Feed acidifiers are organic acids, their salts and acid preparations added to feed to lower pH and microbial load in feed and gut, and the EU Register lists them as preservatives, acidity regulators, silage additives, hygiene condition enhancers and zootechnical additives rather than as one group. Each acid carries its own EU entry, species list and legal content: formic acid is capped at 10 000 mg/kg complete feed (12 % moisture) with every formate source summed, benzoic acid is fixed at 5 000 mg/kg for weaned piglets, and potassium diformate is restricted to pigs.
In the US, formic acid and formates are food additives for feed acidification up to 1.2 % of complete swine and poultry feed, and benzoic acid up to 0.5 % of complete swine feed, while propionic, citric, lactic and sorbic acid are GRAS. Butyrate and medium-chain fatty acids are sold as acidifiers but hold no EU feed additive entry.
Every value here is compiled from EU implementing regulations, the EU Register of Feed Additives, EFSA opinions, the eCFR and named peer-reviewed studies, checked on 3 November 2026; for sources and checks, see the methodology.
What Are Feed Acidifiers?#
A feed acidifier is an organic or inorganic acid, or a salt of one, that a nutritionist adds to compound feed or complementary feed to acidify feed and digesta and to inhibit pH-sensitive microbes. The word "acidifier" is a market term, not a legal category: acidifiers spread over several of the feed additive categories of Regulation (EC) No 1831/2003, which defines a feed additive in Article 2(2)(a) and sets five categories in Article 6(1).
EU functional groups and US status of organic acids#
In the EU, organic acids sit in six functional groups: 1a preservatives, 1j acidity regulators, 1k silage additives and 1n hygiene condition enhancers in category 1, 2b flavouring compounds in category 2, and 4d other zootechnical additives in category 4. One acid often holds several entries: potassium diformate is a preservative (1a237a), an acidity regulator (1j001) and a zootechnical additive for sows (4d800).
Category 1 and 2 entries are generic, while category 4 entries are holder-bound: benzoic acid 4d210 belongs to DSM Nutritional Products Ltd and 4d211 to LANXESS Chemical B.V. The legal frame for the technological acids is Implementing Regulation (EU) 2022/415, which re-evaluated formic, propionic, lactic, citric, sorbic, acetic and malic acids and their salts.
The US uses two paths: formic acid, three formate salts and benzoic acid are listed under 21 CFR 573 with numeric limits, while propionic, citric, lactic and sorbic acid are GRAS under 21 CFR 582. A US listing never implies EU status, and the reverse.
The problems acidifiers address in feed and in young animals#
Acidifiers address five problems, listed below.
- Microbial load and mould in feed and grain.
- Digestion in the weaned piglet.
- Urinary pH and slurry ammonia in pigs.
- Performance in pigs and poultry.
- Salmonella in poultry before slaughter.
Pharmacological zinc oxide is a veterinary medicine whose national authorisations Member States had to withdraw by 26 June 2022; it was never a feed additive.
Member Table: Organic Acids, Salts, Preparations and Acidifier Types#
The 16 rows below list each acid and acid type with its EU entry, species and legal content, act and end date, and US status side by side, and link the eight substance pages and four acidifier types that have their own page. Contents are per kg complete feed (12 % moisture), expressed as the acid where the act says so.
