1. Overview of Poison Plant Situation in the Trans-Pecos Dr. Joh Reager, Head, Diagnostic Toxicology, Texas Veterinary Diagnostic Laboratories, College Station, Texas

2. Livestock Nutrition as Related to Toxic Plant Management Dr. Ed Huston, Associate Professor, Texas Agricultural Experiment Station, San Angelo, Texas

3. Reducing Poisonous Plant Problems Through Grazing Management Dr. Joe Schuster, Professor and Head, Department of Range Science, Texas A&M University, College Station, Texas

4. Prevention of Plant Toxicity Dr. Ray Allen, D.V.M., Marfa Verterinary Hospital, Marfa, Texas

5. Recent Research on the Bitterweed (Hymenoxys odorata) Poisoning Problem in Sheep Dr. Millard Calhoun, Associate Professor, Texas Agricultural Experiment Staion, San Angelo, Texas

6. Ecology, Toxicity and Control of Broom Snakeweed Dr. Kirk McDaniel, Brush and Weed Control Specialist, New Mexico State University, Las Cruces, New Mexico

7. Mangement of Toxic Plants in the Trans-Pecos with Herbicides Dr. Darrell Ueckert, Associate Professor, Texas Agricultural Experiment Station, San Angelo, Texas

Proceedings
of the
Tans-Pecos
Poison Plant
Symposium

December 17,1981
Fort Stockton, Texas
Edited by Allan McGinty
Texas Agricultural Extension Service - Texas A&M University System
Daniel C. Pfannstiel, Director - College Station

Range Management and Poisonous Plants - Introduction

Poisonous plants are amoung the most important causes of the economic losses sustained each year by the livestock industry. Direct economic losses to U.s. cattle producers from poisonous plants in 1978 amounted to $91.3 million (Bedell, 1980). Poisonous plants also contribute to indirect losses, such as reduced animal performance, reducing the optimum level of resource use, and increasing costs of management. The sum total of both direct and indirect losses costs Texas livestock producers from 50 to 100 million dollars a year (Sperry et. al., no date).

The various problems of poisonous range plants have paralleled the development of the range industry in Texas. The earliest research in the area of poisonous plants was concerned with the identification of toxic species and determination of symptoms and toxicity. The Loco Weed Laboratory at Alpine and the Texas Agricultural Substation near Sonora were established for this purpose.

Over the years the problem of poisonous range plants has generally increased in importance. In the past 50 years high stocking rates have generally caused range conditions to deteriorate and thus carrying capacity for much Texas rangeland. The change from open range to fenced pastures has restricted animal movement and choice of forage. Due to high stocking rates, low range condition and restricted animal movement, the diet selection of livestock is altered. In this way poisonous plants, although always present on Texas rangelands, are being consumed by livestock in large quantities.

Diagnosing Poisonous Plant Problems

Over the years, many cases of Livestock poisoning by plants have been improperly diagnosed as disease and millions of dollars spent in testing diseases which were not present. To accurately diagnose a poison plant problem can be extremely difficult. Blood tests can be accurately used insome circumstances, although in gereral, blood tests and chemical analysis of rumen contents are usually of little value. The most valuable tools for use in diagnosing poisonous plant problems include a broad knowledge and experience in the area of plant identificaiton, stage of growth and plant parts that are poisonous, species of animals susceptible, amount necessary for toxic and lethal doses, traing and experince in conducting range plant surveys to determine the types of plants and amount grazed and a knowledge of the clinical and pathological effects cause by poisonous plants.

Management to Reduce Poison Plant Problems

It is a fact that poison plants are a natural component of grassland ecosystems. It is also a fact that managment can influence the severity of livestock losses resulting form consumption of these poisonous plants. Some basic management considerations are as follows:

1. Do not overgraze rangeland. Many poisonous plants are classified as increasers or invaders, thus becoming more prevalent on low condition rangeland.
2. Be cautious introducing livestock to your ranch from another area of the state or county. Such stock are more likely to consume toxic species.
3. Do not turn hungry stock onto infected ranges. When hungry, livestock lose much of their selective grazing behavior.
4. Make certain livestock have free access to salt, phosphorous and other needed elements. Again, deficiencies in these areas will result in a reduction of livestock selective grazing behavior.
5. Provide adequate water.
6. Do not feed hay cut from areas containing poisonous plants.
7. Minimize grazing pressure when poisonous plants are the most dangerous. Flexible grazing systems can be used to avoid high risk areas during periods of greatest toxicity.
8. Use the proper kind and class of livestock. Many tims one class of livestock is more resistant to a toxic plant as compared to others.
9. Move stock carefully through infected areas. Also, avoid crowding of animals. Stock should have full stomachs when trailed or penned.
10. Be aware of special environmental conditons that may restrict animal movement or change diet selection. Such conditions would be periods of drought, snow, or extremely wet conditions.
11. Be cautious when grazing areas recently sprayed with herbicide or burned. Both of these practices have the potential to increase toxic plant palatability.
12. Finally, know the potentially toxic plants and watch for evidence of grazing use on these plants. Losses can many times be kept to a minimum when caught early.

Control of Toxic Plant Species

Poisonous plants can reach such density as to require some type of control. There are three different methods used to reduce density of poisonous plants. These three methods can be classified as mechanical, biotic and chemical (Sperry, 1951).

Mechanical methods include

cultivation in restricted areas, mowing, hand pulling, cutting, grubbing or burning.

Biotic methods include

heavy grazing of limited areas by large numbers of animals so that none are allowed to get a lethal dose, grazing of different classes of livestock, or deferment of infested areas.

Chemicals

have been used to control range plants, at least experimentally since the 1930's. Chemicals, while expensive, can be used to control large acreages of poisonous plants in a short period of time.

Summary

When all is said, poisonous plant losses must be accepted as a natural part of the ranching industry. Although poisonous plants will always be present on rangeland, those managers who have a thorough knowledge of their toxic plants and who follow sound range management practices will keep losses from poisonous plants to a minimum.

7/21/00