I’ve been the veterinary consultant to Precision Microbes for five years. I started as a sceptic. Here’s what changed my mind — and the evidence base on calves that vets, farmers and animal health professionals keep asking me about.
By Tommy Heffernan MVB MRCVS — Veterinary Consultant to Precision Microbes
A working vet’s five-year journey with Precision Microbes liquid probiotic and postbiotic — from initial scepticism to a substantial evidence base across 14 calf trials and 450+ calves, including a BSAS Undergraduate Thesis of the Year 2024 published in Elsevier’s Animal – Science Proceedings. The full evidence on Cryptosporidium, calf scour, antibiotic reduction and growth performance.
Let me start with what just happened
A few days ago, someone remarked to me that we have no evidence on one of our products (Calf Probiotic and postbiotic liquid). It irked me — and I don’t usually let those things sit. We have evidence. I’ve spent five years now as the veterinary consultant to Precision Microbes. I’ve watched the evidence base get built, study by study, farm by farm. Some of it I’ve run myself. Most of it has been done independently by academic researchers I had no involvement with. And the direction is the same every time.
So I want to put it all in one place and walk you through it. If you’re a vet, a farmer, a distributor, or anyone in animal health asking whether there’s real evidence behind probiotics in calves, this is for you. Or should I say evidence for our unique Probiotic and Postbiotic liquid.
How I got here — five years, from sceptic to convinced
I came into this space as a clinician. I qualified as a vet from UCD in 2002, spent years in mixed practice across Ireland, ran my own veterinary business for over a decade, and watched calf scour, pneumonia, mortality and farm margins eat each other alive on hundreds of farms. By the time Precision Microbes asked me to look at their liquid probiotic and postbiotic five years ago, I had heard a lot of probiotic claims — and most of what I’d seen on the market had not lived up to the marketing.
I was a sceptic.
What changed my mind wasn’t a trial. What changed my mind was on-farm results. The first farm I introduced it to, went from chronic scour battles to a system that worked. He’s still using it, four years on. Then another farm. Then another.
My current estimations is there is thousands of farms in Ireland and now across Europe using Precision Microbes to make a real difference in calf health.
And quietly, over five years, I watched calf health on farms I knew well shift in a direction I had not expected. I’ve been completely blown away by the potential of biology when you get the right organisms into the right calf at the right time. Not as a marketing line. As a clinical observation, on farms I’ve walked through for years.
For me, the on-farm results were always the real driver. I trust what I see in calves more than what I read in papers, because calves don’t lie and farmers who’ve been at it for thirty years can spot a difference faster than any statistical test.
But the market — rightly — demands evidence. Vets demand evidence. Distributors demand evidence. Regulators demand evidence. And the moment someone tells you a product has none, the only response that holds water is to put the evidence on the table.
So here it is.
What the evidence actually looks like
The Precision Microbes calf evidence base is now made up of nine detailed independent trials plus five supporting farm observations — fourteen sites in total — conducted between 2021 and 2026:
- Five academic studies at four universities: SRUC in collaboration with the University of Glasgow (Scotland), Harper Adams University (England), Munster Technological University (Ireland), and Waterford Institute of Technology / South East Technological University (Ireland — two studies, plus one MSc-level project).
- One BSAS Undergraduate Thesis of the Year 2024 (the May Allan study at SRUC/Glasgow), published in the peer-reviewed proceedings of the BSAS 2025 conference (Animal – Science Proceedings, Elsevier).
- Three detailed on-farm commercial trials that I ran as veterinary consultant — Kilkenny (2021), Wexford dairy-to-beef (2021), and Wexford long-term cost-benefit (2021).
- Five supporting farm observations — three scour-outbreak therapy contexts and two dairy-to-beef ADG comparisons — that extend the evidence base into clinical-therapy and rearing-system breadth.
More than 450 calves across the combined dataset.
Oh and yes probably a couple of 100,000 calves now on the product for the first 30 + days of life!!!!!
What the trials actually show — the four numbers that matter
I want to keep this practical. Across the dataset, four outcomes come up consistently. These are the numbers I’d put on the wall of a calf shed.
- Average Daily Gain — +50 to +150 g/day, with significant academic backing
The growth advantage of supplemented calves over controls clusters at around +50 to +150 g per day, and weaning weight advantages of 4 to 6 kg show up in six of the nine detailed trials.
