Registration Dossier

Toxicological information

Repeated dose toxicity: oral

Currently viewing:

Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 September 2013 - 15 December 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report Date:
2014

Materials and methods

Principles of method if other than guideline:
The aim of the study was to evaluate the tolerance of weaned piglets to Butylated Hydroxytoluene (BHT) as technological feed additive (E 321). The trial was carried out with 144 weaned piglets weighing 7.66 (± 0.89) kg/head at the start of the study. The feeding treatments were: 1) Control group T1: animals fed basal diet; 2) T2: animals fed basal diet (T1) supplemented with BHT at 150 g/tonne feed (recommended dose); 3) T3: animals fed basal diet (T1) supplemented with BHT at 1000 g/tonne feed (6.7x
recommended dose) and 4) T4: animals fed basal diet (T1) supplemented with BHT at 1500 g/tonne feed (10x recommended dose). The feeds were issued to the appropriate pens for 42 consecutive days (between day 0 and day 42 of the trial). Each feeding treatment was replicated in 9 pens (5 pens of castrated males and 4 pens of female piglets) with 4 animals of the same gender per pen. The data recorded during the feeding phase were live weight (LW) at 0, 14 and 42 days from the start of the study; average daily gain (ADG), daily feed intake and feed:gain ratio (F:G) during the periods 0-14; 14-42 and 0-42 days from the start of the study; blood haematology and biochemistry parameters at D0 and D43.
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
pig
Strain:
other: Goland x Italian Duroc boar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Az. Agr. Guida di Valtulini Cristina – Fabio e Giovanna S.S. Soc. Agricola, Cascina Guida – 26020 Cappella Cantone (CR), Farm code: 076 CR 032.
- Age at study initiation: 28 days of age approx.
- Weight at study initiation: 7.66 (± 0.89) kg
- Fasting period before study:
- Housing: Grouped, 4 piglets per pen (total of 36 pens). The animals were placed in 5 cleaned, disinfected weaning rooms. In rooms 1 to 4 six pens are aligned in one row with a lateral corridor, 1.0 m wide. In room 5 there are 12 pens arranged in two rows separated by a corridor of 1.0 m wide. For animal health reasons, the weaning rooms are managed according to an “all in – all out” system, with at least 7 days between weaning batches.
- Diet (e.g. ad libitum): Ad libitum (steel feeders).
- Water (e.g. ad libitum): Ad libitum (nipple drinkers).
- Acclimation period: 4 days (medicated feed with amoxicillin and colisting).

DETAILS OF FOOD AND WATER QUALITY: See Table no. 1 below.

ENVIRONMENTAL CONDITIONS :
- Temperature (°C): Within specifications.
- Humidity (%): Within specifications.
*The temperature and relative humidity was recorded every 30 minutes during each day of the trial by a computerised automatic system.
- Air changes (per hr): The ventilation rate varied from 0 m3/hour to the maximum ventilation rate required, according to the desired temperature and the age of the
piglets.
- Photoperiod (hrs dark / hrs light): During the whole study period the lighting scheme was natural.

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
- PREPARATION OF DOSING SOLUTIONS:
The test producttreated feeds differed only in test product addition from the T1 control feed. The test product was included as dry product by mixing with part of the basal diet. This mixture was added to the rest of the basal diet. All control feeds (those containing no test products) were made before the test product containing feeds.
Duration of treatment / exposure:
42 days (pre-starter period from day 0 to 14 and starter period from day 14 to 42).
Frequency of treatment:
Daily
Doses / concentrationsopen allclose all
Dose / conc.:
0 other: g/tonne feed
Dose / conc.:
150 other: g/Tonne feed (recommended use level)
Remarks:
ca. 4.6-6.5 mgBHT/kg bw
Dose / conc.:
1 000 other: g/Tonne feed (6.7 x recommended use level)
Remarks:
ca. 29.7-42.1 mgBHT/kg bw
Dose / conc.:
1 500 other: g/tonne feed (10 x recommended use level)
Remarks:
ca. 47.2-61.0 mgBHT/kg bw
No. of animals per sex per dose:
20 castrated pigs and 16 females per dose (divided in 4 replicates each).
Control animals:
yes, plain diet
Details on study design:
- Dose selection rationale: Not available.
- Rationale for animal assignment (if not random): Random.
- Rationale for selecting satellite groups: Not applicable.
- Post-exposure recovery period in satellite groups: Not applicable.
- Section schedule rationale (if not random): Random.

