Water Quality for Horses - Understanding Bacterial Counts

Table of Contents

  1. Introduction
  2. Assessing Water Quality


Water used on horse farms can be supplied from a private well, a public water source, a river, pond or lake. Public water suppliers e.g. municipal water suppliers are responsible for ensuring the quality of the water being supplied to you. If you own your well, it is your responsibility to ensure water quality for you and your animals and to ensure the safety of the ground water.

Drinking water is normally tested for the presence or absence of two groups of bacteria; total coliforms and fecal coliforms. These bacteria are considered indicators of the presence of animal wastes and sewage. Fecal coliforms are present in large numbers in intestinal contents of humans and warm blooded animals. They die fairly easily once they are outside of the body. Their presence in well water indicates relatively recent contamination and a short distance of travel. Water containing f ecal coliform bacteria should not be consumed without adequate treatment e.g. boiling or disinfection (1).

The Ministry of Health provides bacterial analysis of water in Ontario. Contact your local health unit for sterile bottles and sampling and handling instructions. Water testing should be done on a regular basis at different times of the year and during different rainfall situations. If there is a problem, a more specific second test should be done to differentiate, for example, if the high coliform count is fecal coliforms from animal or human waste. Tests for specific chemicals, toxic metals, pesticides, herbicides, solvents or organic compounds can also be done.

Assessing Water Quality

Total Bacteria Count

Water intended for livestock should have a total bacteria count of less than 200 bacteria per 100 ml. of water but, based on research literature and field experience, livestock can tolerate levels up to 1 million bacteria per 100 ml. of water (2).

Total Coliform Bacteria

The Ontario Drinking Water Objective for human consumption states that total coliform bacteria should not be present at 5 or more coliform bacteria per 100 ml. of water when using the Most Probable Number (MPN) test or Membrane Filter (MF) test and should not be present within 48 hours when using the Presence-Absence (P-A) test (3). Calves can contract scours (diarrhea) when drinking water containing coliform bacteria counts of more than 1 coliform bacteria per 100 ml. of water. However, older cattle can tolerate concentrations of 20-50 coliforms per 100 ml. of water with no adverse affects (4) (5).

Fecal Coliforms

Fecal Coliforms should not be detected in any sample for any of the above tests.

As a general recommendation, the minimum distance from any potential source of contamination, e.g. septic tank, manure storage or live animals, should be 50 feet for a drilled well and at least 100 feet for a dug well or surface water source such as a pond.

For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: Dr. Bob Wright - Veterinary Scientist, Equine and Alternative Livestock/OMAFRA
Creation Date: November 1998
Last Reviewed: November 1998