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Drought concerns for livestock producers

By Staff | Oct 13, 2012

Drought conditions not only cause problems for grain producers, but they also increase concerns for livestock producers about cattle and cattle feeds.

Nitrate Poisoning

Excessive summer heat and lack of rain during the growing season has severely stressed many of the corn acres across North Dakota. Many of these stressed corn acres are being harvested for silage rather than grain. With the drought, heat, stunting, and potential high fertilization levels these corn acres have experienced, high nitrate levels in plants are likely and nitrate toxicity becomes a concern. While it is estimated that 40-60% of nitrate may be lost during the fermentation process of ensiling, livestock producers would be wise to analyze these stressed crops for nitrate levels before feeding to cattle or allowing cattle to graze the stubble. When in doubt, have drought-stressed forages tested- better safe than sorry.

According to Charles Stoltenow, NDSU Extension Veterinarian, the majority of nitrate poisoning cases in North Dakota occur with drought-stressed oats, corn, and barley. However, a number of other plants can also accumulate nitrate, including millet, sorghum, sudangrass, kochia, lambsquarter, and canada thistle among others. Plant parts closest to the ground contain the highest concentrations of nitrates, and most of the plant nitrate is in the bottom third of the stalk. Leaving 6-12 inches of stubble when chopping drought-stressed corn can minimize the potential for nitrate toxicity. Additionally, when feeding high nitrate forages producers should avoid feeding them to overly hungry animals, and they should be diluted with low nitrate feeds. Your veterinarian can help you determine the correct ratios of high and low nitrate forages to blend.

Signs of nitrate

poisoning include:

Bluish/chocolate brown mucous membranes

Rapid/difficult or noisy breathing

Rapid pulse (150-plus beats per minute)

Salivation, bloat, tremors, staggering

Dark “chocolate-colored” blood

Weakness, coma and death

If you suspect nitrate poisoning contact your local veterinarian immediately as the onset and progression of symptoms is rapid. Acute poisoning usually occurs from a half hour to four hours after consuming toxic levels of nitrate.

Blue-Green Algae

Provided waterholes and stock ponds still have water in them, producers should also be concerned about the potential for drought-related water quality issues. Once such concern is the buildup of cyanobacteria (commonly referred to as blue-green algae) in livestock surface water supplies. During dry conditions standing water can become stagnant and in combination with other favorable conditions including hot, sunny days and warm, nutrient-rich water (particularly phosphorus and nitrogen), encourage blue-green algae blooms. The bloom is most abundant during late summer and early autumn. Favorable conditions can cause cyanobacteria numbers to multiply rapidly, often doubling in one day or less. Rain, heavy winds or cooler temperatures often inhibit growth or break up the bloom, mixing it into the water body within a few days. However, under continuing favorable conditions blooms may last for several weeks.

According to Roxanne Johnson, NDSU Extension Service Water Quality Associate, most blooms are obvious to the naked eye, but blue-green algae can be present in the water without a visible bloom. Visible signs of blue-green algae are the presence of a green to blue-green scum on the surface of livestock water supplies. Johnson also says, “Not all algae blooms are toxic, but without laboratory analysis, it is impossible to identify poisonous species.” Often times a characteristic musty, earthy, or sewer gas odor accompanies the presence of blue-green algae blooms in a body of water.

Signs of blue-green algae poisoning in livestock include weakness, staggering, difficulty in breathing, convulsions, abdominal pain, and eventually death. The toxins produced by the cyanobacteria are also poisonous to humans. Symptoms in humans may include numbness of the lips, tingling in fingers and toes, dizziness, abdominal pain, diarrhea, and vomiting. Toxicity depends largely on the concentration of toxins in the water, the amount of water consumed, and species consuming the water.

There are no known antidotes for poisoning resulting from cyanobacteria. The best solution is to be aware of conditions which spawn blue-green algae blooms. Under those conditions, keep cattle from drinking in areas having accumulated bacterial concentrations. If you suspect cyanobacteria, contact your veterinarian to determine which samples would be appropriate for your situation.

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