| # | Member | Type | EU entry and group | EU species and content | Act and end date | US status | Function |
|---|---|---|---|---|---|---|---|
| 1 | Formic acid and formates in animal feed | substance | 1k236, 1k237i, 1a238, 1a295 (1a); 1k236, 1k237 (1n); 1k236, 1k237 (1k) | all species max 10 000 mg/kg, all formic acid sources summed; 1a295 max 2 000 mg/kg, not laying hens, sows, dairy ruminants, pets or non-food producing animals | Reg. (EU) 2022/415, act end date 2032-04-03 | food additives, 21 CFR 573.480, 573.696, 573.230, 573.170: max 1.2 % complete swine and poultry feed, all sources | preservative; hygiene; silage |
| 2 | Potassium diformate in animal feed | substance | 1a237a; 1j001; 4d800 (ADDCON Europe GmbH) | pigs only: weaned piglets and pigs for fattening max 6 000 mg/kg; sows max 12 000 mg/kg; 4d800 sows 10 000 to 12 000 mg/kg | 2022/1374 to 2032-08-28; 2021/2092 to 2031-12-20; 2023/1698 to 2033-09-27 | US status not confirmed | preservative; acidity regulator; performance |
| 3 | Propionic acid and propionates in animal feed | substance | 1k280, 1k281, 1a282, 1k284 | pigs max 30 000 mg/kg, poultry 10 000 mg/kg, other species no maximum (as propionic acid) | 2022/415 to 2032-04-03; silage 2025/2186 to 2035-11-19 | GRAS, 21 CFR 582.3081, 582.3221, 582.3784, no numeric limit | preservative; silage |
| 4 | Benzoic acid in animal feed | substance | 4d210 (DSM Nutritional Products Ltd represented by DSM Nutritional Products Sp. z o. o.); 4d211 (LANXESS Chemical B.V.); 4d5 sodium benzoate (Taminco Finland Oy) | 4d210: weaned piglets 5 000 mg/kg (min = max), pigs for fattening 3 000 to 10 000 mg/kg, urinary pH (pigs for fattening, sows) 5 000 to 10 000 mg/kg; 4d211: weaned piglets up to 25 kg 5 000 mg/kg; 4d5: weaned piglets max 4 000 mg/kg | 2026/1832 to 2036-08-18; 2024/1730 to 2034-07-11; 2022/538, act end date 2032-04-25 | benzoic acid: food additive, 21 CFR 573.210, max 0.5 % complete swine feed | performance; urinary pH decrease |
| 5 | Fumaric acid in animal feed | substance | 1a297 | poultry, pigs max 20 000 mg/kg; milk replacers 10 000 mg/kg; other terrestrial species no maximum; not aquatic animals | 2026/171 to 2036-02-16 | US status not confirmed | preservative |
| 6 | Citric acid in animal feed | substance | 1a330 (1a, 1j) | all species max 15 000 mg/kg, all sources including 4d3 summed | 2022/415 to 2032-04-03 | GRAS, 21 CFR 582.1033 | preservative; acidity regulator |
| 7 | Lactic acid in animal feed | substance | 1a270, 1a270i, 1a327 | max 20 000 mg/kg; pigs and ruminants with a functional rumen 50 000 mg/kg; not pre-ruminants | 2022/415 to 2032-04-03; 1a270i 2023/2644 to 2033-12-19 | GRAS, 21 CFR 582.1061 | preservative |
| 8 | Sorbic acid and potassium sorbate in animal feed | substance | 1a200, 1k202 | max 2 500 mg/kg; pre-ruminants 6 700 mg/kg (as sorbic acid) | 2022/415 to 2032-04-03 | GRAS, 21 CFR 582.3089, 582.3640 | preservative; silage |
| 9 | DL-malic acid (section) | acid | 1a296 | species and content not given here | 2022/415 | US status not confirmed | preservative |
| 10 | Acetic acid, sodium diacetate, calcium acetate (section) | acid, salts | 1a260, 1a262, 1a263 | all species other than fish and ruminants max 2 500 mg/kg; ruminants no maximum; fish (1a260) max 2 500 mg/kg | 2022/415 as corrected by 2025/187; fish 2024/1755 to 2034-07-16 | US status not confirmed | preservative |
| 11 | Orthophosphoric acid (section) | inorganic acid | 1a338 | all species, no maximum; phosphorus content on label | 2024/1185 to 2034-05-15 | US status not confirmed | preservative |
| 12 | Sodium bisulphate (section) | inorganic salt | 1j514ii | cats max 20 000 mg/kg; mink 10 000 mg/kg; other species except aquatic animals 4 000 mg/kg | 2024/2393 to 2034-09-30 | US status not confirmed | acidity regulator |
| 13 | Acid blends, protected acids and zootechnical acid preparations | node | 4d3 (Vetagro SpA); 4d10 (DSM Nutritional Products Ltd represented by DSM Nutritional Products Sp. z o. o.); 4d14 (Novus Europe NV) | 4d3: min 200 mg/kg chickens, turkeys, minor avian species; min 1 000 mg/kg weaned and suckling piglets; no maximum. 4d10: 300 mg/kg (min = max) poultry for fattening and reared for laying or reproduction. 4d14: 500 to 1 000 mg/kg chickens and turkeys | 4d3: 2020/2119 to 2031-01-06, 2020/1375 to 2030-10-22; 4d10: 2026/2077 to 2036-10-08; 4d14: 2018/982 to 2028-08-01, 2021/2097 to 2031-12-20 | US status not confirmed | performance (4d) |
| 14 | Drinking-water acidifiers | node | no separate entry | compound feed administered via water, inside each acid's maximum | 2022/415, recital 16 | US status not confirmed | n/a |
| 15 | Butyrate in feed | node | no feed additive entry; flavourings 2b08005 (butyric acid), 2b09211 (tributyrin) | flavouring only: recommended max 125 mg/kg and 5 mg/kg | 2023/1417 to 2033-07-26; 2017/54, printed expiry 2027-02-06, renewal application recorded in the EU Register | tributyrin: GRAS synthetic flavouring, 21 CFR 582.60; sodium butyrate: US status not confirmed | flavouring only |
| 16 | Medium-chain fatty acids in pig and poultry feed | node | no feed additive entry | no legal content | n/a | US status not confirmed | none |
Maxima of different salts of one acid are expressed as that acid and are never added together, and no EU acidifier annex sets a withdrawal period.
