Nitrate poisoning is usually (but NOT always!) specific to livestock that is raised on pasture, and can do much harm in a short amount of time.
While a pasture is an attractive and handy option for feeding your goats, there are certain steps you must take to ensure the prevention of poisoning. Be aware of the potential for the build-up of nitrates in the forages being grazed and take appropriate action.
The long answer: Nitrate poisoning occurs when the nitrite level in the rumen exceeds the capacity of the microbes to convert it to ammonia. When this happens, nitrate and nitrite are absorbed through the rumen wall into the bloodstream. It is the nitrite that causes toxicity. Nitrite combines with hemoglobin to form methemoglobin. Hemoglobin carries oxygen to body tissues, while methemoglobin is unable to do so. When enough hemoglobin is converted to methemoglobin, the animal begins to suffer from oxygen starvation.
The short answer: the animal poisons its own blood and causes the blood to not bring oxygen to its vital organs and the rest of the body resulting in sickness and possibly even death.
There are two kinds of nitrate poisoning:
Clinical signs include loss of energy, depression, fluid accumulation in the abdomen or on the underside of the belly, and muscle wasting. Signs will occur within 2-6 hours of eating, and include:
Nitrate levels can increase in three ways:
Pigweeds (Amaranthus spp.) and lamb's quarters (Chenopodium album) are annual weeds common throughout North America. Both of these weeds can accumulate toxic levels of nitrates when experiencing stress due to the factors listed. Redroot pigweed (Amaranthus retroflexus) can also cause acute kidney damage.
Some other weeds include: bull thistle, fire weed, nightshades, mustard, millet, white ragweed, among others.
Nitrates can also be found in high doses in various crops. Be sure to take samples and get them checked for their nitrate levels before feeding to your herd.
There are weeds and other plants local to your area that are not listed here. Be sure to ask your vet or search online for a list of plants to avoid, specific to your area.
1) Toxic Plants. Dr. Margaret Stalker, Pathologist, AHL
2) Potential for Nitrate Poisoning in Dry Weather. Thomas Ferguson, Forage & Grazier Specialist, OMAFRA
3) Nitrate Poisoning and Feeding Nitrate Feeds to Livestock. Alberta Agriculture and Forestry.
4) Plants poisonous to Livestock. Lisa M. Behnken, Extension educator and Beverly R. Durgan, Extension Dean and Weed Specialist. University of Minnesota Extension.
5) Plant Poisoning of Livestock in Vermont, Sid Bosworth, Extension Agronomy Specialist, Plant and Soil Science Dept, University of Vermont