Poultry Feed Additives: Enzymes, Coccidiostats, Gut Health and Pigments for Broilers, Layers and Turkeys

Poultry feed additives are substances, micro-organisms or preparations added to the feed or water of broilers, laying hens, turkeys and other poultry, and in the EU each one is authorised per verbatim bird category under Regulation (EC) No 1831/2003. A broiler or layer programme rests on coccidiostats, enzymes such as phytase (EU legal minimum 250 to 375 FTU/kg for entry 4a1600), gut-health additives and carotenoid pigments, alongside vitamins, trace minerals and amino acids. In the US, coccidiostats and antibiotics are new animal drugs approved per label population in 21 CFR 558, while enzymes and probiotics carry no FDA approval.

Vitamin D3 is capped at 5 000 IU/kg for chickens for fattening and turkeys but at 3 200 IU/kg for laying hens, no EU coccidiostat entry covers hens in lay, and EU withdrawal periods for poultry coccidiostats run from 0 to 5 days. No EU additive holds a necrotic-enteritis or heat-stress claim; two hold a Salmonella claim and one a Campylobacter claim.

Every value on this page is compiled from the EU authorising acts, the EU Register of Feed Additives, the eCFR, FDA guidance and named peer-reviewed studies, checked on 3 November 2026; the sources and checks are described in the methodology.

What Are Feed Additives in Poultry?#

Feed additives in poultry are the authorised micro-ingredients that a nutritionist adds to a broiler, layer or turkey diet for a stated function, from releasing phosphorus to pigmenting the yolk, as distinct from the feed materials that supply energy and protein. In EU law, poultry additives sit in the five feed additive categories of Regulation (EC) No 1831/2003: technological, sensory, nutritional, zootechnical, and coccidiostats and histomonostats. Zootechnical additives and coccidiostats are authorised to a named holder, while vitamins, trace elements and most technological additives carry generic entries with no holder.

EU legal categories for poultry and US label populations#

EU authorisations name poultry by legal category, so an additive authorised for chickens for fattening may not be fed to laying hens unless its act names them. The EU Register uses eight poultry categories: chickens for fattening, chickens reared for laying, chickens reared for breeding, laying hens, turkeys for fattening, turkeys reared for breeding, minor poultry species and other poultry. Laying hens fall under "other poultry" for vitamin D3 and 25-hydroxycholecalciferol, and the vitamin D3 act (Implementing Regulation (EU) 2017/1492) sets a lower maximum for "other poultry" than for chickens for fattening.

US approvals name poultry differently. Medicated feeds in 21 CFR 558 are approved per label population: broiler chickens, replacement chickens, laying hens and growing turkeys. Coccidiostats in the US fall into Category I or Category II under 21 CFR 558.4, and none of them is a veterinary feed directive (VFD) drug. A US approval for broiler chickens says nothing about EU status for chickens for fattening, and the reverse holds too.

Production context: broilers, layers, turkeys and breeders#

Poultry production splits into four programme types: chickens for fattening on three phase diets, pullets and laying hens across rearing and lay, turkeys, and breeders and minor poultry. Broiler phases follow the Aviagen Ross 2022 nutrition specifications (as-hatched birds under 2.0 kg): starter 0 to 10 days, grower 11 to 24 days and finisher from day 25 to market. Layer programmes run through pullet rearing, pre-lay and lay; the Hy-Line W-36 parent stock guide (August 2025) starts pre-lay no earlier than 15 weeks. Turkey programmes are shaped by the age limits of their coccidiostat entries, 12 or 16 weeks depending on the entry. Breeders and minor poultry receive an additive only where its act names their category. Broiler flocks also face the EU Union target of 1 % or less positive for Salmonella Enteritidis and Typhimurium (Regulation (EU) No 200/2012).

The table matches each programme type to its EU legal categories, its US label population, its phases and its programme page.

Poultry Additive Programme by Production Phase#

A poultry additive programme combines a coccidiostat, enzymes, gut-health additives, vitamins, trace minerals and, for layers and yellow-skinned broilers, pigments, each with its own EU legal value and US status, as the table shows by phase.

Legal minima are not recommended doses, and enzyme units (FTU, U, NFP, LSU(F)) are measured differently and are not comparable. Breed guide values are added levels; EU maxima are total contents per kg complete feed at 12 % moisture.

