The effects of lairage time and handling procedure prior to slaughter on stress and meat quality parameters in pigs

Meat Science 98 (2014) 220–226

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The effects of lairage time and handling procedure prior to slaughter on stress and meat quality parameters in pigs M. Dokmanović a,⁎, A. Velarde b, V. Tomović c, N. Glamočlija a, R. Marković a, J. Janjić a, M.Ž. Baltić a a b c

Department for Food Hygiene Technology, Faculty of Veterinary Medicine, University of Belgrade, Bulevar Oslobodjenja 18, 11000 Belgrade, Serbia Animal Welfare Subprogram, IRTA, Finca Camps i Armet, 17121 Monells, Girona, Spain Faculty of Technology, University of Novi Sad, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia

a r t i c l e

i n f o

Article history: Received 23 September 2013 Received in revised form 19 March 2014 Accepted 2 June 2014 Available online 11 June 2014 Keywords: Pig Lactate Cortisol pH Value Meat quality

a b s t r a c t Lairage time (short — 8 min to 2.7 h, n = 28 vs. long — 14 to 21.5 h, n = 72) and pig handling (gentle — no use of stick or electric prod, pig not slipping, falling, nor emitting high-pitched vocalizations vs. rough — where any of these occurred) effects on pig stress and meat quality were measured. Blood lactate and cortisol, plus postmortem pH (pH60 min; pH24 h), temperature (T60 min), drip loss, sensory and instrumental color and meat quality for the longissimus dorsi, pars lumbalis derived meat were determined. Carcass rigor mortis and skin damages were measured. Lairage time significantly affected blood lactate, carcass rigor mortis, skin damages, drip loss, color and meat quality. Handling procedure influenced blood lactate, pH60 min and T60 min. Long lairage was more stressful, and was detrimental to carcass quality, but caused better meat quality compared to short lairage. Rough handling was related to higher lactate and lower meat quality. © 2014 Elsevier Ltd. All rights reserved.

1. Introduction All meat animals will experience some level of stress prior to slaughter and this in turn, may have detrimental effects on meat quality (Ferguson et al., 2001). After arrival in the slaughterhouse, two important factors that may affect the level of stress in pigs, and consequently pork quality, are lairage time and handling procedure immediately prior to slaughter. Nanni Costa, Lo Fiego, Dall'Olio, Davoli, and Russo (2002) found that lairage time was an important source of variation determining meat quality. After overnight lairage, meat was darker, had a higher ultimate pH, and greater water holding capacity, producing less drip during storage, compared to lairage of two hours (Nanni Costa et al., 2002). Compared to lairage time of less than three hours, overnight lairage reduced carcass weight, backfat thickness and meat temperature (Warriss, Brown, Edwards, & Knowles, 1998). In addition, the percentage of carcasses with skin blemishes and high ultimate pH increased progressively with longer periods of lairage (Warriss et al., 1998). According to Warriss (2003) and Nanni Costa et al. (2002), the optimal lairage time is between one and three hours, since lairage shorter than one hour increases the prevalence of pale, soft and exudative (PSE) meat, while lairage longer than three hours poses a risk for developing dark, firm and dry (DFD) meat and skin damages. ⁎ Correspondding author at: Department for Food Hygiene Technology, Faculty of Veterinary Medicine, University of Belgrade, Bulevar Oslobodjenja 18, 11000 Belgrade, Serbia. Tel.: +381 11 2685936, fax: +381 11 2685936. E-mail address: [email protected] (M. Dokmanović).

http://dx.doi.org/10.1016/j.meatsci.2014.06.003 0309-1740/© 2014 Elsevier Ltd. All rights reserved.

