Feed enzymes are zootechnical feed additives that break down phytate, fibre, protein and starch the animal digests poorly, and the EU Register lists them in functional group 4a, digestibility enhancers, under Regulation (EC) No 1831/2003. Each EU 4a entry names its holder, its production strain and a legal minimum activity per kg complete feed (12 % moisture) for each animal category, for example 500 FTU/kg phytase for piglets under entry 4a1600.
The EU enzyme annexes set no maximum content and no withdrawal period; muramidase 4d16 is the exception with maxima. In the US, no feed enzyme holds a 21 CFR section, so enzymes reach US feed through the AAFCO Official Publication listing or animal-food GRAS notices, never as FDA-approved products. Each enzyme below is matched to its substrate, diet and species, with EU entry, legal minimum, printed expiry and US route side by side.
Every value here is compiled from EU acts, the EU Register, EFSA opinions, the eCFR, FDA GRAS notices and named studies, checked on 3 November 2026; see the methodology.
What Are Feed Enzymes?#
A feed enzyme is a protein preparation, produced by fermentation of a production microorganism, that hydrolyses a feed component the animal cannot break down itself or digests incompletely. In EU law enzymes are authorised in functional group 4a of category 4 among the five feed additive categories of Regulation (EC) No 1831/2003. Each enzyme carries an IUBMB number, for example EC 3.1.3.8 for 3-phytase and EC 3.1.3.26 for 6-phytase (accepted name 4-phytase).
EU functional group 4a and the US classification#
In the EU, feed enzymes form functional group 4a, digestibility enhancers, of category 4 zootechnical additives, and each authorisation is bound to its holder for 10 years and renewable under Article 14. A zootechnical entry names a company, a strain and the animal categories it covers; feed enzymes are never nutritional additives and never 4b gut flora stabilisers.
The US has no legal class called "digestibility enhancer". Enzymes enter US feed through the AAFCO Official Publication enzyme listing or through animal-food GRAS notices answered by FDA with a "no questions" letter.
Some enzyme uses sit outside 4a in the EU. Silage enzymes are technological additives in functional group 1k, fumonisin esterase is a 1m substance that reduces mycotoxin contamination, muramidase 4d16 is an "other zootechnical additive" in 4d, and the 4d12 entry combines Bacillus licheniformis ATCC 53757 with its protease, also in 4d.
The substrates animals cannot digest#
Monogastric animals lack or under-produce the enzymes for five substrates in plant-based feed, so part of the phosphorus, energy and protein pass undigested. Enzymes degrade substrates the animal cannot attack, such as phytate and non-starch polysaccharides, or add to its own secretions, as protease and amylase do. The five substrates are listed below.
- Phytate, the phosphorus store of plant seeds: phytase.
- Arabinoxylans of wheat, rye, triticale and maize fibre: xylanase.
- Mixed-linked beta-glucans of barley and oats: beta-glucanase.
- Beta-mannans of soybean meal, palm kernel meal, copra and guar meal: beta-mannanase.
- Protein and starch: protease and alpha-amylase.
Feed Enzyme Member Table with EU and US Status#
The table lists the eight feed enzyme nodes, the enzyme activities they host as sections and three enzyme entries that sit in other functional groups, with EU entry, species and legal minimum, status and US route side by side.
