Growth Hormones
As early as the 1930s, it was realized that cows injected with material drawn from bovine (cow) pituitary glands (hormone secreting organ) produced more milk. Later, the bovine growth hormone (bGH) from the pituitary glands was found to be responsible for this effect. However, at that time, technology did not exist to harvest enough of this material for large-scale use in animals. In the 1980s, it became possible to produce large quantities of pure bGH by using recombinant DNA technology. In 1993, the Food and Drug Administration (FDA) approved the recombinant bovine growth hormone (rbGH), also known as bovine somatotropin (rbST) for use in dairy cattle. Recent estimates by the manufacturer of this hormone indicate that 30% of the cows in the United States (US) may be treated with rbGH.
The female sex hormone estrogen was also shown to affect growth rates in cattle and poultry in the 1930s. Once the chemistry of estrogen was understood, it became possible to make the hormone synthetically in large amounts. Synthetic estrogens started being used to increase the size of cattle and chickens in the early 1950s. DES was one of the first synthetic estrogens made and used commercially in the US to fatten chickens. DES was also used as a drug in human medicine. DES was found to cause cancer and its use in food production was phased out in
the late 1970s.
What are the different hormones used now by the meat and dairy industries?
There are six different kinds of steroid hormones that are currently approved by FDA for use in food production in the US: estradiol, progesterone, testosterone, zeranol, trenbolone acetate, and melengestrol acetate. Estradiol and progesterone are natural female sex hormones; testosterone is the natural male sex hormone; zeranol, trenbolone acetate and melengesterol acetate are synthetic growth promoters (hormone-like chemicals that can make animals grow faster). Currently, federal regulations allow these hormones to be used on growing cattle and sheep, but not on poultry (chickens, turkeys, ducks) or hogs (pigs). The above hormones are not as useful in increasing weight gain of poultry or hogs. Estradiol and progesterone are natural female sex hormones. As mentioned earlier, FDA allows the use of the protein hormone rbGH to increase milk production in dairy cattle. This protein hormone is not used on beef cattle.
Credits:
Renu Gandhi, Ph.D. BCERF Research Associate and
Suzanne M. Snedeker, Ph.D., Research Project Leader, BCERF
And the Program on Breast Cancer and Environmental Risk Factors in New York State.