How Do Feed Acidifiers Work?#
Feed acidifiers work in four ways: the undissociated acid enters microbial cells and acidifies them, acids lower the acid-binding capacity of the diet, benzoic acid acidifies urine, and butyrate and medium-chain fatty acids act on gut cells and microbial membranes. The first two act in feed and in the upper gut, the third after absorption.
Undissociated acid, pKa and antimicrobial action#
An organic acid inhibits bacteria while it is undissociated: it crosses the cell membrane, dissociates in the neutral cytoplasm and acidifies the cell, so acids with a low pKa such as formic acid (3.75) act most strongly. Formic acid has the strongest antibacterial action among feed acids. The pKa values are 3.75 for formic, 3.86 for lactic, 4.20 for benzoic, 4.76 for sorbic and acetic, 4.82 for butyric and 4.87 for propionic acid; fumaric acid has 3.03 and 4.44, malic acid 3.51 and 5.03, and citric acid 2.79 (PubChem).
Propionic acid is strongly antifungal and sorbic acid antifungal and anti-yeast, and both serve as mould inhibitors. In the gut the effect is weaker: the review by Partanen and Mroz (Nutrition Research Reviews, 1999) found gastric pH reduction difficult to demonstrate and growth effects of acids generally smaller than those of antibiotics.
Urinary acidification by benzoic acid#
Benzoic acid is conjugated with glycine to hippuric acid in the liver and excreted in urine; at 1 % of the diet, urinary pH fell from 7.01 to 4.99, with 85 % of the dietary benzoic acid excreted as hippuric acid (Kristensen et al. 2009, Journal of Animal Science). The 1 % is a trial level. The EU urinary pH decrease claim of 4d210 and 4d211 covers 5 000 to 10 000 mg/kg and is the legal route by which feed lowers slurry ammonia, since functional group 4c holds only 3-NOP (4c1) and no ammonia-emission entry (EU Register, 3 November 2026).
Colonocyte energy and membrane disruption#
Butyrate serves as an energy source for colonocytes, while medium-chain fatty acids and their monoglycerides disrupt the lipid membranes of enveloped viruses and Gram-positive bacteria. Monoglycerides act more potently than the free acids. Neither group holds an EU feed additive entry, so neither carries a legal claim in the EU.
Evidence from meta-analyses#
Acidifiers raised average daily gain by 6.7 % and gain-to-feed ratio by 5.0 % over controls in pigs in a meta-analysis of 52 articles by Wang H. and colleagues (Animal Feed Science and Technology, 2022), most consistently below 60 kg. In poultry, a meta-analysis by Wang J. and colleagues (Poultry Science, 2025) found that organic acids in feed cut the odds of Salmonella-positive crops by 84 % and caeca by 66 %, against 57 % and 62 % for the water route; caecal Salmonella concentration fell by 1.59 log in feed and 0.72 log in water.
Those Salmonella figures are study results, not an EU claim: no acid holds an EU Salmonella-reduction claim. Against antibiotics, the pig meta-analysis found similar gain-to-feed but lower daily gain, so acids are one of several alternatives to antibiotic growth promoters, not a one-for-one replacement.