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS/CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily, in the morning and in the afternoon.
- Parameters: General health status, ensuring constant feed and water supply as well as checking for the correct temperature and ventilation.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Health/illness and diarrhoea was scored daily. Culling and mortality alongside the reason for culling and probable cause of mortality were recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual and mean pen weight of the animals at day 0, 14, and 42.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes
Mean pen feed intake at days 14 and 42 for to calculate the feed intake in the periods D0-D14, D14-D42 and D0-D42

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes. Mean daily gain and feed:gain ratio, calculated per pen

HAEMATOLOGY: Yes / No / Not specified
- Time schedule for collection of blood: At time 0 and at the end of the trial (D43).
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Not specified
- How many animals: At time 0: randomly 20 piglets in total, 10 per sex. At D43: 12 piglets per treatment, 6 per sex.
- Parameters checked: RBC, Haemoglobin, Haematocrit, MCV, MCH, MCHC, WBC, Lymphocytes, Monocytes, Neutrophils, Eosinophils, Basophils, Platelets, reticulocyte count, RPI, MPV, PCT, PDW.

CLINICAL CHEMISTRY: Yes / No / Not specified
- Time schedule for collection of blood: At time 0 and at the end of the trial (D43).
- Animals fasted: Not specified
- How many animals: At time 0: randomply 20 piglets in total, 10 per sex. At D43: 12 piglets per treatment, 6 per sex.
- Parameters checked: Glucose, Calcium, Inorganic P, Cholesterol, Triglycerides, Phospholipids, Uric acid, Urea, Creatinine, Lactate dehydrogenase, Alkaline Phosphatase, GOT (Aspartate Transaminase), GPT (Alanine Transaminase), Total Bilirubin, GGT, haptoglobin, serum albumin, serum total protein, blood clotting: quick/INR value, prothrombin time (PT), thyroid hormones (TSH, T3, T4).

OTHER:
DIETARY ANALYSIS:
- Time schedule: Nine representative samples of at least 250 g were taken from each diet and for each growing period: 3 in the beginning, 3 in the middle and 3 in the end of the production process (during the bagging-of the feeds). These 9 samples were pooled to 3 samples in such a way that 1 sample from the beginning, middle and end were pooled together and thoroughly mixed.
- Parameters checked: Feed moisture, crude protein content, crude fat content, crude fibre content, crude ash, starch, digestible energy.
Statistics:
All data were analysed by the GLM (General Linear Model) procedure of SAS (SAS, 2002-2008, release 9.2) using ANOVA (Analysis of Variance) as the main statistical test. Student’s “t” Test was used to compare the means of each group. The level of significance to indicate differences stated in the ANOVA model was P≤0.05 when the difference was statistically significant, while 0.05