According to Hambrecht, Eissen, Newman, Smits, den Hartog, and Verstegen (2005), great improvement in pork quality can be achieved by reducing stress (actually the use of electric goads), immediately before slaughter. Hemsworth, Barnett, Hofmeyr, Coleman, Dowling and Boyce (2002) found a correlation between negative interactions that pigs received from the stockperson immediately prior to slaughter and meat quality deterioration. Most of these negative interactions were prods with an electric goad. Benjamin et al. (2001) and Rabaste et al. (2007) found that frequent use of electric prods during pig handling leading to the stunning area led to pigs turning back, jumping, slipping and/or falling, and also caused injuries, so the carcasses of these animals had a higher degree of bruising and skin damages, as well as reduced quality of meat (PSE meat). Intense stress before stunning provoked by rough treatment increased concentrations of norepinephrine, cortisol and lactate (Hambrecht et al., 2004), heart rate, body temperature (Griot, Boulard, Chevillon, & Kerisit, 2000) and percentage of carcasses with skin damages (Rabaste et al., 2007). Furthermore, a severe stress one minute before stunning reduced the ultimate pH and increased drip loss of pork (Hambrecht, Eissen, Newman, Smits, den Hartog, et al., 2005; Rabaste et al., 2007; van der Wal, Engel, & Reimert, 1999). Overall, lairage duration and handling immediately prior to slaughter seem to be important in the management of stress in pigs and in the resultant pork meat quality, but these interactions are likely very complex. Therefore, the objective of this study was to evaluate effects of two different lairage times (short, from 8 min to 2.7 h of lairage, n = 28 vs. long, from 14 to 21.5 h of lairage, n = 72) and handling procedures (gentle vs. rough, based on use of stick or electric prod

M. Dokmanović et al. / Meat Science 98 (2014) 220–226

and reaction of pigs) on selected stress indicators (lactate, cortisol and skin damages) and meat quality parameters (initial and ultimate pH values, temperature, rigor mortis, drip loss, instrumental and sensory color) in pigs for slaughter. 2. Material and methods 2.1. Animals, housing and feeding Commercial market pigs (n = 100, comprising 31 gilts, 51 barrows and 18 boars), six months of age and with live weights between 115 and 130 kg were studied. All animals were of the same cross-breed (cross between Naima sows and hybrids P-76 PenArLan boars) and originated from the same farm. Pigs were housed in the finishing facility on partially slatted floors, in pens with 20 animals per pen (stocking density = 1 m2/pig). Pigs were provided with ad libitum feed and water via one automatic feeder and two nipple drinkers in each pen. 2.2. Pre-slaughter and slaughter Feed and water were not withdrawn from the animals before transportation. The distance between pens and the transportation trailer was about 20 m and the loading ramp was sloped downwards at 15°. All the pigs (n = 20) from each pen were transported together as one batch of animals at a stocking density of 0.45 m2/pig. Transport from farm to the abattoir lasted 15 min. The surface of the trailer floor and the unloading dock were on the same level (not sloped). During loading and unloading, sticks and electric prods were used to move pigs. After unloading, pigs entered a 10 m long corridor that led to the lairage pens. During lairage, pigs were not mixed (each batch of 20 pigs was lairaged in one pen), and stocking density was 0.70 m2 per pig. In lairage, pigs had access to water. A 5 m, single-file corridor led from the lairage pens to the stunning area. During pig handling from lairage pens to the stunning area, sticks and electric prods were used according to industry practice in Serbia. After lairage, pigs were head-only electrically stunned (50 Hz, 2 A and 220 V) in batches of 6 animals without restraining. Immediately after stunning pigs were bled on the floor and then hoisted on a rail. The time of current application was on average 3.51 ± 2.08 s and the time from stunning to sticking ranged from 1 to 10 s. Following bleeding, carcasses were processed using conventional industry practice. 2.3. Experimental design One group of pigs entered the lairage in the early morning hours (around 6 AM) and was slaughtered on the same day (short lairage, from 8 min to 2.7 h, average of 1.36 h; n = 28). The other group entered the lairage in the afternoon (around 4 PM), overnighted in the lairage and was slaughtered the following morning (long lairage, from 14 to 21.5 h, average of 17.01 h; n = 72). Three observers assessed handling procedures and pig behaviors for each pig while the animals walked from the lairage pen to the stunning area. Observers stood at three different places to record their observations: at the exit of lairage pen; next to the corridor; and in the stunning area. Pigs were sent to slaughter in groups of 6 animals. At the back of