Acid-Binding Capacity (ABC-4) and pKa in Diet Formulation#
Acid-binding capacity at pH 4 (ABC-4) is the milliequivalents of hydrochloric acid needed to bring 1 kg of feed to pH 4, and acids with a low pKa reduce it most while calcium salts and protein raise it. Calcium formate supplies calcium and raises ABC-4. Piglet phase 1 diets are formulated to a target ABC-4 by lowering limestone, using acids rather than salts, and choosing low-ABC protein and lactose sources.
The values below come from two nursery pig studies; the acid inclusions are trial doses.
| Diet or measure | Value | Study |
|---|---|---|
| Nursery phase 1 diets | ABC-4 234 to 300 meq/kg | Choi and Kim 2026 |
| Nursery phase 3 diets | ABC-4 129 to 197 meq/kg | Choi and Kim 2026 |
| ABC-4 lowered by 40 to 50 meq/kg | stomach pH unchanged at 4.0 | Choi and Kim 2026 |
| ABC-4 targets 200 and 250 meq/kg | gain-to-feed and faecal dry matter improved, no zinc oxide | Stas et al. 2025 |
| 0.6 % formic acid plus 0.46 % fumaric acid | best low-ABC-4 strategy (trial dose) | Stas et al. 2025 |
Diet ABC-4 and stomach pH are different measures: in the trial by Choi and Kim (Journal of Animal Physiology and Animal Nutrition, 2026), stomach dry matter correlated with stomach pH (r = 0.54) while a lower diet ABC-4 did not change it. The low-ABC-4 trial by Stas and colleagues (Translational Animal Science, 2025) still found better feed efficiency and faecal consistency in pigs fed without zinc oxide.
Which Acidifier for Which Objective?#
The objective decides the acid: formates for feed hygiene, propionates and sorbates against mould, benzoic acid and potassium diformate for pig performance, benzoic acid for urinary pH, and 4d preparations for broilers. The table pairs each objective with its acids, the basis of the figure and the page that covers it.
| Objective | Acids and EU entry | Basis | Owner page |
|---|---|---|---|
| Feed hygiene | formic acid 1k236 (Reg. (EU) 2017/940, listed in Annex 2 of the EU Register, end date 2027-06-21); sodium formate 1k237 (2020/106, to 2030-02-13) | EU legal maximum | Feed hygiene additives |
| Mould in feed and grain | propionic acid and propionates; sorbic acid and potassium sorbate | EU legal maximum | Feed preservatives and mould inhibitors |
| Silage | formic acid, sodium formate, potassium sorbate, sodium benzoate (2016/2023, printed expiry 2026-12-09, renewal applications recorded in the EU Register); propionates (2025/2186, to 2035-11-19) | acts | Silage additives |
| Replacing pharmacological zinc oxide | benzoic acid 4d210, 4d211; potassium diformate; formic plus fumaric acid; low ABC-4 | EU maxima; trial | Pharmacological zinc oxide in piglet diets |
| Weaned piglet digestion | low ABC-4 diets; 4d3 | trial; EU legal minimum | Post-weaning diarrhoea in piglets without zinc oxide |
| Urinary pH and slurry ammonia | benzoic acid 4d210, 4d211 | EU legal minimum and maximum | Ammonia and odour reduction through feed |
| Sow performance | potassium diformate 4d800 | EU legal minimum and maximum | n/a |
| Broiler performance | 4d10, 4d14, 4d3 | EU legal content | n/a (member table row 13) |
| Salmonella before slaughter | acids in feed or water, no EU claim | meta-analysis | Salmonella control in poultry |
Two checks follow the choice. The entry must name the species, because potassium diformate covers pigs only and fumaric acid excludes aquatic animals, and every source of the same acid must be summed against one maximum, including formates hidden in a blend. Cleaning and descaling drinking-water lines is a separate water-treatment topic.
