Safety and efficacy of a feed additive consisting of zinc‐lysinate sulfate for all animal species (Phytobiotics Futterzusatzstoffe GmbH)

TL;DR

This study evaluates the safety and effectiveness of a zinc-based feed additive for all animal species, finding it safe for animals and ecosystems but not for marine environments.

Contribution

The study provides a comprehensive scientific evaluation of zinc-lysinate sulfate as a feed additive across all animal species.

Findings

Zinc-lysinate sulfate is safe for target species and terrestrial/freshwater ecosystems.

The additive is an effective source of zinc for all animal species.

It is irritating to skin and eyes and poses a sensitization risk.

Abstract

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Zinc‐lysinate sulfate (Plexomin® L‐Zn) as a nutritional feed additive for all animal species and categories. The applicant has provided evidence that, in essence, the additives under assessment comply with the proposed specifications. The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel) Panel concludes that zinc‐lysinate sulfate in animal nutrition under the conditions of use proposed is safe for the target species and for the terrestrial and freshwater ecosystems. No conclusion can be drawn on its safety for the marine environment. In the absence of adequate data on zinc deposition, the FEEDAP Panel cannot conclude on the safety of the additive for the consumer. The additive is irritant to the skin and eyes and is a dermal and respiratory sensitiser. Exposure of users by any route is considered a risk and should be minimised. The Panel concludes that the additive is an efficacious source of zinc for all animal species.

Tables

TABLE 1. Data on the batch‐to‐batch variation and main impurities of zinc‐lysinate sulfate. The data presented are average values and (range) for batch‐to‐batch variation and ranges for all other parameters. The number of batches analysed per parameter, or group of parameters are indicated in [].

Specifications
Zinc (%)	≥ 20
Lysine (%)	≥ 34
Moisture (%)	≤ 10
Batch‐to‐batch variation
Zinc (%) (1)	■■■■■ [8]
Lysine (%) (2)	■■■■■ [8]
Moisture (%)	■■■■■ [8]
Sulfate (%) (3)	■■■■■ [5]
Impurities	[3]
Lead (mg/kg)	< 0.50
Mercury (mg/kg)	< 0.02
Cadmium (mg/kg)	2.56–2.77
Arsenic (mg/kg)	< 0.50
Chloride (%)	2.37–2.40
Iodine (mg/kg)	39.30–40.50
Nickel (mg/kg)	19.30–21.10
Fluorine, detected as fluoride (mg/kg)	344–361
Iron (mg/kg)	538–574
Manganese (mg/kg)	1600–1690
Dioxins and furans (upper bound) (4)
PCDD/Fs (ng WHO2005‐TEQ/kg)	0.09
PCDD/Fs + PCBs (ng WHO2005‐TEQ/kg)	0.12
nDL‐PCBs (μg/kg)	1.70
Mycotoxins (μg/kg)
Aflatoxin B1	< 0.30
Microbial contamination	[3]
Salmonella spp. (per 25 g)	Not detected
Escherichia coli (per 1 g)	Not detected
Enterobacteriaceae (CFU/g)	< 10
Yeast and moulds (CFU/g)	< 100
Aerobic mesophilic bacteria (total plate count)	< 100–2000

TABLE 2. Data on physical properties of zinc‐lysinate sulfate. The number of batches analysed per parameter, or group of parameters are indicated in [].

Physical properties
Bulk density (kg/m3) (1)	800–1100
Solubility (g/L)	1.05–1.15 [3]
Dusting potential (Stauber Heubach) (mg/m3)	130–465 [3]
Zinc content in dust (%)	22.10–26.50 [3]
Particle‐size distribution (laser diffraction) (% of particles below, v/v)
100 μm	7.30–12.10 [3]
50 μm	3.20–6.0 [3]
10 μm	0.60–1.10 [3]
Particle‐size distribution of the dust (laser diffraction) (% of particles below, v/v)
50 μm	100 [3]
10 μm	36.0–56.0 [3]
Homogeneity (coefficient of variation, 12 subsamples %)
Starter feed, chickens	12.70
Grower feed, chickens	14.40

TABLE 3. Zinc content in the experimental diets offered to the experimental groups.

