Evolution of weight gain in chickens in the last decades
The practice of regularly supplying medicines to animals goes back some 70 years. With the idea that it would be easier to study nutrition in "sterile" chickens, a group of researchers regularly administered antibiotics with the intention of eliminating all their digestive bacteria. The "rather unexpected result," according to that 1946 study, was that the chickens grew faster.
By 1950, researchers had discovered that animals, when given antibiotics, reached their weight before being brought to market and consumed less food. "Back then, we did not know why animals grew faster," says Gail Hansen. "And actually now neither." But the lucrative advantage was well understood, and adding drugs to food became an standard practice.
However, research conducted over the past 15 years suggests that antibiotics are no longer functioning so well to increase growth, at least in some animals. According to Hansen, this may be due to the fact that animals raised today differ genetically from those before or that any possible effect of antibiotics was reduced as the bacteria became resistant to the drugs.
The other reason that producers give low doses of antibiotics to healthy animals is to prevent them from getting sick. Under pressure from large processors, small and medium farms have been replaced in recent decades by industrial scale feedlots and feedlots that confine thousands of animals together, according to an analysis by the Department of Agriculture on Data obtained in a census of breeding sites conducted by Food & Water Watch. In such overcrowding conditions, diseases spread rapidly.
Today's breeders have little voice in raising their animals. "Today, most of the animals for human consumption are raised under contract with large meat-producing companies that require farmers to use the company's supplied feed which may be pre-mixed with antibiotics," says Hansen. "Many have no idea how many medicines their animals receive." Most of the antibiotics that are given to animals do so in the form of water or food mixed with drugs, according to the FDA.
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