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the group, a stock handler forced the pigs on go down the corridor with a stick and an electric prod. Those pigs at the rear were able to jump on pigs in front and consequently those animals involved in these behaviors could slip, fall or vocalize. Handling and behavior parameters were scored as present or absent, but the number of times per animal was not recorded. Handling procedures were defined as rough or gentle. A pig was classified as roughly handled if it was hit with the stick or prodded with the electric prod, or if it slipped, fell or vocalized in a high pitch (Table 1). If any of these handling or behavior parameters or their combination was present for any pig, handling of that pig was characterized as rough. In contrast, the absence of all of these handling and behavior parameters was classified as gentle handling of the observed pig. 2.4. Blood sampling and determination of blood lactate and cortisol content At slaughter, blood samples were collected into plastic tubes and a part of this material was then transferred to Vacutainer tubes containing heparin (against blood coagulation) which were placed on ice. Blood lactate content was immediately determined using a portable lactate analyzer (Lactate Scout, EKF Diagnostic, Magdeburg, Germany), which was calibrated with a standard solution to ensure accuracy. After blood collection and within 4 to 6 h, the Vacutainer tubes were centrifuged at 3000 rpm for 3 min to separate blood supernatant (plasma). Plasma was transferred into microtubes and stored at − 20 °C until the determination of cortisol concentration by radioimmunoassay (RIA-CT Cortisol, INEP, Belgrade, Serbia). 2.5. Carcass and meat quality analyses Carcasses were clearly labeled to ensure that they originated from the 100 live pigs studied. Meat quality measurements were carried out 60 min, 24 and 72 h after slaughter on muscle longissimus dorsi (LD) and pars lumbalis. Values of pH and temperature were measured using a Testo 205 (Germany) pH-meter, calibrated with pH 4.00 and 7.00 phosphate buffer, at 60 min (pH60 min, T60 min) and 24 h (pH24 h) post-mortem. Skin damages were assessed on three regions of the right carcass side (from head to back of shoulder, from back of shoulder to hind-quarters and the region of the hind-quarters) immediately after dressing using scores 1 (no damage), 2 (scratches or small wounds, less than 2 cm), 3 (bleeding wounds between 2 and 5 cm or healed wounds of more than 5 cm) and 4 (deep and open wounds of more than 5 cm). The final score for each carcass was obtained by summing scores for the three regions. The degree of rigor mortis was estimated on the right carcass side 3 h post-mortem by measuring the degree of angle between body axis and foreleg (Davis, Townsend, & McCampbell, 1978). For that purpose, photographic images of carcass sides were taken, at a distance of approximately 2 m and a height of 160 cm, parallel to the plane in which carcass sides were hanging, and the angle was then calculated using an AutoCAD 2010 software (Autodesk, Inc., San Francisco, USA) (Image 1). For determination of drip loss and color, meat samples, which were 2.5 cm thick loin chops, were taken 24 h after slaughter from LD, between the 3rd and 4th lumbar vertebrae. Meat samples were weighed and stored for 48 h at 4 °C in a container (Honikel, 1998). After storage, meat samples were reweighed and the percentage

Table 1 Definition of handling and behavior parameters. Parameters

Definition

Stick use Electric prod use Slipping Falling High-pitched vocalization

A hit with stick to any part of the pig's body An electric prod touches any part of the pig's body Loss of balance without the pig's body touching the floor Loss of balance in which any part of the pig's body (except legs) touches the floor High-pitched squeals during movement through the handling area

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gentle handling 9.24 rough handling 13.21

6.33 15.92 15.92±1.82

mmol/l

16 A

13.21±1.13

14 A

12 9.24±0.59

10

gentle handling

B

6.33±0.92

8

rough handling B

6 n=43 n=29

4

n=23 n=5

2 long lairage

0

short lairage

Fig. 1. Concentrations of lactate (mmol/l) in relation to the lairage time and handling procedure (X  SEM). Bars lacking a common letter differ (p b 0.05).