Source of zinc	Total Zn (mg/kg complete feed)
	Intended	Analysed
		Starter	Grower
■■■■■	■■■■■	■■■■■	■■■■■
■■■■■	■■■■■	■■■■■	■■■■■
	■■■■■	■■■■■	■■■■■
■■■■■	■■■■■	■■■■■	■■■■■
	■■■■■	■■■■■	■■■■■

TABLE 4. Effect of zinc‐lysinate sulfate on performance parameters and mortality, organ weights and blood parameters in chickens for fattening.

	Control	1×	4×
Mortality (%) (1)	■■■■■	■■■■■	■■■■■
Performance parameters (35 days)
Final body weight (g)	■■■■■	■■■■■	■■■■■
Average daily gain (g/day)	■■■■■	■■■■■	■■■■■
Average daily feed intake (g/day)	■■■■■	■■■■■	■■■■■
Feed to gain ratio	■■■■■	■■■■■	■■■■■
Organ weights (% body weight)
Colon	■■■■■	■■■■■	■■■■■
Haematological/biochemistry parameters (2)
Creatinine (mg/dL)	■■■■■	■■■■■	■■■■■
Gamma‐glutamyltransferase (IU/L)	■■■■■	■■■■■	■■■■■

TABLE 5. Zinc deposition in organs/issues (mg/kg dry matter) and zinc concentration in serum (mg/L).

	Treatment groups
	Control	Zinc‐lysinate sulfate 1×	ZnSO4 1×
Liver	■■■■■	■■■■■	■■■■■
Tibia	■■■■■	■■■■■	■■■■■
Breast muscle	■■■■■	■■■■■	■■■■■
Small intestine	■■■■■	■■■■■	■■■■■
Feathers	■■■■■	■■■■■	■■■■■
Serum	■■■■■	■■■■■	■■■■■

Full text

INTRODUCTION

1

Background and Terms of Reference

1.1

Regulation (EC) No 1831/20031 establishes the rules governing the Community authorisation of additives for use in animal nutrition. In particular, Article 4(1) of that Regulation lays down that any person seeking authorisation for a feed additive or for a new use of feed additive shall submit an application in accordance with Article 7.

The European Commission received a request from Phytobiotics Futterzusatzstoffe GmbH2 for the authorisation of the additive consisting of zinc‐lysinate sulfate when used as a feed additive for all animal species (category: nutritional additives; functional group: compounds of trace elements).

According to Article 7(1) of Regulation (EC) No 1831/2003, the Commission forwarded the application to the European Food Safety Authority (EFSA) as an application under Article 4(1) (authorisation of a feed additive or new use of a feed additive). The dossier was received on 22 August 2024 and the general information and supporting documentation are available at https://open.efsa.europa.eu/questions/EFSA‐Q‐2024‐00532. The particulars and documents in support of the application were considered valid by EFSA as of 03 January 2025.

According to Article 8 of Regulation (EC) No 1831/2003, EFSA, after verifying the particulars and documents submitted by the applicant, shall undertake an assessment in order to determine whether the feed additive complies with the conditions laid down in Article 5. EFSA shall deliver an opinion on the safety of the target animals, consumer, user and the environment and on the efficacy of the feed additive consisting of zinc‐lysinate sulfate, when used under the proposed conditions of use (see Section 3.1.3).

Additional information

1.2

The additive zinc‐lysinate sulfate has not been previously authorised as a feed additive in the European Union.

DATA AND METHODOLOGIES

2

Data

2.1

The present assessment is based on data submitted by the applicant in the form of a technical dossier3 in support of the authorisation request for the use of zinc‐lysinate sulfate as a feed additive.

The confidential version of the technical dossier was subject to a target consultation of the interested Member States from 08 January 2025 to 08 April 2025; the comments received were considered for the assessment.

In accordance with Article 38 of the Regulation (EC) No 178/20024 and taking into account the protection of confidential information and of personal data in accordance with Articles 39 to 39e of the same Regulation, and of the Decision of EFSA's Executive Director laying down practical arrangements concerning transparency and confidentiality,5 a non‐confidential version of the dossier has been published on Open.EFSA.

