Subscribe
Share
Share
Embed
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. A beautiful fall day here in Western Minnesota. Again, have had some rain in the last week, but harvest continues slowly but surely. It will happen. I think the soybeans are coming out this week. It's supposed to be really nice in Western Minnesota with no rain, so I'm sure harvest speed will pick up quite a bit.
Just back from Madison, Wisconsin and World Dairy Expo this past week. It was great catching up with lots of friends, former students, lots of people in the dairy industry, cattle breeders. Got to see lots of good cows. The trade show was always wonderful, has given me lots of new ideas on what I might be able to incorporate into our dairy.
Obviously, a lot of those things certainly cost a lot of money, but, you know, maybe we'll, we'll figure some things out, um, and, uh, see where we go from there. But speaking about cows, have you heard about the new genetic defect in Holstein cattle? This just came out last week, and I want to briefly talk about it and see.
So basically, it's a hidden genetic defect. It's the HYAL variant, and it basically shortens the productive life of Holstein cattle. So there were researchers, they identified this specific recessive genetic mutation in this HYAL1 gene, which basically impairs health and longevity and causes joint disease in Holstein cattle, which really leads to early culling and of course, reduced farm profitability.
So let's talk a little bit about this, the basics. Where they found some cows on some farms that had swollen hocks, they were actually missing a letter in the gen- genetic sequence, and so the researchers decided to give it a little bit more study, and we'll kind of go into some of the details of that really.
But this was from the University of Bern, so this is in Germany, where researchers identified this genetic defect in Holstein cattle that basically triggers chronic joint inflammation. And this mutation sits at this HYAL1 gene, and it's on chromosome 22, which basically codes for
It codes for hyaluronic acid. Basically, it's a lubricant for joint fluid. And when the enzyme is absent, this acid accumulates, which causes fluid buildup in the hocks of dairy cattle and causes swollen joints, restricted movement, and visible lameness. So this study wanted to look at French Holstein data.
They looked at a lot of cows in France as well as in Switzerland, looking at Holstein cattle there
And in a nutshell, they found that the gene frequency is about 4.4% in the Holstein breed in Switzerland and 8.4% in the Holstein breed in France. And a lot of those breeds carry a lot of genes from all over the world, so it's probably just as high in many other countries around the world. So let's dive a little bit into this study and see what the researchers actually found and what are some of the implications of this new genetic defect that has been reported.
So this study by the researchers in, in Bern basically investigated this trade-off in Swiss Holstein and Brown Swiss cattle. So they also looked at Brown Swiss to see if it was there as well. And this research, basically they combined non-additive models and fine mapping of the genome to really find this, which was actually completely invisible to conventional additive genetic evaluations.
So here are five takeaways from this research that really looked at what they found. So standard genetic models were kind of blind to this hidden mutant gene. So in the genetics world, we do s- things called GWAS, which is a genome-wide association study that really relies on additive genetic models. So it's not worried about some of the other models, heterosis, dominance, things like that.
This approach really assumes that a gene's effect builds linearly on each copy of an allele an animal inherits. So while additive models capture a majority of the polygenic trait variation, they are really blind to these non-additive genetic structures, which is where we see recessive mutations, because sometimes a single copy causes no visible effect, but two copies actually trigger a clinical disease.
So these researchers found non-additive, so they looked at recessive and dominant models beside the traditional ones, and they uncovered this hidden recessive nonsense variant, which was located on chromosome 22, this HYAL gene in Holstein cattle And really because these standard genetic evaluations kind of look for incremental linear phenotypic changes across different carriers, this mutation really evaded detection and across time was causing significant phenotypic drops in bone structure in the hocks of, of these Holstein cattles
And really the authors, they kind of highlighted in their conclusions that this identification of this recessive allele associated with bone structure in Holstein really uncovered hidden disorders in Holstein cattle. So this discovery really delivers a crucial message to geneticists around the world that really rely on strictly additive breeding evaluations that there may be some recessive deleterious genetic killers out there that circulate quietly within the population.
And we've known that with some of the other variants as well that have kind of been circulating in the different breeds and then they just pop up many, many, many years later. And really so it was this non-additive models that found this. So The second point, so this was kind of a secret killer of cow longevity.
So they wanted to analyze the real-world impact of this mutation, so they analyzed national data sets which included over a million French Holstein cows. Again, they found the variant was at an allele frequency of 8.4%
In French Holsteins and 4.4% in Swiss Holsteins, while it was really absent in some of the other breeds that they had looked at, which was Simmental, Swiss Fleckvieh So they also compared it across the genomes from worldwide global scale populations, and basically it helped them confirm that this HYAL mutation was not localized to just Europe, that it was an international breed issue, and certainly it will be looked at from around the globe now to see if it's in other populations So the researchers tracked six-year survival data across about 300,000 Holstein cattles and basically determined that survival really diverges at three years of age.
So these mutant carriers showed normal survival through their first two years of life. However, starting at age three, so this is after first lactation, their survival plummeted significantly. So from 86% survival at year three to 35% survival in year six. So by year six, only 35% of these HYAL1 carriers remained alive compared to 40% of non-carrier animals.
