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Prussic Acid Poisoning

prussic acid poisoning

Grazing certain forages and weeds can bring the threat of prussic acid poisoning to livestock. If caution is used, this threat can be greatly reduced. Plants such as sorghum, sudangrass, sorghum-sudan hybrids, Johnsongrass, wild cherry and others can contain cyanide-producing compounds. After a frost or during a drought it is important to use extreme caution and it is advised to keep livestock off these pastures for up to three days after a killing frost. If soils that are deficient in phosphorus and potassium are applied with high levels of nitrogen, the levels of prussic acid may increase. Leaves, new shoots, and tillers have higher levels of prussic acid.

 

If large amounts of prussic acid are consumed, the compound interferes with oxygen utilization and livestock can die from respiratory paralysis. Symptoms appear quickly after forage is consumed. These symptoms may include cherry red colored blood, staggering, labored breathing, spasms, foaming at the mouth, falling, thrashing, severe convulsions, and death. Immediate treatment by a veterinarian is needed to save livestock suffering from prussic acid poisoning.

 

When cut for hay, prussic acid content decreases significantly during the curing process. A fair amount of this poison escapes as gas during fermentation when used for silage. Although the risk decreases, it is still important to be cautious when feeding forages with possible high prussic acid content.

 

The risk of prussic acid poisoning this season can be reduced by following these practices:

  • Wait 10-14 days after non-killing frost with no additional frost action before grazing.
  • Do not graze after a killing frost until plant material is dry (the toxin usually dissipates within 72 hours.)
  • Do not graze at night when frost is likely. High levels of toxins are produced within hours after frost occurs.
  • Delay feeding silage for six to eight weeks following ensiling.

Livestock

Cattle
 Calf values are down roughly 50% from 2014 highs, with efficient operations likely covering cash costs and breeding stock depreciation, but resulting in little to no return to capital, land, and management.
 Recent prices have likely slowed expansion, but beef cow numbers will likely be up again in 2017.
 Look for price improvement in the spring of 2017, but a significant drop from spring to fall given mounting meat supplies.
 Fall 2017 could be the bottom of this price cycle.

livestock

Poultry
 Avian Influenza significantly impacted 2015 export values and bird values which also likely impacted the rate of turnover and replacement in KY operations.
 Receipts should be back on track in 2016 and growth appears to be continuing in 2017.

Equine/Hay
 Horse receipts have been flat for several years, rebounding from the depressed market during the 2009-2012 period.
 September yearling sales were down around 3%, but early November breeding stock sales were solid before slumping at the end when mid to lower quality horses were placed on the market.
 Equine sales and receipts are likely to be steady for 2017.
 Alfalfa hay production is down for 2016 with prices slightly higher for higher quality hay. Grass hay production is likely steady with prices a bit lower. The wet spring and dry fall impacted quality and quantity across the state.

Hogs
 Year-over-year prices were down about 10% in 2016, with the largest differences in the beginning and end of the year.
 USDA Hogs and Pigs report suggested significant growth in hog numbers in KY for 2016.
 Fourth quarter hog slaughter has pushed slaughter capacity and drastically impacted hog prices.
 Price improvement is likely in 2017 as some new plants begin operations and growth in KY hog numbers is likely to continue.

Dairy
 KY mailbox dairy prices for 2016 were down 12 to 13% from 2015 levels.
 The first significant payments were made from MPP-Dairy program this past summer, but most KY dairy producers chose very low coverage levels and did not receive any payments.
 Some improvement in prices occurred in the second half of 2016 and is likely to continue into 2017.

Source: 2016-2017 Kentucky Agricultural Economic Situation and Outlook, University of Kentucky College of Agriculture, Food and Environment

Late Summer Cattle Fly Check Can Catch Control Breakdown

Horn fly and face fly numbers will continue to build for a few weeks, which will put pressure on control programs. It is a good time to evaluate the pasture fly situation in your herd; check during the early afternoon on a sunny day (Figure 1). Less than 100 horn flies per side and less than 10 face flies per head is a good target for animal protection. Consider an adjustment or supplemental measure if fly numbers exceed these guidelines.

Figure 1. Evaluate horn fly and face fly control (Photo: Lee Townsend, UK)

Management

Late season fly control is important. Pasture flies are approaching peak numbers for the season, so their impacts are near maximum levels. Also, exposure of flies to less than recommended rates of insecticide due to less effective treatment selects for resistant individuals and increased chance for control failure.  To ensure flys are kept in check, evaluate management options by following suggestions:

Ear Tags

Insecticide-impregnated cattle ear tags can provide 12 to 15 weeks or protection. Effectiveness may be running out in herds that were tagged a little early in the season.

Feed-thru Insecticides

Feed-thru insecticides in mineral supplements require a minimum level of daily consumption by each animal. Be sure that the product is available and that the consumption rate appears to be on-target. This alternative is based on controlling horn fly and face fly maggots that develop only in cow manure. Face flies and horn flies can move a mile or two, so action may be needed to control flies that move in from nearby herds. Provide supplemental control, as necessary.

Figure 2.  Mineral feeder with fly wipe (Photo: Lee Townsend, UK)

Self-applicators

Be sure that self-applicators are charged and working. The fly wipe in Figure 2 appears to be dry so the reservoir tank may need to be filled. In some cases, dust can build up enough to reduce the wicking action in wipes and oilers. Be sure dust bags have not been damaged and that the insecticide in them is dry and flowing.

Pour-on

Pour-on and spray applications generally provide about 4 weeks of fly control. Check the last treatment date and be sure doses are measured accurately.

 

By Lee Townsend, Extension Entomologist