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
The general performance parameters were good and similar to those expected under commercial rearing of weaned piglets in Italy. The veterinarian considered piglet health and husbandry to be generally good with no mortality and normal consistency of the faeces.
Mortality:
no mortality observed
Description (incidence):
No mortality was observed throughout the study.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No statistically-significant differences were found for live weight and average daily gain among feeding treatments. See Table no. 2. below.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No statistically significant differences were found for daily feed intake among feeding treatments in the all phases of the study. See Table no. 3 below.
Food efficiency:
no effects observed
Description (incidence and severity):
No statistically significant differences were found for feed: gain ratio among feeding treatments in the all phases of the study. See Table no. 3 below.
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
No statistical differences were found among feeding treatments with the exception of haemoglobin and haematocrit that were higher in T2 vs. T1, T3 and T4 groups (respectively 11.14 vs. 10.23, 10.46 and 10.46 %; P=0.0457 and 38.60 vs. 35.73, 36.23 and 35.94 %; P=0.0432) but no difference occurred between T1 and T4 group. Tendentially higher was WBC in T2 vs. T1 and T3 groups (9.90 vs. 8.27 and 8.27 1,000/ml respectively; P=0.0503). All measured blood haematological parameters on D0 and D43 were within the respective reference ranges. See Table no. 4.
For MCV and MCH statistically significant (treatment x gender) interactions were found. See Table no. 5. In females, both MCV and MCH parameters resulted higher in the T3 and T4 vs. T1 group (MCV: 60.53 and 59.65 vs. 56.23 fl; P=0.0225) (MCH: 17.72 and 17.32 vs. 16.28 pg; P=0.0222). See Table no. 6. In castrated males, MCV resulted higher in the T1 and T2 vs. T3 group (respectively 59.43 and 61.13 vs. 54.20 fl; P=0.0354) and MCH resulted tendentially higher in the T2 and T4 vs. T3 group (respectively 17.53 and 17.13 vs. 15.43 pg; P=0.0618). See Table no. 7.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Statistical significant differences were found for lactate dehydrogenase higher in T4 vs. T1, T2 and T3 groups (respectively 370.58 vs. 334.50, 344.92 and 335.08 U/l; P = 0.0066), while for triglycerides, GPT and serum total protein the differences were only tendentially. Triglycerides were tendentially lower in T2 and T3 vs. T1 group (respectively 72.67 and 71.67 vs. 80.17 mg/dl; P = 0.0976). GPT was tendentially higher in T2 and T4 vs. T1 group (respectively 44.75 and 44.17 vs.
35.42 U/l; P = 0.0959). Serum total protein was tendentially higher in T4 vs. T1, T2 and T3 groups (respectively 7.81 vs. 7.41, 7.44 and 7.47 g/dl; P = 0.0739). All measured blood biochemical parameters on D0 and D43 were within the respective reference ranges. For none of the blood biochemical parameters statistically significant (treatment x gender) interactions were found. See Table no. 8 below. It is important to point out that no differences were observed between the control and the treatment groups regarding neither the thyroid hormones (TSH, T3, T4) nor hepatic function related enzymes (GOT, GPT, GGT). Individual results for thyroid hormones have been included in Table no. 9.
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined

Effect levels

Key result
Dose descriptor:
NOAEL
Effect level:
>= 61 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No significant adverse effects observed at the highest dose tested.
Remarks on result:
other: 1500 g/tonne feed (ca. 47.2-61.0 mgBHT/kg bw)

Target system / organ toxicity

Key result
Critical effects observed:
no

Any other information on results incl. tables

Table 1. Feed analysis:

BHT, mg/kg (mean ± standard deviation; n=4)

Experimental

period

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000 g/ton. feed

T4

BHT

1500 g/ton. feed

D0 - D14

Not detected

149.2± 5.4

1007.3± 40.0

1424.9± 50.2

D14 - D42

Not detected

149.5±4.6

1005.6± 26.5

1413.8± 75.4

The actual BHT content was within the nominal values and within the tolerance limits given.

Table 2. Body weight:

Zootechnical performance: live weight and average daily gain (mean; n = 36)

Experimental

period

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment

Effect (P)

Standard

error of the mean

Live weight (kg)

D0

7.55

7.83

7.60

7.68

0.5815

0.1458

D14

10.31

10.56

10.26

10.53

0.6433

0.2008

D42

20.76

20.89

20.27

20.93

0.2064

0.2400

Average daily gain (g)

D0-D14

196.63

195.04

189.88

203.57

0.7952

9.6637

D14-D42

373.31

386.71

357.34

371.43

0.4259

12.2961

D0-D42

314.42

322.82

301.52

315.48

0.3358

8.1768

Table 3. Food intake and feed:gain ratio:

Daily feed intake and feed:gain ratio (mean, n = 9)

Experimental

period

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment

Effect(P)

Standard error of the

mean

Feed intake (g)

D0-D14

274.78

282.86

263.53

301.87

0.1819

12.3017

D14-D42

677.36

678.39

639.36

673.22

0.3470

17.4249

D0-D42

543.17

546.55

514.08

549.44

0.1324

11.5380

Feed:Gain ratio

D0-D14

1.42

1.46

1.39

1.49

0.4217

0.0480

D14-D42

1.82

1.77

1.79

1.82

0.8459

0.0403

D0-D42

1.73

1.70

1.71

1.74

0.8188

0.0314

Table 4. Haematology:

  Blood haematological parameters at D43 days from the start of the study (mean; n =12 [6 castrated males + 6 females])