Image 1. Determination of degree of angle between body axis and foreleg.

of drip loss was calculated. Sensory and instrumental color (CIE L*a*b*; CIE, 1976) were determined at 24 h post-mortem, after approximately 60 min of blooming time (Honikel, 1998). L*, a* and b* (CIE, 1976) values were determined using a Minolta chroma meter CR-400 (Minolta Co., Ltd., Osaka, Japan) utilizing a 65 light source and a 2° observer. Color and drip loss were analyzed in duplicate. An analytical panel of three trained members assessed the sensory color of meat samples by using a 1–6 scaling method (NPPC, 2000). Meat quality classes (pale, soft and exudative — PSE; reddish-pink, soft and exudative — RSE; red, firm and non-exudative — RFN; pale, firm and non-exudative — PFN; and dark, firm and dry — DFD) were determined according to Kauffman, Cassens, Scherer, and Meeker (1992), using the pH24 h, drip loss after 48 h of storage and L* parameter (CIE, 1976) after 24 h postmortem (Table 2). 2.6. Statistical analysis Statistical analysis of the results was conducted using the software GraphPad Prism version 5.00 for Windows (GraphPad Software, San Diego, California USA, www.graphpad.com). All parameters were described by descriptive statistics (mean, standard deviation, minimum and maximum values). Student t-test was used to examine the effects of lairage time (short vs. long) and handling procedure (gentle vs. rough) on stress and meat quality parameters in pigs. Two-way

ANOVA with Tukey's multiple comparison test was used to test combined effects of two lairage times and handling procedures on lactate and cortisol contents. Differences between long and short lairage times, and between gentle and rough handling for meat in the differing quality classes (PSE, RSE, RFN, PFN and DFD) were determined by Fisher's exact test. Values of p b 0.05 were considered significant. 3. Results and discussion 3.1. Characterization of the experimental population Table 3 shows mean values of stress and meat quality parameters in pigs. Blood lactate at exsanguination ranged from 1.3 to 24.6 mmol/l which is in accordance with the results of other authors, who detected from 1.1 to 20.6 mmol/l (Edwards, Grandin, et al., 2010), from 4.0 to 19.7 mmol/l (Edwards, Engle, et al., 2010) and from 0.11 to 20.57 mmol/l (Hemsworth et al., 2002). Blood cortisol content varied within studies, on average from 49.5 to 80.8 ng/ml (Hambrecht et al., 2004) and from 55.1 to 77.9 ng/ml (Hambrecht, Eissen, Newman, Smits, den Hartog, et al., 2005), with a range from 1.70 to 300.9 ng/mg (Foury et al., 2005), which was close to the range observed in the current study (3 to 248 nmol/l). These large variations in cortisol content could be due to influences of species, breed, time of day, stress, meal, physical or sexual activity, change of environment, individual variability gentle handling rough handling

64.65 73

nmol/l 73.00±23.05

80 70 60 50

Table 2 Assessment of meat quality classes according to Kauffman et al. (1992).

53.71 60.62

64.65±14.33 60.62±10.83 53.71±8.42 A A

A

A

gentle handling

40

Meat quality

pH24 h

Drip loss (%)

L* value

PSE RSE RFN PFN DFD

b6.0 b6.0 b6.0 b6.0 ≥6.0

≥5 ≥5 b5 b5 b5

≥50 42–50 42–50 ≥50 b42

pH24 h — pH value measured 24 h post-mortem; L* — lightness; PSE — pale, soft and exudative; RSE — reddish-pink, soft and exudative; RFN — red, firm and non-exudative; PFN — pale, firm and non-exudative; and DFD — dark, firm and dry meat.

rough handling

30 20

n=43 n=29

n=23

n=5

10 0

long lairage

short lairage

Fig. 2. Concentrations of cortisol (nmol/l) in relation to the lairage time and handling procedure (X  SEM). Bars lacking a common letter differ (p b 0.05).

M. Dokmanović et al. / Meat Science 98 (2014) 220–226 Table 3 Characterization of the experimental population (n = 100): Stress and meat quality parameters. Parameter

X  SD

Blood lactate (mmol/l) Plasma cortisol (nmol/l) pH60 min pH24 h T60 min (°C) Rigor mortis (°) Skin damages score Drip loss (%) CIE L* value CIE a* value CIE b* value Sensory color

10.06 ± 58.36 ± 6.33 ± 5.55 ± 38.58 ± 124.80 ± 7.09 ± 6.30 ± 50.20 ± 7.71 ± 4.21 ± 2.44 ±

5.47 57.46 0.21 0.13 0.74 4.62 2.30 1.40 3.02 1.26 0.96 0.52

Min.

