The following article written by Madeline McCurry-Schmidt is from the American Society of Animal Science web page “Taking Stock”. It is interesting to note how often sheep are used to study humans. More importantly for livestock producers it shows how management of the ewe impacts the future offspring.
As health officials debate the causes of the obesity “epidemic,” some animals scientists are looking to sheep for answers.
Saturday morning, at the JAM preconference symposium on “Agri-Medical Research: Providing Dual Benefit for Agriculture and Human Health,” several scientists discussed the effects of epigenetics on appetite development and weight gain.
Epigenetics is the study of how environmental factors influence genetic expression. Epigenetic changes often occur during pregnancy, when a fetus is exposed to environmental pressures, like nutrition, as it develops.
Dr. Steve Ford, a professor at the University of Wyoming and Director of the Center for the Study of Fetal Programming, studied how pregnant sheep react to changes in nutrition. In his study, he provided a group of pregnant ewes with 150 percent of their required diet to
see how fetuses developed as their mothers gained weight. He wanted to see if changes in the womb would affect the next generation.
Indeed, when measuring differences like body length, and appetite, Ford noticed significant difference between the offspring of obese sheep and the offspring of the control group.
“Management can affect the expression of genes,” said Ford during his lecture.
The offspring were predisposed to have a shorter length from rump to crown and increased body fat. While they spent the same amount of time feeding as control sheep, the test sheep ate more food, faster. Ford also saw big changes in pancreatic development. The offspring of obese sheep had higher glucose levels but more resistance to insulin.
Oddly, Ford also saw changes when he bred a third generation of sheep. In this trial, Ford took the offspring of the sheep in the first trial and fed them just 100 percent of their required diet, an amount which did not promote obesity. He then studied the changes in their offspring. Again, the offspring showed differences in body length and body fat.
“It only takes a few generations for those sheep to change phenotypically,” Ford said.
He plans to raise this third generation up to see if they show any other changes.
Ford’s research gives clues to how conditions in the womb may affect human
offspring. For example, both neonatal humans and sheep receive a surge of leptin hormones after birth. Studies have shown that this leptin surge plays a role in establishing appetite behavior throughout life. But in Ford’s study, the offspring of the obese sheep were resistant to leptin. As these leptin-resistant sheep grew, they were more likely to gain weight when fed ad-libitum.
Ford’s data may help researchers in human health who wonder why obesity tends to run in families.
“Maybe their appetite is being set very early,” Ford said.
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