Safety and efficacy of a feed additive consisting of butylated hydroxyanisole (BHA) for use in cats (FEDIAF).

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of butylated hydroxy anisole (BHA) when used as a technological additive (antioxidant) in feed for cats. BHA is a waxy solid consisting for > 98.5% of the active substance, a mixture of 3-tert-butyl-4-hydroxyanisole and 2-tert-butyl-4-hydroxyanisole and is currently authorised for use in all animal species except in cats. In support of the safety of the additive for the target species, the applicant has submitted a tolerance study which demonstrated that BHA is tolerated by cats at a concentration up to 150 mg/kg complete feed. The additive should be considered a skin, eye irritant and a potential skin sensitiser. Exposure of the user via inhalation was considered unlikely; therefore, a risk is not expected. BHA is authorised as an antioxidant for food use at comparable use levels; therefore, no studies were required to demonstrate the efficacy of BHA as an antioxidant in complete feed for cats.

Introduction

Background and Terms of Reference as provided by the requestor

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 a feed additive shall submit an application in accordance with Article 7.

The European Commission received a request from FEDIAF2 for authorisation of the additive consisting of butylated hydroxyanisole (BHA), when used as a feed additive for cats (category: technological additive; functional group: antioxidants).

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 particulars and documents in support of the application were considered valid by EFSA as of 26 February 2021.

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 for the target animals and user and on the efficacy of the product butylated hydroxyanisole (BHA), when used under the proposed conditions of use (see Section 3.1.1).

Additional information

The additive butylated hydroanisole (BHA), hereinafter referred to as BHA, is currently authorised as a technological additive in feed for all animal species other than cats with a maximum content of 150 mg/kg complete feed.3

In 2018, EFSA issued an opinion on the safety and efficacy of BHA when used as a feed additive for all animal species (EFSA FEEDAP Panel, 2018a,b) and another opinion on the safety of BHA in cats (EFSA FEEDAP Panel, 2019).

BHA is authorised according to Directive 95/2/EC14 as a food additive (antioxidant), up to a maximum level of 400 mg/kg. The Scientific Committee on Food (SCF), the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and EFSA ANS Panel have delivered several opinions on the use of BHA as a food additive (JECFA, 1974, 1976, 1982, 1986, 1987, 1989, 1999, 2006; SCF, 1989; EFSA ANS Panel, 2011, 2012).

Data and methodologies

Data

The present assessment is based on data submitted by the applicant in the form of a technical dossier5 in support of the authorisation request for the use of BHA as a feed additive.

The European Union Reference Laboratory (EURL) considered that the conclusions and recommendations reached in the previous assessment regarding the methods used for the control of BHA in animal feed are valid and applicable for the current application.6

Methodologies

The approach followed by the FEEDAP Panel to assess the safety and the efficacy of BHA is in line with the principles laid down in Regulation (EC) No 429/20087 and the relevant guidance documents: Guidance on studies concerning the safety of use of the additive for users/workers (EFSA FEEDAP Panel, 2012), Guidance on the identity, characterisation and conditions of use of feed additives (EFSA FEEDAP Panel, 2017a), Guidance on the assessment of the safety of feed additives for the target species (EFSA FEEDAP Panel, 2017b) and Guidance on the assessment of the efficacy of feed additives (EFSA FEEDAP Panel, 2018a,b).

Assessment

The additive under assessment, BHA, is intended to be used as a feed additive (category: technological additives; functional group: (b) antioxidants) in complete feed for cats.

The additive is currently authorised for use in feeding stuffs for all animal species other than cats.

Characterisation

The active substance BHA is identical to the additive. BHA is a white, waxy solid (white to cream coloured flakes) with a characteristic odour and consists of a mixture of 3‐tert‐butyl‐4‐hydroxyanisole and 2‐tert‐butyl‐4‐hydroxyanisole.

The additive has been characterised in a previous opinion of the FEEDAP Panel (EFSA FEEDAP Panel, 2018a,b). New information has been submitted on the composition and impurities, which is presented below.