| # | Member | Type | EU entry and group | EU species and content (examples) | EU status | US status | Function |
|---|---|---|---|---|---|---|---|
| 1 | Phytase in animal feed | node | 4a: 4a1600, 4a19, 4a37 and others | 4a1600 piglets and sows min 500, pigs for fattening 100, chickens for fattening 375 FTU/kg; 4a19 poultry other than for laying or reproduction 250, piglets 500 FTU/kg; 4a37 all poultry except poultry for laying and all pigs 500 FTU/kg | Impl. Reg. (EU) 2020/172 to 2030-02-27; 2026/91 to 2036-02-04; 2023/1167 to 2033-07-06 | no 21 CFR section; GRAS notices AGRN 14, 15, 21, 27, 32 | digestibility enhancer |
| 2 | 3-phytase (section of row 1) | activity | 4a1600, 4a25, 4a50 | see row 1 | see row 1 | see row 1 | phytate hydrolysis (EC 3.1.3.8) |
| 3 | 6-phytase (section of row 1) | activity | 4a19, 4a37 and others; 4a23; 4a24 (2016/899) | see row 1 | 4a23 (2016/329): printed expiry 2026-03-29; 4a24 (2016/899): printed expiry 2026-06-29; for both, the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003) | see row 1 | phytate hydrolysis (EC 3.1.3.26) |
| 4 | Xylanase in feed | node | 4a8i, 4a11 and others | 4a8i chickens for fattening 8 000, turkeys 16 000, weaned piglets 24 000 BXU/kg; 4a11 all poultry species 625, pigs for fattening and piglets 2 000 U/kg | 2023/1332 to 2033-07-20; 2025/1386 to 2035-08-05; 2021/2096 to 2031-12-20 | no 21 CFR section; AAFCO OP listing or GRAS notice | digestibility enhancer |
| 5 | Endo-1,4-beta-xylanase (section of row 4) | activity | 4a entries of row 4; 1k107, 1k108 silage | see row 4; silage: all animal species | 1k107, 1k108: 2023/61 to 2033-01-26 | see row 4 | arabinoxylan hydrolysis |
| 6 | Beta-glucanase in feed | node | 4a1603, 4a1616; 4a20 | 4a1603 chickens for fattening, weaned piglets 10 FBG/kg; 4a1616 poultry for fattening or reared 500, suckling and weaned piglets 350 CU/kg | 2023/1333 to 2033-07-20; 2024/262 to 2034-02-07; 4a20 (No 302/2014): printed expiry 2024-04-15; the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003) | no 21 CFR section; GRAS notices AGRN 31, 50 (beta-glucanase corn) | digestibility enhancer |
| 7 | Endo-1,3(4)-beta-glucanase (section of row 6) | activity | 4a1603, 4a20; 1k104 to 1k106 silage glucanases | see row 6; silage: all animal species | see row 6; 1k104: 2019/454 to 2029-04-11; 1k105, 1k106: 2023/61 to 2033-01-26 | see row 6 | beta-glucan hydrolysis |
| 8 | Beta-mannanase in feed | node | 4a45, 4a47 and others | 4a45 chickens and pigs for fattening 32 000, turkeys and weaned piglets 48 000 U/kg; 4a47 all poultry for fattening 800 TMU/kg | 2023/2645 to 2033-12-19; 2024/1743 to 2034-07-14 | no 21 CFR section; GRAS notices AGRN 67, 82 | digestibility enhancer |
| 9 | Endo-1,4-beta-mannanase (section of row 8) | activity | see row 8 | see row 8 | see row 8 | see row 8 | beta-mannan hydrolysis |
| 10 | Protease in animal feed | node | 4a13, 4a43; 4a63 (protease with Bacillus strains) | 4a13 chickens for fattening 15 000 PROT/kg; 4a43 poultry for fattening or reared 30 000 NFP/kg; 4a63 pigs for fattening of all Suidae 5 000 U protease + 1.5 x 10^8 CFU/kg | 2021/1426 to 2031-09-21; 2024/778 to 2034-03-26; 2025/2502 to 2036-01-01 | no 21 CFR section; AAFCO OP listing or GRAS notice | digestibility enhancer |
| 11 | Serine protease, subtilisin (section of row 10) | activity | 4a13, 4a43; within 4a10, 4a40 | see rows 10 and 14 | see rows 10 and 14 | see row 10 | protein hydrolysis |
| 12 | Alpha-amylase in feed | node | 4a21; 1k101 to 1k103 silage | 4a21 dairy cows 300 KNU/kg to week 14 of lactation; silage: all animal species | 4a21 (2015/47): printed expiry 2025-02-04; the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003); 1k101 to 1k103: 2019/454 to 2029-04-11 | no 21 CFR section; AAFCO OP listing or GRAS notice | digestibility enhancer; silage additive |
| 13 | Alpha-amylase activity (section of row 12) | activity | 4a21; within 4a10, 4a40, 4a1612i, 4a1620i, 4a1621i | see rows 12 and 14 | see row 12 | see row 12 | starch hydrolysis |