According to Article 32c(2) of Regulation (EC) No 178/2002 and to the Decision of EFSA's Executive Director laying down the practical arrangements on pre‐submission phase and public consultations, EFSA carried out a public consultation on the non‐confidential version of the technical dossier from 02 May to 23 May 2025 for which no comments were received.

The FEEDAP Panel used the data provided by the applicant together with data from other sources, such as previous risk assessments by EFSA or other expert bodies, peer‐reviewed scientific papers, other scientific reports and experts' (elicitation) knowledge, to deliver the present output.

EFSA has verified the European Union Reference Laboratory (EURL) report as it relates to the methods used for the control of the zinc‐lysinate sulfate in animal feed.6

Methodologies

2.2

The approach followed by the FEEDAP Panel to assess the safety and the efficacy of zinc‐lysinate sulfate is in line with the principles laid down in Regulation (EC) No 429/20087 and the relevant guidance documents: Guidance on the assessment of the safety of feed additives for the consumer (EFSA FEEDAP Panel, 2017a), Guidance on the identity, characterisation and conditions of use of feed additives (EFSA FEEDAP Panel, 2017b), Guidance on the assessment of the safety of feed additives for the target species (EFSA FEEDAP Panel, 2017c), Guidance on the assessment of the safety of feed additives for the environment (EFSA FEEDAP Panel, 2019), Guidance on the assessment of the safety of feed additives for the users (EFSA FEEDAP Panel, 2023), Guidance on the assessment of the efficacy of feed additives (EFSA FEEDAP Panel, 2024).

ASSESSMENT

3

The additive zinc‐lysinate sulfate is intended to be used as a nutritional additive (functional group: compounds of trace elements) as a source of zinc in feed for all animal species and categories.

Characterisation

3.1

Characterisation of the additive

3.1.1

The additive zinc‐lysinate sulfate is a 1:1 complex of l‐lysine and zinc sulfate hydrate. This complex tends to crystallise from water as a hydrate. Its chemical formula is C_6_H_14_N_2_O_6_SZn · 1H_2_O, corresponding to a molecular weight of 325.64 g/mol. International Union of Pure and Applied Chemistry (IUPAC) chemical name is Aqua(l‐lysinato‐κN^2^,κO^1^)[sulfato(2‐)‐κO]zincate(1‐) and Chemical Abstracts Service (CAS) number is 1007631‐69‐7.8

The applicant provided analytical data with infrared (IR) spectroscopy that showed the formation of a complex between zinc sulfate and l‐lysine.9

The product is specified to contain a minimum of 20% Zn and 34% lysine and a maximum of 10% moisture. The data provided by the applicant on the batch‐to‐batch variation,10 main impurities11 and physical properties12 of the additive are reported in Tables 1 and 2.

The data provided showed compliance with the proposed specifications for zinc‐lysinate sulfate, except for two batches in which the zinc value was slightly below the specification. The FEEDAP Panel considers that microbial contamination and the amounts of the detected impurities do not raise safety concerns, except nickel which is further addressed in the user safety section (Section 3.2.3).

Manufacturing process

3.1.2

The additive is produced by mixing the raw ingredients ■■■■■.13 ■■■■■14 ■■■■■15 ■■■■■.

Conditions of use

3.1.3

The additive is intended to be used in feed for all animal species and categories up to the current maximum authorised contents of zinc (total) in complete feed:

• –Dogs and cats: 200 mg/kg
• –Salmonids and milk replacers for calves: 180 mg/kg
• –Piglets, sows, rabbits and all fish other than salmonids: 150 mg/kg
• –Other species and categories: 120 mg/kg

The additive is intended to be incorporated in feed in the form of a premixture.