The additive is specified to contain at least 98.5% of BHA (International Union of Pure and Applied Chemistry (IUPAC) name: 2‐tert‐butyl‐4‐hydroxyanisole and 3‐tert‐butyl‐4‐hydroxyanisole, Chemical Abstracts Service (CAS) number 25013‐16‐5, chemical formula C11H16O2, and molecular weight 180.25 Da) and not less than 85% of the 3‐tert‐butyl‐4‐hydroxyanisole isomer. These specifications are in line with the current authorisation of BHA as a feed additive for all animal species except cats8 and also as food additive.9

The analysis of six batches of the additive resulted in a mean content of BHA ■■■■■ and of 3‐tert‐butyl‐4‐hydroxyanisole of ■■■■■10 in compliance with the existing specifications.

The same batches were analysed for possible presence of impurities, including heavy metals. Arsenic, lead, mercury, cadmium and fluorine were below the respective limit of detection (LOD)■■■■■ in all the batches analysed. ■■■■■ Based on the results obtained, no concern is expected from the possible presence of the tested impurities.

Conditions of use

BHA is intended to be used as an antioxidant in complete feed for cats with a maximum content of 150 mg/kg complete feed (alone or in combination with butylated hydroxytoluene (BHT)).

Safety

Safety for cats

In its previous opinion (EFSA FEEDAP Panel, 2018a,b), the Panel concluded that ‘a weight of evidence’ of the limited data supports that 150 mg BHA/kg complete feed would be a safe dose for all animal species. However, a possible exception could be the cat, with its known lower capacity for glucuronidation of phenolic compounds and for which no specific data were available.’ Following the submission of new information to support the safety for cats (a review of the literature on of the metabolism of phenolic compounds in cats and an in vivo study with cats), the FEEDAP Panel issued another opinion on BHA (EFSA FEEDAP Panel, 2019) and concluded that ‘No specific information on metabolic fate of BHA has been made available for the feline species’. The lack of knowledge is of particular relevance considering the additional load of phenolic compounds by dietary BHA for the full lifetime expectancy of cats. Considering the lack of information on the metabolism of BHA in cats and the absence of a well‐designed tolerance study, the FEEDAP Panel confirms its previous assessment on the safety of BHA for cats. Consequently, the Panel reiterates that no safe concentration of BHA in complete feed for cats could be established’.

In the current application, the applicant has submitted a tolerance study conducted in cats.12

Sixty healthy cats (both males and females, aged 3–10 years, body weight at start: 2–7 kg) were allocated to four experimental groups (15 animals/group) which were balanced for body weight, age, gender and housing room.13 The cats were group housed in common rooms, but at the time of feeding (twice a day) they were housed individually. Water was available for ad libitum intake. An acclimatisation period of 4 weeks took place prior to the start of the study where the same diet was offered to all cats. The groups were fed a control diet (without supplemental BHA), or diets supplemented with BHA at 150 mg BHA/kg feed (1× maximum proposed level), 450 mg BHA/kg feed (3×) or 750 mg BHA/kg feed (5×), respectively. The intended BHA levels were analytically confirmed (< 10, 202, 451 and 857 mg/kg as average of 3 samples taken at start, middle and end of production). The trial lasted 28 days.

All four treatment diets were identical in composition (same batch) except for the inclusion level of BHA which was applied as spray post‐extrusion. ■■■■■■■■■■■■■■■

General health status and behaviour of the cats was observed at least twice a day. Faecal consistency was monitored and scored (using a 1–5 classification scale)15 at the group level throughout the study, any vomiting was recorded. Feed intake was recorded daily. Body weight and body condition scores were recorded weekly. Blood samples were taken from fasted animals before start of the study, and at days 7, 14 and 28. All samples were analysed for biochemistry parameters,16 the samples before start and from day 28 also for additional biochemistry parameters17 and for haematology.18

Alanine aminotransferase (ALT) and alkaline phosphatase (ALP), considered as key liver health markers, and symmetric dimethyl arginine (SDMA), creatinine and urea, kidney health markers, were the primary parameters for the study. Body weight and feed intake were considered secondary parameters.