| 14 | NSP enzymes and multi-enzyme carbohydrase complexes | node | 4a10, 4a15, 4a40, 4a1602i and others | 4a10 fattening poultry except ducks: xylanase 187.5, subtilisin 2 500, amylase 250 U/kg; 4a1602i fattening poultry other than turkeys: xylanase 135, two glucanases 35 and 40 U/kg; 4a40 broilers 2 000 U xylanase, 4 000 U protease, 200 U amylase/kg | 2025/193 to 2035-02-23; 2024/221 to 2034-02-04; 2023/1713 to 2033-09-28 | no 21 CFR section; AAFCO OP listing or GRAS notice | digestibility enhancer, minimum per activity |
| 15 | Alpha-galactosidase (section of row 14) | activity | 4a17, 4a33 | see row 14 | 4a17: 2024/781 to 2034-03-26; 4a33: 2022/1470 to 2032-09-26 | see row 14 | alpha-galactoside hydrolysis |
| 16 | Bacillolysin (section of row 14) | activity | within 4a1620i | see row 14 | 2017/963 to 2027-06-28 | see row 14 | protein hydrolysis |
| 17 | Polygalacturonase (section of row 14) | activity | 4a14 (piglets) | see row 14 | 2025/284 to 2035-03-05 | see row 14 | pectin hydrolysis |
| 18 | Xyloglucanase (section of row 14) | activity | 4a39 | see row 14 | see row 14 | see row 14 | xyloglucan hydrolysis |
| 19 | Muramidase in animal feed | node | 4d16 (4d, not 4a) | chickens for fattening min 25 000; weaned piglets min 50 000, max 65 000; laying hens min 30 000, max 60 000 LSU(F)/kg | 2019/805 to 2029-06-09; 2020/163 to 2030-02-26; 2021/1431 to 2031-09-22; 2025/161 to 2035-02-19; holder Novozymes A/S | no US status verified | other zootechnical additive |
| 20 | Fumonisin esterase | 1m entry | 1m03i | all pigs, all poultry min 10 U/kg; maize-based silage, all species, min 40 U/kg fresh material | 2018/1568 to 2028-11-08; 2021/363 to 2031-03-21 | not approved | mycotoxin reduction |
| 21 | Silage additives | 1k entries | 1k101 to 1k108 | all animal species; no minimum in the content column | 2019/454 to 2029-04-11; 2023/61 to 2033-01-26 | no US status verified | silage additive |
| 22 | B. licheniformis ATCC 53757 with its protease (Bacillus probiotics in feed) | 4d entry | 4d12 (other zootechnical additives) | chickens for fattening and reared for laying; minor poultry species for fattening and reared for laying; ornamental birds; min 5 x 10^8 CFU + 3 x 10^5 U protease/kg | 2016/898: printed expiry 2026-06-29; the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003) | no US status verified | other zootechnical additive |
Values are EU legal minima per kg complete feed (12 % moisture) unless marked; units of different products are measured differently and are not comparable, and no withdrawal period is set for the 4a enzymes. Muramidase 4d16 is the table's exception with legal maxima.
How Do Feed Enzymes Work?#
Feed enzymes work in four ways: they release nutrients bound in phytate, cut viscous fibre, open plant cell walls so the contents become accessible, and add to the animal's own protein and starch digestion. Fibre breakdown also generates oligosaccharides and lowers endogenous losses.
Releasing phosphorus locked in phytate#
Phytase removes phosphate groups from phytate (myo-inositol hexakisphosphate) step by step, releasing phosphorus and the calcium, zinc and amino acids phytate binds. The enzyme acts early in the tract: in poultry in the crop, proventriculus and gizzard, and in pigs in the stomach and upper small intestine, where the low pH keeps phytate soluble (Dersjant-Li, Awati, Schulze and Partridge, Journal of the Science of Food and Agriculture, 2015).
Released phosphorus lets the nutritionist cut dietary phosphate, so phytase replaces part of the inorganic phosphorus sources in feed. In formulation the enzyme carries a matrix value for the phosphorus, calcium and other nutrients it is credited with releasing, validated per product. The EU best available techniques for intensive pig and poultry farming name the use of authorised feed additives that reduce total phosphorus excreted, "e.g. phytase", as BAT 4 (Implementing Decision (EU) 2017/302).
