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The Research Corner: Early Puberty in Girls; Is it Really the Beef ?

Gilt eating a Burger
Gilt eating a Burger
Photo taken by Xin Sun, NDSU
Research Project evaluates impacts of tofu and beef from implanted and non-implanted steers on age at puberty, sex-hormone blood profile and body composition at sexaul maturity of female pigs. Research in Progress. James Magolski, Graduate Student; Eric Berg and Kim Vonnahme, Research and Teaching Faculty, NDSU Department of Animal Sciences

As girls in today’ society reach puberty at a younger age than their mothers and grandmothers did, many people wonder what the cause may be. Some people claim consuming beef, particularly from implanted steers, is the cause of this early onset of puberty.

Our research project, funded by the North Dakota Beef Commission and the State Board of Agriculture, Research and Education, uses young female pigs as a biomedical model of human females to determine if consumption of beef from cattle administered estrogenic growth promotants (implants) results in premature puberty and obesity.          

Our hypothesis is that consuming beef obtained from cattle receiving an estrogenic implant strategy during feedlot finishing does not alter the timing of puberty or the body composition post-puberty, compared with consuming nonimplanted “natural” beef or a common meat alternative, tofu. The objective of our study is to determine the age at puberty, sex-hormone blood profile and body composition (degree of fatness) at sexual maturity of gilts fed beef from implanted steers, nonimplanted (lableled “natural”) steers or tofu.         

Our experiment consists of 24 gilts selected on the day of birth. They were born from identical sire and dam genetic lines. All the gilts were born within 12 hours of each other, and a minimum of four gilts were born alive from each sow. At approximately 35 pounds, the gilts were penned individually and fed based on a percentage of body weight.

The base diet contains a very low estrogen content (no soybean meal), which serves as our control, with three other treatments: tofu or beef from an implanted and nonimplanted source. Quarter-pound beef patties are fed daily as a supplement to the base diet. Tofu is supplied in comparable protein and caloric density. Blood samples are taken twice a week to monitor hormone profiles because we are using the presence of progesterone as a marker for the onset of puberty.           

Following visual signs of estrus, the gilts will be harvested at the NDSU Meat Lab for collection of their reproductive tract, muscle and fat samples, and to determine the percentage of fat and muscle in the carcass. Fat and muscle samples will be analyzed for estrogen residues to determine the influence of estrogen from feed sources on estrogen circulating in the blood and how much ultimately ends up in the muscle.          

The National Institutes of Health recommends swine as an excellent biomedical model for humans in the area of how the diet consumed influences physiology (including hormone production). Using pigs allows us as researchers to completely control all aspects of genetics and environment during the experimental period. This is extremely difficult to control with human research, especially with pre-adolescent girls. The project will provide solid science toward answering the question about growth-promoting technology (implants) and onset of puberty in young girls.

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