Burcham (1961) described how California coastal and central valley rangelands were converted to annual grasslands. That began with the first establishment of permanent Spanish settlements in the mid-late 1700s, which led to the incidental introduction of Mediterranean grasses and forbs. The spread of those plants seemed gradual until the 25 year period from 1845 to 1870 in which a rush of livestock into California with the Gold Rush, followed by a historically severe drought, and then widespread plowing of grasslands for wheat production decimated many native grass populations. During the Gold Rush, the human population, surging from 26,000 to 380,000 from 1849-1860, generated massive increases in demand for food (Jelinek, 1999). In that decade, cattle numbers grew from 250,000 in 1850 to one million by 1860 (Stewart, 1936). The first California sheep census in 1850 found 17,514 animals remaining, compared to the 17 million estimated in 1825. Sheep were rushed into California from nearby states during that period. A half-million came from New Mexico alone between 1852 and 1870. By the mid-1870s, California sheep numbers had recovered to 6 million (Miller, 1930). Now, grazing of domestic livestock is a widespread use in California, with up to 40% of California being grazed each year. According to Saitone (2018), beef cow numbers, which are the primary type of livestock grazing on California’s grazing lands, peaked in 1982 at nearly 1.2 million head. In January 2020 the state livestock inventory listed 665,000 beef cows; 570,000 sheep (including lambs); and 87,000 meat & other goats (NASS, 2020).

Developing a Grazing Prescription

Grazing is simply a means of removing biomass that is similar to mowing or burning. A management prescription to conduct grazing is important to optimize grazing to achieve your objectives while minimizing environmental risk. It can only be as good as the data which informs it. A prescription begins with clear and specific objectives for the activity.

Example:

We will use cattle here for the numbers, but you may substitute any species by using the Animal Unit equivalent (AU), the weight of an animal in relation to 1000 pounds. A 200-pound sheep, for example, would count as 0.2 AU (200lb ÷ 1000lb = 0.2).

Suppose a local fuels management specialist advises managing for not more than 1,000 pounds per acre (lbs/ac) fine fuel that blends into brush on a 1,200-acre hillslope opposite a residential area based on UC recommendations for RDM. The site typically produces an average of 2,100 lbs/ac, with peak production normally reached between March 1 and April 15 (Ecological Site Description; Fig 1). The local NRCS soil conservationist recommends managing for not less than 800 lbs/ac residues on the hillslopes in order to guard against soil erosion. Your consulting CRM recommends estimating a 7%/month residue decay rate between June 1 and Nov 1 (5 months; the optimistically estimated return of germinating fall rains; Fig 2). That works out to a minimum of 756 lbs/ac of residues that needs to be left on the ground on June 1 (assuming no further grazing after that time). That gives about 30 days of grazing at higher grazing pressures, or several months of grazing at lower grazing pressures.

Math:

If a couple neighboring ranches offer to graze that hillside, and it was covered mostly in vegetation that the cows would eat, how many cows would it take to do the job in 45 days (March 1-April 15)?

To figure that out, we would start with the best data we had on grassland productivity for that site. If no actual measurement data is available, we could go to the USDA-NRCS soil survey or an Ecological Site Description for the area (if one exists). Let’s say a local conservation organization has been monitoring grassland productivity nearby, and their data indicates an average of 2,100 lbs/acre.

Can you just ask the ranchers to take all the vegetation off this hillslope to make it extra safe for the homeowners on the other side? That would likely create a crisis for many wildlife species and native plants, not to mention probably lead to significant soil erosion. So take the NRCS conservationist’s advice and leave 800 lbs/ac in place at the time the fall rains normally begin. That means you can graze it down to 800 lbs/ac on April 15, and leave the dead grass until November? No. The dead grass decays – even in summer. The University of California Cooperative Extension conducted research in Kern County that found the decay rate there was about 7% per month. Probably that varies, depending on location and moisture levels. But we’ll assume that using should be adequate here. If we need 800 lbs/ac on the ground Nov 1, and it decays at a rate of 7% per month (we assume), how much should there be on April 15? To do that we’ll multiply the Nov 1 RDM objective (800 lbs/ac) by (1+7%) raised to the 6.5 months to get us to Nov 1. That gets us to 1,242 lbs/ac.