Selection by Species and Diet#
Species narrows the choice because each act names its animals: potassium diformate covers pigs only, fumaric acid excludes aquatic animals, and lactic acid excludes ruminants without a functional rumen. The table lists the EU entries and US limits per species.
| Species | EU entries (member table rows) | US | Programme page |
|---|---|---|---|
| Poultry | formic acid sources, propionates, fumaric acid, citric acid, 4d3, 4d10, 4d14 (rows 1, 3, 5, 6, 13); no potassium diformate | formates max 1.2 % | Poultry feed additives |
| Weaned piglets | 4d210, 4d211 5 000 mg/kg; 4d5 max 4 000 mg/kg; potassium diformate max 6 000 mg/kg; fumaric acid max 20 000 mg/kg; 4d3 min 1 000 mg/kg | benzoic acid max 0.5 %; formates max 1.2 % | Piglet and weaner feed additives |
| Pigs for fattening and sows | 4d210; potassium diformate 6 000 and 12 000 mg/kg; 4d800; propionates 30 000 mg/kg; lactic acid 50 000 mg/kg | benzoic acid max 0.5 % | Pig feed additives |
| Cattle and calves | lactic acid functional rumen only; fumaric acid milk replacers 10 000 mg/kg; sorbic acid pre-ruminants 6 700 mg/kg; acetic acid ruminants no maximum | GRAS citric and lactic acid | Cattle feed additives |
| Fish and shrimp | acetic acid 1a260 max 2 500 mg/kg; no fumaric acid; potassium diformate only in raw fish, 9 000 mg/kg raw fish | n/a | Aquafeed additives |
| Pet food | sodium bisulphate cats 20 000 mg/kg; sorbic and acetic acid 2 500 mg/kg; no ammonium formate | GRAS sorbic acid | Pet food additives |
Acidifiers in poultry feed#
Acidifiers in poultry feed are formic acid and formates up to 10 000 mg/kg, propionic acid up to 10 000 mg/kg, fumaric acid up to 20 000 mg/kg, citric acid up to 15 000 mg/kg, and three 4d preparations with performance claims. Potassium diformate is not among them, since its EU entries name pigs only.
Preparation 4d10 of DSM Nutritional Products Ltd (benzoic acid, thymol, eugenol, piperine) is fixed at 300 mg/kg for poultry for fattening and reared for laying or reproduction under Implementing Regulation (EU) 2026/2077. Preparation 4d14 of Novus Europe NV (benzoic acid, calcium formate, fumaric acid) ranges from 500 to 1 000 mg/kg for chickens and turkeys. Preparation 4d3 of Vetagro SpA (protected citric acid, sorbic acid, thymol, vanillin) has a legal minimum content of 200 mg/kg, a floor and not a dose.
Acidifiers for pigs: piglets, fatteners and sows#
Weaned piglets have the widest EU acidifier choice: benzoic acid at exactly 5 000 mg/kg (4d210, 4d211), sodium benzoate up to 4 000 mg/kg (4d5), potassium diformate up to 6 000 mg/kg and fumaric acid up to 20 000 mg/kg. The potassium diformate ceiling matches the maximum safe level for weaned piglets that EFSA set in 2022 (EFSA Journal 2022;20(3):7167).
Benzoic acid 4d210 covers pigs for fattening at 3 000 to 10 000 mg/kg for performance and pigs for fattening and sows at 5 000 to 10 000 mg/kg for urinary pH. Sows take potassium diformate up to 12 000 mg/kg as a preservative or, as 4d800 of ADDCON Europe GmbH, at 10 000 to 12 000 mg/kg for performance. Propionates reach 30 000 mg/kg and lactic acid 50 000 mg/kg in pig feed. In the US, benzoic acid is listed for complete swine feed under 21 CFR 573.210.
Calves, ruminants, fish and pet food#
Outside pigs and poultry the acts narrow further: fumaric acid is capped at 10 000 mg/kg in milk replacers, sorbic acid reaches 6 700 mg/kg for pre-ruminants, and lactic acid is excluded for pre-ruminants under Implementing Regulation (EU) 2024/762. Acetic acid and its salts carry no maximum for ruminants. Fish feed may contain acetic acid 1a260 up to 2 500 mg/kg, while fumaric acid has no aquatic use and potassium diformate reaches fish only as a raw-fish preservative. In pet food, sodium bisulphate reaches 20 000 mg/kg for cats, and ammonium formate is excluded.
