Go with the flow

Biophotonics helps researchers better see animal physiology

By: Vanessa Beeson

Go with the <span>flow</span>

Brahman cows graze at the MSU Beef Unit on the MAFES H. H. Leveck Animal Research Center (South Farm). Brahman and Angus cows were bred with a Hereford bull in a study that determined how the fetal environment affected different breeds of calves. (Photo by David Ammon)

Two MAFES scientists, Dr. Caleb Lemley and Dr. Derris Devost-Burnett, are leading a team of researchers who are using biophotonics to study how maternal nutrient restriction affects calves.

Lemley, an animal and dairy science assistant professor, focuses on the mother while Burnett focuses on the calves. The researchers evaluated the placentas, fetuses, and offspring of Angus and Brahman heifers sired by a Hereford bull.

Twelve placentas and fetuses (six from each breed) were examined about two-thirds of the way through gestation to provide an essential snapshot of the impact of nutrient deficiency. Additionally, 16 calves were carried to term, delivered, and tissue samples will be evaluated throughout grow-out to harvest.

Lemley explained why studying maternal nutrition is important.

"Low forage quality and drought conditions can contribute to nutrient restrictions in cows and we have found that if a cow is pregnant at the time of that restriction, the deficit can cause lifelong consequences in the offspring," Lemley said.

He said the team evaluated the placenta because it connects the mother to the fetus, noting that blood flow, in particular, can impact how nutrients the mother intakes reach the fetus. The team sought to learn how maternal nutrient restriction affected the placenta's development. They also wanted to detect blood vessel density in the placenta using in-vivo biophotonics imaging technology. The team perfused florescent antibodies into the placenta's blood vessels to track blood flow.

"We learned that when the mother's nutrients are restricted, the placenta compensates by increasing blood vessels, which is a phenomenal feat," Lemley said. "We also found that this technique matches up with previous research. The difference is that this technique allows us to look at all the blood vessels in the placenta while previous research was limited to specific zones."

Lemley said understanding alterations of placental development during pregnancy will help producers to maximize fetal development in-utero, possibly decreasing the instances of calf morbidity and mortality. He also said by providing the team funding to examine novel imaging techniques, the Biophotonics Initiative has allowed their work to have a potentially greater impact for other researchers and the cattle industry as a whole.

"We expect these techniques to have direct applications in the scientific community as well as leading us to novel therapeutic supplementation strategies to improve pregnancies and offspring development," Lemley said.

While Lemley focused on the maternal side, Burnett, who is also an animal and dairy science assistant professor, is the principal investigator examining fetal and postnatal development of the calves.

"Dr. Lemley and I have the same interest in how the in-utero environment affects offspring growth and development so it was a natural partnership," Burnett said.

"Telling two sides of the same story allows for a more comprehensive story. While he focuses on the maternal environment itself, I evaluate how that environment affects the growth of muscle and fat in the offspring."

Burnett said that cows spend about a third of their life in-utero so it's not surprising that the time spent in the womb can have a big impact on overall production efficiency once the calf is born.

"Traditionally, we thought offspring challenged in-utero could recover. We now know that a compromised in-utero experience programs how the calf's metabolism responds to postnatal management strategies," Burnett said.

He said that an in-utero deficiency can lead to low birth weight, delayed or less than optimal growth and reduced feed efficiency.

"These calves can't hit the ground running because their metabolic paradigm-the ability to efficiently utilize and partition nutrients-has already been established," Burnett explained.

"Healthier in-utero experiences make it more likely for calves to reach their full genetic potential. Having good genetics isn't enough. A phenotype, or animal, comes from genotype and the environment," he continued.

The team analyzed muscle and fat-related gene expression using muscle histology, measuring the size and number of muscle fibers. Immunohistochemistry allowed them to visualize those fibers. A machine called a cryostat took a five micrometer cross section sample of the muscle fibers and the sample was infused with florescent antibodies that allowed the team to evaluate the nuclei of the fiber. Burnett said delineating which fibers are primary and which are secondary can help determine if the in-utero experience the fetus underwent was an enhancement or detriment to their postnatal muscle growth potential.

"While we are still analyzing the fetal muscle fiber data, understanding the number and ratio of primary to secondary muscle fibers gives us a better understanding of the framework the animal has to work with for postnatal life as there is no net increase in muscle fiber number after primary and secondary myogenesis are complete in fetal life," Burnett said.

Thus far, the researchers have observed birth weight reduction and the development of less muscle fibers in offspring that were nutrient-restricted in-utero. Burnett said he's also seen a difference between breeds.

"Brahman cattle are thriftier in this study. While we've known this for years, we are now looking at the mechanisms behind it and are able to provide mechanistic data to support the phenotypes that we observe. These aren't just observations but are supported by some novel mechanistic data," he said.

Burnett said he hopes to further explore why Brahmans are thriftier on the molecular level.

"We hope to glean information from this study to inform breeding strategies. Perhaps this will lead to a more optimal ratio of Brahman to Angus in terms of crossbreeding," he said.

He also said the research could one day help producers determine custom management strategies if their animals experience nutrient restriction.

"Producers may try to mitigate the negative response or try to market their cattle earlier or in a different market," Burnett said. "We hope research like this allows us to provide producers with data-based information that helps move the industry forward."

Contributors include Dr. Brian Rude, professor; Caitlin Hart, former research associate; Dr. Seong Park, post-doctoral associate and Racheal Lemire, master's student, all in the Department of Animal and Dairy Sciences; along with Drs. Heath King and Richard Hopper in the College of Veterinary Medicine. The research is supported by the National Institute of Food and Agriculture and the U.S. Department of Agriculture, Hatch project under accession number 1011100. Additional funding was provided by the U.S. Department of Agriculture's Agricultural Research Service, Biophotonic Initiative number 58-6402-3-018 and a MAFES SRI grant.