Fetal programming, in both concept and reality, has captured the attention of the cattle business in remarkable ways. And while research has shown that fetal programming is a very real thing—that the nutritional plane of the dam as the fetus develops has significant effects on the calf after it’s born—research results have been inconsistent.
“Research is trying to find out what these cattle can handle and what they can’t,” says South Dakota State University (SDSU) graduate Janna Kincheloe, who researched fetal programming for her Ph.D. dissertation. “Some studies indicate we might see fertility issues in offspring with a severe restriction during mid-gestation when those reproductive organs are being formed.” The SDSU study didn’t look at that, because the calves were all fed out and harvested, but much still needs to be discovered about how nutrition in the dam affects the future of their calves.
“This is a hot topic right now, with a variety of trials being conducted, with many inconsistencies in the results. We can measure responses of animals, but we don’t have a thorough understanding of the metabolic and physiological mechanisms that actually drive these responses,” she says.
According to SDSU Extension Beef Specialist Ken Olson, there is a lot more to learn about timing of nutrition. “Even though we didn’t see any big picture differences in the calves’ feedlot performance or carcass characteristics, what we did see convinced us that timing mattered.”
The SDSU study looked at protein restriction, whereas most studies just restrict total intake. “I think we need to do more studies—picking a specific nutrient—to understand what is driving the fetal programming, and when it happens,” says Olson.
This could be similar to a herd in real life where cows had plenty of hay, but it was low quality and lacking certain nutrients. “This is why we chose protein, because in many cases cows are turned out in corn stalks or on winter range. Ranchers usually try to supplement them because we know they will be short on protein,” he says.
“We have more to learn about how forage quality may drive fetal programming. This is an area of research that can provide valuable information about how we manage nutrition in the cow herd to improve offspring performance, carcass traits, and ultimately meat quality.”
Part of the inconsistency in research results may stem from how the dam reacts to nutrient restrictions in an effort to protect the fetus. “We saw significant response in the heifers themselves, in terms of body weight and body condition, but the dam’s treatment had very little impact on her offspring,” says Kincheloe. The heifers sacrificed their own performance to provide appropriate nutrients to the fetus.
The heifers that had protein restrictions at either mid- or late-gestation, and some throughout gestation, weighed less, had reduced body condition score and decreased ribeye area compared to heifers on the control treatment. There was no impact on backfat and only a few minor differences in intramuscular fat.
“Overall, the protein restriction appeared to cause them to mobilize their body protein stores, with minor impacts on fat stores,” she says. When the heifers calved, there were no differences in calf birth weight or calving difficulty, and calf vigor was acceptable in all groups.
“The heifers were all bred again as two-year-olds, and pregnancy rate was the same among all the groups,” says Olson. “Even though we caused changes in body condition scores during pregnancy, they compensated for it.
“It was amazing that we didn’t affect reproductive performance, even though they seemed to be protecting their offspring by absorbing the protein restriction themselves,” he says. They recovered adequately enough to breed back, and became pregnant in a 60-day breeding season.