 

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000 g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment effect (P)

Standard error of the mean

WBC (1,000/ml)

8.27 x

9.90 y

8.27 x

9.27 xy

0.0503

0.4789

RBC (1,000,000/ml)

6.20

6.47

6.32

6.07

0.1171

0.1187

Haemoglobin(%)

10.23a

11.14b

10.46a

10.46a

0.0457

0.2314

Haematocrit(%)

35.73a

38.60b

36.23a

35.94a

0.0432

0.7774

MCHC(%)

28.68

28.85

28.83

29.12

0.6196

0.2375

Neutrophils(%)

42.58

36.75

35.17

36.67

0.2665

0.8061

Lymphocytes(%)

45.38

50.50

53.08

51.00

0.3436

3.0663

Monocytes(%)

7.08

8.42

7.67

8.25

0.5848

0.7497

Eosinophils(%)

3.42

3.00

2.92

3.21

0.9151

0.5410

Basophils(%)

1.54

1.33

1.17

0.88

0.3939

0.2791

Platelets (1,000/mmc)

332.92

303.08

308.67

304.50

0.4431

14.6137

Reticulocyte(%)

0.94

0.97

0.98

1.01

0.6718

0.0390

RPI(%)

0.95

1.05

1.01

1.02

0.4108

0.0446

MPV (fl)

7.57

7.85

9.02

7.60

0.1606

0.5107

PCT(%)

0.40

0.35

0.44

0.40

0.5880

0.0452

PDW

20.09

20.19

21.09

19.86

0.2699

0.4654

WBC = white blood cells; RBC = red blood cells; MCHC = mean concentration of haemoglobin in erythrocytes; RPI = Reticulocyte production index; MPV = mean platelet volume; PCT = platelet crit (percent volume of the blood occupied by platelets); PDW = platelet distribution width.

a,b.: Different letters in the same row = differences significant (P<0.05)

x,y.: Different letter in the same row = differences tendentially significant (0.0.5 < P < 0.1)

Table 5. Haematology - MCV and MCH (treatment x gender)

Blood haematological parameters at D43 days from the start of the study (mean; n = 6)

 

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000 g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment

effect (P)

Treatment * sex interaction (P)

Standard error of the mean

MCV (fl)

57.83

59.80

57.37

59.14

0.2281

0.0054

0.3092

MCH (pg)

16.55

17.24

16.58

17.23

0.2151

0.0099

0.2314

MCV = mean volume of erythrocytes; MCH = mean content of haemoglobin.

Table 6. Haematology - MCV and MCH (treatment x females)

Blood haematological parameters at D43 days from the start of the study - females (mean; n = 6)

 

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment

Effect (P)

Standard error of the mean

MCV (fl)

56.23a

58.47ab

60.53b

59.65b

0.0225

0.9334

MCH (pg)

16.28a

16.95ab

17.72b

17.32b

0.0222

0.3047

MCV = mean volume of erythrocytes; MCH = mean content of haemoglobin.

a,b.: Different letters in the same row = differences significant (P<0.05)

Table 7. Haematology - MCV and MCH (treatment x castrated males)

Blood haematological parameters at D43 days from the start of the study - castrated males (mean; n = 6)

 

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment

Effect (P)

Standard error of the mean

MCV (fl)

59.43b

61.13b

54.20a

58.63ab

0.0354

1.5871

MCH (pg)

16.82xy

17.53y

15.43x

17.13y

0.0618

0.5381

MCV = mean volume of erythrocytes; MCH = mean content of haemoglobin.

a,b.: Different letters in the same row = differences significant (P<0.05)

x,y.: Different letter in the same row = differences tendentially significant (0.05 < P < 0.1)

Table 8. Biochemistry

Blood biochemical parameters at D43 days from the start of the study (mean; n =12 [6 castrated males + 6 females])

 

T1

Control

T2

BHT

150 g/ton. feed

T3

BHT

1000g/ton. feed

T4

BHT

1500 g/ton. feed

Treatment effect (P)

Standard error of the mean

Glucose (mg/dl)

89.17

94.33

93.83

94.58

0.6725

3.5603

Urea (mg/dl)

23.80

22.24

22.78

23.02

0.7618

13.0450

Uric acid (mg/dl)

