Boston was untouchable at +1645 ISET. Four months later, he’s lost 52 points and his crown. The new Swiss #1? Hadley son Monset at +1603.
Executive Summary: Switzerland’s December 2025 ISET rankings delivered a stunning reversal: TGD-Holstein Monset (+1603), a Hadley x Gameday cross, seized the genomic throne after Sous-Moron Boston plummeted 52 points—from +1645 to +1593—in just four months. This collapse, among the sharpest ever recorded for a reigning Swiss #1, starkly illustrates the volatility risk of concentrating matings on young genomic sires. The Gameday maternal line now underpins three of five top bulls, creating genetic concentration that demands careful inbreeding management in progressive herds. Breeders seeking production alternatives should consider Progenesis Timeout (+141 kg fat, +0.83%) and Torchlight (+92 kg protein, +1584 ISET)—elite components outside the Hadley stack. For conformation priority, DG Blackburn leads genomic type at +136 ITP, while daughter-proven NH DG Arrow (+128 ITP) offers proven reliability over genomic projection. The December lesson is unambiguous: rankings reward diversified mating strategies, and any sire—regardless of peak index—can lose 50+ points before his first daughters calve.
A New Name at the Top
The December 2025 Swiss genetic evaluations have reshuffled the genomic leaderboard in ways that should give every breeder pause. TGD-Holstein Monset, a Hadley son bred from a Gameday dam, now sits atop the ISET (Total Index) rankings with a score of +1603. That’s not a typo—the new #1 actually posts a lower index than the old #1 held just four months ago.
What’s interesting here is how this leadership change happened. Monset didn’t surge past Boston through some spectacular gain. Rather, Sous-Moron Boston—the bull who looked bulletproof in August at +1645 ISET—experienced a 52-point correction that dropped him to +1593. In genomic evaluation terms, that’s a significant recalibration. Boston, a Casting son also out of a Gameday dam, now sits in second place behind a bull he would have comfortably outranked just one evaluation cycle ago.
Rounding out the top three is TGD-Holstein Beautyman, a Globed x Astral cross holding steady at +1586 ISET. Beautyman has proven remarkably consistent across evaluations—he sat at +1590 in August—which is exactly the kind of stability progressive breeders should value.
December 2025 Genomic ISET Top Performers
Here is a look at the top rankings in the genomic list for December 2025:
| Rank (Dec ’25) | Name | Sire x Dam’s Sire | ISET Score | Fat kg / % | Protein kg / % |
| 1 | TGD-Holstein MONSET | HADLEY x GAMEDAY | 1603 | 97 kg / 0.51% | 68 kg / 0.30% |
| 2 | Sous-Moron BOSTON | CASTING x GAMEDAY | 1593 | 87 kg / 0.38% | 65 kg / 0.25% |
| 3 | TGD-Holstein BEAUTYMAN | GLOBED x ASTRAL | 1586 | 49 kg / -0.02% | 57 kg / 0.17% |
| 4 | Progenesis TIMEOUT | PEREGRINE x DZUNDA | 1584 | 141 kg / 0.83% | 78 kg / 0.29% |
| 5 | Progenesis TORCHLIGHT | SHEEPSTER x GAMEDAY | 1584 | 133 kg / 0.48% | 92 kg / 0.23% |
August 2025 Genomic ISET Top Performers
For comparison, here’s where things stood in August—note how dramatically the picture has shifted:
| Rank (Aug ’25) | Name | Sire x Dam’s Sire | ISET Score | Fat kg / % | Protein kg / % |
| 1 | Sous-Moron BOSTON | CASTING x GAMEDAY | 1645 | 98 kg / 0.44% | 68 kg / 0.24% |
| 2 | Cookiecutter HADLEY | PATTERN x GAMEDAY | 1592 | 140 kg / 0.56% | 93 kg / 0.24% |
| 3 | TGD-Holstein BEAUTYMAN | GLOBED x ASTRAL | 1590 | 50 kg / 0.00% | 54 kg / 0.14% |
| 4 | Progenesis TORCHLIGHT | SHEEPSTER x GAMEDAY | 1583 | 128 kg / 0.45% | 90 kg / 0.23% |
| 5 | Swissgen EMPIRE | BLAKELY x CAPTIVATING | 1573 | 74 kg / 0.45% | 48 kg / 0.22% |
Understanding Boston’s 52-Point Correction
So what happened to Boston? This is where the mechanics of genomic evaluation matter for practical breeding decisions.
Young genomic sires carry what geneticists call “reliability risk.” When a bull has no milking daughters—or very few—his genomic prediction is essentially a statistical estimate based on DNA marker associations with the reference population. Research from the Council on Dairy Cattle Breeding shows that genomic evaluations for young bulls typically carry reliabilities around 70-75%, compared to 90%+ for daughter-proven sires. That 25-30% uncertainty has to go somewhere, and sometimes it goes against you.
As more data accumulates—whether from the bull’s own daughters entering production, updates to the reference population, or methodology refinements—those predictions get recalibrated. The dramatic swings we’re seeing in genomic rankings aren’t bugs in the system; they’re features. They reflect the reality that early genomic predictions are educated estimates, not guarantees.
I’ve noticed that bulls gaining or losing 50+ points in a single evaluation cycle aren’t unusual in genomic rankings, though it’s certainly jarring when it happens to the reigning #1. What’s worth noting is that Boston’s component predictions also shifted—his fat yield estimate dropped from 98 kg to 87 kg, while his fat percentage moved from 0.44% to 0.38%. These aren’t minor adjustments.
The practical takeaway? Any breeding program built heavily around a single young genomic sire carries a concentration risk that can materialize faster than most producers expect.
