Trace Minerals in Animal Feed: Sources, Bioavailability, Limits and Organic Forms

Trace minerals for livestock are feed additives that supply zinc, copper, manganese, iron, selenium, iodine, cobalt and molybdenum, and the EU Register lists them as functional group 3b, "compounds of trace elements", of the nutritional additives category. EU maxima are total contents per kilogram of complete feed at 12 % moisture, background from feed materials included, for example 0.50 mg/kg selenium for all species and 120 mg/kg zinc for most species, while US law lists most sources as GRAS under 21 CFR 582.80 with no federal numeric limit.

Chromium shows how far the two systems diverge. The EU has no chromium compound in group 3b and authorises chromium chelate of DL-methionine only as zootechnical additive 4d30 for salmonids, while the US food additive sections 21 CFR 573.304 and 573.302 cover broilers, laying hens, breeder chickens, growing turkeys, horses and cattle. A US listing never implies EU status, and the reverse.

Every value below is compiled from the EU authorising acts, the EU Register of Feed Additives, EFSA opinions, the eCFR and named peer-reviewed studies, checked on 3 November 2026; see the methodology.

What Are Trace Minerals in Animal Feed?#

Trace minerals in animal feed are feed additives made of compounds of essential metals and iodine, added in milligrams per kilogram, that supply the elements a diet of feed materials does not provide in the amount or form the animal can use. EU law places them in functional group 3b of category 3 among the five feed additive categories of Regulation (EC) No 1831/2003 (in force since 18 October 2004), whose feed additive definition excludes feed materials and premixtures (Article 2(2)(a)).

EU functional group 3b and the US classification#

Functional group 3b, "compounds of trace elements", belongs to category 3 nutritional additives, and each entry carries its own identification number, such as 3b603 for zinc oxide. In the US, most sources are generally recognized as safe (GRAS) under 21 CFR 582.80 "at levels consistent with good feeding practice", while selenium and chromium sources are food additives under 21 CFR 573. Every 3b authorisation is generic: it names a substance and its conditions, never a holder, and no EU act or US section sets a withdrawal period for these additives.

Two metal additives sit outside group 3b: chromium chelate of DL-methionine (4d30) and iron(III) citrate chelate (4d22) are zootechnical additives in functional group 4d, so each names a holder (Zinpro Animal Nutrition Europe, Inc. for 4d30; Akeso Biomedical, Inc. USA for 4d22).

Organic forms, such as metal amino acid chelates and metal proteinates, are not listed in 582.80 and are marketed in the US under AAFCO ingredient definitions. Hydroxychlorides are not named in 582.80 either, although copper, zinc and manganese chlorides are.

The supply gap trace mineral additives close#

Feed materials carry trace elements in amounts and forms that vary, and EU maxima count that background toward the legal total. Feed phosphates, for example, carry zinc and iron. Calcium, phosphorus, sodium and magnesium sources such as feed phosphates and limestone are feed materials (Catalogue entries 11.1.1 and 11.3.x), not additives.

Antagonists then cut what the animal absorbs from that supply. In the rumen, molybdenum and sulphur form thiomolybdates that bind copper, and high dietary iron lowers copper and manganese status in every species. A ration with adequate copper on paper can therefore leave a ruminant short of usable copper.

Trace Mineral Member Table: Elements, Sources and Topic Pages#

The nine element pages below give the EU entries, species and maxima beside the US status for each trace element; two molybdenum entries close the first table, and the second table lists five topic pages on forms, uptake, limits and macro-mineral sources.

No withdrawal period is set in any of these acts or US sections. The second table maps each topic page to the EU value that applies now and the entries it explains.

What Do Trace Minerals Do in the Animal?#

Trace minerals work as parts of enzymes, hormones and vitamin B12: zinc, copper, manganese and selenium sit in metalloenzymes and antioxidant selenoproteins, iodine builds thyroid hormones, and rumen microbes use cobalt to make cobalamin. Uptake differs by chemical form, dietary antagonists and animal status.

Enzyme cofactors and antioxidant defence: zinc, copper, manganese and selenium#

Zinc, copper, manganese and selenium each join named enzymes and structural proteins. Zinc is a cofactor of alkaline phosphatase and copper-zinc superoxide dismutase (CuZn-SOD) and supports keratin; copper serves cytochrome c oxidase, ceruloplasmin and lysyl oxidase; manganese builds bone, cartilage and eggshell matrix and activates Mn-SOD. Selenium sits in glutathione peroxidases, thioredoxin reductases and iodothyronine deiodinases, an antioxidant defence it shares with vitamin E.