Breaking down cell walls and viscous fibre#
Xylanase and beta-glucanase cut the soluble arabinoxylans of wheat, rye and triticale and the beta-glucans of barley and oats, which lowers gut viscosity and opens the cell walls that enclose starch and protein. Viscosity reduction dominates the response in wheat, rye and barley diets for poultry, and in barley diets the classic sign of undigested beta-glucan is sticky droppings and wet litter.
In maize-soy diets the xylanase response is attributed to cell-wall disruption and xylo-oligosaccharides. Beta-mannanase hydrolyses the beta-mannans of soybean meal, palm kernel meal, copra and guar meal; mannans are recognised by innate immune receptors and trigger a feed-induced immune response, which the enzyme reduces along with digesta viscosity.
Supplementing the animal's own protein and starch digestion#
Protease and alpha-amylase add to enzymes the animal already secretes, so their value lies in low-protein or variable-protein diets and in young animals and high-starch dairy rations. Protease hydrolyses protein and anti-nutritional factors such as trypsin inhibitors and lectins, which allows lower crude protein diets; the EU BAT conclusions name NSP enzymes and proteases as additives that favourably affect feed efficiency (2017/302).
Alpha-amylase supplements immature pancreatic amylase in young animals and raises starch digestion in dairy cows; entry 4a21 sets 300 KNU/kg for dairy cows up to week 14 of lactation (2015/47). Muramidase works differently: the 4d16 enzyme hydrolyses peptidoglycan, the cell-wall debris of gut bacteria, sits in functional group 4d rather than 4a, and does not act as an antimicrobial at feed dose.
Evidence on feed conversion from reviews and meta-analyses#
In weaned pigs, feed enzymes improved the gain-to-feed ratio in 55 of 90 studies, left it unchanged in 28 and worsened it in 7, with phytase the most consistent, according to the review by Torres-Pitarch and colleagues (Animal Feed Science and Technology, 2017). In grow-finish pigs it improved in 38, stayed unchanged in 78 and worsened in 4 of 120 comparisons; multi-enzyme complexes improved it, xylanase alone did not (Torres-Pitarch et al., 2019).
Two meta-analyses add enzyme-specific results: protease at 5 000 to 6 000 U/kg increased daily gain and gain-to-feed in grower pigs across three studies (Payling, Kim, Walsh and Kiarie, Journal of Animal Science, 2017), and beta-mannanase improved gain and feed conversion in broilers on low-energy diets across 27 studies, most in the starter phase (Nuamah and colleagues, Poultry Science, 2026). How feed conversion ratio is measured and which other additives move it is set out separately.
Selection by Target: Which Enzyme for Which Substrate#
Choose a feed enzyme by the substrate in the diet: phytase for phytate in almost every monogastric diet, xylanase for wheat, rye and triticale, beta-glucanase for barley and oats, mannanase for high soybean, palm kernel, copra or guar meal, protease for low-protein diets. The table pairs each target with its enzyme, the diets where it applies and example EU entries.
| Target | Enzyme | Main diets | Example EU entries | Related page |
|---|---|---|---|---|
| Phosphorus from phytate | phytase | all monogastric diets | 4a1600, 4a19, 4a37 | none |
| Viscosity and cell walls | xylanase | wheat, rye, triticale, maize fibre | 4a8i, 4a11 | none |
| Beta-glucans | beta-glucanase | barley, oats | 4a1603, 4a1616 | none |
| Beta-mannans | beta-mannanase | high soybean meal, palm kernel meal, copra, guar meal | 4a45, 4a47 | none |
| Protein and nitrogen excretion | protease | low-protein diets | 4a13, 4a43 | Ammonia and odour reduction through feed |
| Starch | alpha-amylase | young animals, dairy rations | 4a21 (status in the member table) | none |
| Several substrates | multi-enzyme carbohydrases | mixed diets | 4a10, 4a15, 4a40, 4a1602i | none |
A multi-enzyme entry sets a separate legal minimum for each declared activity, as 4a10 does for xylanase, subtilisin and amylase. Each activity is checked against its own minimum at the planned inclusion, and a side activity without its substrate in the diet has nothing to act on.
