Central Coast Agriculture Highlights Newsletter -- June 2000

From our Central Coast Agriculture Highlights newsletter June 2000 issue:

RESIDUE MANAGEMENT

Now that the rains are over (I think) for this grass year, except for some browsing that may provide some nutrients, the majority of the forage available is the residue of this year’s annuals. Since annual-type ranges contribute about 80 percent of the range forage for California’s livestock industry, their management is important to the state’s agricultural economy and the conservation of its natural resources.

Annual rangelands differ from perennial range-lands because they are occupied primarily by annual plants. Perennial range plants are influenced by conditions in current and proceeding years, which affect their root reserves and regrowth. Annual forage responds each year to conditions that influence plant germination and establishment in the fall. Fall weather has the greatest impact on early annual plant growth. This growth also is further influenced by the water-holding capacity of the soil and residual dry matter (the amount of dry plant material left on the ground from the previous year’s growth). Residual dry matter provides favorable microenvironments for early seedling growth, soil protection, adequate soil organic matter, and a source of low-moisture fall forage for livestock feed. Residue is the variable in the fall that can be most controlled by management.

Now that we are in the mode of residue management of the forage from last year’s production, I thought it would be useful to provide information to help you manage this feed supply.

The following guidelines draw on research conducted at the San Joaquin Experimental Range, Hopland Field Station, and numerous other field plots by the University of California and the U.S. Forest Service and some work we started last year comparing our local conditions with those in other locations.

Amounts of residual dry matter (RDM) per acre vary according to geographical, soil and livestock use situations. Areas with heavy rainfall, erosive soils, or steep hills need more residual dry matter than do flat, stable soils in drier climates. The guidelines mentioned here represent a range of minimum or lower threshold levels for California. As a manager you are encouraged to test these minimum level guidelines and develop your own levels to meet requirements of specific sites and conditions.

A livestock stocking rate that leaves too much RDM reduces both forage and livestock production. Annual legumes and filaree require adequate, but not too much, residual dry matter for their optimum growth. It is also important to consider residual dry matter as important for soil protection. Observing the guidelines for management should maintain soil erosion at natural levels.

Adjusting the cattle livestock rate according to residual dry matter available requires flexibility— livestock needs must be balanced against available forage. If rainfall is low, utilization may exceed established guidelines, although this situation should be the exception and not the rule. Periodic heavy grazing has short-term effects only. Heavy grazing over a long period reduces production and causes an increase in low-growing plants.

Using residual dry matter standards requires an ability to distinguish between the influences of grazing and environmental effects. This is difficult because the annual grassland is so responsive to weather, especially the amount and distribution of rainfall and daily temperature. Careful interpretations and even alterations of the general guidelines must be made for local situations. Criteria for evaluation of desired levels of residual dry matter for a specific situation includes herbage productivity, desired plant species composition, livestock performance and ground cover.

When estimating residual dry matter you can learn to make a visual determination or if you want to be more precise, you can clip and weight the amount of dry matter in a given representative area (usually a square foot or 1/10 square meter area). However, low intensity sampling methods are adequate for most range-management decisions. An easy and quick method is to visually check the residual dry matter left prior to the first effective fall rains, usually late September or early October. The "moderate" level of grazing has been recommended for the best livestock performance and range protection in this zone. Moderate grazing also provides more residual dry matter than listed in the minimum guidelines described earlier. The other grazing intensities described, "light" and "heavy," are examples of too little and too much utilization.

Light grazing leaves little or no patchy appearance. Unused plant matter averages 3 or more inches in height and small objects are masked. The residual dry matter is more than an average of 800 pounds per acre. Moderate grazing leaves an average of 2 inches of unused plant matter, a patchy appearance, and little bare soil. Small objects will not show at a distance of 20 feet or more, and the residual dry matter ranges from 400 to 700 pounds per acre. Heavy grazing leaves less than 2 inches of unused plant matter. Small objects and areas of bare soil are visible at 20 feet or more, and the residual dry matter is less than 400 pounds per acre.

Early guidelines suggested for our local conditions should require a minimum or lower threshold level of residue to be as follows:

On lower or flat slopes, a minimum of 400 pounds per acre
On average or gentle slopes, a minimum of 600 pounds per acre
On upper or steep slopes, a minimum of 800 pounds per acre

However, these recommendations for the amount (lbs./acre) of RDM to be left on annual rangeland have existed for close to 20 years. There has not been an investigation where the relationship of the amount of residual dry matter and bare soil has been reported. Our preliminary results indicate that in the foothills of the Sierra Nevada Mountains, the current recommendation of at least 600 lbs./acre residual dry matter generally results in less than 15 percent bare soil. In contrast, it appears that to provide at least 85 percent soil cover on coastal rangeland areas, the amount of residual dry matter required will be greater, perhaps as much as 1200 lbs./acre. The fall of 1999 will provide us with the third year of data to strengthen our assessment of the needed residual dry matter to ensure a base level of soil cover.