Zinc and manganese uptake depends on the plant fraction and the calcium level of the diet. Phytate in plant feed binds zinc, and high dietary calcium reduces the uptake of both zinc and manganese; manganese also competes with iron for absorption. The enzyme that acts on this phytate is phytase: phytase in animal feed hydrolyses phytate and releases the calcium, zinc and amino acids bound to it.

Hormones, vitamin B12 and blood: iodine, cobalt and iron#

Iodine builds the thyroid hormones T3 and T4, and the thyroid traps absorbed iodide efficiently. Glucosinolates from rapeseed and thiocyanates antagonise that uptake. Calcium iodate anhydrous is the stable iodine source preferred in premixes, while potassium iodide oxidises and volatilises in humid, acidic premixes.

Cobalt matters to ruminants because rumen microbes build it into cobalamin (vitamin B12), and oral vitamin B12 is largely degraded in the rumen, so the animal depends on a cobalt supply. Iron forms haemoglobin, myoglobin and cytochromes, and ferrous iron is absorbed in the duodenum while ferric oxides are largely unavailable. Trivalent chromium potentiates insulin action.

Evidence from meta-analyses#

Organic trace minerals raised milk yield by 0.93 kg per cow per day (95 % CI 0.61 to 1.25) in the meta-analysis by Rabiee and colleagues (Journal of Dairy Science, 2010), which pooled 20 papers on zinc, manganese, copper and cobalt complexes fed to dairy cows. The same analysis found 13.5 fewer days open and 0.27 fewer services per conception.

Oral selenium raised milk selenium by 0.16 µmol/L (95 % CI 0.117 to 0.207) across 42 studies in the meta-analysis by Ceballos and colleagues (Journal of Dairy Science, 2009), and selenised yeast produced higher milk selenium than inorganic sources. In broilers, a pooled analysis of 9 Chinese studies by Wei and colleagues (Open Life Sciences, 2021) found no significant growth difference between organic and inorganic selenium fed at equal dose (standardised mean difference for feed to gain -0.39, for average daily gain 0.26).

Selection by Target: Source, Form and Premix Behaviour#

A trace mineral source is chosen on five criteria: price per unit of bioavailable element, the species maximum, the antagonist load of the diet, behaviour in the premix and the identity the target market accepts (an EU 3b number or a US 582.80 or 573 listing); Kansas State University extension frames price per unit of bioavailable element, not per kilogram of product. The maximum is the same for every source of one element, with one exception: supplementation from organic selenium is capped at 0.20 mg/kg inside the selenium total.

The table compares the three source families on legal maximum, minimum element content, premix behaviour and US listing.

Copper oxide shows why element content alone misleads: it carries at least 77 % copper, yet in the systematic review by Byrne and Murphy (Animals, 2022), whose authors work for an organic trace mineral manufacturer, its bioavailability relative to copper sulphate reached no more than 64 % in cattle. Organic and inorganic sources differ on relative bioavailability, cost and premix stability, and the attribute-by-attribute contrast sits in organic vs inorganic trace minerals.

Selection by Species and Diet#

Species decides the ceiling before it decides the source, because EU maxima differ by animal for copper, zinc, iron and iodine, cobalt is open only to ruminants with a functional rumen, equidae and lagomorphs, and molybdenum only to sheep. The table lists the values that differ and the programme page for each species.

Trace minerals for cattle and dairy cows#

Cattle carry two EU copper ceilings: 15 mg/kg total for bovines before the start of rumination and 30 mg/kg for other bovines, under Implementing Regulation (EU) 2018/1039. Bovine feed after the start of rumination with less than 20 mg/kg copper must warn of copper deficiencies in cattle grazing pastures high in molybdenum or sulphur. Dairy cows have an iodine maximum of 5 mg/kg (recommended 2 mg/kg).

US cattle rules differ in kind: selenium sources may supply 0.3 ppm added selenium, chromium DL-methionine chelate 0.5 mg Cr/kg complete feed under 21 CFR 573.302 since 91 FR 53526 (19 August 2026), and the other sources follow good feeding practice. Forage, feed, minerals and water all contribute molybdenum, sulphur and iron to the antagonist load.

Trace minerals for sheep and goats#

Sheep carry an EU copper maximum of 15 mg/kg total, goats 35 mg/kg (2018/1039). Ovine feed above 10 mg/kg copper must carry the label sentence "The level of copper in this feed may cause poisoning in certain breeds of sheep." In the US, 21 CFR 507.33 names excessive copper in food for sheep as an example of a nutrient hazard.

Molybdenum enters sheep feed only through sodium molybdate dihydrate 3b701, at up to 2.5 mg Mo/kg with a dietary copper to molybdenum ratio of 3 to 10 on the label (Implementing Regulation (EU) 2019/1965). US free-choice salt-mineral for sheep may contain up to 90 ppm selenium (0.7 mg/head/day).