The strongest single piece of evidence here is the Williams MSc trial at Harper Adams University, with 88 calves and a published p-value of 0.007 on weaning weight — that’s not noise. Backed by the McElduff MSc trial at SETU (2026), where the ADG advantage over an untreated control reached p = 0.005 with a very large effect size (Cohen’s d = 1.42). And by Allan’s SRUC study showing a significant additional weight gain by day 14 (p < 0.001) during a Cryptosporidium challenge period.
- Antibiotic use reduction — 41% in commercial conditions, 80% in academic on-farm
Two trials directly quantified antibiotic use. The first, my own Wexford long-term cost-benefit trial in 2021 during a combined Cryptosporidium / Rotavirus / pneumonia outbreak, used the Nottingham antimicrobial calculator to measure mg/PCU and found a 41.4% reduction in antibiotic use in the Precision Microbes group versus standard-managed controls. The second, the O’Mahony 2025 MTU thesis on an Irish dairy farm, measured an 80% reduction in calves requiring antibiotic treatment under more standard disease pressure (the one calf in the PM group that needed antibiotics had a swollen navel — not GI disease).
That kind of effect on antibiotic use is genuinely significant in the current EU regulatory environment. Bord Bia’s Sustainable Dairy Assurance Scheme, Red Tractor, EU 2030 stewardship targets — they all push in the same direction. Calf probiotic use of this magnitude moves the dial.
- Scour severity — 50% reduction in commercial outbreak; statistically significant academic effect
In the Wexford long-term trial, with both groups going through a Crypto and Rotavirus outbreak, scour severity was reduced by approximately 50% in the supplemented group, and recovery time was approximately twice as fast. In O’Mahony’s MTU 2025 trial, zero severe scour events occurred in the Precision Microbes group, against two severe events in the matched control.
Allan’s SRUC study brought formal statistical inference to this point, using a cumulative link mixed model on Alltech scour scoring. The result: a 1.83-unit reduction in scour score in the treated group, p < 0.001. That’s a clinically large effect on an ordinal scale and one of the cleanest pieces of statistical evidence in the entire dataset.
Practically what we see on farm is reduced severity of scours and improved recovery times. Farmers talk simply about less time spent with sick calves.
- Cryptosporidium — the single most strategically important finding
This is where the Allan SRUC thesis matters most. Cryptosporidium parvum is the leading cause of pre-weaning calf scour in dairy systems where rotavirus is vaccinated against. Halofuginone is the only EU-licensed pharmaceutical preventative, and it’s far from a complete solution. There has been almost nothing else on the market with credible Crypto-specific evidence.
Allan’s trial — 50 calves, 25 versus 25, six weeks on a Scottish commercial dairy under genuine disease pressure — found a statistically significant reduction in Cryptosporidium prevalence (p < 0.001) using a cumulative link mixed model analysis. Alongside that, lower fever responses during infection, maintained milk intake during infection, and significantly higher weight gain by day 14.
This isn’t a generic gut-health claim. This is a specific, statistically significant, independently-conducted, BSAS-award-winning piece of evidence on a major animal health pathogen. That award — BSAS Undergraduate Thesis of the Year 2024 — is third-party validation of the quality of the underlying research.
What’s actually in the bottle (and why it might work biologically)
Precision Microbes is a multi-organism liquid probiotic and postbiotic. The named characterised strain is Enterococcus lactis NCIMB 10415 — the strain previously catalogued as E. faecium and re-identified as E. lactis under modern phylogenomic. It’s one of the longest-studied feed-grade probiotic strains in the world, with multiple EFSA positive opinions and decades of safety data.
The whole consortium is propagated on an organic herb and organic molasses substrate, in a liquid medium. That fermentation produces — alongside the live probiotic — a postbiotic fraction containing:
- Lactic acid and acetic acid in the ratios you’d expect from a mixed lactic-acid-bacteria and Bifidobacterium fermentation.
- Bacteriocins (enterocins from lactis) with documented activity against E. coli, Salmonella, Clostridium, and Listeria.
- Exopolysaccharides from the Lactobacillus and Bifidobacterium
- Polyphenolics liberated from the herb substrate by the fermentation.
- Bioactive peptides with documented antimicrobial activity.
In plain English: the postbiotic does immediate work on the gut environment — acidification, antimicrobial peptide presence, barrier support — and the live probiotic does the longer colonisation work as the gut microbiome establishes through the first three weeks of life.
