Dr. Penner describes two primary factors of gut health to be absorption and barrier function or permeability. His lab’s work on permeability is suggesting that intestinal regions really drive total gut permeability to a much greater extent than ruminal permeability in dairy cows. (7:06)
Ms. Bertens is Dr. Penner’s Ph.D. student and explains some new methodologies she developed for measuring gut permeability using chromium EDTA and cobalt EDTA. It’s common to use an oral dose of chromium EDTA as a marker to measure total tract permeability. Claire’s work, using cannulated cows, used a ruminal dose of chromium EDTA for total tract permeability and an abomasal dose of cobalt EDTA for post-ruminal permeability. Both of these markers are indigestible, non-metabolizable and have no transcellular transport mechanisms. Claire is working to publish the new method as a complete validation study has been completed. (9:15)
While this method is currently limited to using cannulated animals, Greg and Claire could envision a less sophisticated and more applied on-farm technique to assess permeability. Until then, there are still a lot of management observations that can identify potential issues with gut permeability. The appearance of feces and the presence of mucin casts can both be indicative of gut issues. Certainly dry matter intake is a major influencer on gut health, and Claire also sees potential in new technologies like rumination collars or rumination ear tags. (13:47)
Are there certain time points in a dairy cow’s life when she is at risk for increased gut permeability? Dr. Penner describes research suggesting if weaning is implemented too abruptly, that really increases the risk for decreased barrier function of the gut. Erratic feed intake patterns resulting from withholding feed for any reason at any age can also increase the risk of leaky gut. For example, depressed intake during the transition phase, along with anything that drives a response through an underlying systemic inflammatory response, probably creates risky situations for leaky gut. Claire is currently running a study looking at the impacts of intramammary LPS infusion on gut function. Greg envisions that learning more about gut function could create a new philosophy for treating sick animals. In the past, only antimicrobials were used to treat mastitis, but now it’s common to also treat with a NSAID for pain. Perhaps in the future, we will also provide treatment to accelerate the recovery of the gut to prevent secondary disorders. (16:15)
How long does an off-feed event have to last to cause an issue in the gut? It seems a fairly acute time period is all that is needed. Most studies are trying to replicate what happens on-farm, for example during mastitis, heat stress or the transition period. Greg indicates that not only will permeability be impacted, but ruminal absorptive capacity can also decline rapidly in these conditions. In Claire’s LPS challenge study, cows’ rectal temperatures peak around six hours after the LPS infusion and usually resolve within 12 hours. But most cows do not eat for a solid 12 hours during the challenge, and they are slow to recover feed intake over the next few days. In cows that aren’t sick but experience feed restriction in experimental protocols, they tend to overeat when they are allotted the full ration and this can lead to ruminal acidosis. (21:57)
Increased incidences of liver abscesses in beef-on-dairy calves are being reported in the industry. Dr. Penner speculates that perhaps these calves are not always achieving adequate passive transfer, and may not be receiving high enough levels of milk replacer to support a more robust immune system. It may be the increased beef cattle genetics in the calves are putting an added requirement on growth or muscle development that may not be met by lower levels of milk replacer or even lower colostrum feeding levels. (34:40)
In closing, providing cows with a consistent environment where they can meet their needs by their own behavior such as free access to feed when hungry and to a comfortable stall when it’s time to rest. Cows reward consistency with health and production. Gut health in a commercial setting is a relevant issue and it might go undiagnosed or undetected. Research into where in the gut permeability is occurring will help define strategies to modulate response. While off-feed events for individual animals might be harder to recognize in a large dairy environment, new technology may allow for earlier diagnosis. (40:43)
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