Tall fescue is a cool-season perennial grass adapted to a wide range of soil and climatic conditions; it is used in Australia and New Zealand for stabilizing the banks of watercourses. It is the predominant pasture grass in the transition zone in the eastern and central USA. The causative toxic substance, ergovaline, has actions similar to those produced by sclerotia of Claviceps purpurea.
However, ergot poisoning see Ergotism Ergotism Ergotism is a worldwide disease of farm animals that results from ingestion of sclerotia of the parasitic fungus Claviceps purpurea, which replaces the grain or seed of rye and other small grains Ergotism is most prevalent in late summer when the seed heads of grass mature. Fescue lameness is most common in late fall and winter and has been reproduced in cattle by feeding dried fescue free of seed heads and ergot.
However, occasionally, ergotized fescue seed produced in early summer may inadvertently be baled and result in ergot toxicosis instead of or in addition to fescue toxicosis. The endophyte fungus N coenophialum growing within the fescue plant can synthesize ergot alkaloids. Susceptible species from most to least sensitive are horses, cattle, and sheep. Endophyte-infected fescue that does not produce ergovaline has not caused fescue toxicosis. Removal of animals from infected fescue pasture reduces urinary ergovaline below detectable concentrations within 48 hr.
Ergovaline is an agonist for dopamine D2 receptors, which initiate several physiologic abnormalities. First, inhibition of prolactin secretion causes agalactia in horses and swine and reduced lactation in cattle. The dopaminergic effect also causes imbalances of progesterone and estrogen, associated with early parturition for cattle and prolonged gestation with oversized fetuses in mares.
Some reports indicate an increased incidence of fescue lameness as plants age and after severe droughts. Many pasture mixes will include tall fescue, because of its ability to rapidly produce forage.
There are a few drawbacks to utilizing a tall fescue stand; however, if you can identify tall fescue, you can better manage that forage stand for the future. Tall fescue can be identified by its dull upper surface and its shiny underside. The veins on the leaf are very distinct Figure 1. Auricles are usually blunt and hairy Figure 2.
Tall fescue also has a low ligule Figure 3. The seed head is an open panicle with 5 to 9 florets per spikelet Figure 4. Figure 1: A tall fescue leaf has very distinct veins, a dull upper surface and a shiny underside. Figure 2: The auricles on tall fescue are blunt and hairy. Figure 3: The ligule on tall fescue is very low, almost non-existent.
Figure 4: A tall fescue seed head is an open panicle with 5 to 9 florets per spikelet. One drawback to tall fescue is palatability. Cattle tend to avoid consuming tall fescue, because it is a more course and fibrous forage. Animal gains tend to be lower on these fields but are a good source of forage for the beef cow herd.
When cattle are turned out to graze a fescue mixed stand, the cattle will eat around the less palatable fescue. Tall Fescue outcompetes other forages, so less grazing pressure will lead to a purer stand of tall fescue. Grazing at a higher intensity and a shorter time period will force cattle to graze more evenly, which can help manage this forage in an existing stand.
I should also mention that there is at least one university Extension specialist who believes a particular anthelmintic has a function independent of its efficacy on parasites.
To date, however, that theory is not widely accepted, nor to the best of my knowledge is the product manufacturer seeking a label claim. Manage With Clover Other than planting endophyte-free fescue, probably the best agronomic practice is to interseed clover a good idea even with endophyte-free varieties. That is, during the hottest of weather, clover grows most vigorously. Cattle will preferentially root around the fescue to graze the clover, which reduces the consumption of fescue during the most critical period.
Of course, there can be problems. Bloat is always a potential problem with legumes. Beyond that, during breeding season the excess protein contained in clover can affect conception.
But these are problems that can be managed through supplemental feeding. Something else to keep in mind is that endophyte levels are the highest in fescue seed. So, cattle should not be allowed to graze mature fescue. Ideally, grazing management should not allow fescue to reach maturity.
As a practical matter this means rotational grazing is required. If you do not rotationally graze, at some point mature fescue will emerge. Under continuous grazing cattle do not graze uniformly.
In addition, they tend to be less resistant to parasitic challenges. Studies have shown that cattle receiving proper copper nutrition tend to be less susceptible to infections and have less severe infections when disease does occur. It is widely known that copper deficiencies in cattle result in reduced reproductive efficiency and performance. The typical copper deficiency symptoms include decreased conception rates, increased days open, increased cases of retained placenta, delayed puberty, and increased repeat breeders in cows and decreased libido and semen quality in bulls.
Proper copper nutrition in pregnant females is critical for the health of newborn calves. Newborns are very dependent on the copper acquired during the pre-natal period, since milk is a relatively poor source of copper. Calves use the copper acquired during the pre-natal period to meet their elevated copper demands during the first few months of life.
Additionally, the copper status of the dam is critical to the production of high-quality colostrum. Colostrum provides passive immunity for the calf until its own immune system develops fully.
Calves born to copper-deficient cows experience increased death losses, reduced growth, reduced immunity and poor production efficiency. This is especially important with weaned calves. Studies have shown that copper-deficient calves have more health problems, gain weight less efficiently and have lower net returns.
For this reason, it is vital that calves receive adequate mineral nutrition BEFORE weaning, because even a proper mineral program cannot overcome existing mineral deficiencies once stress sets in. Calves going into stocker or feedlot situations will perform better when they have received adequate copper nutrition prior to weaning. Unfortunately, there is no silver bullet that will allow you to avoid the negative effects of the fescue endophyte in all situations.
There are a variety of supplement forms available to match your management style and the needs of your cattle, including pressed blocks, low-moisture blocks and loose minerals. In summary, cattle producers that utilize fescue pastures who also observe rough, discolored hair coats e.
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