Clove essential oil decreases antemortem stress and acts as an antioxidant in Nile tilapia

Figures & data

Figure 1. Indication of the position for cranial percussion blow. In image a, the ideal distance for applying the blow is observed. Image b, operator. Source: Author.

Figure 2. Protocol for observing self-initiated behavior, stimulus-response, and clinical reflex post-stunning. Source: Adapted from Kestin et al. (2002).

Table 1. Percent (%) of stunned tilapia evaluating swimming behaviors, balance, stimulus response, and vestibulo-ocular reflex (VOR) with respect to the interaction between stunning methods (cranial percussion and hypothermia) and the use or non-use of clove essential oil.

Stunning methods
	Cranial percussion		Hypothermia
	Without clove essential oil	With clove essential oil	Without clove essential oil	With clove essential oil
Swimming	72 Bb	100 Aa	96 Aa	96 Aa
Balance	72 Bb	96 Aa	96 Aa	96 Aa
Response to stimulus	68 Ab	100 Aa	80 Ab	96 Aa
VOR	64 Bb	96 Aa	100 Aa	100 Aa

^A-B Averages followed by different capital letters in the same row differ between control group and with eugenol. ^a-b Averages followed by different lower case letters in the same row differ between stunning methods.

Table 2. Mean values and standard error of glucose and lactate variables, in relation to the interaction between stunning method and treatment with clove essential oil in tilapia.

Stunning methods					*p-Value
	Cranial percussion		Hypothermia
	Without clove essential oil	With clove essential oil	Without clove essential oil	With clove essential oil	Stunning methods × clove essential oil
Glucose (mg dL^−1)	132.09 ± 2.93ab	95.1 ± 3.98b	139.00 ± 2.68a	126.88 ± 3.29b	0.000098
Lactate (mmol L^−1)	8.18 ± 0.05a	4.82 ± 0.03b	1.26 ± 0.04c	0.82 ± 0.04c	0.0046141

^a-b Different letters indicate significant difference between treatments by Tukey's test at 5% probability.

Table 3. Mean values and standard error of pH, water holding capacity (WHC), yellow/blue hue (b*), Schiff bases, protein carbonylation (DNPH), glutathione reductase (GSH) and catalase activity (CAT) of tilapia stunned by two stunning methods (cranial percussion and hypothermia), using and not using clove essential oil.

	Stunning methods		Clove essential oil		*p-Value
	Cranial percussion	Hypothermia	Without	With	Stunning methods	Clove essential oil	Stunning methods × clove essential oil
pH	6.13 ± 0.01 b	6.22 ± 0.01 a	6.18 ± 0.01 a	6.16 ± 0.01 a	0.00000	0.07351	0.10796
WHC (%)	70.57 ± 0.25 b	73.67 ± 0.27 a	71.65 ± 0.27 a	72.57 ± 0.28 a	0.00000	0.04076	0.69837
b*_Surface	7.63 ± 0.07 a	6.04 ± 0.06 b	7.07 ± 0.10 a	6.59 ± 0.10 b	0.00000	0.00129	0.65277
Schiff bases (fluorescence intensity)	563.57 ± 3.86 a	483.85 ± 5.49 b	557.98 ± 3.89 a	489.43 ± 6.22 b	0.00000	0.00000	0.05216
DNPH (nmol carbonyls / mg protein)	1.270 ± 0.01 a	0.873 ± 0.01 b	1.139 ± 0.02 a	1.005 ± 0.02 b	0.00000	0.01301	0.40739
GSH (µg of GSH mg ^protein−1)	5.19 ± 0.11 b	7.31 ± 0.14 a	6.23 ± 0.01 a	6.22 ± 0.01 a	0.00000	0.63319	0.81380
CAT (μmoL H2O2 min^−1 mg de ^protein−1)	0.26 ± 0.01 b	0.35 ± 0.01 a	0.33 ± 0.15 a	0.28 ± 0.12 b	0.00001	0.02059	0.10619

^a-b Different letters indicate significant difference between treatments by Tukey's test at 5% probability.

Table 4. Mean values and standard error of L* (Luminosity), a* (red/green tonality) variables, in relation to the interaction between stunning method and treatment with clove essential oil in tilapia.

Stunning methods					*p-Value
	Cranial percussion		Hypothermia
	Without clove essential oil	With clove essential oil	Without clove essential oil	With clove essential oil	Stunning methods × clove essential oil
L* _Surface	49.88 ± 0.09a	45.54 ± 0.19c	46.47 ± 0.13b	46.47 ± 0.22b	0.010866
a*_Surface	−1.35 ± 0.05a	−1.73 ± 0.03b	−2.21 ± 0.03c	−2.20 ± 0.01c	0.00094271

^a-b Different letters indicate significant difference between treatments by Tukey’s test at 5% probability.

Table 5. Mean values and standard error of TBARS (thiobarbituric acid reactive substances) and tryptophan variables, in relation to the interaction between stunning method and treatment with clove essential oil in tilapia.

Stunning methods					*p-Value
	Cranial percussion		Hypothermia
	Without clove essential oil	With clove essential oil	Without clove essential oil	With clove essential oil	Stunning methods × clove essential oil
TBARS (nmol TBARS /nmol mg protein^−1)	0.0154 ± 0.00ab	0.0095 ± 0.00ab	0.0326 ± 0.00a	0.0046 ± 0.00b	0.009368
Tryptophan (mg NATA/g protein)	9.81 ± 0.05a	9.57 ± 0.11a	9.71 ± 0.05a	7.70 ± 0.13b	0.00125375

^a-b Different letters indicate significant difference between treatments by Tukey’s test at 5% probability.

Kestin SC, van de Vis JW, Robb DHF. 2002. Protocol for assessing brain function in fish and the effectiveness of methods used to stun and kill them. Vet Rec. 150(10):302–307. doi:10.1136/vr.150.10.302.

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Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.