|CERES No. 097 - January - February 1984 (FAO Ceres, 1984, 50 p.)|
Practical farmers have long recognized the value of cow dung as a fertilizer, but they likely have also observed some of its drawbacks. If not well mixed with the soil, cattle droppings linger on the surface, smothering forage growth and offering an ideal breeding ground to flies and intestinal worms that can exact a heavy toll on domestic livestock, wildlife, and humans. Some US studies have indicated that cattle will not graze close to droppings if they can avoid it. Australian research has shown that 80 per cent of the nitrogen in cattle manure escapes into the air when droppings are left on the surface until dry. Someone else, presumably a mathematician, has calculated that the annual droppings from 25 cattle would cover a full hectare.
With about 25 million head of cattle, mostly on the range, Australian farmers obviously have some interest in dung management and they are now getting help from Australian scientists in this respect. The Australian solution has been to turn to dung" eating beetles - the scarabs once so revered in ancient Egypt - which they began to import from Africa in the late 1960s.
The value of the dung beetle, of which more than 4 500 species have been identified worldwide, lies in its habit of aggressively searching for fresh manure. They will fly several miles to find it and once it is located they fight fiercely among themselves for the most succulent morsels.
After feeding on the fluids, they break off small balls of dung and push them down tiny tunnels they dig in the soil beneath the droppings. Female beetles then lay an egg in each dung ball. Not only does this activity help to remove the offending dung heap, providing perhaps as much as five per cent more pasture, but it also disrupts the reproductive cycles of internal cattle parasites who also lay their eggs in dung - but require an above-ground environment for their survival.
The first batches of African beetles were set loose in Australia's Northern Territory and in Western Australia in 1967. Finding few natural enemies they established themselves quickly and went to work. Since then some 20 species have been introduced and many are becoming acclimatized. Today, tens of millions of African beetles are busily burying Australian cow manure.
In the United States, Department of Agriculture entomologists have also been working with dung beetles for the past 15 years and have been introducing new species from Africa, Pakistan, and Argentina. One entomologist worked out detailed economic benefits that would accrue to cattle producers if dung beetles could promptly bury all the cattle droppings on US grazing lands; he reached the figure of $2 billion annually
Although the establishment of new colonies of dung beetles takes time, scientists appear optimistic about their potential. The fact is that cattle are alien species on many of the world's grazing lands and their droppings are only slowly destroyed by native organisms. Australia's native dung beetles, for instance, successfully remove kangaroo and koala dung in the woodlands, but rarely venture out on the range to attack cattle droppings.
Most scientists agree that the dung beetles are unlikely to become pests. Adults have no jaws and feed only on the fluids of the dung. They live three quarters of their lives in the dark, under dung, or underground. The larvae cannot survive outside the dung ball.