Study tests lower-protein dairy diets with Actisaf Sc 47
Bottom line
A new Animals study suggests dairy rations can be formulated with less crude protein without sacrificing key digestive outcomes, and that adding the yeast probiotic Actisaf Sc 47 may further improve how cows use nitrogen. In the April 21, 2026 paper, researchers Nizar Salah and colleagues used a 3 × 3 Latin square design in six dairy cows to compare a control diet at 16.5% crude protein with a reduced-protein diet at 14.5%, with or without Actisaf Sc 47 at 5 g/cow/day. The study focused on nitrogen utilization, digestibility, and rumen microbial protein synthesis, an area that matters as dairy systems face more pressure to curb nitrogen losses and improve feed efficiency. (mdpi.com)
Why it matters: For veterinary professionals and dairy advisers, the paper adds to a growing body of evidence that modest crude-protein reductions can improve nitrogen-use efficiency and reduce urinary nitrogen losses, which are closely tied to ammonia emissions, while maintaining rumen function when diets are balanced appropriately. That’s especially relevant for herd health planning because protein oversupply can raise urea loads and worsen nutrient inefficiency, while underfeeding protein or amino acids can compromise production. The Actisaf angle is notable because live yeast products are marketed as rumen stabilizers and digestibility aids, but this study narrows the question to whether probiotic support can help offset risks when protein is trimmed. (sciencedirect.com)
What to watch: Watch for follow-up work in larger commercial herds to see whether these nitrogen-efficiency gains hold up in higher-producing cows, over longer feeding periods, and under real-world milk production conditions. (mdpi.com)
A newly published paper in Animals examines a question that’s getting more urgent across dairy production: can nutritionists lower crude protein in lactating-cow diets to reduce nitrogen losses without disrupting digestion or rumen microbial protein supply? In the April 21, 2026 study, Nizar Salah and co-authors tested that strategy with and without supplementation from the yeast probiotic Actisaf Sc 47, a commercial Saccharomyces cerevisiae product from Phileo by Lesaffre. The trial compared a 16.5% crude-protein control ration with a 14.5% crude-protein ration, either unsupplemented or supplemented with 5 g/cow/day of Actisaf Sc 47. (mdpi.com)
The backdrop is familiar to anyone working in dairy medicine or production consulting. Nitrogen-use efficiency in dairy cows is typically low, and excess dietary protein tends to show up as urinary nitrogen, which can contribute to ammonia emissions and downstream environmental losses. Recent reviews and field-oriented guidance have pointed to lower-protein feeding as one of the main levers for improving nitrogen efficiency, but the tradeoff is that poorly balanced reductions can limit essential amino acids, depress milk protein output, or alter rumen fermentation in ways that hurt performance. (sciencedirect.com)
In that context, the new study is trying to answer a practical formulation question, not just a theoretical one. According to the article record, six cows were enrolled in a 3 × 3 Latin square design, with each study period including 23 days of diet adaptation and 5 days of sampling and data collection. The three diets were a 16.5% crude-protein control, a 14.5% crude-protein low-CP ration without Actisaf, and the same 14.5% low-CP ration with Actisaf Sc 47 supplementation. The primary endpoints were nitrogen utilization, digestibility, and rumen microbial protein synthesis. (mdpi.com)
That design matters because it places the probiotic question inside a protein-reduction strategy that many farms are already considering for cost and compliance reasons. Phileo describes Actisaf Sc 47 as a live yeast probiotic intended to support rumen microbiota, fiber digestion, and feed efficiency in dairy cattle, and the company has also promoted sustainability claims around the additive, including life-cycle-assessment work tied to lower environmental impact in dairy and beef systems. Those company materials don’t substitute for independent data, but they do help explain why this specific additive was paired with a reduced-protein ration in the trial. (phileo-lesaffre.com)
Outside this paper, the broader literature points in the same direction, with caveats. A recent Journal of Animal Science and Biotechnology report found that reducing crude protein improved nitrogen-use efficiency and reduced urinary nitrogen excretion without obvious disruption to the rumen microbiome in lactating dairy cows. At the same time, other recent work in Journal of Dairy Science has shown that lowering crude protein can reduce urinary nitrogen but may also expose amino acid limitations and reduce milk protein production if the ration is pushed too far or not balanced correctly. In other words, lower crude protein is promising, but it isn’t a free pass. (pmc.ncbi.nlm.nih.gov)
Expert reaction specific to this paper was limited in early coverage, but the wider nutrition conversation is active. A March 2026 invited review in Journal of Dairy Science framed low-protein diets as a meaningful opportunity to improve milk nitrogen efficiency and reduce emissions, while also stressing the importance of energy-protein interactions and microbial protein synthesis when predicting cow response. Survey data from U.S. dairy nutritionists likewise suggest the industry increasingly expects tighter nitrogen oversight and sees lower crude-protein feeding as a practical management tool, provided rations are monitored with enough precision. (sciencedirect.com)
Why it matters: For veterinary professionals, this is less about one feed additive and more about how nutrition, environmental stewardship, and herd performance are converging. If reduced-protein diets can reliably lower urinary nitrogen while maintaining digestibility and rumen microbial protein supply, that could support cleaner nutrient management without creating new risks for production or metabolic stability. But the small sample size here, just six cows, means the findings should be read as directional rather than definitive. For veterinarians advising dairy clients, the practical takeaway is to treat protein reduction as a precision strategy: watch milk components, urea metrics, intake, manure patterns, and transition-cow resilience, and make sure any probiotic or yeast product is evaluated as part of the whole ration rather than as a stand-alone fix. (mdpi.com)
What to watch: The next step is validation in larger, commercial-scale trials that report not just nitrogen partitioning and digestibility, but also milk yield, milk protein, health events, and economics over longer timeframes. If those data are positive, reduced-protein diets with targeted microbial support could become a more mainstream tool in dairy herd nutrition, especially in regions facing stronger ammonia or nutrient-management pressure. (mdpi.com)