Dairy farms proliferated in the early 20th century as bush was cleared, land drained, and pasture improved with superphosphate fertiliser and faster-growing grasses and clovers. Although dairying required more labour and capital than sheep and beef farming, it provided regular income, and home-bred animals could be added to the herd to either replace culled animals or increase herd size. Farmers could start small and build their herd size comparatively quickly.
Dairying was developed in regions where rainfall was reliable and winters were warmer, such as Northland, Waikato, Taranaki, Bay of Plenty, Manawatū, Nelson and the West Coast. Farms were small, usually near factories, and could graze two cows per hectare.
Cows, like other animals that eat pasture, have a four-chambered stomach called a rumen. Such animals are called ruminants. The rumen digests food with high cellulose content such as grass. The ingested pasture moves from chamber to chamber, progressively broken down by bacteria, fungi and protozoa, to a form that can be passed into the intestine.
Grass to milk conversion
Only 10% of the world’s dairy cows live solely on grazed pasture. This is an important advantage of the New Zealand dairy industry. New Zealand has a climate that, in most regions, grows grass year-round, and is mild enough that cows can be kept outside in all seasons. This means that the cost of feeding and caring for dairy cows is lower than anywhere else in the world. In most other countries cows live in stalls, and eat ‘cut and carry’ feed (pasture or grain harvested and taken indoors) and grain-based supplements.
The price of milk
It takes about 1 kilogram of dry pasture eaten by a cow to produce one kilogram (about a litre) of milk. Mature cows eat about 17 kilograms of dry pasture each day and drink up to 50 litres of water. Grazed pasture costs less than 5 cents per kilogram to produce. Including capital farm costs, the cost of producing one litre of milk is 10–12 cents. In 2007/8 New Zealand farmers were paid more than 90 cents per litre.
New Zealand farmers use fencing to ration pastures, making sure cows receive the required daily allowance but not too much. Fencing off areas minimises the amount of pasture that is trampled, fouled and wasted, especially in winter. In the 1930s Bill Gallagher in Hamilton invented low-voltage electric fencing, which is used to divide paddocks into strips that are grazed between milkings.
Farmers who know the total pasture area, the growth rate of grass and clover, and the numbers of cows and their requirements, can devise a grazing rotation over the farm to prevent a shortage of feed and maximise milk yield.
Any surplus grass in spring, which is when grass grows fastest, is made into silage in pits, stacks or bags, and stored to supplement winter feed.