by: Stephen B. Blezinger

Part 3

In this final part of our discussion of issues which must be considered when working through drought periods and low forage situations, we will continue to look at toxic substances as well as other items of concern. At the conclusion of the last part we reviewed the presence and effects of compounds such as nitrates, prussic acid, and mycotoxins. In this part of this series, we will continue this discussion and attempt to provide information on other areas to which attention should be given.

Toxic Compounds, continued.

D. Acorn Poisoning

During periods of decreased forage availability, cattle may seek out acorns as a food source. They may also consume acorns inadvertently as they have to graze more closely to the ground. Acorns can be an important part of the diet in the fall of the year; however, acorns have the potential to cause fatal poisoning. When forage is low, cattle may seek out acorns as food. Ingestion of too many acorns can lead to poisoning. The goal of this section is to provide some basic facts on acorn poisoning and alert producers to be aware of a potential problem.

Acorns contain a substance called gallotannin. In the rumen, gallotannin is metabolized to gallic acid and tannic acid. Tannic acid causes ulceration of the mouth, esophagus, and gastrointestinal tract. Tannic acid is especially toxic to the renal (kidney) tubules, and renal failure tends to be the most significant result of this disease. In the fall, this substance concentrates in acorns and increases the risk of animal poisoning when acorns are ingested.

The signs of acorn toxicity, in the early stages, include constipation followed by a decreased appetite. If the cattle are removed from the acorn area, most will recover in two to three days. Continued exposure leads to a black (GI ulceration), watery diarrhea, which is often foul smelling and may contain blood. Blood may be draining from the nose at this point. Despite treatment, these calves can progress to exhibit severe depression, straining to urinate and defecate; with marked edema in the abdomen and extremities.

These signs mimic the symptoms of Type 2 BVD. Remember Type 2 BVD generally presents with very high fevers. Acorn toxicity will have near normal temperatures in most cases. If pregnant animals ingest acorns, birth defects can occur.

E.Toxic Plants

In addition to the previously listed compounds some basic plants or plant types can also be toxic to cattle. Poisonous plants are among the most important causes of economic loss to the livestock industry. They should generally be considered when evaluating livestock illness and decreased productivity. Poisonous plants affect cattle in many ways: death, chronic illness and debilitation, decreased weight gain, abortion, birth defects, increased calving interval and sensitivity to sunlight. In general, most poisonous plants fall into two categories. First, those that are indigenous or native to a range or pasture and increase with heavy grazing. Second, those that invade a pasture or range after a period of heavy grazing or disturbance to the land. There is actually a third category which includes species such as locoweed and larkspurs which are a common part of the plant population. It is not uncommon to find poisonous species as part of most plant communities and should be considered as a part of most grazing situations.

In many cases, plant poisoning of cattle can often be linked to a problem with management, pasture and range conditions or environmental conditions (drought periods). In most cases, cattle are poisoned because hunger or other conditions cause them to graze abnormally, in many cases consuming plants or plant types they would not in “normal” conditions.

One thing that can make the issue with poisonous plants complicated is that there are quite a number of these and different types thrive in different parts of the country and/or in different seasons of the year. The Merk Vet Manual (seventh edition, 1991) lists 76 different plants that can be toxic to livestock. Secondly, there are some plants which may be toxic under certain circumstances. In a previous part of this section we discussed plant types (mainly sorghums and related species) which can accumulate nitrates or prussic acid, both of which can be very toxic if managed improperly. It is important to be able to recognize these plants and plant types and know how to manage the grazing of these plants when certain conditions occur – such as right now in drought affected areas.

Below you will find several websites listed that can be helpful in better understanding poisonous plants and how they affect cattle and livestock in general.

University of Missouri Extension - http://extension.missouri. edu/p/G4970

Cornell University - http://www.ansci.cornell.edu/plants/php/plants.php?action=display&ispecies=cattle

The following website may be particularly useful since it provides actual pictures of quite a number of toxic plants and can be useful in identification. This presentation was composed by researchers at the Universities of Arkansas and Georgia and North Carolina State University and focuses largely on poisonous plant species of the Southeastern United States.


Contact your veterinarian to discuss poisonous plants in your area that you should be on the lookout for. Your local county extension office can also be helpful.

Other Considerations

There are a variety of other issues and considerations the producer must keep in mind when navigating drought periods. Let's take a moment and go through some of these.