Selection by Species and Diet#
Species decides which EU entry applies, because each authorisation names its animal categories and sets a separate legal minimum for each: 4a19 phytase, for example, requires 500 FTU/kg for piglets but 250 FTU/kg for pigs for fattening and sows. The table lists example entries per species group with their minima.
| Species group | Example EU entries naming it (legal minimum per kg complete feed) | Programme page |
|---|---|---|
| Poultry | 4a1600 375 FTU/kg (chickens for fattening); 4a8i 8 000 BXU/kg; 4a47 800 TMU/kg; 4d16 25 000 LSU(F)/kg | Poultry feed additives |
| Pigs | 4a1600 500 FTU/kg (piglets, sows) and 100 FTU/kg (pigs for fattening); 4a8i 24 000 BXU/kg (weaned piglets) and 20 000 BXU/kg (pigs for fattening); 4a45 48 000 and 32 000 U/kg | Pig feed additives |
| Dairy cows | 4a2 (Impl. Reg. (EU) 2023/1711); 4a21 (status in the member table) | Dairy cow feed additives |
| Fish | 4a19 salmonids and ornamental fish 500, other fin fish 2 500 FTU/kg | Aquafeed additives |
Enzymes in poultry feed#
Poultry diets carry phytase in almost every formula, with xylanase and beta-glucanase added where wheat or barley is the cereal. Legal minima differ by bird category: 4a1600 sets 375 FTU/kg for chickens for fattening, 250 FTU/kg for laying hens and turkeys and 300 FTU/kg for ducks, while 4a8i sets 8 000 BXU/kg for chickens and 16 000 BXU/kg for turkeys.
In a single broiler trial with a corn-soy negative-control diet (40 % less available phosphorus, 17 % less calcium), 2 000 FTU/kg Buttiauxella phytase raised body weight gain by 20 %, improved feed conversion by 7.4 % and raised tibia ash by 18 % (Kiarie, Woyengo and Nyachoti, Asian-Australasian Journal of Animal Sciences, 2015). That is a trial result under deficiency, not a general effect.
Enzymes in pig feed#
Pig entries split by category, and in the entries cited here piglets carry the highest legal minimum: 4a1600 phytase sets 500 FTU/kg for piglets and sows against 100 FTU/kg for pigs for fattening. The same pattern holds for 4a8i xylanase (24 000 BXU/kg weaned piglets, 20 000 BXU/kg pigs for fattening) and 4a45 mannanase (48 000 U/kg weaned piglets, 32 000 U/kg pigs for fattening).
In four trials reported by Velayudhan and colleagues (Journal of Animal Science, 2022, abstract), a multi-enzyme product with xylanase 4 000, beta-glucanase 200, amylase 100 and protease 2 000 U/kg on top of 750 FTU phytase raised final body weight of weaned pigs by 1.1 kg (4.1 %) and lowered overall feed conversion by 4.4 %. The 4a63 entry combines a protease with three Bacillus strains for pigs for fattening.
Ruminants, fish and other species#
Ruminant entries are few: 4a2, a fermentation product of Aspergillus oryzae NRRL 458, names dairy cows (Implementing Regulation (EU) 2023/1711, runs to 2033-09-28), and alpha-amylase 4a21 appears only with its printed expiry. For 4a21 the printed expiry is 2025-02-04; the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003).
Fish have phytase entries of their own. 4a19 sets 500 FTU/kg for salmonids and ornamental fish and 2 500 FTU/kg for other fin fish (Implementing Regulation (EU) 2025/142, runs to 2035-02-19), 4a48 sets 1 000 FYT/kg for all fin fish, and xylanase 4a1617 names carp at 1 050 EPU/kg.
Dosing Logic: Legal Minimum Contents, Activity Units and Heat Stability#
EU feed enzyme authorisations set a legal minimum content per kg complete feed (12 % moisture) and no maximum, so the number on the act is a floor the feed must reach, not a recommended dose. Some acts add a "maximum recommended dose" under other provisions, such as 2 000 FTU/kg for 4a24, which is not a legal maximum. US figures are GRAS-notice intended-use ranges, not approvals. The table gives each figure with its basis.