Safety

3.2

Safety for the target species

3.2.1

The applicant provided a combined tolerance and efficacy (bioavailability) study with zinc‐lysinate sulfate in chickens for fattening to support the safety for the target species.16 ■■■■■ ■■■■■ ■■■■■ ■■■■■17 ■■■■■18 ■■■■■

■■■■■

Mortality was low and not affected by zinc‐lysinate sulfate supplementation. No differences were observed in the zootechnical performance parameters between groups. The average daily gain and the average daily feed intake showed not to be inferior in the overdose groups compared to the control.

Relative organ weights were generally comparable among groups. A small, dose‐related decrease in relative colon weight was observed, reaching statistical significance at the overdose level compared to the control. No histopathological examination was performed. However, the absence of histopathology was not considered critical as the magnitude of the change was small and no macroscopic lesions were reported.

Regarding the blood parameters the only relevant differences related to a dose‐dependent reduction of creatinine and gamma‐glutamyltransferase with increasing levels of the additive, which became significant at the overdose level compared to the control. However, values remained within physiological ranges and were not considered adverse.

Based on the results of the tolerance study, the Panel concludes that the additive is safe for chickens for fattening at the maximum authorised level of zinc in feed. This conclusion is extrapolated to all animal species and categories at the respective maximum authorised levels in the EU for total zinc in feed.3, 4

Safety for the consumer

3.2.2

l‐Lysine and zinc sulfate hydrate, ■■■■■, are feed additives authorised in the EU and their safety has been established. Since the complex is expected to dissociate under physiological conditions into lysine, zinc(II) and sulfate ions, the FEEDAP Panel considers that Zn only is of interest for the safety for the consumer.

The toxicological profile of zinc compounds have been extensively described by the Scientific Committee on Food (SCF) (EC, 2003), Sandstead (2015) and the FEEDAP Panel (EFSA FEEDAP Panel, 2012, 2015). Depressed zinc uptake with associated zinc deficiency is the most sensitive and well characterised effect of chronic excess of zinc intake in humans and animals. No substantial toxicological differences between inorganic and organic zinc compounds are expected.

A tolerable upper intake level (UL) for zinc of 25 mg/day in adults was previously established by SCF (EC, 2003).

Assessment of consumer exposure

3.2.2.1

Zinc deposition data following the use of the additive were available from the combined tolerance/efficacy study conducted with zinc‐lysinate sulfate in chickens for fattening (Section 3.3; Table 5). The experimental groups in the study were the negative control and the groups supplemented with zinc‐lysinate sulfate or zinc sulfate at the maximum authorised use level (120 mg Zn/kg complete feed). Samples of muscle (breast), liver, bone (tibia), small intestine and feathers (interscapular feathers) were collected at the end of the study (35 days) and analysed for zinc content. Zinc deposition in skin/fat and kidney was not measured in the study.

Detailed results on the zinc deposition are reported in the efficacy section (Section 3.3; Table 5). No statistically significant differences on zinc deposition in liver and muscle were observed between the groups supplemented with zinc and the control. Additionally, zinc deposition in animals receiving the additive under assessment was equivalent and not statistically different to the one observed in the animals fed zinc sulfate.

The applicant conducted a literature search to retrieve relevant information related to zinc deposition in skin/fat and kidney and provided some explanation on zinc homeostasis regulation, absorption and deposition.19 Some papers were retrieved reporting the following: (i) a moderate increase of zinc in feed would not significantly influence the zinc deposition in liver and kidney in chickens for fattening (Weigand & Kirchgessner, 1980); (ii) kidney is not the main target organ for zinc deposition (Brugger & Windisch, 2019); and (iii) similar zinc deposition in liver and kidney in different animal species (Sandoval et al., 1997, 1999).

However, the FEEDAP Panel considered that the lack of deposition data in skin/fat and kidney in chickens for fattening and the lack of information on any other relevant target species, coming from experimental studies conducted with the additive under assessment at the proposed conditions of use, represents a data gap which prevents the FEEDAP Panel to perform a complete consumer exposure assessment.

Conclusions on the safety for the consumers

3.2.2.2

Due to the lack of adequate data on possible zinc deposition in the relevant tissues and products of animals fed with the additive under assessment, the FEEDAP Panel cannot conclude on the safety of zinc‐lysinate sulfate for the consumers.