Max.

1.30 3.00 5.64 5.26 37.10 115.10 3.00 3.01 35.11 4.15 2.23 1.00

24.60 248.00 6.81 5.93 40.30 136.60 12.00 9.50 60.22 11.83 7.41 4.00

pH60 min and pH24 h — pH values measured 60 min and 24 h post-mortem; T60 min — meat temperature measured 60 min post-mortem; L* — lightness; a* — redness; and b* — yellowness.

and other factors (Mormede, 2007). In the current study, though, the pigs were of the same cross-breed, reared under an identical production regime, with similar pre-slaughter handling before entering lairage pens, and were all slaughtered in the morning to limit the confounding effect of diurnal cortisol fluctuation (Mormede, 2007). At this time, cortisol concentrations were likely higher than they would have been in the afternoon or evening, although measurement of this was not an aim of the current study. Therefore, the great variation in cortisol levels that we have observed could be, at least partly, a consequence of individual variability. The higher concentrations of cortisol measured in individual pigs could reflect exquisite sensitivity of the hypothalamic– pituitary–adrenal axis to stressors rather than a high level of stress (Foury, Geverink, Gil, Gispert, Hortos, Font, Furnols, Carrion, Blott, Plastow & Mormede, 2007). Values of pH after 60 min ranged from 5.64 to 6.81, and after 24 h from 5.26 to 5.93. The highest carcass temperature was 40.3 °C and the highest drip loss of meat samples was 9.50%. Rigor mortis was from 115.1 to 136.6°. Some carcasses were without any skin blemishes (score 3), while others scored the maximum for skin blemishes (score 12). CIE parameters ranged from 35.11 to 60.22 (CIE L* value), from 4.15 to 11.83 (CIE a* value) and from 2.23 to 7.41 (CIE b* value), while sensory color scores ranged from 1.0 to 4.0.

3.2. Lairage time Table 4 shows stress and meat quality parameters in relation to the short and long lairage times. Pigs undergoing long lairage had significantly higher (p b 0.05) blood lactate content (10.86 mmol/l)

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compared to short lairage (8.04 mmol/l), which may be due to higher stress reactions of those pigs because they were more exposed to stressful procedures in lairage, such as rough handling, fights, change of environment and food deprivation (Bruijnzeel, Stam, Compaan, & Wiegant, 2001; Stam, Bruijnzeel, & Wiegant, 2000; Stam, van Laar, Akkermans, & Wiegant, 2002). Perez, Palacio, Santolaria, Del Aceña, Chacón, Verde, Calvo, Zaragoza, Gascón and García-Belenguer (2002) did not find that lairage time had any significant effect on blood lactate, while Salajpal, Dikic, Karolyi, Sinjeri, Liker, Kostelic and Juric (2005) determined that one group of pigs after short lairage (2 h) had higher blood lactate levels compared to pigs in long lairage (24 h). In the current study, there was no significant difference between the two compared cortisol concentrations (Table 4). Although Nanni Costa et al. (2002) found lower initial and ultimate pH values after short lairage compared to long lairage, in the current study, no differences in meat pH were seen among pigs undergoing short or long lairage. Similarly, no significant difference was determined in meat temperature between the two lairage time groups. As the degree of rigor mortis can be used to assess stress level prior to slaughter (Knowles & Warriss, 2007; Warriss, Brown, & Knowles, 2003), the significantly higher (p b 0.01) degree of rigor mortis (124.1°) after a long lairage could indicate a procedure more stressful, in accordance with lactate concentrations. The results of the current study show that longer lairage significantly (p b 0.001) increased skin damage score, as found by other authors (Guardia et al., 2009; Nanni Costa et al., 2002; Warriss et al., 1998), because pigs were more aggressive due to the prolonged period of food withdrawal. After short lairage, drip loss (6.93%) was significantly higher (p b 0.01) compared to long lairage (6.05%), which is in accordance with the results of other authors (Hoffman & Fisher, 2010; Salajpal et al., 2005). Lower drip loss of meat after long lairage could be a consequence of higher muscle glycogen degradation and higher meat pH value, meaning meat released less water (Dalmau, Velarde, & Gispert, 2009). Significantly (p b 0.001) darker meat color (lower CIE L* value) was found after long lairage, which was also confirmed by a significantly (p b 0.05) higher value for sensory color. Similar changes in color were also found by Nanni Costa et al. (2002) and Hoffman and Fisher (2010). After short lairage, significantly higher CIE a* (8.16) and CIE b* (4.78) values were found compared to long lairage (7.53 and 3.97). In addition, lairage times had an effect on meat quality classes (Table 5). For example, after short lairage a significantly higher (p b 0.001) incidence of PSE (82.14%) and lower incidences of RSE (17.86%) and RFN meat (0%) were found, compared to the group with long lairage (30.55, 41.67 and 20.83%, respectively) (Table 5). Similarly Perez, Palacio, Santolaria, Del Aceña, Chacón, Verde, Calvo, Zaragoza, Gascón and García-Belenguer (2002) and Nanni Costa et al. (2002) found that longer lairage had a positive effect in reducing the incidence of PSE meat. Moreover, a high percentage of carcasses with PSE (45.0%)