Chickens for fattening: starter, grower and finisher#

In chickens for fattening the coccidiostat and phytase run through every phase, NSP enzymes join in wheat and barley diets, and the coccidiostat is followed by withdrawal feed wherever its act sets a withdrawal period. Coccidiostats run continuously, as a shuttle or in rotation, typically with a chemical coccidiostat or an ionophore plus nicarbazin in the starter and ionophores later; nicarbazin raises heat-stress mortality. Under subclinical necrotic enteritis, NSP enzymes gave a benefit in wheat-based but not maize-based diets (Kim and colleagues, Animal Nutrition, 2022).

A 4b probiotic, a 4d blend such as the essential-oil preparation 4d11 and, for yellow-skinned birds, canthaxanthin at up to 25 mg/kg complete the broiler programme. Ross 2022 lists added vitamin E of 80, 65 and 55 IU/kg by phase. Ross figures are added levels, while EU maxima for vitamin A, vitamin D3 and zinc are totals, so a breed figure is never compared with an EU maximum before basal content is counted. Vitamin A for chickens for fattening is capped at 20 000 IU/kg to day 14 and 10 000 IU/kg after (Implementing Regulation (EU) 2015/724).

Pullets and laying hens: rearing, pre-lay and lay#

Pullets may receive a coccidiostat only where the act names chickens reared for laying and within its age limit, and in the EU hens in lay receive none, so the laying programme rests on vitamin D3, 25-hydroxycholecalciferol, trace minerals, enzymes and pigments. Coxidin 51701 covers chickens reared for laying to 16 weeks and Sacox 51766 to 12 weeks, while lasalocid for chickens reared for laying was denied by Implementing Regulation (EU) 2023/1172. In the US the picture differs: amprolium is approved for laying chickens under 21 CFR 558.55.

Vitamin D3 shows the gap between breed practice and EU law. The Hy-Line W-36 guide lists 4 400 IU/kg in its production premix, which already exceeds the EU maximum of 3 200 IU/kg for laying hens before basal vitamin D3 is counted. 25-hydroxycholecalciferol 3a670a is capped at 0.080 mg/kg for laying hens. Iodine is capped at 5 mg/kg total (Implementing Regulation (EU) 2015/861), muramidase 4d16 runs at 30 000 to 60 000 LSU(F)/kg (2025/161), and for yolk colour canthaxanthin is capped at 8 mg/kg and lutein at 80 mg total carotenoids/kg. Limestone supplies calcium as a feed material, not as an additive.

Turkeys, breeders and minor poultry#

Turkeys have their own coccidiostat entries with a 12- or 16-week age limit and no EU histomonostat, and breeders and minor poultry are covered only where an act names them. Coxidin 51701 covers turkeys for fattening and turkeys reared for reproduction at 60 to 100 mg/kg to 16 weeks, and Stenorol 51764 covers turkeys for fattening and reared for breeding at 2 to 3 mg/kg to 12 weeks with a 3-day withdrawal. Vitamin A for turkeys is capped at 20 000 IU/kg to day 28 and 10 000 IU/kg after.

Muramidase 4d16 names turkeys and poultry reared for breeding at a minimum of 25 000 LSU(F)/kg (Implementing Regulation (EU) 2020/163), and the Salmonella-claim yeast 4d1703 names turkeys for fattening (2020/162). Mills making turkey and broiler feed share a risk: the US salinomycin label warns "May be fatal if accidentally fed to adult turkeys or horses" (21 CFR 558.550).

Which Additives Address Which Production Problem?#

Most poultry production problems have additive classes that act on them but no EU claim: necrotic enteritis and heat stress have none, Salmonella has two claim additives and Campylobacter one. The table maps eight problems to the classes that act on them, the EU claim status and the US status.

EU feed additives never "prevent, treat or cure"; an authorisation states its effect, and for 4d1703 that is the "reduction of Salmonella spp. contamination on carcasses through its decrease in faeces". The second Salmonella-claim additive, the bacteriophage preparation 4d29 from Proteon Pharmaceuticals S.A., is used in drinking water only, at a minimum of 6 x 10^6 PFU/L and 2 x 10^6 PFU per bird per day. Treatment of drinking-water systems themselves is not covered here.