If you would like to use this information to help you make decisions on your ranch, and you need help in either the technique of clipping/weighing RDM’s or estimating them by visual determination, please contact me.

BOVINE TUBERCULOSIS

As a regular reader of our newsletter, you are probably aware I include timely information prepared by Dr. John Maas, our Extension Veterinarian, at UC Davis. This continues to be an effective method of informing producers about health issues that can affect their cattle. The topic, Bovine Tuberculosis, is one that is rarely discussed but can have serious consequences if your cattle have been exposed to infected animals.

What is Bovine Tuberculosis? It is an infection in cattle caused by Mycobacterium bovis. This bacterial agent is closely related to Mycobacterium tuberculosis and both agents can cause tuberculosis in humans. The agent of Bovine Tuberculosis (TB) can infect many other mammalian species in addition to cattle and man. The infection in cattle mainly affects the respiratory system and can be easily spread by a number of methods.

What is the current status of Bovine TB? There has been an ongoing eradication program for Bovine TB in the U.S. for many years and currently all states are free of Bovine TB except certain zones within Texas and Michigan. The discovery of TB in wildlife in Michigan has been a major setback for the TB eradication program.

Where is the infection in Michigan? For the most part, bovine TB has been found in the northeastern portion of the Lower Peninsula of Michigan. As far back as 1975, a wild white-tailed deer from Alcona County was found to be infected with Bovine TB. Since 1995, about 35,000 deer in Michigan have been tested for TB and 281 have been confirmed positive. Bovine TB has also been found in coyotes, raccoons, a black bear, a red fox, and a bobcat. Most recently, deer infected with Bovine TB have been found outside the known infected area.

What is Michigan doing? The Michigan Department of Agriculture (MDA) has been testing all livestock in the area where TB had been identified in deer. They have tested more than 50,000 cattle and goats on about 1,100 farms. Four beef herds and one captive deer herd that were positive have been depopulated. A dairy herd has just been confirmed positive, and another beef herd is awaiting final results. The area affected with Bovine TB has been quarantined. Surveillance by the MDA and other agencies such as the USDA continues in livestock, white-tailed deer, and other wildlife in Michigan.

What is California doing? The USDA declared California free of Bovine TB in October 1999 (no evidence of TB during the previous 5 years). The California Department of Food and Agriculture (CDFA) has been very concerned about the Bovine TB in Michigan since 1995 when the disease was found to be endemic in wild white-tailed deer.

Because infected wildlife may have exposed livestock to TB outside the quarantine area in Michigan, CDFA is tracing all breeding cattle imported into California from Michigan over the last two years and is testing these animals for Bovine TB. CDFA will require future shipments of cattle, bison, goats, and captive deer species from Michigan to be from herds tested negative for Bovine TB. Imported animals will also require a negative TB test within 30 days before their arrival in California and will be re-tested within 60-120 days after arrival (90-120 days for captive deer species). This plan will help protect California livestock from the introduction of Bovine TB. For additional information you can call the California Cattlemen’s Association headquarters (916.444.0845), or the Animal Health Branch of the CDFA (916.654.1447).

ON-LINE BEEF RESOURCE NOW AVAILABLE

A critical decision-making tool for beef producers and agri-support personnel was launched at the 2000 Cattle Industry Annual Convention and Trade Show in Phoenix on January 24-30, 2000.

Complete with the latest University and Extension research, the Beef InfoBase, developed at the Agricultural Databases for Decision Support (ADDS) Center, puts a wealth of useful information at the fingertips of its users. Available on CD and the Web, information on the Beef InfoBase is split into 16 subject areas, ranging from business management to breeding and genetics to quality assurance. The information is easy to find and readily adaptable to any Microsoft® system. This product is a must-have for any producer and agri-support person who needs access to the latest technologies. The ADDS Center is a cooperative effort between the USDA and private industry to develop and market databases for various industry groups. Currently, databases are available for dairy, pig, sheep and goat commodity groups. New databases are currently under production, including the National Dairy Database, version 4.0, the National Pig Database, version 2.0, as well as new databases for the poultry and catfish industries.

Located in Verona, Wisconsin, the ADDS Center brings together experts from across the country and around the world to combine leading-edge technology with the latest information available on making business grow.

The CD version of the Beef InfoBase sells for $99 and includes a one-year subscription to the website. An order can be placed by visiting the ADDS Center website at www.adds.org, by calling the ADDS Center at 608.848.9055, or by mail at the ADDS Center, 415 Venture Ct., P.O. Box 930369, Verona, WI 53593.

For more information, contact Mike Opperman at mopperman@adds.org

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