Now we can figure out how much there is for the cattle to eat. If the total amount is 2,100 lbs/ac, and we have to leave 1,242 lbs/ac behind, that leaves us with 858 lbs/ac that is grazable. There we go, right? Nope. Turns out that when you let animals walk through their food, they trample and poop on about as much as they actually eat. So we plan to use 50% of that (called “harvest efficiency” by the USDA-NRCS). That gets us to 429 lbs/ac. That times 1,200 acres gives us 514,864 total pounds of forage that the cattle could remove by eating.

Last steps. Let’s say the ranchers say their cows average about 1,300 lbs in weight. Using an intake estimate of 2.6%¹ of body weight for these animals, that gets us 33.8 lbs/cow/day. If we are giving ourselves 45 days to get this job done, how many cows would it take? That will be the total amount of consumable forage (514,864 lbs) divided by the daily intake per cow (33.8) times the number of days (45). That gives 339 cows.

This probably already seems fairly complicated, but it is a relatively simple problem as grazing projects go. And we’ve simplified a number of things in it (not least, if cattle are only actually eating half of what remains in the field, why didn’t we just roll that back into the RDM objective?). These are examples of things for which it is useful to seek the advice of local specialists. For large projects, professionals like CRMs make sense and can be worth the extra expense. For smaller projects, UCCE and staff from conservation organizations can be sufficiently helpful as well as most reputable grazing managers. Grazing managers (ranchers) calculate the feed available for livestock on a regular basis.

Also keep in mind that members of the ranching community who consistently employ good management practices (and there are many of them) provide substantial community benefits by managing their lands in ways that minimize fire hazards while also maintaining habitats for wildlife and native plants. Their fuel management on their own lands, through grazing, brush management, and (in some areas of the state) prescribed burns, protects not only them, but others to whom fires passing through their properties could potentially spread.

¹The US Animal Unit Month (AUM) system assumes an average annual forage consumption rate of 2.6% of live weight for mature cows. The actual consumption rate can vary from as low as 1.5% (losing weight in the dormant season) to as high as 3.5% (lactating on fresh, abundant grass).

Classes Livestock

Cattle. A cow-calf pair is a cow (female) with her calf up until she weans her calf at roughly eight to nine months. A dry cow is a cow who is no longer nursing her calf, from when the calf was weaned until she has her next calf. A stocker or yearling is a weaned calf (heifer- female; steer- castrated male) up to two years of age. Typically, in California stockers are shipped into the state roughly in November, and graze for one more growing season. Bulls are the males and most ranches only have the bulls with the cows during the breeding season, ranging from November to possibly March for fall calves as part of a normal husbandry practice. Cow-calf pairs are the most common type of livestock grazing in California. Calves and stockers are typically removed from California’s grasslands when forage does not provide adequate nutrition to support growth.

Sheep. Sheep have a different production cycle than cattle, a shorter gestation length, shorter period of time they nurse their lambs, and a smaller window to be bred. Terminology for sheep will be ewes (mature females), lambs (babies), wethers (castrated males) and rams or bucks (mature, intact males). Ewes tend to have twins more often than singles, and it is not uncommon to have triplets.

Goats. Goats are similar to sheep in terms of having a short production cycle, typically having twins, and requiring protection from predators. Terminology changes to nanny goats, kids, and billy goats, and wether is still used. Many breeds used for contract grazing have horns (Spanish, kiko as examples). Wethers are more often used for contract grazing than breeding flocks are.