Minerals for pigs and piglets#

Piglets carry the highest EU copper maximum: 150 mg/kg up to 4 weeks after weaning and 100 mg/kg in weeks 5 to 8, against 25 mg/kg for other pigs. Zinc is capped at 150 mg/kg for piglets and sows and 120 mg/kg for other pigs. Pharmacological zinc oxide at 1 000 to 3 000 mg/kg was a veterinary medicine, not a feed additive; the Commission decision of 26 June 2017 withdrew its EU marketing authorisations, with Member State deferral up to June 2022.

A mineral premix for pigs is the legal route, not an option, because the zinc, copper, manganese, selenium, iodine and cobalt compounds enter feed only as a premixture. The iron of iron(III) citrate chelate 4d22, a zootechnical additive for suckling and weaned piglets, counts toward the total iron maximum.

Minerals for chickens and other poultry#

Poultry feed carries an EU iron maximum of 450 mg/kg total, and laying hens an iodine maximum of 5 mg/kg (recommended 3 mg/kg). Iron(II) carbonate 3b101 is excluded for chickens up to 14 days and turkeys up to 28 days, and its label warns of limited bioavailability for young animals.

In the US, chromium propionate may supply 0.2 mg Cr/kg complete feed for broilers, laying hens, breeder chickens and growing turkeys (21 CFR 573.304 as amended by 91 FR 65110, 14 October 2026), and zinc-L-selenomethionine is listed for broilers only (90 FR 21220, 19 May 2025). The Aviagen Ross 2022 broiler specification lists added amounts, never legal limits.

Horses, fish, crustaceans, dogs and cats#

Horses have the lowest EU iodine maximum, 4 mg/kg total, and share the cobalt ceiling of ruminants; in the US, chromium propionate may supply up to 4 mg Cr per head per day, and 21 CFR 573.920 grants no selenium approval for horses, goats or pets. Fish other than salmonids may receive 150 mg/kg zinc, fish 20 mg/kg iodine and crustaceans 50 mg/kg copper, and salmonids are the only species in the EU chromium entry 4d30.

Dogs and cats carry the highest zinc maximum, 200 mg/kg, and pet animals an iron maximum of 600 mg/kg.

Dosing Logic: EU Total Maxima, US Limits and Formulation Specifications#

Trace mineral doses come in three kinds that are never interchangeable: EU legal maxima are total contents per kilogram of complete feed including background, US numeric limits apply only to the selenium and chromium food additives, and every other figure is a requirement or a manufacturer specification. The table gives each value with its basis and instrument.

Ross values are added amounts, not legal limits; EU values include background from feed materials.

A maximum is a ceiling, not a target: the amount a premix may add is limited by what the feed materials already carry, and per-salt figures are never added together where an act sets one total. Complementary feed and feed materials may contain at most 100 times the complete-feed maximum of an additive (Regulation (EC) No 767/2009, Article 8(1)), a rule that does not apply to premixtures.

Zinc, copper, manganese, selenium, iodine and cobalt compounds reach compound feed only through vitamin and mineral premixes, with zinc chloride anhydrous and iron(III) chloride as liquid premixtures. Establishments that make premixtures containing copper or selenium need approval under Regulation (EC) No 183/2005, Article 10(1)(b).

Regulation Summary: EU 3b Entries and US Status#

An EU trace element source used as a nutritional additive exists only as a 3b entry under Regulation (EC) No 1831/2003, with its own element maximum and expiry, while in the US most sources are GRAS under 21 CFR 582.80 and selenium and chromium sources are food additives under 21 CFR 573. Neither system's status implies the other's.

EU 3b entries, expiry and renewal status#

The element maxima come from Implementing Regulations (EU) 2016/1095 (zinc), 2018/1039 (copper), 2017/1490 (manganese), 2017/2330 (iron), 2015/861 (iodine), 2019/49 and 2019/804 (selenium), 2023/1455 (cobalt) and 2019/1965 (molybdenum for sheep). On 3 November 2026 their entries fall into four status groups: entries that run to a printed date, such as copper under 2018/1039 to 2028-08-13; entries past their printed expiry for which the EU Register records a renewal application; entries past their printed expiry with no register note; and entries given only by act and printed expiry. The table sets out each group by act.

For the zinc compounds 3b601, 3b603 to 3b608 and 3b612, the iodine compounds and dicopper chloride trihydroxide 3b409, no renewal act was found as of 3 November 2026 in a search of the EU Publications Office records. Implementing Regulation (EU) 2023/1455 granted cobalt 3b301, 3b302, 3b303 and 3b305 an urgent provisional authorisation under Article 15 after no renewal application was filed in time. How Article 14 renewals work is explained under EU feed additive regulation.