Safety for the user

3.2.3

The FEEDAP Panel notes that the additive contains nickel (Section 3.1.1). The European Directive (EU) 2022/43120 set an occupational exposure limit (OEL) of 0.01 and 0.05 mg/m^3^ for both respirable and inhalable fraction, respectively as nickel meets the criteria for classification as carcinogenic (category 1A). Due to the presence of nickel, the additive should be considered as a skin and respiratory sensitiser.

The skin irritation potential of the additive was tested in a study performed according to the OECD Testing Guideline (TG) 439 which showed that the additive is a skin irritant (UN GHS Category 1 or 2).21

The eye irritation potential of the additive was tested in a study performed according to the OECD TG 437. Based on the results obtained, no stand‐alone prediction can be made.22

Considering that the additive is a skin irritant, it should also be regarded as an eye irritant.

Conclusions on safety for the user

3.2.3.1

The additive is irritant to the skin and eyes and is a dermal and respiratory sensitiser. Exposure of users by any route is considered a risk and should be minimised.

Safety for the environment

3.2.4

The additive under assessment contains zinc, l‐lysine and sulfate. The environmental risk assessment is made assuming that the whole amount of the additive ingested by the animals is excreted.

Sulfates are naturally abundant in the environment, and the use of the additive will not result in a substantial increase above its background concentration under the current conditions of use.

The amino acid l‐lysine is a physiological and natural component in animals and plants. When supplemented to feed, as component of the additive under assessment, it will be incorporated into animal proteins and any potential excess will be catabolised and excreted.

To assess the environmental risk of zinc from the additive, the Panel compared the worst‐case predicted environmental concentrations (PECs), calculated at the maximum authorised level of zinc, with the natural background concentration considered as 90th percentile value from FOREGS database (FOREGS, 2025).23 If the predicted concentrations (PECs) fall below 10% of this value, no further risk assessment is needed. Determination of the natural background concentration for metals in water is described in the Guidance for implementing environmental quality standards (EQSs) for metals, by the Water Framework Directive implementation strategy.24

In Europe, the soil concentration of zinc in 834 topsoil samples collected throughout Europe for the FOREGS survey ranged from < 3.0 to 2900 mg/kg, with 90th percentile at 111 mg Zn/kg soil dry weight (dw).

The 90th percentile concentration of zinc in freshwater obtained from occurrence data from 807 water samples collected throughout Europe for the FOREGS survey was 10.2 μg Zn/L (FOREGS, 2005).25

According to the Oslo and Paris Conventions (OSPAR) commission (2014), the natural background concentration of Zn in the marine sediment is 90 mg/kg. From the study by Monteiro, the median background zinc concentration in the marine sediment from different EU countries was 140 mg/kg (Monteiro et al., 2010).

The worst‐case PEC_soil_ after 1 year application calculated at the maximum authorised level is 2.7 mg Zn/kg soil dw for veal calf fed milk replacer. Since the PEC_soil_ is far below 11.1 mg/kg (10% of the natural background concentration), no concern is expected for terrestrial compartment at the proposed level of use for all animal species.

Calculated PEC_swaq_ is 0.38 μg/L for aquaculture, which is below 10.2 μg/L. The risk to surface freshwater is acceptable when using zinc in aquaculture feed on land‐based fish farms under the current conditions of use.

Calculated PEC_sed_ in marine sediment is 397 mg/kg dw. Considering the background concentration of 90 mg Zn/kg, as reported by Ospar Commission (OSPAR Commission, 2014), the use of the additive in sea cage‐based fish farming may pose a risk to marine environment. The data available does not allow to conclude on the safety of the additive when used in sea cages.

Conclusions on safety for the environment

3.2.4.1

The use of the additive in animal nutrition for terrestrial animals and land‐based aquaculture at the proposed use levels is considered safe for terrestrial and freshwater ecosystems. The available data do not allow to conclude on the safety of the additive for the environment when used in sea cages.

