Episode 370 - How Calf Housing Shapes the Gut Microbiome: Individual, Group, and Dam-Reared Calves - UMN Extension's The Moos Room

How does raising calves individually, in groups, or alongside their dams shape their gut microbiome? In this episode of The Moos Room, Brad  discusses a University of Minnesota study examining how these three rearing systems influence microbial communities, growth, and the transition through weaning.

Individually housed calves and calves raised in groups of six received similar diets and developed similar gut microbiomes, suggesting that calf-to-calf contact alone had little influence on microbial diversity. Dam-reared calves, however, developed distinct microbial communities and had the highest average daily gains. Their lower microbial diversity before weaning did not correspond with poorer growth.

Brad explores how access to milk, contact with adult cows, and exposure to solid feeds may help explain these differences. Within three to four days after weaning, microbial diversity increased in dam-reared calves as they transitioned away from milk, although some differences among rearing systems remained. Because the systems differed in several ways, the findings reflect the combined effects of diet, environment, and maternal contact.

The episode also includes updates on fall grazing, virtual fencing, and ongoing calf research at the West Central Research and Outreach Center, plus a preview of Brad’s upcoming trip to Sweden.

Questions, comments, scathing rebuttals? -> [e-mail] or call 612-624-3610 and leave us a message!

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Hosted by members of the University of Minnesota Extension Beef and Dairy Teams, The Moos Room discusses relevant topics to help beef and dairy producers be more successful. The information is evidence-based and presented as an informal conversation between the hosts and guests.

 Welcome to The Moo's Room. It's the end of October, and it's starting to get a little bit colder here in the Midwest. Today, temperature's 40 degrees, so we're almost done grazing. We have one group of heifers still out grazing on some pastures, kind of trying to clean some things up. They're on a virtual fencing system, so we're still moving with...

I think there's 65 heifers out there. So we're still going okay. It might be another week or two, and then they'll all be done as well. So the grazing season is, well, about done for this year. We're also having lots of calves. So far, I think we got 50, almost 50 heifer calves born, working for our polled genetic study and disbudding study, so that's going well, and we have 45 Angus and Angus crossbred calves on the ground.

So we got calves everywhere, doing lots of calf studies. It's quite interesting. We've got some of those calves on the auto feeder, and a lot of the Angus, Angus cross calves, I see the oldest ones now are a- about seven weeks old or so. They're a couple weeks yet from weaning, and they're drinking about 14 liters on the auto feeder.

Maybe not as much as what I expected them to drink. It was kind of crazy. I did this before, and some of them were drinking 20 liters at the time. So it is interesting to see what's actually happening in those calves. So I wanted to talk about a calf study that we did that was actually just came out, and kind of interesting looking at the microbiome of calves.

So we'll talk a little bit briefly about this calf study, and we've talked some about this calf study before. It was the study that we did with individual hutches, group hutches, and dam-reared calves. And so we took some samples from them to really look at how their gut microbiome kind of shaped with housing system, and did housing system have a real big effect on that?

You know, because for decades we've kind of grappled with this dilemma, you know, should calves be raised as individuals? Should they be isolated to protect them from disease? Or should they be housed in socially encouraging natural behavior to express their true welfare? And I think that still is relevant till today.

We still have this debate on whether we should house calves in pairs and individuals or groups or dam-raised, and it's kind of all over the board yet. So let's talk a little bit about what we did and maybe about what we found. So we had calves that were raised individually by themselves. They had ten liters of milk per day, ad libitum starter and water.

The group-fed calves were in groups of six, so normally were in groups of ten, but we kept these calves to six. Again, they were fed ten liters a day, as much calf starter as what they could get. And then we had our dam-raised calves. So they were raised in outdoor access alongside their dams in kind of cow-calf pairs.

They were maybe away from their mom for an hour a day during milking, but otherwise they were allowed to drink as much milk directly from the cow, like unpasteurized, obviously. The group and the individual calves, it was pasteurized. But these dam calves, they had creep-feeding area where they could eat as much grain as what they wanted, but they also had access to adult feed bunks, TMR, silage, you name it.

So they had access to about everything in the world. So these calves were weaned about nine weeks of age, and then they were co-mingled into kind of shared super hutches with calves from the other treatments, again fed calf starter hay, grain. So we took fecal samples from these animals- pre, pre-weaning, so just before they were weaned, and then we took samples three to four days after they were weaned and kind of did a genetic sequence on these manure samples from these calves to see what we could find and look at their microbiome

Obviously, our big thing were average daily gain, so we found gain was much higher in the dam-raised calves compared to the group or the individual ones

Now let's talk about the microbiome research and what we found there

So here's our first takeaway Putting baby calves together had surprisingly little impact on their gut microbiomes. So it seemed, seems logical that grouping calves together would maybe spark some gut microbiome differences with social play, mutual grooming, shared feeders. But really, we found that the study revealed that calf-to-calf contact during the pre-weaning period almost had no effect on their gut microbiome structure.

When we compared individually housed calves with the group-housed calves, we found no difference in diversity of microbial species in those calves. So really about the same, no matter if they were housed individually or whether they were housed in groups So really this calf to calf contact alone was not a big driving force in early gut colonies.