| Entry or product | Animals | Value | Basis | Instrument or study |
|---|---|---|---|---|
| 4a1600 | piglets, sows | min 500 FTU/kg complete feed (12 % moisture) | EU legal minimum | Impl. Reg. (EU) 2020/172 |
| 4a19 | other fin fish | min 2 500 FTU/kg | EU legal minimum | Impl. Reg. (EU) 2025/142 |
| 4a24 | all poultry species; all porcine species other than suckling piglets | 2 000 FTU/kg | maximum recommended dose in other provisions, not a legal maximum | Impl. Reg. (EU) 2017/896 |
| 4a8i | weaned piglets | min 24 000 BXU/kg | EU legal minimum | Impl. Reg. (EU) 2023/1332 |
| 4a45 | turkeys, weaned piglets | min 48 000 U/kg | EU legal minimum | Impl. Reg. (EU) 2023/2645 |
| 4d16 | weaned piglets | 50 000 to 65 000 LSU(F)/kg | EU legal minimum and maximum | Impl. Reg. (EU) 2021/1431 |
| C. braakii phytase | poultry; swine | 250 to 4,000; 500 to 4,000 FYT/kg | GRAS notice intended use (AGRN 14, 15) | FDA no-questions letters |
| Phytase corn grain | poultry; swine | 250 to 6,000; 500 to 4,500 FTU/kg | GRAS notice intended use (AGRN 21, 27, 32) | FDA no-questions letters |
| Buttiauxella phytase | broilers | 2 000 FTU/kg | single trial | Kiarie et al. 2015 |
Units differ by product and are not comparable.
Activity units are product-specific#
Activity units differ by product: FTU, FYT, OTU and PPU all count phosphate released from phytate, but at different phytate concentrations or pH, so 500 units of one phytase never equal 500 units of another. The main unit families in the EU acts are listed below.
- Phytase: FTU, 1 µmol phosphate per minute from sodium phytate at pH 5.5 and 37 °C; FYT at 5.0 mM phytate; OTU at 5.1 mM; PPU at pH 5.0.
- Xylanase: BXU on birch xylan at pH 5.3; EPU on oat spelt xylan; TXU on wheat arabinoxylan at pH 3.5; FXU at pH 6.0; VU by viscosimetry.
- Others: KNU (amylase, pH 7.0), TMU (mannanase, locust bean gum) and LSU(F) (muramidase, labelled peptidoglycan, pH 6.0).
Pelleting, liquid application and premix storage#
Heat destroys enzyme activity: raising conditioning from 74 to 85 °C lowered phytase stability in a linear trend while pellet durability rose from 84.3 to 88.2 % and hot pellet temperature from 80.1 to 87.5 °C (Truelock and colleagues, Journal of Animal Science, 2020). Storage of enzymes in feed premixes depends on temperature and humidity: in a premix storage study, phytase stayed stable at 22 °C and 28.4 % relative humidity, fell sharply at 39.5 °C and 78.8 % relative humidity, and lost 20 % after a 60 °C heat pulse of about 9.5 hours.
The 4a1600 act requires the directions for use to state storage conditions and heat stability, and the 4a35 xylanase act (Implementing Regulation (EU) 2023/669) states that the additive shall not be used in premixtures. Enzymes come as coated thermostable granulates, powders and liquids for application after the pellet press; liquid application avoids conditioning heat but needs calibrated equipment.
Regulation Summary: EU Authorisations and US Status#
A feed enzyme enters the EU market only through a holder-bound authorisation under Regulation (EC) No 1831/2003, while in the US it reaches feed through the AAFCO Official Publication enzyme listing or an animal-food GRAS notice, not through a 21 CFR section.
EU 4a entries, holders and expiry#
Each 4a entry names its holder, its production strain, the animal categories, the legal minimum per activity and a printed expiry 10 years after entry into force. Renewal under Article 14 is explained under EU feed additive regulation. Implementing Regulation (EU) 2026/91, for example, renewed 4a19 to 2036-02-04, and holder names also change by act, as 2024/2183 did for the Danisco entries, now held by Genencor International B.V.
Some entries have passed their printed expiry without a renewal act found: 4a20 (Implementing Regulation (EU) No 302/2014, printed expiry 2024-04-15), 4a21 (2015/47, printed expiry 2025-02-04), 4a23 (2016/329, printed expiry 2026-03-29), 4a24 liquid (2016/899, printed expiry 2026-06-29) and 4d12 (2016/898, printed expiry 2026-06-29). For each of them the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003). Entries can also end by act: Implementing Regulation (EU) 2023/1173 removed an alpha-amylase from A. oryzae CBS 585.94 and a xylanase from T. longibrachiatum CNCM MA 6-10 W.