Table 4 Stress and meat quality parameters in relation to the lairage time. Parameter

Short lairage (n = 28) X  SD

Blood lactate (mmol/l) Plasma cortisol (nmol/l) pH60 min pH24 h T60 min (°C) Rigor mortis (°) Skin damages score Drip loss (%) CIE L* value CIE a* value CIE b* value Sensory color

8.04a 67.04 6.33 5.54 38.71 126.70x 5.88α 6.93x 52.30α 8.16a 4.78α 2.26a

± ± ± ± ± ± ± ± ± ± ± ±

5.70 63.28 0.21 0.11 0.77 3.85 2.41 1.08 2.86 1.17 1.13 0.52

Long lairage (n = 72) Min.

Max.

X  SD

1.3 5 6.03 5.26 37.1 116.5 3 5.03 48.97 5.37 3.47 1.0

21.5 247 6.74 5.77 40.2 134.1 12 8.97 60.22 10.62 7.41 3.5

10.86b 54.89 6.33 5.57 38.44 124.10y 7.57β 6.05y 49.37β 7.53b 3.97β 2.50b

± ± ± ± ± ± ± ± ± ± ± ±

5.21 55.06 0.21 0.13 0.70 4.71 2.08 1.44 2.67 1.25 0.78 0.54

Min.

Max.

2.6 3 5.64 5.30 37.2 115.1 3 3.01 35.11 4.15 2.23 1.0

24.6 248 6.81 5.93 40.3 136.6 12 9.50 57.44 11.83 6.62 4.0

pH60 min and pH24 h — pH values measured 60 min and 24 h post-mortem; T60 min — meat temperature measured 60 min post-mortem; L* — lightness; a* — redness; and b* — yellowness; within a row different letters indicate a significant difference between groups (a,b — p b 0.05; x,y — p b 0.01; α, β — p b 0.001).

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Table 5 The effect of lairage time on incidences of meat quality classes (n = 100). Lairage

Total n

Short Long Total

28 72 100

PSE % 100 100 100

n 23 22 45

RSE %

n α

82.14 30.55β 45

5 30 35

RFN %

n a

17.86 41.67b 35

0 15 15

PFN % x

0 20.83y 15

DFD

n

%

n

%

0 4 4

0 5.55 4

0 1 1

0 1.4 1

PSE — pale, soft and exudative; RSE — reddish-pink, soft and exudative; RFN — red, firm and non-exudative; PFN — pale, firm and non-exudative; and DFD — dark, firm and dry meat; within a column different letters indicate significant difference between groups (a,b — p b 0.05; x,y — p b 0.01; α, β — p b 0.001).

and RSE (35.0%) meat in the current study indicated a problem with meat softness and exudation, which was also observed by PanellaRiera, Gispert, Gil, Soler, Tibau, Oliver, Velarde and Fabrega (2012). In our study, 49% of carcasses had a pale color (CIE L* ≥ 50) compared to 51% of carcasses with red and dark color (CIE L* b 50), which is similar to those carcasses observed by Tomović, