How to feed a cow during pregnancy may not be a new concern, but have you ever thought that how you managed the cow could also affect the fetus both during development and post-birth?
Increasing evidence suggests what happens to the cow while she’s pregnant can influence the development of her calf in both good and bad ways. This is often referred to as fetal programming, and producers can use this concept to help manage their cow herd to produce desired outcomes in calves. Feed efficiency has proven to be especially influenced by fetal programming.
The concept uses the fact that what the cow eats matters and can impact the lifetime performance of her offspring. This potential can include health, growth performance, reproductive performance, and meat yield and quality.
Dr. Amanda Blair, a professor and extension meat science specialist at South Dakota State University, and Dr. Janna Kincheloe, a livestock systems extension specialist at North Dakota State University, discussed fetal programming at the 2019 NCBA Cattlemen’s College.
Blair explained that genetics and environment interact to produce phenotypes; the observable characteristics. Black hide, large rib-eye, and high marbling are all examples of phenotype.
Genetics obviously play a big role in phenotype. You can’t get a black-hided calf out of two red-hided parents, for instance. But the environment can have a big impact on how some genetic traits are expressed.
For example, if you take two steers with the genetic potential for excellent average daily gain and place one steer on low quality pasture with no supplementation and the other steer on the same pasture type but with supplemented hay and grain, the first steer may not gain as well as the second. This is an example of how managing the environment, nutrition especially, can give the opportunity for genetic potential to be expressed better.
Management factors
Management of the gestational environment can have a similar impact on the fetus just as the nutritional environment can have on the growing steer. Changes in forage quality, diet, and extreme weather are all factors in affecting the gestational environment of a cow, Blair said.
There are many environmental stressors on the cow that can affect systems or processes in the fetus. A cow’s age or body condition is a main driver. The stage of gestation development will also affect responses to fetal programming. See “The ‘seasons’ of the gestational environment” for more information.
Forage quality and the environment are important considerations that may vary based on region. Underfeeding the cow can have a large impact on the fetus’ fat and muscle tissue, development of the brain, cardiovascular system, endocrine system, and the placenta, and kidneys.
In a forage-based system, nutrient deficiencies are bound to occur. Heifers and younger cows have higher nutrient requirements up to about 4 years of age, so they are eating for their own growth as well as that of the fetus. Managing these animals during gestation may need to be different than how mature cows are being managed, because the younger cows may not be able to buffer nutrient deficiencies as well. Kincheloe added that nutrition directly affects reproduction, which then affects profitability.
An example of the impact of cow nutrition on fetal development came from a study conducted at University of Wyoming. Cows were placed on a control diet, gaining 1.5 lbs. day or placed on a nutrient restricted diet, where they were given 68 percent of their net energy requirements and 87 percent of their metabolizable protein requirements.
At day 125 of gestation, a portion of each group was harvested and fetus and placenta responses were measured. The remainder of cows were fed in their respective groups until day 245, and necropsies were then performed.
The results of the group necropsied on day 125 showed 40 percent of fetuses as intrauterine growth restricted (IUGR). Fetal weights decreased by 21 percent, but brain weight and heart rate increased by around 10 percent, proving the emphasis on supplying survival organs with nutrients first. The placenta on the fetal side showed a 38 percent decrease in weight. Cows under the age of five were shown to be more susceptible to IUGR.
Fetuses necropsied at day 245 of gestation from nutrient-restricted cows did not show a difference in fetal weights or organ weights, but the fetus placenta did show a decrease in weight by 33 percent. These findings suggested that a case of IUGR could happen and not be identified by calf birth weight.
Fetal programming research has been conducted for the past 25 to 30 years but is still in the beginning phases. However, existing data suggests there is potential to influence health and immunology, metabolism and performance, and carcass traits. These influences concern every segment of the industry, Kincheloe said, whether a cow-calf producer, stocker, or in the feedlot industry.
Long-term impacts
Fetal programming is a concept that allows for a producer to actively participate in the outcomes of their calves. If the gestational environment is managed properly, there is the potential to “program” calves to have better muscle patterns, higher immunity, and higher fertility rates.
However, if managed incorrectly, a negative gestational environment could lead to limited muscle tissue development, a poor immune system and even decreased marbling levels.
Blair concluded that there is limited availability of data on lifetime or generational effects for fetal programming and the mechanisms are not yet completely understood. There isn’t yet enough research available to make specific recommendations about management because some studies have conflicting data. However, fetal programming is real, and it is up to producers to decide when and how it matters for each individual operation, Blair finished. — Anna Miller, WLJ correspondent
