Extended drought raises potential health issues

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The extended drought being experienced across most of Kansas has reacquainted livestock producers and veterinarians with many drought-related problems. Not only has the drought caused a shortage of pasture and hay, but has threatened livestock with other problems that do not occur every year.

Feed-related problems
In many cases, grasses and desirable forbs (weeds) either did not get enough rain to initiate spring growth, or grew for a short period and then either died out or did not regrow due to the heat and lack of rainfall. In some pastures, drought-tolerant weedy species are the predominant green plants available. In some cases, these plants are toxic to livestock. Good pasture and cattle management calls for knowing toxic plant species common in area pastures. Livestock producers should recognize when pastures are getting short enough that cattle may be forced to consider consuming undesirable plants. They should supplement the cattle with hay or other feedstuffs, move the cattle to pastures where available forages do not pose a toxicity threat, or move cattle to a drylot situation where they can be fed. Cattle will eat toxic plants, especially when starved.

Nitrate toxicity always becomes a potential problem during dry periods but may be a bigger problem this year than most. Many corn and milo fields did not receive enough moisture to fill ears or heads with grain, and some farmers want to harvest the standing forage and make hay out of it. Insist that they test for nitrate levels before harvesting because many fields will be too high in nitrate to consider using for feed. Test the more stunted plants in the field to determine the highest nitrate levels present. Remind producers that nitrate does not dissipate from hay like prussic acid does. Also, test pigweed or Johnsongrass that might be in the field because it often contains higher levels of nitrate than corn or sorghum varieties. Forage sorghums/haygrazer should be tested before being grazed or hayed. Prussic acid (HCN) also can be a problem, especially following a rain on drought-stressed forages. The prussic acid will build up in any new green growth following the rain (new leaves, suckers, tillers, etc.) and can be extremely toxic until the new growth matures. Regrowth should be tested until it reaches maturity or at least a week after the first killing frost.

Vitamin A deficiency is frequently a hidden problem that surfaces after cattle have gone without consuming green forage for an extended period of time and when the vitamin has not been included in feed or mineral supplements. Vitamin A deficiency can lead to retained placentas when cows calve next spring, as well as increased problems with mastitis. Deficiencies also can lead to improper fetal development and calf growth and set the stage for decreased resistance to calf scours and pneumonia.

Water-related problems
When cattle are watering from surface water sources, problems may begin to occur as the water source is beginning to dry up. Non-volatile contents in the water tend to concentrate as the water level recedes, causing an increase in such problems as increased nitrate and sulfate toxicity, increased hardness/salinity, increased coliform-related diseases, decreased water consumption, and ultimately, decreased intake of whatever feedstuffs are available. Also, problems such as cyanobacterial (blue-green algae) toxicity tends to increase as the water becomes stagnant and ponds heat up. This is compounded if chemical fertilizer or manure runoff enriches the ponds.

Options
Early weaning of calves and extensive culling of cows are both management decisions that producers should consider or implement. Depending on whether early weaned calves are shipped directly to market or the feedlot or held and preconditioned before being shipped, the higher protein and more concentrated energy needs of these lighter weight animals must be  considered and provided. If producers normally market calves through a value-added or other preconditioning program and they have sufficient time and feed resources to meet the needs of those programs, they should be encouraged to continue to participate. Some producers have waited so long hoping that it would rain that they now have no choice but to wean the calves on the truck on the way to the auction market. Cow culling criteria should include open cows, old cows, or cows in poor body condition score that need extra supplementation to make it through the winter, cows that will be late calving next spring and not match the bulk of the herd’s calving dates, oddball-looking cows that do not match well phenotypically with the rest of the herd, and ornery cows (those with disposition problems). Pregnancy checking is imperative this year, and with many herds needs to be done within 45 days after the bulls are removed so that open cows can be marketed as soon as possible to reduce the number of head that have to be fed from now until green grass arrives next spring.

It has been a tough summer on cattle producers and veterinarians, alike. Hopefully it will begin raining again in time for pastures to regrow, ponds to refill, and producers not to have to depopulate or buy super-expensive feed to make it through the upcoming fall and winter. Encourage them to manage well based on resources and options.

Source: Larry C. Hollis, D.V.M., M.Ag. Extension Beef Veterinarian



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