Cattle

Cattle turn standing grass into meat. A pasture is full of food no person can digest, and a grazing animal converts it. The herd is not left in one field: it moves through a series of fenced paddocks, grazing each for a few days and then leaving it long enough to grow back. That rest is the whole idea. Ground grazed continuously is eaten as fast as it grows; rotating the animals tends to leave more grass standing, about 30 percent more on average, not less.

Everything is sized from the animal unit: the daily feed of a 450 kg (1000 lb) dry cow, about 11 kg (25 lb) of dry forage. Beef cattle can hold a paddock three days or more. How long it then rests depends on the weather - 10 to 14 days when cool and moist, 40 to 60 when hot and dry - and the paddocks needed are that longest rest divided by the grazing period, plus one. Two paddocks is a continuous system with extra fencing. Water has to reach all of them: at 32 C (90 F) a cow drinks about 8 litres for every 100 kg of body weight (1 gallon per 100 lb) daily, twice that with a calf at foot, and the requirement doubles between 10 and 35 C (50 and 95 F).

Letting cattle stand in a pond is the first mistake: they break the banks into shallow weedy margins, and calves whose mothers drank from a trough gained 9 percent more weight. Water quality fails invisibly - dissolved solids above 5000 parts per million are unusable and nitrate above 300 unsafe - so it is tested, not judged. Heat is next: risk rises above 27 C (80 F) and is serious above 32 C (90 F), and a night above 21 C (70 F) removes the recovery a hot day needs. Shade of 2 to 4 square metres (20 to 40 sq ft) a head, set 2.4 m (8 ft) up so air moves below it, is part of the system. Full stocking held through a drought leaves bare ground, then weeds. The commonest failure is quiet: a rotation drifting back to continuous grazing because nobody wrote it down.