The Campylobacter entry 4d28 is a zootechnical additive with a Campylobacter claim, not a gut flora stabiliser; the applicant withdrew that claim on 10 July 2024. Processing matters for the micro-organisms behind the gut-health claims: EFSA reported a loss under 0.5 log after pelleting at 95 °C for one Bacillus preparation, and the acts for such preparations require the directions for use to state storage conditions and stability to heat treatment.

Poultry-Specific Regulation: Maximum Contents, Withdrawal and Authorisations#

Poultry regulation turns on three questions per additive: does the act name the bird category, is there a maximum content or an age limit, and is a withdrawal period set before slaughter. Enzymes and micro-organisms carry a legal minimum per kg complete feed with no maximum and no withdrawal period, while vitamins, trace elements and coccidiostats carry maxima that differ by category.

EU maximum contents that differ by bird category#

EU maxima for vitamin D3, 25-hydroxycholecalciferol, vitamin A, zinc, iodine and the carotenoid pigments differ between chickens for fattening, laying hens and turkeys, and all are total contents per kg complete feed at 12 % moisture. The table sets the poultry values side by side with their instrument.

"See the act" marks a category whose value the act sets but the table does not show. The zinc and iodine values sit with the other maximum trace element contents in feed, where each element is set out by species. Every zinc source, including potentiated zinc oxide, counts toward the 120 mg/kg total for chickens for fattening.

For pigments, the 80 mg/kg ceiling caps the total of all carotenoids in a mixture, not each pigment. Lutein and zeaxanthin forms other than the authorised Tagetes erecta extracts were withdrawn for poultry by Implementing Regulation (EU) 2025/2575: stocks of the additive may be used until 8 January 2027, premixtures until 8 April 2027 and compound feed until 8 January 2028.

Coccidiostats: age limits, withdrawal and the laying-hen exclusion#

An EU coccidiostat entry for poultry names its bird categories, a minimum and maximum content (one fixed value for some products) and, for chickens reared for laying and turkeys, a maximum age; EU withdrawal periods run from 0 to 5 days and US periods from 0 to 7 days. The table gives six entries as examples, with their US withdrawal side by side.

No EU coccidiostat entry covers laying hens in lay; in the US, amprolium is approved for laying chickens (21 CFR 558.55).

The annexes forbid mixing coccidiostats, except authorised fixed combinations such as Interban, and a mill that also makes layer, turkey or horse feed has to keep residues within the EU limits for coccidiostat carry-over. Under Regulation (EU) No 744/2012 those limits are 1.25 mg/kg in sensitive feed and 3.75 mg/kg in other feed for monensin, lasalocid and nicarbazin, 0.7 and 2.1 mg/kg for narasin, salinomycin and robenidine, and 0.01 and 0.03 mg/kg for diclazuril.

The bentonite entry 1m558 contraindicates other coccidiostats above 5 000 mg/kg bentonite in poultry and rules out robenidine. Probiotic acts can name the coccidiostats they may be combined with; 4b1822 (Implementing Regulation (EU) 2020/1395), for example, names diclazuril, monensin sodium and nicarbazin.

Antibiotics, arsenicals and histomonostats: EU and US status#

In the EU no antibiotic other than a coccidiostat has been a feed additive since 1 January 2006, while US poultry feed may still carry approved antibiotics with necrotic-enteritis claims, several only under a veterinary feed directive. Article 5(4) of Regulation (EC) No 1831/2003 rules out antibiotics as feed additives; the last growth promoters were marketed until 31 December 2005 and deleted from 1 January 2006 under Article 11(2). Antimicrobial medicated feed "shall not be used for prophylaxis" (Regulation (EU) 2019/4, Article 17(3), from 28 January 2022), and no histomonostat is in the EU Register (checked 3 November 2026).

Bacitracin methylene disalicylate is approved at 50 g/ton for prevention and 100 to 200 g/ton for control of necrotic enteritis without a VFD (21 CFR 558.76). Virginiamycin at 20 g/ton (558.635), lincomycin at 2 g/ton, excluding layers, breeders and turkeys (558.325), and avilamycin at 13.6 to 40.9 g/ton for 21 days (558.68) require a VFD. Arsenicals no longer appear in US poultry feed approvals: the last arsenical, nitarsone, had its approvals withdrawn effective 31 December 2015 (80 FR 78970), and no antihistomonal feed drug is approved in the US.