0.34

0.32

0.34

0.32

0.8398

0.0177

Creatinine (mg/dl)

1.34

1.39

1.41

1.33

0.2992

0.0341

Cholesterol (mg/dl)

85.33

76.08

77.92

85.00

0.1618

3.5634

Triglycerides (mg/dl)

80.17y

72.67x

71.67x

73.83xy

0.0976

2.5601

Bilirubin (mg/dl)

0.13

0.14

0.13

0.12

0.8483

0.0119

GOT (U/l)

43.08

42.75

44.08

46.08

0.8780

3.1572

GPT (U/l)

35.42x

44.75y

42.00xy

44.17y

0.0959

2.8527

GGT (U/l)

28.22

28.95

28.40

32.24

0.2057

1.4945

Alkaline phosphate (U/l)

280.17

319.33

295.75

301.42

0.3014

14.4340

Lactate dehydrogenase (U/l

334.50a

344.92a

335.08a

370.58b

0.0066

7.8378

Calcium (mg/dl)

10.66

10.06

10.61

10.02

0.2558

0.2889

Inorganic P (mg/dl)

8.47

9.10

9.28

9.34

0.1128

0.2761

Phospholipides (mg/dl)

110.25

103.95

105.17

113.78

0.2255

3.7170

Haptoglobin (mg/dl)

1.12

1.13

1.12

1.12

0.9907

0.0290

Serum albumin (g/dl)

2.48

2.63

2.49

2.41

0.5113

0.1041

Serum total protein (g/dl)

7.41 x

7.44 x

7.47 x

7.81 y

0.0739

0.0173

INR value

0.96

0.97

0.95

0.95

0.6826

0.0099

Prothrombin value (sec)

10.73

10.72

10.83

10.80

0.9178

0.1320

TSH (mU/ml)

0.02

0.02

0.02

0.02

0.9474

0.0011

T3 (pg/ml)

2.47

2.44

2.48

2.56

0.9067

0.1171

T4 (ng/dl)

1.38

1.34

1.27

1.27

0.6250

0.0672

GOT = Aspartate Transminase; GPT = Alanine Transminase, GGT = gamma-glutamyl transpeptidase, INR value = International Normalised Ratio; TSH = Thyroid stimulating hormone; T3 = Triiodothyronine; T4 = Thyroxine.

a,b.: Different letters in the same row = differences significant (P<0.05)

x,y.: Different letter in the same row = differences tendentially significant (0.05 < P < 0.1)

Table 9: Individual results on T3, T4 and TSH (thyroid hormones):

