Flooded forage cut for hay may affect livestock

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By David Harrison

Flood damaged forage may have elevated levels of ash or bacterial contamination. Both must be considered when feeding livestock.
Internal mineral content of forages is usually 6 to 8 percent and forage normally has 2 to 4 percent soil contamination is largely silica (sand) and of no nutritional value to animals. This means that forage fed to animals should be increased when ash levels are above 10 to 12 percent and the value of forage reduced correspondingly.
Horses can be particularly sensitive to high ash content in the hay as the sand building up in the intestinal tract can cause sand colic. The sand/silica causes pain by two methods:
1. Sand presses on the bottom of the intestine, preventing blood from entering the area. This causes the long term, low-grade pain that can cause a horse to eat poorly without ever really acting colicky.
2. Eventually sand can build up to the point that it totally blocks a loop of intestine. This causes a very painful buildup of hay and water in front of the blockage.
A second major problem caused by flooding is that bacteria and other microorganisms may have contaminated the forage, especially if flood water flowed across manure piles or runoff from manured land. Flood water may contain microorganisms that cause illness and death.
Bacteria and fungi may grow and produce mycotoxins on alfalfa/grass lying in the field. This microbial growth may be less of a problem if harvested forage is fermented because the associated heat will reduce microbes; though forage may still contain mycotoxins. Microbial populations will be less of a problem for cattle than sheep and horses.
This article is based on information from Dan Undersander at the University of Wisconsin.