Dosing Logic: Legal Maxima, Summed Sources and Trial Doses#
Acidifier doses come in three kinds that are never interchangeable: technological acids carry a legal maximum per kg complete feed (12 % moisture) summed over all sources, 4d preparations carry a legal minimum and often a maximum, and everything else is a trial dose. US figures add a fourth kind, a percentage limit of complete feed.
| Acid (ID) | Species | Dose | Basis | Instrument or study |
|---|---|---|---|---|
| Formic acid, all sources | all | max 10 000 mg/kg | EU legal maximum, summed | Reg. (EU) 2022/415 |
| Ammonium formate 1a295 | listed species | max 2 000 mg/kg | EU legal maximum | Reg. (EU) 2022/415 |
| Potassium diformate 1a237a | piglets, fatteners / sows | max 6 000 / 12 000 mg/kg | EU legal maximum | Reg. (EU) 2022/1374 |
| Potassium diformate 4d800 | sows | 10 000 to 12 000 mg/kg (= 6 993 to 8 391 mg/kg formic acid) | EU legal minimum and maximum | Reg. (EU) 2023/1698 |
| Propionic acid sources | pigs / poultry | max 30 000 / 10 000 mg/kg | EU legal maximum | Reg. (EU) 2022/415 |
| Benzoic acid 4d210 | weaned piglets / pigs for fattening | 5 000 / 3 000 to 10 000 mg/kg | EU legal minimum and maximum | Reg. (EU) 2026/1832 |
| Sodium benzoate 4d5 | weaned piglets | max 4 000 mg/kg | EU legal maximum | Reg. (EU) 2022/538 |
| Fumaric acid 1a297 | poultry, pigs / milk replacers | max 20 000 / 10 000 mg/kg | EU legal maximum | Reg. (EU) 2026/171 |
| Citric acid 1a330 | all | max 15 000 mg/kg, summed with 4d3 | EU legal maximum | Reg. (EU) 2022/415 |
| Lactic acid 1a270 | others / pigs, functional rumen | max 20 000 / 50 000 mg/kg | EU legal maximum | Reg. (EU) 2022/415 |
| Sorbic acid 1a200 | all / pre-ruminants | max 2 500 / 6 700 mg/kg | EU legal maximum | Reg. (EU) 2022/415 |
| Preparation 4d10 | listed poultry | 300 mg/kg | EU legal minimum and maximum | Reg. (EU) 2026/2077 |
| Preparation 4d14 | chickens, turkeys | 500 to 1 000 mg/kg | EU legal minimum and maximum | Reg. (EU) 2018/982, 2021/2097 |
| Preparation 4d3 | poultry / piglets | min 200 / 1 000 mg/kg | EU legal minimum, not a dose | Reg. (EU) 2020/2119, 2020/1375 |
| Formic acid and formates | swine, poultry (US) | max 1.2 % [24 lb/ton] | US limit | 21 CFR 573.480 |
| Benzoic acid | swine (US) | max 0.5 % [10 lb/ton] | US limit | 21 CFR 573.210 |
| Benzoic acid | pigs, weaning to market | 0.53 % (daily gain), 0.57 % (gain-to-feed) | trial optimum | Kim et al. 2025 |
| Formic plus fumaric acid | weaned pigs | 0.6 % plus 0.46 % | trial | Stas et al. 2025 |
A legal maximum is a ceiling, not a target, and the summed-sources rule turns it into a budget. Potassium diformate shows how: 10 000 mg/kg of it equals 6 993 mg/kg formic acid under Implementing Regulation (EU) 2023/1698 and counts toward the same formic acid total as every other formate. Acids given through drinking water count too, because recital 16 of 2022/415 allows them only as compound feed administered via water, inside the same maxima. The trial optimum of Kim and colleagues (Journal of Animal Science, 2025) is a single study, not a dose for all pig systems.
Regulation Summary: EU Entries and US Status#
The EU regulates each acid through its own entry under Regulation (EC) No 1831/2003, most re-evaluated by Implementing Regulation (EU) 2022/415, while the US lists formates and benzoic acid as food additives under 21 CFR 573 and other acids as GRAS under 21 CFR 582. The two systems share no list and no claim.
EU entries, re-evaluation and expiry dates#
Implementing Regulation (EU) 2022/415 re-evaluated malic, citric, sorbic, acetic, propionic, formic and lactic acids and their salts under Article 10 and set the end of the period at 3 April 2032. The former feed numbers E 236, E 237, E 238 and E 295 were deleted from the register with effect from 11 March 2023. Later acts renewed single entries: fumaric acid by 2026/171, benzoic acid 4d210 by 2026/1832 of 28 July 2026, and preparation 4d10 by 2026/2077.
