“My dream is to have a cell phone-based device that I can take to the farm and tell you exactly which bacteria are making your animal sick, and exactly which antibiotic at which dose is going to make it get healthy fast. But we’re a long way away,” Erika Ganda said during a recent interview on the “Cornell Cow Convos” podcast.
The monthly podcast is hosted by Kaitlyn Lutz and Daniela Gonzalez, regional dairy management specialists with Cornell Cooperative Extension.
Ganda is an associate professor of food animal microbiomes at Penn State, where her research lab focuses on studying the microbiome to improve animal health and productivity. While the cell phone app may be a pipedream, Ganda and her team are slowly unlocking the mysteries of the cattle microbiome, along with other species of livestock.
A cow’s microbiome is simply the collection of microorganisms that lives in and around an animal and its environment. Ganda said it irritates her that people talk about the microbiome as if it is a novel idea.
“Anyone that has ever worked with a cow before has been extremely in tune with its microbiome, especially the rumen microbiome,” Ganda said.
Providing fluid therapy, which often includes beneficial microbes and nutritional support for the rumen bugs, is one example of how dairy farmers influence the microbiome. Transferring rumen fluid containing microorganisms from a healthy animal to a sick animal – a process called transfaunation – is another common practice on dairy farms that has an impact on the microbiome.
Most of the current understanding of the microbiome is related to bacteria because bacteria are easy to grow in the lab. Fungi, viruses, protozoa and other components of the microbiome are difficult to research since the tools to study are limited.
“It sounds like we know a lot about the microbiome already, which we do, but there is yet a lot to be learned,” Ganda said.
Milk Microbiome
Ganda’s doctoral research focused on mastitis and the microbiome of milk. Specifically, she studied no-growth and gram-negative mastitis. This research is important because antimicrobial resistance can be transmitted to other organisms. Resistant bacteria, for example, can be shed in manure, potentially transferring resistance genes to other bacteria in the environment and even to humans.
According to Ganda, antimicrobial resistance infections will kill more people than cancer in the next 20 years.
There was a big takeaway from her doctoral work and other studies that look at the milk microbiome: Antibiotics are not always the best course of action for no-growth and gram-negative mastitis. According to Ganda, these types of mastitis will resolve themselves at the same rate (or faster) when the cow is provided with supportive therapies such as fluid therapy rather than antibiotics.
“A lot of the time we are misusing drugs that we already have very few options of, and shooting ourselves in the foot by increasing the selective pressure for antibiotic resistant organisms,” she
said.
Cow/Calf Microbiome
Some of Ganda’s recent research compared the microbiomes of mature cows vs. calves. A 2020 study found that there were more drug resistance genes in the calves’ manure than in that of the mature cows. One hypothesis is that this is caused by feeding waste milk to calves.
“Those little bits of antibiotics that are in the waste milk can be playing a major role in selecting for antibiotic resistance genes within the calf gastrointestinal tract,” she said.
It’s also important to note that calves are undergoing lots of changes and stress in a short period of time. Group housing, weaning and diet changes all contribute to a less stable microbiome than that of adult cows. Calves are also more susceptible to various diseases depending on their age, contributing to differences in the kinds of microbes they carry and how often they change.
This research is important because calves are the future of any farm and require a significant investment of time and money. It’s in the best interest of every farmer to understand the challenges calves face at different times in their lives, and manage them accordingly, to maximize the chances of calves becoming healthy adult cattle.
Learning more about the microbes that live in, on and around your livestock can help keep them healthier.
Foot Microbiome
Bovine digital dermatitis (BDD) is a common disease of dairy cows. To study BDD, Ganda collaborated with the University of Liverpool in the UK, where they tested the hooves of 259 cows. They looked at the bacteria living on the feet to better understand how they might be connected to BDD.
They found that even before cows showed any signs of BDD, the mix of bacteria on their feet was already different in those that would eventually get the disease compared to those who stayed healthy.
The study also showed that a cow’s genes influence which bacteria live on its feet. For example, the presence of certain harmful bacteria was linked to specific areas of a cow’s DNA.
This is relevant to dairy farmers because in the future there might be a test that can help identify which cows are susceptible to BDD, either through foot or genetic testing.
Importance of the Microbiome
Studying the microbiome is important because the microbiome is an essential component of animal health. It might not be obvious but, according to Ganda, many on-farm decisions are ultimately related to the microbiome.
For example, certain feeds can lead to acidosis causing a microbial imbalance in the rumen. Farmers also optimize diets for the best production of volatile fatty acids, which are microbial products.
Additionally, the cleaning, sanitation and vaccination programs on a farm are ultimately targeted at decreasing the incidence of disease. This prevents the “bad guys” from taking a hold of the farm environment and the animals’ microbiome.
Ganda said, “Once we see the microbiome as this essential component of health it is much easier to see the value of studying this ecosystem of microbes that live in our animals. If we understand it better, we can manage it better.”
by Sonja Heyck-Merlin
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