S6E7 | New Tools for Understanding Stress in Transition Cows with Dr. Laura Hernandez

Описание: Measuring hair cortisol in dairy cows reveals how stress affects reproduction, milk yield, disease risk, and supports better farm management decisions.

Timestamps & Summary

Chris Gwyn (02:11)
At JEFO, we've been looking at stressors across species, in particular in dairy cows. I was wondering if you could give our audience an overview of this study and why it's important.
Dr. Laura Hernandez
Sure. This was an ongoing collaboration with my colleague Dr. Milo Wiltbank, who's a reproductive physiologist here at the University of Wisconsin. We had a shared scientist who's now a professor at the vet school at the University of Florida, Pedro Monteiro. […] He's traditionally a reproductive physiologist. He developed this question about how this might impact return to cyclicity and timing of parturition. His main complaint was that in our projects, we could never figure out when the cows would calve, so they'd be sampling forever and ever and ever. And then finally the cow would calve earlier or late, of course. And so he was like, there's got to be a way we can figure this out. It also might be really critical to how successfully a cow comes back into cyclicity or what might happen with reproductive diseases, knowing that there are all these losses that occur that are due to a variety of problems in the first 60 days postpartum. […]
We know that cortisol is a major stress regulator of all things, and it changes all the time in relation to a variety of stresses. [Dr. Monteiro] had read this paper, and I believe it was beef cattle, and they had shown that you could measure cortisol in the hair. Really, the hair cortisol is reflective that day for about two weeks prior to the actual date you took the hair sample. Because the cortisol deposits in the hair, and the hair doesn't go away. It grows, and then you shave it off, and you can do this measurement via RIA or ELISA of the cortisol. […]

Chris Gwyn (10:10)
You had demonstrated that if we can just take out some of the key points: low stress, low cortisol versus high. You were able to see a production performance different, wasn't there?
Dr. Laura Hernandez
That would be from a practical standpoint that if our data continues to go in the way that it has been, that if a farm wanted us to come, that this is something that could be done by a nutritionist or nutrition groups or veterinarian groups, that if they wanted to know what it looked like, say, in the prepartum period, they could take a hair sample when they dried cows off, and then maybe, depending on what their dry off protocol was, three weeks later, get another hair sample. That could be run, and they would have a good idea of what's happening. Or if they wanted to do it in a post-fresh cow, say 10 days postpartum, they could really take a look at what some of these pen changes might look like, if they did it in a new facility, or if they were having problems, is it due to stress? What's the stress level? How might that look on a threshold if we can develop one? It would be a really easy way to do so without bleeding a cow. All you have to do is shave the tail head. It's just a regular shaving. […]

Chris Gwyn (12:43)
Inherently, we may understand that certain periods of lactation or management practices have a different level of applied stress or stressors. Calving, regrouping, the whole process, mixing groups, but we don't know what costs us. Some association of a simple cortisol test with a number of studies that support milk loss or impacts on reproduction will reestablish or reinforce the need to perhaps change some management.
Dr. Laura Hernandez
That's my hope. I'm a very basic scientist, but all the things I root my science in are providing information to make good decisions that work the very best for a particular farm within the means of their ability to do things. I think that's why we're here, is to help them. We try to really make our work as translational as possible.