US status: AAFCO listing and GRAS notices#
In the US, no phytase, xylanase, glucanase, mannanase, protease or amylase has a 21 CFR 573 or 558 section, so no feed enzyme is FDA-approved and none carries a US withdrawal period. FDA has answered animal-food GRAS notices with "no questions" letters for Citrobacter braakii phytase (AGRN 14 poultry, AGRN 15 swine), phytase corn grain (AGRN 21, 27, 32), beta-glucanase corn (AGRN 31, 50) and a beta-mannanase (AGRN 67 poultry, AGRN 82 swine); such a letter is not an approval and covers only the notified strain.
The FDA-AAFCO memorandum of understanding ran out on 1 October 2024 without renewal, and the Animal Food Ingredient Consultation (AFIC) is an FDA process. On 11 August 2026 FDA proposed to make GRAS notification mandatory for human and animal food (91 FR 51834); proposed 21 CFR 570.205(b) lists seven circumstances needing no notice, comments close on 9 December 2026, and the rule is not final. The wider frame of GRAS notices and AFIC sits under US feed additive regulation.
Use conditions: no maximum, no withdrawal, labelling and organic feed#
Three conditions apply to every 4a enzyme: a legal minimum without a legal maximum, no withdrawal period, and a label that names each activity with its IUB number and units. The minimum is the lowest content at which the authorisation applies.
Annex III of Regulation (EC) No 1831/2003 sets the label for enzymes in premixtures: the name of each active component, its IUB identification number, units of activity per g or ml, the expiry date or storage life and directions for use.
EU organic production admits enzymes: Annex III Part B of Implementing Regulation (EU) 2021/1165 limits zootechnical additives in organic feed to enzymes and microorganisms. Ammonium chloride (4d7, 4d8) for cats is the further zootechnical exception on the full list of feed additives in organic production.
Sourcing Checklist for Feed Enzymes#
Source a feed enzyme in seven checks, from the identification number on the label to the certificate of analysis.
- Confirm the identification number, holder and animal category in the EU Register of Feed Additives.
- Check that each declared activity reaches its legal minimum at your inclusion rate.
- Compare products only within one unit definition.
- Ask for heat-stability data at your conditioning temperature and form.
- Check premix compatibility and storage conditions.
- Check the label against feed additive labelling rules.
- Ask for FAMI-QS or GMP+ certification and a certificate of analysis naming the method, such as EN ISO 30024 for phytase.
A feed analysis needs care: ISO 30024 (second edition 2024) cannot separate added phytase from the phytase native to plant ingredients, and the AOAC 2000.12 collaborative study found between-laboratory variation (RSDR) of 14 to 27.6 % (Engelen and colleagues, 2001). Branded enzymes carry no public price; quotes depend on activity per gram, form and coating.
Feed Enzyme Questions#
Two questions about feed enzymes come up outside formulation: the risks and who holds the authorisations.
Is there a downside to enzymes in animal feed?#
The main downside sits with the people who handle them: enzyme acts describe the preparations as respiratory sensitisers and require breathing protection where the risk cannot be removed, while EFSA sees no consumer concern. EFSA set no maximum residue limit or acceptable daily intake for the 4a1600 phytase (EFSA Journal 2019). For hazard codes, see the product SDS. The other pitfalls are commercial: comparing unit numbers across products and ignoring pelleting losses.
Which companies hold EU feed enzyme authorisations?#
EU feed enzyme authorisations are held by named companies, for example BASF SE (4a1600, 4a47), Genencor International B.V. (4a11, 4a37), AB Enzymes Finland Oy (4a8i, 4a19), Novozymes A/S (4a13, 4a43, 4d16), Elanco GmbH (4a45) and Huvepharma NV (4a1616). Holders change by act: Novonesis completed the purchase of the dsm-firmenich share of the Feed Enzyme Alliance on 2 June 2025, and Implementing Regulation (EU) 2026/180 then moved eight entries from DSM Nutritional Products Ltd to Novozymes A/S.
These holder names are register facts, not a ranking. Analysts publish their own estimates of the feed additives market by segment, and those figures differ by publisher and year.