The study was powered to detect a 1.6‐fold change19 between control and test diets at the final sampling occasion for the primary parameters and a 1.2‐fold change within each diet between baseline and final sample for the secondary parameters. The P‐values were unadjusted and then tested against 10% significance divided by the number of test diets (3). Equivalence tests in the form of TOST (two‐one‐sided T‐tests) were carried out for primary and secondary parameters. Equivalence was defined as when both p‐values ≤ 0.033.

No mortality was recorded during the study. An initial not significant decrease in feed intake of the 5 × BHA overdose group was observed; however, this was transient, recovering over the 28‐day study period. Two cats from 5× BHA were removed from the study (at days 4 and 17, due to reduced feed intake, reduction > 10% compared to baseline, data not provided). The applicant suggested that the effect on feed intake could be probably due to a palatability issue. Faecal scores remained consistent for all the cats during the whole study, except for one cat (in the treated group 150 mg/kg feed) that had several occasions of poor faeces, lasting not more than 1 day. Only one case of vomiting was reported in a cat in the control group.

ALP and ALT remained with their 95% confidence intervals below the upper reference ranges for all cats throughout the full study period. Within each group, results of ALP and ALT were equivalent between the values measured before study start and at study end (p ≤ 0.033). Comparisons with each BHA supplemented group to the control (before the study: 24.2; study end: 24.6 IU/L) revealed equivalence for all groups for ALP (p ≤ 0.033). For ALT, equivalence was seen for both the BHA use level and BHA 5× overdose groups when compared to the control (p ≤ 0.033) (before the study: 47.8; study end: 40 IU/L for BHA use level and before the study: 44.3 and study end: 47.4 IU/L for BHA 5 ×); but was not significant for the 450 mg BHA diet (3 ×) (before the study: 45; study end: 54.9 IU/L) (p > 0.033). The latter finding is not considered BHA‐related since equivalence for the higher dose group was shown.

Creatinine and urea, expressed as blood urea nitrogen (BUN), remained with their 95% confidence intervals within the normal reference ranges, and within individual groups both parameters were equivalent between study start and study end (p ≤ 0.033). Comparisons between the BHA supplemented groups and the control group indicated equivalence (BUN, before the study: 7.9; study end: 8.2 mmol/L; creatinine, before the study: 135; study end: 128 μmol/L) (p ≤ 0.033).

SDMA levels for some cats were above the upper reference range throughout the study, this was seen already before study start, across all sampling occasions and was not unique to a single group. Equivalence analysis confirmed that there was no change of SDMA values before study start (11.4 μg/dL) to those at study end (11.5 μg/dL), nor were differences detected between the groups with BHA supplemented feed and the control group (p ≤ 0.033) (Table 1).

Table 1

Liver and kidney health marker before study start and at study end (n = 15/group, except the group with 750 mg supplemental BHA/kg with n = 13)

Parameters evaluated		Intended supplemental BHA (mg/kg feed)
		0	150	450	750
ALP (IU/L)a	Before study start	24.2	26.1	25.2	21.9
	Study end	24.6	27.6	27.8	23.3
ALT (IU/L)b	Before study start	47.8	41.1	45.0	44.3
	Study end	40.0	38.3	54.9	47.4
Urea (BUN in mmol/L)c	Before study start	7.9	8.3	8.2	7.4
	Study end	8.2	8.7	8.8	8.4
Creatinine (μmol/L)d	Before study start	135	148	143	133
	Study end	128	133	132	132
SDMA (μg/dL)e	Before study start	11.4	12.1	11.3	10.4
	Study end	11.5	11.7	11.6	11.4

ALT: alanine aminotransferase; ALP: alkaline phosphatase; BUN: blood urea nitrogen; SDMA: symmetric dimethyl arginine.

Parameter reference range: ALP 12–59 IU/L.

Parameter reference range: ALT 27–158 IU/L.

Parameter reference range: BUN 5.7–13.2 μmol/L.