Less than optimal nutrition is a major concern. Dealing with drought periods typically means dealing with short forage supplies.

a. As we discussed earlier this commonly means that the producer will be buying forage and feed sources that he or she would not otherwise. As periods such as this drag on, availability of reasonable quality forage becomes less and less. Hay, when located, will be expensive and in many cases of very questionable quality. This may mean that the plants harvested simply are overly mature, drought affected themselves, contaminated with weeds and any number of other undesirable materials. For instance, in recent hay bales purchase in the north Texas areas, materials such as thorny vines, weeds, sticks (limbs), rocks, bones, small boards, wire and other materials have been found since the person doing the baling is harvesting any standing plants he sees in an effort to supply hay or generate a profit. Obviously, any of the listed materials, while they may generate bulk and weight, don't provide for the nutrient needs of the cows very well.

b. If at all possible, purchase your hay from a known, reputable supplier and purchase in quantities that will last you some time. That way, you can take a sample of the hay and send it off for testing so you have some idea of the nutrient content. Hay supplies as we have discussed are commonly low in protein and high in fiber components that reduce the digestibility of the plant material. One of your first priorities is to provide for the animal's protein requirements. This is important to provide the necessary protein for the rumen microbes so they can process the fiber components as efficiently as possible. One very obvious way to observe if cattle are getting the necessary protein in their diet is to look at the manure piles. If the manure is piling up very high and the fiber particles are obvious, the plant material is not being digested well and the cows are probably not meeting other nutrient requirements either. After providing for the basic forage needs of the cattle, protein is your top priority.

c. After protein, meeting the cow's energy requirement is close behind on the priority list. Energy intake is required for a wide range of physiological functions but one of the greatest is maintaining the animal's body condition. When energy intake drops, the cow begins processing fat stores to meet demands. When this occurs, weight maintenance and gains stop and she begins losing weight. The first physiological system that begins to suffer is the reproductive system. Reproduction is not required for survival and thus is one of the first functions to be “shut off.” While this is not an instantaneous process you will see cycling and conception rates become more extended to the point where the cow will stop altogether. You will also see a decrease in milk production for lactating cows. You will see calves born at lighter than normal birth weights or abortions may occur. Providing for the cow's energy requirements are critical to helping her remain productive. The first part of this process is meeting protein requirements so that the microbial population in the rumen can break down the fiber in forages as efficiently as possible. This is the first line of energy sources. Subsequently, in many cases to maintain body condition and the other processes named it may be necessary to supplement energy as well. This can be done most effectively by feeding a combination of more digestible fiber sources such as alfalfa hay, soybean hulls, beet or citrus pulp, etc. Whatever is available in your area at as reasonable price (I know, I know, don't laugh) as possible. Secondly, energy requirements can be fed with moderate amounts of starch from different grains. You want to be careful to not over feed starch since “slug” amounts fed at one time can, in fact, be detrimental to the rumen microbe's ability to break down fiber particles. Finally, fat sources are also a very good source of energy since they are 2.25 times more energy dense than grains. Again, judicious amounts can be fed since overfeeding fat can also create problems.

d. Mineral and vitamins – during drought periods attempting to maintain mineral balance and status in the cow can become challenging. Close grazing where cows consume a higher percentage of soil than normal, consumption of water from ponds that are running low and where concentration of total dissolved solids has increased and finally, feeding of poor quality forages can all go to disrupting normal mineral status in the animal. While always important, it is especially critical at this time to keep a quality mineral and vitamin supplement available to the animal. The right mineral needs to be selected based on forage sampling and possibly even water sampling. Some minerals will be very out of balance in the animal's diet under these circumstances so addressing these needs can be critical. Minerals and vitamins are the “nuts and bolts” which hold the animal together physiologically and can make the difference between maintaining reproductive, health and growth performance during these difficult periods. Also remember that during these times, cattle have been under exceptional stress, especially those cattle in the south that endure record heats for a large part of the summer. Based on some data by Orr and co-workers, it has been shown that the excretion of certain minerals (copper and zinc in particular) actually goes up during periods of stress. If these stores are not replaced at this time, suboptimal and deficiency conditions can develop rapidly in the animal.

Proper nutrition is ALWAYS critical on cattle operations. During stressful periods such as drought the importance grows even more.


It becomes obvious fairly quickly that extended drought periods are stressful not only on the animal but on the producer as well. The various issues discussed in this series only serves to highlight the variety of management considerations that have to be made. Many producers have chosen to simply sell out and thus are avoiding the headaches and the extra costs. Hopefully, those choosing to stay in will be able to “weather the storm.” It will rain again; it's just a matter of when. Being aware of the areas that can make or break an operation during these periods will help the producer cross the bridge to better production times.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at sblez@verizon.net. You can also follow us on Facebook at Reveille Livestock Concepts.

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