Treatment

Sex

Room

Pen

FT3

FT4

TSH

T1

F

1

5

2.5

1.29

0.015

T1

F

1

5

2.1

1.27

0.019

T1

F

4

2

2.6

1.36

0.026

T1

F

4

2

2.9

1.06

0.021

T1

F

4

6

2.1

1.36

0.019

T1

F

5

5

2.7

1.6

0.017

T1

M

1

1

2

1.9

0.015

T1

M

1

1

2.2

1.6

0.018

T1

M

2

3

3.1

1.41

0.017

T1

M

5

1

2.5

1.15

0.021

T1

M

5

10

2.8

1.26

0.021

T1

M

5

10

2.1

1.26

0.028

T2

F

1

2

2.4

1.2

0.024

T2

F

2

4

2.5

1.26

0.025

T2

F

3

5

2.1

1.6

0.015

T2

F

3

5

2.3

1.15

0.018

T2

F

5

6

2.1

1.8

0.024

T2

F

5

6

2.4

1.4

0.015

T2

M

1

6

2.3

1.29

0.021

T2

M

1

6

2.2

1.31

0.024

T2

M

3

1

3

1.15

0.019

T2

M

4

3

3

1.19

0.016

T2

M

5

2

2.4

1.29

0.024

T2

M

5

9

2.6

1.41

0.015

T3

F

2

1

2.6

1.02

0.022

T3

F

2

1

2.6

1

0.021

T3

F

3

2

2.9

1.12

0.023

T3

F

4

4

3.1

1.26

0.019

T3

F

5

8

2

1.45

0.016

T3

F

5

8

2.5

1.66

0.021

T3

M

1

3

2

1.23

0.027

T3

M

1

3

2

1.22

0.018

T3

M

2

5

2.1

1.27

0.014

T3

M

3

6

2.5

1.81

0.019

T3

M

5

3

3.2

1.11

0.027

T3

M

2

12

2.3

1.12

0.015

T4

F

1

4

2.1

1.7

0.02

T4

F

1

4

2.5

1.36

0.019

T4

F

1

4

2.1

1.24

0.027

T4

F

2

6

3.1

0.99

0.022

T4

F

4

5

2.7

1.27

0.017

T4

F

5

11

2

1.15

0.021

T4

M

2

4

2.4

1.09

0.019

T4

M

2

2

3

1.35

0.015

T4

M

3

3

2.4

0.96

0.014

T4

M

4

1

2.1

1.45

0.022

T4

M

5

7

3.7

1.7

0.019

T4

M

5

2

2.6

1

0.016

Applicant's summary and conclusion

Conclusions:
The administration of BHT to chickens for fattening for 35 consecutive days up to 1500 g/tonne feed (ca. 47.2-61.0 mgBHT/kg bw), did not cause any adverse effects under the test conditions. No adverse effects were observed related neither to the thyroid hormones (TSH, T3, T4) nor hepatic function (GOT, GPT, GGT).
Executive summary:

In the present study, the tolerance of weaned piglets to Butylated hydroxytoluene (BHT) at technological feed additive was evaluated (GLP study). The trial was carried out with 144 weaned piglets weighing 7.66 (± 0.89) kg/head at the start of the study. The feeding treatments were: 1) Control group T1: animals fed basal diet; 2) T2: animals fed basal diet (T1) supplemented with BHT at 150 g/tonne feed (recommended dose, ca. 4.6 -6.5 mgBHT/kg bw); 3) T3: animals fed basal diet (T1) supplemented with BHT at 1000 g/tonne feed (6.7x recommended dose, ca. 29.7 -42.1 mgBHT/kg bw) and 4) T4: animals fed basal diet (T1) supplemented with BHT at 1500 g/tonne feed (10x recommended dose, ca. 47.2 -61.0 mgBHT/kg bw). The feeds were issued to the appropriate pens for 42 consecutive days (between day 0 and day 42 of the trial). Each feeding treatment was replicated in 9 pens (5 pens of castrated males and 4 pens of female piglets) with 4 animals of the same gender per pen. The data recorded during the feeding phase were live weight (LW) at 0, 14 and 42 days from the start of the study; average daily gain (ADG), daily feed intake and feed:gain ratio (F:G) during the periods 0-14; 14-42 and 0-42 days from the start of the study; blood haematology and biochemistry parameters at D0 and D43. The piglets were considered of good health, no mortality was observed and the faeces were of normal consistency. No statistically significant differences were found for piglets performance (LW, ADG, daily feed intake and feed:gain ratio) among feeding treatments in all phases of the study. No statistical differences were found for haematological parameters at D43 among feeding treatments with the exception of haemoglobin and haematocrit that were higher in T2 vs. T1, T3 and T4 groups but no difference occurred between T1 and T4 group. Tendentially higher was WBC in T2 vs. T1 and T3 groups. Some statistically significant treatment * gender interactions were found for MCV and MCH and a statistical analysis for each gender was performed. In female pigs both MCV and MCH resulted higher in the T3 and T4 vs. T1 group while in castrated male pigs MCV resulted higher in the T1 and T2 vs. T3 group and MCH resulted tendentially higher in the T2 and T4 vs. T3 group. Concerning the biochemical parameters at D43 LDH was lower in T1, T2 and T3 vs. T4 group; triglycerides were tendentially higher in T1 vs. T2 and T3 groups; GPT was tendentially lower in T1 vs. T2 and T4 groups and serum total protein was tendentially higher in T4 vs. T1, T2 and T3 groups. All measured blood haematological and biochemical parameters were within the respective reference ranges. In conclusion, the administration of BHT to weaned piglets for 42 consecutive days up to 1500 g/tonne fed (ca. 47.2 -61.0 mgBHT/kg bw), did not cause significant adverse effects under the test conditions. It should be highlighted that no test item related adverse effects were observed regarding neither the thyroid hormones (TSH, T3, T4) nor the hepatic function (GOT, GPT, GGT).