Parameter reference range: creatinine 80–221 μmol/L.

Parameter reference range: SDMA 0–14 μg/dL.

All other additional biochemistry and haematology parameters including their 95% confidence limits were, with few and not relevant exceptions (for the lower and upper 95% confidence limits), within the reference ranges.

Equivalence testing did not identify differences in feed intake during the test period (p ≤ 0.033) for any group. Comparisons of feed intake between BHA supplemented groups and the control group indicated equivalence too (p ≤ 0.033). These findings were also reflected in the body weight data during the test period, with no differences within or between group detected (before the study: 4.7; study end: 4.7 kg) (p ≤ 0.033) (Table 2).

Table 2

Feed intake (weekly average) and body weight (n = 15/group, except the group with 750 mg supplemental BHA/kg with n = 13)

Parameters evaluated		Intended supplemental BHA (mg/kg feed)
		0	150	450	750
Feed Intake (g/kg bw)	Before study start	10.1	10.0	9.2	10.4
	Week 1	11.4	11.1	9.7	8.9
	Week 2	11.6	11.1	9.9	9.9
	Week 3	11.2	11.0	10.0	9.9
	Week 4	11.5	11.1	10.4	10.0
Body weight (kg)	Before study start	4.7	4.9	5.3	4.5
	Week 1	4.8	4.9	5.3	4.4
	Week 2	4.8	4.9	5.3	4.4
	Week 3	4.8	4.9	5.3	4.4
	Week 4	4.7	4.9	5.3	4.4

bw: body weight.

Conclusions on safety for cats

The results of the tolerance study indicate that dietary BHA levels up to the fivefold overdose were tolerated by cats. Therefore, the FEEDAP Panel concludes that 150 mg BHA/kg complete feed, the highest proposed feed concentration, is safe for cats.

Safety for user

The safety of BHA has been evaluated in a previous EFSA opinion (EFSA FEEDAP Panel, 2018a,b). No new data have been submitted that would allow to reconsider the conclusions previously reached. The additive should be considered a skin and eye irritant and a potential skin sensitiser. Exposure of the user via inhalation is considered unlikely due to the lack of dusting potential; therefore, a risk is not expected.

Efficacy

BHA is authorised to be added as an antioxidant to foods with a wide range of moisture content at concentrations of 40–400 mg/kg. Since the same effect can be reasonably assumed for complete feed, no studies are required to demonstrate the efficacy of BHA as an antioxidant in complete feed for cats.

Conclusions

The FEEDAP Panel considers the use of BHA at concentrations up to 150 mg/kg complete feed to be safe for cats.

The additive should be considered a skin and eye irritant and a potential skin sensitiser. Exposure of the user via inhalation is considered unlikely; therefore, a risk is not expected.

Since BHA is authorised as an antioxidant for food use at comparable use levels, no studies are required to demonstrate the efficacy of BHA as an antioxidant in complete feed for cats.

Documentation as provided to EFSA/Chronology

Abbreviations

alkaline phosphatase

alanine aminotrasferase

EFSA Scientific Panel on Additives and Nutrient Sources added to Food

butylated hydroxy anisole

butylated hydroxytoluene

blood urea nitrogen

body weight

Chemical Abstracts Service

Panel on Additives and Products or Substances used in Animal Feed

International Union of Pure and Applied Chemistry

The Joint FAO/WHO Expert Committee on Food Additives

limit of detection

Scientific Committee on Animal Nutrition

Scientific Committee on Food

symmetric dimethyl arginine

World Health Organization

Date	Event
22/09/2020	Reception of the Evaluation report of the European Union Reference Laboratory for Feed Additives
10/11/2020	Dossier received by EFSA. Butylated hydroxyanisole (BHA) for cats. Submitted by FEDIAF.
20/11/2020	Reception mandate from the European Commission
26/02/2021	Application validated by EFSA – Start of the scientific assessment
27/05/2021	Comments received from Member States
23/06/2021	Opinion adopted by the FEEDAP Panel. End of the Scientific assessment