A healthy gastrointestinal (GI) tract is inextricably linked to the nervous system and is generally a strong predictor of a pig’s overall health, said a research veterinarian who specializes in animal neuroscience.
Most people don’t see a connection between the GI tract and the nervous system, but “there are just as many neurons in your GI tract as there are in your spinal cord,” said Adam Moeser, DVM, PhD, an associate professor of large-animal clinical sciences at Michigan State University.
“The nervous system controls so many important functions in the gut, from absorption to secretion.”
Moeser said an important part of his research has been trying to determine how various forms of stress cause or trigger disease in swine.
Perhaps the most stressful event in a pig’s life is the weaning period.
During this period “the animal is exposed to a number of pretty profound stressors, such as separation from the mother, transportation halfway around the country, exposure to new pathogens and new food sources,” Moeser said. “That’s why the weaning period is often linked to a lot of disease.”
One of the surest ways to ensure that a pig develops a healthy gut system is to extend the weaning period, he said. On average, the barrier systems in pigs are not fully developed until they are 3 months old. On the other hand, in commercial production many piglets are weaned when they are only 2 or 3 weeks old.
“That creates a lot of stress and activation of systems,” he said, adding that such an approach predisposes the animal to infections.
“Weaning stress will break down barriers to the gut that would normally block enteric pathogens,” he said. “These toxins now get access to the immune system.”
He hesitates prescribing a weaning age because so many factors, many of them economic, must be taken into consideration.
But he said increasing the weaning age is critically important to the health of the animal.
Moeser also suggests eliminating stressors or potential stressors as a strategy for producing healthy pigs.
“If there are ways to alleviate one, two or three of the stressors, you are going to see benefits,” he said, adding that the best time to develop and protect the gut of a pig is early in its life. “Anything that happens during gut development will have long-lasting impact on pig health and performance.”
Moeser said antimicrobials are also important for keeping swine healthy. He said they are effective because they eliminate stressors in the environment.
“However, when you take that kind of protection away you will see susceptibility to the environment,” he said. “Reduced antimicrobials could lead to more disease in the animal.”
Moeser and other researchers are studying other factors in the early life of swine that can shape or predict how the gut will develop. He said a few of these factors are specific immune cells that can respond to stress and mitigate intestinal injury.
One area Moeser and his fellow researchers haven’t examined is gender differences in swine.
“There are differences between gilts and boars even at very young ages,” Moeser said. “We are seeing that there are pretty dramatic differences in how the animals respond to stress. Females are more susceptible to stress-induced GI dysfunction.”