Blue-Green Algae – A Potential Hazard for Horses, Pets and People

drinkingCurrent weather and water conditions in many parts of the country have created conditions favorable for the rapid growth of blue-green algae. Please be on alert with your horses and dogs, and use precaution when around unfamiliar water sources.

These primative organisms are actually algae-like bacteria instead of being true algae and are also referred to as Cyanobacteria.  They grow rapidly and may produce the pea-soup green color in some bodies of water, along with some foul odors.  These rapid growth periods, called “blooms” most frequently occur when there is a combination of warm weather, intermittent or limited rainfall and an accumulation of nutrients, particularly phosphorus and nitrogen.

The planktonic groups produce the pea green water while the mat-forming groups produce dark mats that start on the bottom and float to the surface.  The planktonic species (Anabena, Aphanizomenon and Microcystis) are believed to be most likely to produce toxins which can be harmful or fatal to animals when ingested. (Fact Sheet on Toxic Blue-Green Algae, Purdue University, Carole A. Lembi)

These toxins may be ingested when animals drink the water or when they lick their coats after being in the water.  Animals are more likely to consume the water if fresh water supplies are limited from other sources.  Any animals that drink the water during a period when toxins are being produced may be affected, but toxins are not always produced when there is a bloom.

Providing a source of fresh, clean, safe drinking water is the best way to avoid causing animals to consume questionable water.  If pets go swimming, they should be cleaned off before they have a chance to lick their coats.

Toxic symptoms may include:

  • Vomiting
  • Diarrhea
  • Rash and skin irritation

Preventing run-off of nutrients into ponds and lakes is also important to help reduce the risk of these algae blooms.  Prolonged drought conditions in some areas have also increased the concentration of nutrients in the remaining water in ponds and lakes.

While not all “blooms” may produce toxins, avoiding exposure to or consumption of suspect water is recommended.  More information is available from local and state pollution control sites or extension sites.   A recent case in Minnesota reported that 2 pets had been killed and a boy was sent to the hospital (MPLS Star Tribune, July 4, 2015, Liz Sawyer) due to exposure to blue-green algae.

Water-The Most Important Nutrient for Horses

Water is the most important nutrient that we provide for horses on a year around basis. Horses need 2 to 3 times more water than other feedstuffs. An 1100 lb horse on a dry forage diet at an average temperature of 68 degrees Fahrenheit will need a minimum of 6-7 gallons of water per day or 48-56 lbs of water, and many horses will drink more water than the minimum. We all appreciate that the water requirement may double at high temperatures, but may not realize that at -4 degrees Fahrenheit; the quantity required is about 10-12 gallons per day, or actually higher than at moderate temperature. The onset of cold weather can actually increase the requirement for water because there is no fresh grass and the air is very dry.

There is a misconception that domestic horses can easily eat enough snow to survive. While horses in the wild do adapt to lower water intakes, partially because food intake is also frequently reduced, horses can survive longer without food than they can without water. Reduced water intake can also impair digestion and potentially contribute to the incidence of impaction colic.

It also requires a great deal of energy to eat snow, melt the snow in the body and raise the fluid temperature to normal body temperature of 99.5- 100.5. Increasing the temperature of 10 gallons of water from 32 degrees to 100 degrees takes about 1372 Calories or about the amount of digestible energy in a pound of feed. Melting the snow to get to water will take a great deal more energy and the horses will not readily eat a pile of snow the size of 20 five gallon buckets. It takes about 10 inches of snow to have one inch of water.

Providing horses with fresh clean water at an appropriate temperature all year around is a great management tool to reduce the risk of colic, maintain healthy digestion, maintain body condition and even save a bit of money on feed cost!