Starting with the cowherd: Gestational environment impacts calves long-term
New Orleans, La. – Fetal programming has been a topic of conversation in the beef cattle industry for the last decade, and Amanda Blair of South Dakota State University’s Animal Science Department commented, “This evolving area of research has highlighted the fact that what mom eats matters.”
Blair continued, “The concept is generally called fetal or developmental programming, but it centers on the theory that what the cow eats and what she encounters or endures during pregnancy can affect the lifetime performance of the calf she’s carrying.”
Recent research has highlighted the importance of the gestational environment in a number of factors, including health, reproductive performance and quality, added Blair.
Blair and colleague Jana Block of North Dakota State University’s Hettinger Research Center presented during the 26th Annual Cattlemen’s College, held during the 2019 National Cattlemen’s Beef Association Cattle Convention and Trade Show.
While the term fetal programming may be relatively new, she added, “We’ve known for a long time that what moms do during pregnancy can affect the baby. What we are beginning to understand more and more about are the mechanisms for how this works.”
Blair noted the environment and genes within an animal combine to result in the outward appearance and its physical characteristics, known as phenotype.
“We are often told this is a 50-50 relationship, meaning 50 percent is attributed to the genotype and 50 percent to the environment,” she said. “If we sit and think about the genetics on the cattle side, many are much less than 50 percent heritable, so the weight of the environment in this equation can’t be overlooked.”
After the cow has been mated and pregnancy has been established,
Blair said the genotype has been set, which means producers at that point are responsible for making sure the environment is able to maximize the potential of the phenotype.
As an example, Blair said increased marbling is a trait commonly sought by producers.
“If we think of some of the strategies we might utilize to ensure the environment maximizes the marbling potential of the individual, we might think of strategies such as optimizing nutrition at critical points during growing and finishing or extended time on feed,” she said.
Producers might also utilize technology to maximize potential.
“If we think about all these things together, they’re all post-natal strategies and things we think about after the calf hits the ground,” Blair explained. “We often forget about the genotype-environment interaction prior to birth or during gestation.”
Insufficient placental development, compromised nutrient transfer, limited nutrient availability or stress events can all alter the uterine environment, which can alter gene expression.
“We can think about the expression of the gene as a dial, in some cases, where we can turn things up or down with different signals,” explained Blair.
Changes in the uterine environment can also result in epigenetic changes, which are heritable changes.
She said, “These are changes that are not encoded in the DNA but are stable and can be passed on to the next generation.”
Changes in gene expression cause a change in the phenotype without changing DNA, Blair said.
“If the gestational environment can influence lifetime productivity in cattle, think about some of the highs and lows our cowherds have seen during gestation,” Blair said, marking changes in forage quality and quantity, weather extremes or changes in diet as examples of things that impact the cow. “As researchers, we’re focused on how these changes affect the calf.”
In particular, the timing during gestation that a cow experiences stress influences the developing calf.
During its lifetime, the cow should never be eating just for herself, said Block.
“She should always be nursing a calf or pregnant,” Block explained. “If she’s ever eating just for herself, she should probably be culled.”
Underfeeding is a common situation encountered during production, she continued, noting underfeeding impacts fat and muscle development, the cardiovascular system and a variety of organs.
“Many cattle producers are fairly dependent on forages as theirmain feed sources, and we know there’s a wide range between forage quality and quantity,” Block mentioned. “Nutrient deficiencies in a forage-based program are pretty common.”
During pregnancy, in addition to feeding their growing calves, cows must also maintain themselves, which makes them more sensitive to changes in nutrients, Block said.Growing evidence suggests cow nutrition impacts everything from calf health to feedlot performance and carcass characteristics in cattle.
“There are critical windows of develop where different processes are forming the fetus, which changes the way a fetus responds to the treatment we’re giving them,” Block continued. “How we manage cows during pregnancy affects our bottom line.”
In next week’s Roundup, Block and Blair will discuss the critical windows of development and how nutrient restriction at those stages impacts growing calves.
Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.