Despite, you know, they shared bedding, outdoor pens, they were exposed to manure, they had multiple nipple feeders, these group house calves developed microbial gut microbiome that was virtually identical to those raised in individual hutches. Maybe some tiny variations, but really nothing meaningful that really shifted their gut microbiome The second thing, dam raised calves, so calves that were raised on their mom, had lower bacterial diversity, and that actually maybe was a good thing.

So obviously peer socialization, so the group housed calves, didn't alter the gut microbiome. So the question was, what happens when the calf stays with the mom? Well, it was interesting. So the calves that were raised by their dam had lower pre-weaning alpha diversity. So what does that mean? They had fewer total bacteria species and lower overall diversity than calves housed individually or in groups So let's sort of break that down.

In kind of the microbiome science, higher diversity is often assumed to be better. However, young calves with lower diversity may indicate a highly specialized milk-optimized digestive system. So they were just drinking more milk So the two driving factors in this lower diversity were obviously the dietary treatment.

So these calves had unlimited access to drink as much milk as what they wanted from their mom or other cows as well in the pen. And so that maintained a rich milk diet. And so really their gut microbiome favored milk-fermenting microbes rather than a broad mix of microbiome that would actually work in breaking down grain

We also think that milk pasteurization played a role in this as well. So while the individual and the group calves received pasteurized milk, which would intentionally reduce the environmental bacterial load, the dam calves ingested raw milk directly from the mom, and this combination of raw milk and drinking as much as what you wanted kind of created this specialized microbiome in, in all of these calves that were raised on mom

So even though those calves were exposed to a greater variety of bacteria, you know, they were in pens, TMR, exposed to mom, you name it The socialized treatments in the study didn't show a higher microbiome diversity than individual calves So really this lower microbial diversity didn't translate into poor health or reduced growth in these calves, 'cause actually the dam-raised calves had the highest average daily gain

So takeaway number three The dam's presence actually fast-tracked gut maturation with what we would call maybe adult ferment of bacteria. So while these calves actually had lower species diversity, their microbial community was very different than the calves that were individually raised or in group, and probably about thirty percent or more

So the

Pre-weaning dam calves, they were heavily dim- dominated by this firmicutes, which made up about seventy-two percent of their microbial gut microbiome, compared to only about fifty percent in individual and group-raised calves. So this is basically a gut bacteria that is working with fermentative bacteria and usually dominant in cow rooms.

So we found bacteria that helped with gut wall builder, that converted lactic acid into short-chain fatty acids like propionate and butyrate, which prevents dangerous gut acidification. We found a lot of fermentative microbiomes that were specific to things that we find in the digestive tracts of animals that are consuming plant diets, so silages.

So obviously, these calves that were raised on mom were probably consuming some silage while they were raised with the mom as they got older. Obviously, the calves that were a few weeks old were probably not doing it, but the ones that were getting close to weaning, we definitely were probably consuming silages

So when they lived alongside these adult cows, they were basically acting like mom, which kind of fast-tracked their gut microbiome toward adulthood So the last takeaway was what happens at weaning. So weaning obviously was the complete removal of milk from these calves and onto solid food. And obviously this is the biggest event in young ruminants' life.

So again, they were weaned at about nine weeks of age, and obviously for those calves that were raised on mom, they lost access to milk, which immediately triggered a surge in alpha diversity. So they adjusted to solid feed, and they had more diverse microbiome now But they still r- retain some of this unique microbial gut microbiome that kind of set them apart from the individual and the group-fed calves.

But they started to transition to that, so which really helped sort of adjust to weaning. So this really, this three-day post-weaning period kind of represented a critical transition phase for those calves Previous research has kind of showed that microbial distinctions were there between dam-raised calves and individual calves about six days post-weaning, but we actually found this to happen maybe a little bit quicker than what we would expect.

So what does this actually mean? What does this study actually mean? Well, basically, this research highlighted a big distinction in calf management. So while group housing offered clear social benefits, and we know that, and it didn't really alter the gut microbiome, obviously the maternal contact with the cow provided some advantages.

So this full cow-calf contact kind of acted as a natural microbial bridge, which really helped adjust their rumens to more fermentative bacteria that actually accelerated their gut maturation prior to weaning. So they were maybe easier to wean and get onto solid food, hay especially, because they were already consuming some silage So really it kind of shows that what happens when these animals are younger, and this may help direct future dairy systems to kind of maybe combine some of these things and think about, you know, there's this big debate on whether we should feed hay when they're young or not, and maybe this provides some information that those animals actually adapted much easier than what we thought

So with that, I think we'll leave it for today. I'll actually be in Sweden next week. Still gonna put out some podcasts, uh, but I'm gonna go there, visit some farms, and maybe we'll give a little travel vlog, uh, when I get back, kind of talk a little bit about the Swedish dairy industry. So with that, if you have any comments, questions, or scathing rebuttals, feel free to contact me at the Moo's Room.

That's T-H-E M-O-O-S @umn.edu, or find us on the web at University of Minnesota Livestock Extension or UMN WCROC Dairy. And with that, I hope you have a great week. Bye.