Waterquality, livestock and rural communities

Many of the world’s livestock farmers and rural communities are faced with having to use water straight from the source. These farmers and communities have virtually no ability to control the quality of the water they are exposed to. Most often they do not even know what constitutes good quality water. In developing healthier and more sustainable livelihoods it is important to measure waterquality at intervals to determine the risk posed by waterquality constituents (WQC).

Either organic or inorganic WQC determine waterquality. The risk to livestock is likely to be from inorganic WQC where animals drink directly from a source, particularly groundwater. The WQC levels change with seasons and prevailing climatic conditions such as in drought situations.

Water is a potential source of macro and micro minerals that might be lacking in the feed. To determine this, minerals in the water are measured and compared with minerals in the feed. An example is selenium. The concentration (mg/L) of a WQC however may not appear to be a potentially hazardous constituent (PHC), or may be bound into initially physiologically inert complex molecules. This can change in the animal’s digestive tract and the constituent would become a PHC.

WQC concentrations may not be hazardous to the animal, but may become hazardous if the physiological state demands a high water intake and turnover rate. This may happen during early stages of growth when animals have a high water intake and retention. Nursing females have a high water intake and turnover. A hot environment and relatively dry feed, increase intake and thereby increase potential risks significantly. Some PHC may accumulate in animal tissues and become hazardous to humans via food of animal origin.

Research in South Africa showed that livestock may react to WQC in different ways, depending on the WQC properties and concentrations, or the physiology, or the demands of the environment on the livestock. Rural communities using the water sources in common with the livestock are exposed to the same potential risks as the animals. In people, it is the children and nursing mothers who would be most at risk.

The table shows a range of naturally occurring WQC (mg/L) measured in groundwater from two districts in South Africa against relevant guideline levels. In Source A, selenium (Se) is the highest, and in Source B bromide (Br) and mercury (Hg) are multiples of the guideline levels and PHC to livestock and humans. Bromide is a potential endocrine disruptor while mercury can accumulate in the tissue of livestock and become a secondary source of ingestion to people. In most instances the negative effect of a WQC is sub-clinical effecting growth, production and general wellbeing before it is expressed clinically.

Research has shown that ingestion rates, WQC concentration (mg/L) and interactions with other constituents pose the highest risk. The type of digestion system and the physiological production status contribute to the risk. Genotype determines much of the physiological reactions to the environment and need for water, for example, dairy and non dairy animals, fast growing broiler chickens and animals with a genetic predisposition to heat stress or not.

This complex, interactive situation is managed best by considering all the components simultaneously in a computer simulation model for a specific set of livestock, production and environmental circumstances. The acronym CIRRA represents the process of constituent ingestion rate risk assessment.

Interventions include managing exposure to water sources, balancing chemical profiles of the WQC, providing livestock with supplementary minerals and ensuring the use of livestock most suitable for given production and environmental circumstances.

Reducing the risk to livestock and vulnerable rural communities by monitoring and managing waterquality remains a moral and economic obligation.

Norman Casey
Professor in Animal Science
University of Pretoria
0002, South Africa

Email: norman.casey@up.ac.za
Website: www.waterquality.co.za