US status: GRAS sources under 582.80 and food additives under 573#

21 CFR 582.80 lists GRAS sources of cobalt, copper, iodine, iron, manganese and zinc, such as zinc oxide, copper sulfate, cobalt carbonate and potassium iodide, "at levels consistent with good feeding practice", with no federal numeric limit. Iron oxide is one of those GRAS iron sources, although Article 3 of Implementing Regulation (EU) 2017/2330 denies it as an EU nutritional additive.

Selenium sources are food additives under 21 CFR 573.920: sodium selenite or selenate at up to 0.3 ppm added selenium (about 0.27 g/ton) for chickens, swine, turkeys, sheep, cattle and ducks, with selenium yeast and the selenomethionine hydroxy analogue at the same level for chickens, turkeys, swine, beef and dairy cattle. Chromium propionate (573.304), chromium DL-methionine chelate (573.302) and calcium periodate (573.240) are the other food additives.

Food additive petitions and GRAS notices are explained under US feed additive regulation.

Use conditions: premixture route, drinking water, labelling and contaminants#

Zinc, copper, manganese, selenium, iodine and cobalt compounds enter EU feed only as a premixture, and three further use conditions apply: bans in water for drinking, label texts and contaminant ceilings. Labels follow the acts, such as the sheep poisoning warning on ovine feed above 10 mg/kg copper.

Water for drinking is closed to three elements: copper compounds must not be used in it (2018/1039, Article 2), iron compounds are prohibited (2017/2330, Article 2) and manganese compounds are denied for that use (2017/1490, Article 2). Treatment of livestock drinking-water systems is a separate topic.

Contaminant ceilings apply to the sources themselves under Directive 2002/32/EC (consolidated 2019-11-28): arsenic 30 mg/kg for compounds of trace elements (100 mg/kg for zinc oxide, manganous oxide and cupric oxide), cadmium 10 mg/kg and lead 100 mg/kg (400 mg/kg for zinc oxide). Dioxins are capped at 1.0 ng WHO-PCDD/F-TEQ/kg in trace elements. These ceilings sit with the other undesirable substances in feed.

Sourcing Checklist for Trace Mineral Sources#

Source a trace mineral in seven checks, from the identification number on the label to the contaminant certificate.

1. Confirm the EU identification number, element and species, or the US 582.80 or 573 listing (for example 3b405 for copper(II) sulphate pentahydrate).
2. Check the minimum element content against the act, such as 63.5 % iodine in calcium iodate anhydrous or 69 % in potassium iodide.
3. Ask for the chelated fraction and ligand of an organic source; zinc chelate of protein hydrolysates needs at least 85 % zinc chelated, measured by FTIR.
4. Ask for the X-ray diffraction result on the crystal form of a hydroxy source.
5. Request a certificate for arsenic, cadmium, lead and dioxins against Directive 2002/32/EC.
6. Ask which official method produced the certificate of analysis: EN 15510 (ICP-AES), EN 17053 (ICP-MS), EN 16159:2012 for selenium or EN 15111:2007 for iodine.
7. Ask for FAMI-QS certification or GMP+ certification, and for premix plant approval where copper or selenium premixtures are made.

A buyer should read "chelated" on a label as a claim to check against a specific EU chelate entry. For selenised yeast, a certificate should show both values the EU entries fix: selenium content and the selenomethionine share of total selenium.

Trace Mineral Questions#

Two questions about trace minerals come up when feed buyers move from the label to the trough.

Are trace mineral blocks good for cattle?#

A trace mineral block is mineral feed, a complementary feed with at least 40 % crude ash under Regulation (EC) No 767/2009, and its trace elements count toward the same EU total maxima as the rest of the ration. As a complementary feed, a block may carry at most 100 times the complete-feed maximum of each additive. In the US, free-choice salt-mineral mixtures for beef cattle may contain up to 120 ppm selenium, at an intake of no more than 3 mg per head per day (21 CFR 573.920).

Do chicken and fish feeds need vitamins as well as minerals?#

Yes: vitamins are a separate functional group of nutritional additives, and they often travel with trace minerals in one premixture, defined as "mixtures of feed additives or mixtures of one or more feed additives with feed materials or water used as carriers, not intended for direct feeding to animals".

In that shared premixture, sulphates act as pro-oxidants, while oxides, hydroxychlorides and chelates are less reactive. Requirements and stability of the vitamins themselves are covered under vitamins in animal feed.