Study tests enzyme dosing in reduced-protein layer diets

CURRENT FULL VERSION: A new Animals paper takes a closer look at a question nutrition teams keep running into: can enzyme programs make reduced-protein layer diets work more consistently? The study, by Aamir Nawab, Hiep Thi Dao, and Sukirno Sukirno, evaluated phytase plus a xylanase/β-glucanase blend in laying hens and found that enzyme inclusion rate was a meaningful variable, not just an add-on. In the reported summary, reduced-protein diets could be supported by enzyme supplementation, but the response depended on dose and combination. (pmc.ncbi.nlm.nih.gov)

That question sits inside a bigger industry push to lower crude protein without giving up production. Reduced-protein diets are attractive because they can cut feed costs, lower nitrogen output, and improve sustainability, especially as soybean meal prices and amino acid economics shift. But these diets also change the substrate profile in the gut, often increasing reliance on cereals and making enzyme response less predictable. Australian Eggs, which described related University of New England work in this area, has framed the challenge as finding the right combination of protein reduction and enzyme support to preserve performance while reducing nutrient losses. (australianeggs.org.au)

In this trial, researchers compared standard-protein and reduced-protein diets at 16.5% versus 14.5% crude protein, along with phytase at 600 or 1200 FTU/kg and a xylanase/β-glucanase blend at 100 or 150 g/ton in a factorial design. According to the indexed study summary, the higher xylanase/β-glucanase inclusion rate of 150 g/ton lowered hen-day egg production during weeks 48 to 57, suggesting that pushing inclusion upward didn’t uniformly improve outcomes. The same summary reports that 150 g/ton xylanase/β-glucanase with 600 FTU/kg phytase improved shell breaking strength, but that effect reversed at 1200 FTU/kg phytase, underscoring how enzyme interactions can be nonlinear. (pmc.ncbi.nlm.nih.gov)

Those findings fit with the broader enzyme literature in layers, where benefit is often context-dependent. A recent review on feed additives in laying hens notes that enzymes may be used either “over the top” in fully formulated diets or in nutrient-reduced diets to restore lost value, but also points to ongoing uncertainty around optimal inclusion, especially for phytase super-dosing. That broader pattern is not unique to poultry layers. In weaned piglets, a Veterinary Sciences study found that reducing crude protein by 2% depressed body weight and average daily gain across the nursery period, and adding protease only partially restored performance, without significantly changing digestibility or fecal score. The practical message is similar: enzyme support can help reduced-protein programs, but it does not automatically erase the biological cost of cutting nutrients too far. Other recent layer studies have likewise shown that xylanase and β-glucanase can improve nutrient utilization and performance in some high-fiber or nutrient-constrained settings, while older poultry literature has long warned that responses to phytase and carbohydrases can vary with diet composition, age, and ingredient mix. (pmc.ncbi.nlm.nih.gov)

Industry context also helps explain why this study matters now. The Australian Eggs summary of the UNE research program says reduced-protein diets typically contain more cereals and less soybean meal, which can alter the way phytase and xylanase function. That’s important because many commercial formulations already rely on matrix values for enzymes, and the new paper suggests that those assumptions may need finer adjustment when crude protein is reduced. In practical terms, the message isn’t simply “add more enzyme.” It’s that enzyme strategy has to match substrate availability, nutrient specifications, and the production stage of the flock. That’s an inference based on the study’s dose-response pattern and the broader review literature. (australianeggs.org.au)

There is also a useful mineral nutrition angle to that point. A separate Animals broiler study on zinc source and dose under different calcium and phosphorus programs, with or without phytase, emphasized that phytate is a strong chelator of macro- and microminerals and that rapid phytate hydrolysis can improve absorption of calcium, phosphorus, zinc, and other cations. In that trial, birds fed diets designed to optimize phytate hydrolysis and supplemented with zinc as an amino acid complex outperformed birds given zinc sulfate at 90 ppm on several measures, including body weight at multiple time points, early tibia ash and tibia zinc content, and breast yield; birds fed 40 ppm or more of the organic zinc source also had less severe back scratches at term. While that was a broiler mineral study rather than a layer reduced-protein trial, it reinforces the same formulation lesson: phytase responses are tied to the wider mineral and ingredient matrix, not just the enzyme label dose.

Why it matters: For veterinarians, nutritionists, and technical service teams supporting layer operations, the study reinforces that reduced-protein feeding programs are not just an ingredient-cost decision. They can affect egg production, shell quality, nutrient digestibility, and manure nutrient output, all of which feed back into flock health, environmental management, and producer margins. The cross-species and cross-nutrient literature adds a cautionary note here. In piglets, protease only partly rescued growth after a larger protein reduction, and in broilers, phytase-linked mineral release interacted with calcium, phosphorus, and zinc source. If enzyme inclusion is too low, expected digestibility gains may not materialize. If it’s too aggressive or mismatched to the diet, performance may slip. That makes validation in the target production system especially important before broad commercial rollout. (pmc.ncbi.nlm.nih.gov)

There wasn’t a clear independent expert reaction or company press release surfaced in accessible search results, but the surrounding scientific commentary is consistent: reduced-protein diets are promising, enzyme responses are real, and optimization is still the hard part. Recent related work in laying hens has also explored amino acid balancing, fiber-degrading enzymes, and energy-protein ratios, suggesting that enzyme dose is only one part of a broader formulation strategy. (mdpi.com)

What to watch: The next step is likely more applied validation, including commercial-scale trials and clearer guidance on when higher phytase or xylanase/β-glucanase inclusion pays off in reduced-protein diets, and when it starts to erode egg output instead. It will also be worth watching for work that better links enzyme decisions to mineral strategy, especially calcium-phosphorus specifications and trace mineral source, given evidence from broilers that optimizing phytate hydrolysis can change zinc utilization, bone mineralization, carcass yield, and even welfare-related outcomes. (pmc.ncbi.nlm.nih.gov)