Integrative analysis of gut microbiome and metabolome reveals the growth rate differences in Dezhou donkeys
This study reveals that the superior growth performance of Dezhou donkeys is driven by a coordinated network of fiber-degrading gut bacteria and growth-promoting metabolites, whereas slow growth is associated with inflammation-linked microbes and metabolic inefficiency.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every living animal carries within its gut a vast, invisible community of microscopic life. These trillions of bacteria, fungi, and other microbes form a complex ecosystem that acts as a second digestive system, helping the host break down food, extract energy, and maintain health. In many animals, the balance of this internal world is just as important to growth as the food itself. For centuries, humans have relied on donkeys for labor and transport, but today, as the demand for donkey products like meat and milk rises, farmers are shifting toward more intensive breeding methods. Yet, even when raised in the exact same conditions with the same diet, some donkeys grow quickly while others lag behind. Scientists have long suspected that the gut microbiome holds the key to these differences, but the precise link between specific microbes, the chemicals they produce, and the speed of growth in donkeys has remained a mystery.
To solve this puzzle, researchers followed a group of sixteen male Dezhou donkeys from the moment they were born until they were eighteen and a half months old. They raised the animals together, feeding them the same milk, hay, and grain, ensuring that any differences in their development were not caused by their environment or diet. By the end of the study, the team divided the donkeys into two groups based on their average daily weight gain: a fast-growing group and a slow-growing group. The researchers then collected fecal samples from each animal to analyze the genetic makeup of their gut bacteria and the chemical compounds present in their waste. This dual approach allowed them to see not just which microbes were living in the gut, but also what those microbes were actually doing.
The investigation revealed that the two groups of donkeys were not just different in size; their internal biological worlds were fundamentally distinct. The fast-growing donkeys hosted a higher abundance of specific bacteria known for their ability to break down tough plant fibers, such as cellulose. These fiber-eating microbes are essential for herbivores because they unlock energy from the grass and straw that the animal cannot digest on its own. In contrast, the slow-growing donkeys were enriched with different types of bacteria that are often associated with inflammation and poor gut health. The researchers found that the fast-growing group possessed a more efficient microbial community, one that was better suited to extracting energy from a high-fiber diet.
Beyond the bacteria themselves, the study looked at the chemical landscape of the gut. The fast-growing donkeys showed higher levels of specific metabolites, which are small molecules produced during digestion and metabolism. These included certain amino acids, which are the building blocks of protein, and compounds related to folate, a vital B vitamin that helps cells divide and grow. The researchers also found elevated levels of bile acids, which help the body absorb fats, and short-chain fatty acids that provide energy to the gut lining. In the slow-growing donkeys, however, the chemical profile was different. They had higher levels of a compound called methylmalonic acid, a marker often linked to a deficiency in vitamin B12, suggesting that their bodies were struggling to process nutrients efficiently.
The most significant finding was the connection between the microbes and the chemicals. The fiber-degrading bacteria found in the fast-growing donkeys were directly linked to the production of the growth-promoting chemicals. It appears that these beneficial microbes work together in a coordinated network: they break down the tough plant material and convert it into the specific nutrients and energy sources that drive rapid growth. Conversely, the bacteria found in the slow-growing donkeys seemed to disrupt this process, correlating with lower levels of beneficial nutrients and higher levels of inflammatory markers. This suggests that the slow growth was not merely a matter of genetics or appetite, but a result of a less efficient internal ecosystem that failed to harvest energy effectively from the same food.
This study provides a clear picture of how the gut microbiome influences the growth of donkeys. It shows that a healthy, fiber-fermenting bacterial community, supported by the right metabolic pathways, creates a biological environment where rapid growth can thrive. For the donkey industry, these findings offer a new way to look at animal health. By monitoring the specific types of bacteria and chemical markers identified in this research, farmers may be able to identify animals that are struggling to grow and adjust their management or nutrition to restore a healthy gut balance. Ultimately, understanding this invisible partnership between the animal and its microbes could lead to more efficient and sustainable ways to raise these resilient animals.
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