Efficacy

3.3

The applicant provided a combined tolerance/efficacy study in chickens for fattening (see Section 3.2.1)26 in which zinc deposition in liver, breast muscle, tibia, small intestine and feathers as well as serum levels of zinc were measured (Table 5). The experimental groups in the study were the negative control and the groups supplemented with zinc‐lysinate sulfate or zinc sulfate (ZnSO_4_) at the maximum authorised use level (120 mg Zn/kg complete feed).

No differences in performance were observed (1–35 days period) among the experimental groups (see Section 3.2.1).27 Regarding zinc deposition, no differences were observed between the experimental groups in zinc concentration in liver, breast muscle, small intestine or serum, which is consistent with the tight homeostatic regulation of zinc when dietary requirements are met (Table 5). However, the zinc‐lysinate sulfate group showed significantly higher zinc deposition in tibia and feathers. Bone is a well‐recognised target tissue reflecting long‐term zinc supply and bioavailability, whereas zinc deposition in feathers reflects incorporation into keratinised tissues during growth. The zinc deposition in tibia and feathers was similar between the two sources of zinc, and in both cases higher than the control, indicating that zinc from zinc‐lysinate sulfate is bioavailable.

The data submitted provides evidence of higher zinc deposition in bones and feathers in the zinc‐lysinate sulfate group supplemented birds relative to the unsupplemented group. Therefore, the Panel concludes that the additive is an efficacious source of zinc. This conclusion is extrapolated to all animal species and categories.

Post‐market monitoring

3.4

The FEEDAP Panel considers that there is no need for specific requirements for a post‐market monitoring plan other than those established in the Feed Hygiene Regulation28 and Good Manufacturing Practice.

CONCLUSIONS

4

The use of feed zinc‐lysinate sulfate in animal nutrition under the conditions of use proposed is safe for the target species and for the terrestrial and aquatic ecosystems. However, no conclusion can be drawn on its safety for the marine environment.

In the absence of adequate data on the Zn deposition, the FEEDAP Panel cannot conclude on the safety of the additive for the consumer.

Regarding user safety, the additive is irritant to the skin and eyes and is a dermal and respiratory sensitiser. Exposure of users by any route is considered a risk and should be minimised.

The Panel concludes that the additive is an efficacious source of zinc for all animal species.

ABBREVIATIONSADFIaverage daily feed intakeADGaverage daily gainADIacceptable daily intakeBWbody weightCASChemical Abstracts ServiceCDCommission DecisionCDGchemically defined groupCGchemical groupCVcoefficient of variationDMdry matterECHAEuropean Chemicals AgencyEURLEuropean Union Reference LaboratoryFEEDAPEFSA Scientific Panel on Additives and Products or Substances used in Animal FeedIUPACInternational Union of Pure and Applied ChemistryLODlimit of detectionLOQlimit of quantificationMWmolecular weightnDL PCBsnon‐dioxin‐like PCBsOECDOrganisation for Economic Co‐operation and DevelopmentPCBspolychlorinated biphenylsPCDDspolychlorinated dibenzo‐p‐dioxinsPCDFspolychlorinated dibenzofuransSCFScientific Committee on FoodTEQtoxic equivalent factors for dioxins, furans and dioxin‐like PCBsWHOWorld Health Organization

REQUESTOR

European Commission

QUESTION NUMBER

EFSA‐Q‐2024‐00532

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PANEL MEMBERS

Roberto Edoardo Villa, Giovanna Azimonti, Eleftherios Bonos, Henrik Christensen, Mojca Durjava, Birgit Dusemund, Ronette Gehring, Boet Glandorf, Maryline Kouba, Marta López‐Alonso, Francesca Marcon, Carlo Nebbia, Alena Pechová, Miguel Prieto‐Maradona and Katerina Theodoridou.

LEGAL NOTICE

Relevant information or parts of this scientific output have been blackened in accordance with the confidentiality requests formulated by the applicant pending a decision thereon by EFSA. The full output has been shared with the European Commission, EU Member States (if applicable) and the applicant. The blackening may be subject to review once the decision on the confidentiality requests is adopted by EFSA and in case it rejects some of the confidentiality requests.