US status: 21 CFR 558 label populations and 21 CFR 573 listings#

In the US, coccidiostats and antibiotics for poultry are new animal drugs approved per label population in 21 CFR 558, while enzymes, acids and microbials reach poultry feed as food additives, GRAS substances or direct-fed microbials. Monensin for broiler chickens is approved at 90 to 110 g/ton with no withdrawal as a Category I drug (21 CFR 558.355). Category II covers amprolium, clopidol, halofuginone, maduramicin, nicarbazin and robenidine.

No 21 CFR 573 or 558 section covers phytase, xylanase, glucanase, mannanase, protease or amylase. Formic acid and formates are limited to 1.2 % of complete poultry feed (573.480), chromium propionate to 0.2 mg Cr/kg (573.304) and taurine to 0.054 % in feed of growing chickens (573.980). Direct-fed microbials fall under CPG Sec. 689.100; a disease claim makes the product a drug.

A Type B or C feed made from a Category II Type A article needs a medicated feed mill licence (21 CFR 558.4), and the wider rules for mixing drugs into feed sit under medicated feed.

What the Evidence Shows Across Poultry Additive Classes#

Meta-analyses give poultry additives measurable but modest effects: probiotics improved broiler body weight by 66.6 g and FCR by 0.058 across 53 studies in the meta-analysis by Bilal and colleagues (Poultry Science, 2026). The five meta-analyses below cover broilers and laying hens; each figure holds only for the birds and conditions named.

The Ghimire figures show that Bacillus subtilis improved FCR and lesion scores under challenge, yet the mortality effect was not significant, and no EU additive carries a necrotic-enteritis claim. In one trial by Kiarie, Woyengo and Nyachoti (2015), 2 000 FTU/kg of a Buttiauxella phytase in a corn-soy diet reduced in calcium and available phosphorus raised broiler weight gain by 20 % and improved FCR by 7.4 % against the deficient control; that is one trial, not a general effect.

Sourcing Checklist for Poultry Feed Additives#

Source a poultry feed additive in seven checks, from the bird category on the label to the carry-over plan of the mill, listed below in buying order.

1. Match the identification number and verbatim bird category to the act.
2. Check whether the value is a legal minimum or maximum, and its basis.
3. Ask which coccidiostats the probiotic or binder act names.
4. Compare enzyme units only within one definition (FTU is not FYT, OTU or U).
5. Ask for pelleting stability data.
6. Plan carry-over into layer, turkey and horse feed.
7. Ask for FAMI-QS or GMP+ certification and a certificate of analysis.

A US purchase adds one check: the 21 CFR section or direct-fed microbial status behind the label.

Questions About Poultry Feed Additives#

Three questions about poultry feed additives come up in purchasing and formulation.

Which natural feed additives are used in the poultry industry?#

The natural additives used in poultry are plant preparations such as essential-oil blends and Macleaya cordata extract, organic acids, probiotics and enzymes, each authorised in the EU under its own identification number. The main examples with their EU entries are listed below.

• Essential-oil blend 4d11 (carvacrol, cinnamaldehyde, capsicum oleoresin): 100 mg/kg (2026/1777)
• Benzoic acid, thymol, eugenol and piperine blend 4d10: 300 mg/kg (2026/2077)
• Macleaya cordata preparation 4d26: 45 to 150 mg/kg (2023/2732)
• Propionic acid and propionates: max 10 000 mg/kg (2022/415)

Organic poultry feed is narrower. Only additives listed in Annex III Part B of Implementing Regulation (EU) 2021/1165 may be used, and among zootechnical additives only enzymes and micro-organisms qualify; the Annex III list is explained under feed additives in organic production.

Are feed supplements for poultry the same as feed additives?#

Not always: in EU law a feed additive is a substance, micro-organism or preparation other than a feed material or premixture, so a product sold as a poultry supplement may be a premixture or feed carrying additives. The legal test is the definition in Article 2(2)(a) of Regulation (EC) No 1831/2003, not the trade name, and the five additive categories apply only to the additive itself.

Who makes poultry feed additives?#

EU acts name the holders of zootechnical and coccidiostat entries, for example Huvepharma NV for Stenorol, Phibro Animal Health SA for Avatec 150 G and Novozymes A/S for muramidase 4d16, while generic entries such as vitamins and trace minerals carry no holder. Holder-bound authorisations cover zootechnical additives, coccidiostats and GMO additives. Generic entries, such as vitamin D3 or zinc compounds, name a substance and its conditions but no holder.