References

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Contributing Authors

Lead Author: Theresa Becchetti, Range Management Specialist, UC Extension

Co-authors:

Sheila Barry, Livestock & Natural Resource Advisor, UCCE Bay Area
Denise Defreese, East Bay Regional Parks District Wildland Vegetation Program Manager, Vollmar Natural Lands Consulting
Carlos de la Rosa, Conservation Program Director, San Diego Zoo
Robert Freese, Senior Project Manager, Irvine Ranch Conservancy
Marc Horney, Professor, Cal Poly San Luis Obispo
Rebecca Ozeran, Range Management Specialist, University of California
Zach Principe, Stewardship Ecologist, The Nature Conservancy
Devii Rao, Range Management Specialist, University of California
Brian Shomo, Director of Natural Resources, Western Riverside County Association of Governors

Additional Contributors: None

Efficacies

Ratings: Excellent (>95% control); Good (81–95% control); Fair (50–80% control); Poor or ineffective (<50% control)

Results are based on an estimation of maximum possible single-season reduction in weed cover and propagule production (=control). Control efficacy was scored for each plant and site characteristic for each management practice individually using best available information, assuming other conditions were optimal. Results for management practices are organized by efficacy rating based on the lowest rating they received for the combination of plant and site characteristics chosen. Rating results provided by the WeedCUT tool are generalized and may not be suitable for all plants or site conditions with the characteristics chosen. Ratings assume that a multi-year strategy will be employed to achieve management goals.

			Rating
Plant	Flowering Period
		Winter	Good
		Spring	Good
		Summer	Good
		Fall	Good
		Multiple Seasons	Fair
		None	Good
Plant	Germination
		Winter	Good
		Winter / Spring	Good
		Spring / Summer	Good
		Opportunistic	Fair
Plant	Palatability
		Yes	Good
		No	N/A
		Partial	Fair
Plant	Plant Growth Form
		Grass	Fair
		Forb	Good
		Shrub	Fair
		Tree	Fair
		Vine	Fair
Plant	Plant Type
		Annual	Good
		Biennial	Good
		Perennial	Fair
Plant	Propagule Production
		Low (<1000/square meter)	Good
		Moderate (1000–10,000/square meter)	Good
		High (>10,000/square meter)	Fair
Plant	Rate of Spread
		High (doubling in <10 year)	Good
		Moderate (50–75% increase in 10 years)	Good
		Slow Rate (25% increase in 10 years)	Good
Plant	Resprouting / Regenerative Capacity
		Low	Good
		Moderate	Good
		High	Fair
		None	Good
Plant	Seed Life
		Short (≤3 years)	Good
		Moderate (4–10 years)	Good
		Long (>10 years)	Fair
Plant	Type of Reproduction
		Seed	Good
		Vegetative	Fair
		Seed & Vegetative	Fair
Plant	Type of Vegetative Reproduction
		Rhizome / Stolon / Stem	Poor
		Bulb / Corm / Tuber	Poor
		Root sprout / Sucker / Crown sprout	Fair
Site	Existing Desirable Plant Cover
		<10%	Good
		10–25%	Good
		26–50%	Good
		51–75%	Fair
		>75%	Poor
Site	Ground Condition
		Muddy	Fair
		Smooth	Good
		Cobbly	Good
		Rocky	Good
Site	Habitat
		Marsh / Wetland	Poor
		Riparian	Fair
		Grassland	Fair
		Shrubland	Good
		Woodland / Forest	Good
Site	Level of Tolerable Disturbance
		Low	Poor
		Medium	Good
		High	Good
Site	Slope
		Flat	Good
		Moderate (10–40%)	Good
		Steep (>40%)	Fair
Site	Target Area
		<40 square feet	Ineffective
		0.001–0.01 acre	Ineffective
		0.02–0.1 acre	Ineffective
		0.2–1 acre	Good
		2–10 acres	Good
		11–50 acres	Good
		51–100 acres	Good
		>100 acres	Fair
Site	Targeted Invasive Plant Cover
		<1%	Poor
		1–10%	Fair
		11–25%	Good
		26–50%	Good
		51–75%	Good
		>75%	Fair
Site	Vehicle Accessibility
		Roadside	Good
		<100 feet from road	Good
		100–1000 feet from road	Good
		>1000 feet from road	Good