So 5% less survival there So really this timeline directly intersects with standard dairy management practices. So obviously cows typically calve for the first time around two years of age. They complete a 305-day lactation. Reaching three years of age basically marks the end of their first lactation cycle.
And then we see this huge drop in survival, and basically it revealed that farmers were forced to cull these animals probably prematurely due to physical and functional problems in their feet and legs with these cows as they really should be entering their most productive years, and they're culling them way too early because of this genetic mutation
So they also found that Among cows, because they had survival rates that significantly dropped, these cows that had the genetic variant also showed lower milk fat and protein yields compared to the cows that were not carriers. And the cows that were carriers had really negative effects to their locomotion, rear legs, and overall bone structure.
And so it became a problem as these cows got older. We see less production, more problems, more lameness, which really affected their longevity. And it was interesting because these researchers did compare this study that things that might be paralleled in human diseases. So obviously you kind of see this maybe in humans as well.
So they looked at some Holstein females on commercial farms that maybe were identified as a target. And so they looked at heifers, some cows that range in age. And basically these physical examinations revealed consistent non-warm, so it wasn't hot to the touch, soft bilateral joint enlargements, which involved the hocks in all of the animals.
As well as the fetlock joints in older cows. So they used ultrasound where they confirmed kind of distension of these joints and had lots of fluid. So their buildup of fluid in these cows and basically they called it polysynovitis, which was joint effusion. So you're having joint problems in these animals really before they even calve.
So they found joint issues in seven-month-old heifers before they ever produced milk. So it was an early onset type of syndrome that we're seeing. So it really affects them when they're heifers. And that's why we see the early culling happening in these animals. So basically it does kind of parallel some of the things that, that humans see.
Basically joint issues, fluid accumulation in, in joints, and it's really kind of caused by the same genetic mutation that we see or similar mutation. Basically causing chronic lameness, reduced mobility, everything like that
So let's talk about conformation scoring. Now they did do some conformation scoring, so they looked at on-farm recording of some of these lesions, uh, across the population and looked at conformation trait scores, bone structure, rear leg side view, rear legs rear view, foot angle, heel depth, locomotion. And, you know, that's what breeding programs really rely on for linear scoring of hoof and leg conformations.
So they found heritabilities around 10% to 25% for a lot of these different conformation traits that we see, which indicated because these traits had stable heritabilities, kind of what we saw and see in many other populations, linear scoring may provide a, a proxy for herd health
And indirectly selecting for some of these conformation traits allows breeders to improve joint soundness and kind of build a resistance against lameness that we see
So they also looked at fine mapping. So obviously, like I talked about before, a major challenge with some of these traditional GWAS studies is that some of these things might be difficult to isolate the underlying causal gene. And so they looked at a lot of different meth-methods looking at non-additive ways to do this.
And across breeds, really this mapping prioritized three candidate variants in Holsteins, uh, one for bone structure and two for locomotion. They also found a little bit in Brown Swiss, but not-- the signal just wasn't there like it was in the Holstein breed. But really several key genes emerge for locomotion, leg health, and joint structure, and basically they have things that are related to skess- to neuromuscular signaling, skeletal muscle contraction associations with locomotion.
So a lot of these genes that they actually found were related to the skeletal system and locomotion and lameness So basically these findings kind of highlight something in modern agriculture. Obviously, genetic data or genomic data is certainly not enough on its own to determine this genetic mutations that we see.
So we actually need to see this non-additive models. We need to capture these phenotypes that we're seeing. You know, without these phenotypes of these animals that were evaluated, we would have never have seen this from a genomic standpoint. So we still need those phenotypes to be able to determine this.
So obviously, this genetic mutation is being certainly looked at quite a bit into the future
And this new HYL1 variant is kind of under review by the World Holstein Federation to recognize this as a genetic defect, and it will be recognized under the HL designation. And obviously, we'll be able to look at it from mating software programs, genomic tests in the commercial world, and really we can probably help eliminate some of these single recessive disorders that really prevent painful joint disease and lameness in these cattle So in the end, we'll obviously, once we get some reliable genomic tests and designations, this will be able to eliminate these carrier matings that we see to prevent some of these calves from being born that have these genetic defects.
Obviously, we can cull some of these mutants early because they're gonna get culled a lot faster than what we normally see because of low milk yield, locomotion problems, et cetera. So in the end, basically, researchers found a new genetic mutation that causes joint pain, joint fluid buildup in Holstein cattle, and the prevalence is quite high, 4 to 8%.
That's, that's quite high. 8% of French Holsteins have it. That's really high. And it causes a big drop in survival after the third year of life. It causes lower fat, milk, protein yields, and causes problems with locomotion and overall bone structure So I think we'll be hearing more about this genetic defect as we go into the future, and it's a little more discoverable, and people find it more in their cattle.
So with that, hopefully you learned a little bit today, and there's always more recessive genes being discovered every single day. And with that, I think we'll leave it there today. If you, uh, have any comments, questions, or scathing rebuttals, feel free to contact me at the Moose Room. That's T-H-E-M-O-S-R-O-O-M @umn.edu, or find us on the web, University of Minnesota Livestock Extension, or UMN WCROC Dairy.
And with that, I hope you have a great week. Bye.