Formic acid has other entries with other dates. The silage entries of 2016/2023 carry a printed expiry of 2026-12-09 with renewal applications recorded in the EU Register, and the hygiene condition enhancer entry 1k236 of 2017/940 is listed in Annex 2 of the register with an end date of 2027-06-21. How Article 10 re-evaluation and Article 14 renewal work is explained under EU feed additive regulation.
US status: feed acidifying agents and GRAS listings#
In the US, formic acid and three formate salts are food additives for use as feed acidifying agents up to 1.2 % of complete swine and poultry feed from all sources, and benzoic acid up to 0.5 % of complete swine feed. The three US paths are listed below.
- Formates: 21 CFR 573.480 (formic acid), 573.696 (sodium formate), 573.230 (calcium formate, final rule of 19 December 2023) and 573.170 (ammonium formate, swine only); never GRAS.
- Benzoic acid: 21 CFR 573.210, purity at least 99.5 %, published at 79 FR 14176 on 13 March 2014
- GRAS acids: propionic acid and propionates (582.3081, 582.3221, 582.3784), citric acid (582.1033), lactic acid (582.1061), sorbic acid and potassium sorbate (582.3089, 582.3640) and tributyrin as a synthetic flavouring (582.60).
Use conditions: label statement, summed sources and incompatibilities#
Every 2022/415 acid label carries the statement: "The simultaneous use of different organic acids or their salts is contraindicated where one or more of them is used at or near the maximum permitted content." Formic acid, the formates and potassium diformate share one formic acid total.
The zootechnical acids add incompatibility clauses. Benzoic acid 4d210, 4d211 and sodium benzoate 4d5 may not be combined with another benzoic acid or benzoate source, including preparations 4d10 and 4d14, and 4d14 may not be combined with benzoates, calcium formate, other formates or fumaric acid. Official methods are EN 17294 (ion chromatography) for formic, propionic, lactic, citric and fumaric acid and EN 17298 (HPLC-UV) for sorbic and benzoic acid.
Sourcing Checklist for Feed Acidifiers#
Source a feed acidifier in seven checks, from the EU identification number on the label to the acid content on the certificate of analysis.
- Confirm the EU identification number, the species and the maximum on the label, for example 1a237a for pigs only or 4d211 for weaned piglets up to 25 kg.
- Compare purity with the act: formic acid at least 84.5 % (1k236), benzoic acid at least 99.9 % (4d210).
- Sum every source of the same acid, including water products and blends.
- Check the incompatibility clauses of 4d210, 4d211, 4d5 and 4d14.
- Ask for the heat-stability data that 4d210, 1a297 and 4d800 require on the label.
- Ask for a certificate of analysis that names the test method, EN 17294 or EN 17298.
- Ask for FAMI-QS or GMP+ certification and for user-safety data, since liquid formic acid is corrosive.
A buyer should count a coated acid as the sum of its declared acids. Market-size estimates by publisher and year are collected under feed acidifiers market.
Feed Acidifier Questions#
Three questions about feed acidifiers come up before purchase: which acids exist, what can go wrong, and what sets the price.
What are some examples of acidifiers?#
Examples of feed acidifiers are formic, propionic, benzoic, fumaric, citric, lactic, sorbic, malic and acetic acid, salts such as potassium diformate, calcium formate and sodium benzoate, and orthophosphoric acid and sodium bisulphate. Butyrate sources and medium-chain fatty acids are sold alongside them without an EU feed additive entry.
What are the side effects of organic acids in animal feed?#
Organic acids are safe for the target animals at the authorised maxima according to EFSA, but liquid acids are corrosive to users, and benzoic acid reduced nursery pig growth in crude-protein-deficient diets in one study (de Azevedo et al. 2025). Formic acid, sodium formate and ammonium formate are corrosive (2022/415, recital 11), fumaric acid is a skin and respiratory sensitiser (EFSA 2024), and benzoic acid irritates skin, eyes and the respiratory tract (EFSA 2026).
What drives the price of an acidifier for poultry?#
Acidifier prices depend on the acid and its form (liquid acid, salt or coated preparation), purity, whether it is a holder-bound 4d preparation, the carrier, certification and volume, so no single price per kg applies. A quote request that names the identification number, the form and the yearly volume lets suppliers quote on the same basis.