Soybean meal has long been the backbone of broiler chicken nutrition, typically making up 20 to 30 percent of the diet thanks to its high crude protein content and well-balanced amino acid profile. But the global soybean market is volatile, supply chains are fragile, and sustainability concerns are mounting, particularly in regions that rely heavily on imported soybean meal. That has pushed poultry nutritionists to look hard at alternatives, and few candidates have attracted as much attention as canola seed and canola meal. The catch is that canola products carry a baggage of antinutritional factors, including tannins, lignin, phytate and glucosinolates, which can depress feed intake and impair growth, especially in young birds. As a result, inclusion levels have traditionally been capped at around 80 grams per kilogram in starter diets and 120 to 130 grams per kilogram in finisher diets.

A new study published in Veterinary Medicine and Science suggests that a carefully chosen pair of feed enzymes can dismantle many of those barriers. Researchers set out to determine whether phytase, protease, or the two together could alleviate the digestive limitations imposed by canola seed in broiler chickens, with a practical eye on which single enzyme delivers the most value when budgets allow only one. The question matters commercially: with protein-rich feed ingredients fluctuating wildly in price, industry stakeholders want to know exactly where their enzyme dollars are best spent.

The experiment involved 300 one-day-old male Ross 308 chicks, distributed in a completely randomised design across five treatments with five replicates of twelve birds each. One group received a corn-soybean meal control diet with no canola seed. A second received a diet containing 10 percent canola seed without enzymes. The remaining three groups ate the canola-seed diet supplemented with protease, with phytase, or with both enzymes together. Protease was included at 0.15 grams per kilogram of feed and phytase at 0.05 grams per kilogram. Birds were raised through starter, grower and finisher phases spanning 42 days, with feed and water available freely and standard vaccination protocols against Newcastle disease and infectious bursal disease applied.

The canola seed itself was thoroughly characterised before the trial began. Analysis showed 21.25 percent crude protein, a striking 42.76 percent ether extract, 18.39 percent crude fibre, and a gross energy content of 7063 kilocalories per kilogram. The seed also contained 5264 milligrams per kilogram of phytate phosphorus, 0.36 percent tannins and 9.37 micromoles per gram of glucosinolates, the very compounds suspected of constraining bird performance. Diets were formulated to be nutritionally comparable across treatments, with the canola diets naturally higher in fat and linoleic acid owing to the oil-rich seed.

The performance results told a clear story. Birds fed the unsupplemented canola diet ate significantly less, gaining roughly 6 to 7 grams less feed per day during the starter phase than controls, and their body weight gain suffered accordingly across the starter, grower and overall periods. Feed conversion ratio was also worse in the canola group during the grower phase. But adding enzymes changed the picture. Protease alone improved weight gain and feed intake relative to the canola-only diet, though its effect on intake was modest. Phytase alone produced a more pronounced lift in feed intake. The combination of both enzymes, however, was the standout: birds on the dual-enzyme diet ate and grew at rates statistically indistinguishable from the soybean-fed controls, effectively erasing the canola penalty.

Digestibility data revealed why. Apparent metabolisable energy, which fell to around 2687 kilocalories per kilogram in the canola-only group, rebounded to control levels of roughly 2860 kilocalories per kilogram in the phytase and combination groups. Crude protein digestibility told an equally interesting tale: the protease and combination diets actually exceeded the control diet, reaching about 74 to 75 percent digestibility compared with 71.7 percent in the soybean control. Ash and crude fibre digestibility were also restored by phytase-containing treatments. In other words, the enzymes did not merely compensate for canola’s drawbacks; in the case of protein digestion, they pushed nutrient utilisation beyond what the conventional soybean diet achieved.

The physiological mechanisms behind these gains emerged from a battery of measurements on the birds’ digestive systems. At 10 days of age, when the endogenous enzyme system is still immature, activities of amylase, lipase and total protease in the jejunum were depressed in the canola-only group but elevated in all enzyme-supplemented groups, with the combination treatment producing the highest amylase and lipase values. By day 42, when the birds’ own digestive machinery had matured, these differences had disappeared, underscoring that exogenous enzymes matter most in early life. Jejunal morphology followed a similar pattern: villus height and the villus-height-to-crypt-depth ratio, key indicators of absorptive capacity, were significantly higher in phytase and combination groups, while the canola-only diet drove deeper crypts, a sign of increased epithelial turnover under intestinal stress.

The gut microbiota and the physical properties of the intestinal contents added further layers of explanation. At day 10, birds on the combination diet harboured the highest Lactobacillus populations and the lowest Escherichia coli counts in the ileum, while Clostridium perfringens was lowest in that group compared with the canola-only treatment. Intestinal digesta viscosity, a critical determinant of how easily nutrients diffuse to digestive enzymes, was significantly elevated in the duodenum and jejunum of canola-fed birds but reduced by enzyme supplementation, particularly in the ileum. The researchers attribute this to phytase disrupting viscous phytate-protein complexes and protease breaking down peptide-fibre networks, together creating a more fluid digestive environment where enzymes and substrates can interact efficiently.

Perhaps the most striking findings concerned bone health. The unsupplemented canola diet significantly impaired tibia development: bones were lighter and shorter, breaking strength dropped to about 3074 newtons compared with 4279 newtons in controls, and bone ash, calcium and phosphorus percentages all declined. These deficits trace directly back to phytate, which forms insoluble complexes with essential minerals and renders them unavailable for skeletal mineralisation. The protease-plus-phytase combination restored bone weight, length, strength and mineral chemistry to levels comparable with or exceeding the control group, with bone ash reaching 41.93 percent and calcium 15.57 percent. The authors note that improved protein digestibility from protease likely supported collagen matrix synthesis, providing the organic scaffold upon which calcium and phosphorus are deposited, while phytase liberated the minerals themselves.

The study’s conclusion carries real weight for feed formulators. Replacing soybean meal with 10 percent canola seed without enzyme support demonstrably harms growth, gut function and bone mineralisation in broilers. Yet the combined application of protease and phytase overcame these constraints, performing better than either enzyme alone. The synergy is mechanistically elegant: phytase dismantles the structural and chemical barriers that phytate erects around proteins and minerals, creating conditions in which protease can work more effectively, while protease maximises the value of the nutrients phytase releases. For producers weighing enzyme purchases against volatile protein prices, the message is that the two enzymes are genuinely complementary, and that canola seed, long treated as a second-tier ingredient, can approach soybean meal performance when the right enzymatic tools are applied.

Subject of Research: Effects of protease and phytase supplementation on growth performance, nutrient digestibility, gut health and bone mineralisation in broiler chickens fed canola seed diets

Article Title: Protease and Phytase Alleviate Digestive Limitations of Canola Seed in Broiler Chickens

Article References: Sheikh‐Nazari, R., Jafari‐Khorshidi, K., & Jafari, M. A. (2026). Protease and Phytase Alleviate Digestive Limitations of Canola Seed in Broiler Chickens. Veterinary Medicine and Science, 12(6), Article e71259. https://doi.org/10.1002/vms3.71259

Image Credits: AI Generated

DOI: 10.1002/vms3.71259

Keywords: broiler chickens, canola seed, phytase, protease, soybean meal replacement, nutrient digestibility, gut microbiota, intestinal morphology, tibia mineralisation, antinutritional factors, feed enzymes, poultry nutrition

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