How much a farm actually drinks
Water planning starts with honest numbers, and the KZN Department of Agriculture publishes them. Per animal per day, in moderate weather:
| Animal | Litres per day |
|---|---|
| Beef cow | 40–50 |
| Dairy cow in milk | 5 L per litre of milk, on top of maintenance |
| Ewe (dry / with lamb) | 8 / 11 |
| Lactating sow | 18–23 |
| Layers (per 100 birds) | 20–40 |
| Broilers (per 100 birds) | 10–15 |
Two corrections turn these into drought numbers. Heat: cattle drink roughly 3 L of water per kilogram of feed at 5 °C but 8 L/kg at 32 °C, and a sheep's summer intake can reach twelve times its winter intake. Time: cattle and sheep survive weeks without food but only two to three days without water — which is why the same department's storage rule (at least eight days' supply in main storage, two more days at the drinking points) appears in the drought-proofing article in this section.
Salt: the species disagree
The South African livestock guideline (DWAF, Volume 5) measures salt load as TDS — total dissolved solids, in mg/L (your lab report may give EC instead; multiply mS/m by about 6.5). The target for all stock is under 1 000 mg/L, but tolerance above that differs sharply by species:
| Species | Comfortable up to (mg/L TDS) |
|---|---|
| Dairy cattle, pigs, poultry | 1 000 |
| Beef cattle, horses | 2 000 |
| Sheep | 3 000 |
Above its band, an animal first refuses the water briefly, then adapts; push further and intake, growth and milk yield fall — the animals drink less, so they eat less. Sheep can survive water over 10 000 mg/L; a dairy herd is already losing production at a fifth of that. Three practical warnings from the guideline: salts are not equal (magnesium sulphate — "bitter salt" — hurts at levels ordinary table-salt waters tolerate); never move stock suddenly onto saltier water, because refusal followed by desperate drinking causes salt poisoning — introduce it stepwise; and the classic management move costs nothing: give the salty borehole to the dry stock and keep the best water for the animals in milk. Where the only water is brackish and the dairy is the business, blending through a small reverse osmosis plant is the modern fix for exactly this situation.
The short list of real poisons
- Nitrate — the guideline's limit is 100 mg/L as nitrate for all stock. Mind the units: many labs report nitrate-as-nitrogen (NO₃-N); multiply that figure by 4.4 before comparing. Ruminants convert nitrate to nitrite — ten to fifteen times more toxic — and acute poisoning can kill within hours; pregnant animals are most at risk. Water and heavily fertilised pasture add together.
- Sulphate — fine to 1 000 mg/L; above that expect scouring and refusal, with young stock hit first. Animals adapt over days if the change is gradual.
- Fluoride — keep under 2 mg/L. Long exposure above that mottles teeth first, then damages joints and bone: lame animals that eat less.
- Dung in the water — the guideline's bacterial target (under 200 faecal coliforms per 100 mL) exists mainly for calves, lambs, pigs and poultry; mature ruminants tolerate worse. Stagnant, oxygen-dead pools carry a further risk of botulism. Fencing stock out of the dam and reticulating to troughs solves most of it — and a UV unit or chlorination covers the young-stock lines.
Troughs: the last metre matters
The best analysis is undone by a green trough. The published practice is simple: check troughs daily; scrub them out at least every three days (daily in feedlots); disinfect twice a year with a strong bleach solution, fifteen minutes' contact, rinsed well; and shade or cover both trough and storage — algae need sunlight, and so does the reaction that strips chlorine. Keep troughs well away from feed lines so mouths full of feed don't foul them. Take trough algae seriously: some species photosensitise cattle, and in one Limpopo case a toxic algal mat growing in a cement trough killed eighteen goats. A trough is part of the water system, not furniture.
Rule of thumb
Budget 50 L a day for a beef cow, five litres per litre of milk on top of maintenance for the dairy cow, and double your summer figure in a heatwave. Match water to stock class — best water to the animals in milk and the young; salty water, introduced gradually, to dry stock. Test again mid-drought, because evaporation concentrates everything the last test found. And clean the troughs — three days, not three months.