The Gameday Question: Maternal Dominance and Inbreeding Pressure
Looking at the December rankings, something jumps out immediately: three of the top five ISET sires trace to Gameday dams. Monset, Boston, and Torchlight all carry Gameday on their maternal side. That’s a lot of genetic eggs in one basket.
Gameday (RMD-Dotterer SSI Gameday-ET) earned his reputation honestly—he was the breed’s #1 sire for Net Merit and GTPI when he debuted, combining high production with solid health and type traits. His influence through both sons and daughters has been enormous. But when a single bull’s genetics dominate multiple pathways to the top of the rankings, inbreeding management becomes a real operational concern.
For herds that have used Gameday-sired bulls heavily over the past few years—and many have—the December rankings present a practical challenge. Using Monset or Boston on Gameday granddaughters pushes inbreeding coefficients into territory that can affect fertility, calf vigor, and lifetime productivity. What farmers are finding is that mating software becomes essential, not optional, when the top of the rankings shares this much common ancestry. The alternative—breeding for maximum ISET without inbreeding checks—is a strategy that works until it doesn’t.
Component Alternatives Worth Considering
Not every herd needs to chase the top ISET number. For operations focused on butterfat performance or protein premiums, the December rankings offer some compelling alternatives that fly a bit under the radar.
Progenesis Timeout (+1584 ISET) posts remarkable component numbers: +141 kg fat with a +0.83% butterfat deviation. That’s elite fat production with the percentage improvement that component-focused markets reward. His Peregrine x Dzunda pedigree also sits outside the Hadley/Gameday concentration, offering some genetic diversity for herds looking to manage inbreeding pressure.
Progenesis Torchlight (+1584 ISET) takes a different angle—he’s the protein king of this group at +92 kg protein with a +0.23% deviation. For cheese-market producers or those selling into protein-premium contracts, Torchlight’s profile makes a lot of sense. He does carry Gameday on his dam’s side, though, so inbreeding checks remain important.
What’s interesting here is the production gap between these component specialists and the ISET leaders. Beautyman, sitting at #3 ISET, posts just +49 kg fat and +57 kg protein—strong index, but not the component punch that Timeout and Torchlight deliver. Different bulls for different breeding objectives.
Type Index (ITP): Balancing Genomic Promise and Proven Reliability
For breeders who prioritize conformation alongside production, the type rankings tell their own story.
DG Blackburn leads the genomic ITP category with a +136 type index, a genuinely impressive type index. He’s a Davinci son tracing to the Regancrest-PR Barbie EX-92-USA cow family—genetics that have consistently produced style and dairy strength. For herds targeting show-ring success or breeding-stock sales, Blackburn’s genomic type profile is hard to ignore.
But here’s where the discussion of genomic volatility becomes relevant again. Blackburn’s +136 ITP is a genomic prediction with the same reliability considerations we discussed with ISET rankings. Bulls can and do move significantly on type evaluations as daughter information accumulates.
That’s why NH DG Arrow deserves attention as the #3 daughter-proven ITP sire at +128 ITP. Arrow, bred by Nosbisch Holsteins and Diamond Genetics, offers something Blackburn can’t yet provide: actual daughter performance data backing up his type prediction. The 8-point gap between Blackburn’s genomic +136 and Arrow’s proven +128 represents the premium breeders pay for certainty versus projection.
Strategic Breeding Takeaways
December’s Swiss rankings offer several clear signals for breeding program planning:
- For high-index programs: Monset’s rise to #1 makes him an obvious choice for herds chasing maximum ISET. But his Hadley x Gameday pedigree demands careful inbreeding management. Consider pairing Monset matings with outcross alternatives, such as Timeout or Beautyman, to maintain genetic diversity across the herd.
- For component-focused operations: Timeout (+141 kg fat, +0.83%) and Torchlight (+92 kg protein) offer elite production traits that may actually deliver more economic value than top ISET bulls in premium-market situations. Don’t let index rankings blind you to component opportunities.
- For type-priority breeders, the genomic-versus-proven trade-off between Blackburn (+136 ITP genomic) and Arrow (+128 ITP proven) is a fundamental risk-management decision. Using both strategically—Arrow on your best cows where you can’t afford a miss, Blackburn on animals where you can accept more variance—often makes more sense than choosing one approach exclusively.
- For everyone: Boston’s 52-point correction is a reminder that genomic rankings are probability distributions, not certainties. The generation interval advantages of young genomic sires are real—research shows the sire-of-bulls pathway has compressed from nearly 7.5 years to under 2.5 years since genomic selection began. But those advantages come with volatility that daughter-proven sires don’t carry.
The Bigger Picture
What December’s Swiss evaluations really demonstrate is something geneticists have been saying since genomic selection launched: these tools work best when used thoughtfully, not blindly.
The dramatic swings we see in genomic rankings aren’t evidence that the system is broken. They’re evidence that early predictions carry meaningful uncertainty—uncertainty that resolves as more data accumulates. Bulls like Beautyman, who hold relatively steady across evaluations, may ultimately prove more valuable than higher-indexed bulls who experience significant corrections.
For breeders, the lesson isn’t to abandon genomic sires—their contribution to genetic progress has been profound. The lesson is to build breeding programs around diversification rather than concentration. Use multiple sire lines. Balance genomic potential with proven reliability. Run inbreeding checks before every mating decision, not just occasionally. The bull who sits at #1 today may not be there in April. But a breeding program built on sound genetic principles will perform regardless of which individual bull wears the crown.
Complete Lists:
- SWITZERLAND – ISET – Genomic 12/25
- SWITZERLAND – ISET – Interbull Dtr proof – 12/25
- SWITZERLAND – ISET – Domestic dtr proven 12/25
- SWITZERLAND – Top 100 ISET heifers 12/25
- SWITZERLAND – Top 100 ISET cows 12/25
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