Recent information indicates gene expression of fetal calves can be manipulated by factors like the nutritional status of the cow. Randy Wiedmeier, livestock specialist with University of Missouri Extension, says this differs from what he has taught for several decades.
"I was taught that farm animal production is controlled by two factors: the genetic code, and environmental factors like nutrition, climate, and health. I also understood that the genetic code was set in stone but apparently, it is a little more complicated than that," said Wiedmeier.
Researchers at the University of Nebraska grazed a large group of dry, pregnant beef cows on native rangeland. Half of the cows received a small amount of supplemental protein. The other half of the cows received no such supplement. Protein supplementation did not seem to have any effects on cow or calf performance through the weaning phase.
"However, when heifer calves from this study were being developed as replacements, a difference was found. Heifers from cows that received the protein supplement exhibited a pregnancy rate 13 percentage points higher than that of the heifers from cows that did not receive the supplement," said Wiedmeier.
At South Dakota State University researchers fed a large group of dry, pregnant cows. Half of these cows received adequate nutrition throughout the entire gestation period. The other half of the cows received adequate nutrition during the first and third trimesters but received inadequate nutrition during the second trimester when most of the fetal calves' muscle mass is developing.
"Nutrient restriction during the second trimester is common on many operations. No difference in cow or calf performance was measured through the calf weaning phase," said Wiedmeier.
However, when these calves were fed out in the feedlot, Wiedmeier says researchers found differences. Calves from cows that had nutrient restriction during the second trimester produced carcasses that were higher concerning USDA quality and yield grades compared to calves from the cows receiving adequate nutrition the entire gestation period.
"Apparently, in some manner, signals are being sent to the fetal calf throughout gestation that alter or tweak the DNA of the calf. Perhaps these signals are in some way helping prepare the calf for the environment into which it will be born," said Wiedmeier.