That matters because the first three weeks are the window where the calf gut microbiome is most plastic and most easily disrupted. Get that window right and you set the calf up for the rest of its productive life. Get it wrong and you spend the next eight weeks chasing scour, antibiotic courses, and growth setback. I’ve seen both pictures on hundreds of farms. The biology of why the right product helps is not mysterious.
What I tell vets and farmers when they ask me directly
The honest answer most vets want is “does it work, when do I use it, and how much do I dose.”
Does it work? Across 14 sites and more than 450 calves, the direction of effect is consistent — better growth, less scour, fewer antibiotics, faster recovery, and specifically lower Cryptosporidium prevalence in the academic data. The single most rigorous trial in the set is independently conducted, BSAS-awarded, and peer-published.
When do I use it? From arrival or birth, ideally through to weaning. Prevention is where the strongest cumulative effect is. But the product is also effective alongside standard veterinary treatment during active scour outbreaks — the three supporting farm observations under my supervision in 2021 showed approximately twice the recovery speed in calves on the active-disease dose compared with standard treatment alone.
Dose protocol:
- Prevention: 30 ml daily from arrival/birth through the neonatal and pre-weaning window. Top up with an extra 30 ml during digestive upsets.
- Therapy during active scour: 60 ml daily for 5–7 days, oral in milk.
- Severe scour cases: 60 ml twice daily for 4–5 days.
Compatibility: Compatible with antibiotics, oral rehydration solutions, and halofuginone. Zero withdrawal period for milk or meat — it’s an organic-certified probiotic and postbiotic supplement, not a veterinary medicinal product.
When should I expect to see something? In sick calves on the therapy dose, expect visible improvement on appetite and faecal consistency within 24–48 hours. In healthy calves on the prevention protocol, expect group-level differences in faecal consistency, calf appearance, and clinical incidents to emerge within the first 7–21 days. The strongest cumulative benefit shows through weeks 2–8 as the gut microbiome settles.
What the evidence doesn’t yet show — owned honestly
I want to be straight about this. The evidence base has gaps that I want to close in future trial work:
- No molecular microbiome data (16S rRNA sequencing) yet. The mechanism story I’ve described is backed by general probiotic literature and the published biology of the strains involved. We don’t yet have direct compositional evidence from PM-supplemented calves showing exactly how the microbiome shifts. That’s a priority for the next phase.
- Lifetime performance benefits are extrapolated. The economic case for €25 input cost against €300+ in lifetime performance gain is built from published dairy cost-of-disease literature (Esslemont, Bennett, Atkinson and others). It’s not yet directly measured to first calving in our own dataset.
- Sample sizes vary. The biggest study has 88 calves. Several have 20–30. Combined evidence is robust at 450+ calves, but individual trial power varies.
- Three of the on-farm trials were not blinded. They were on-farm vet-led observations under commercial conditions. The academic studies provide the statistical anchor.
What lifts the evidence base despite these gaps is its convergence: five academic studies and four on-farm trials, in different countries, by different researchers, on different farms, with different protocols — all pointing in the same direction. That kind of replication is the strongest signal a real-world evidence base can produce short of a multi-centre RCT.
Three things I want vets and farmers to take away
- The “is there evidence?” question can now be answered specifically and concretely. It isn’t “trust me” or “we have testimonials.” It’s nine detailed trials, five supporting farms, a BSAS-award-winning thesis in peer-reviewed proceedings, more than 450 calves, statistical significance on the academic primary outcomes. That’s a real evidence base. Also watch this space I hopefully about to embark on a huge dataset again on dairy to beef systems over the coming 24 months.
- The biggest commercial argument is antibiotic stewardship. A 41–80% reduction in antibiotic use isn’t a marginal claim — and the regulatory environment over the next five years is going to make this the most important number in dairy and beef calf-rearing.
- The biology underneath is real. Live probiotic plus postbiotic, multi-organism, on a herbal-molasses substrate, with bacteriocin and SCFA production hitting the calf gut in the right window. It’s mechanistically plausible because the mechanism is doing exactly what the trials are showing.
The evidence is here. The product is here. The question for the next two years is not whether probiotics work in calves — it’s whether the industry will adopt at the scale the data now justifies.
Tommy Heffernan MVB MRCVS is a veterinary consultant specialising in calf and ruminant health, gut microbiology, and animal health commercial strategy. He is veterinary consultant to Precision Microbes.
The full Vet Evidence Dossier — with per-trial methodology, statistical detail, mechanism review, and complete bibliography — is available to vets and animal health professionals on request. Contact info@tommythevet.ie.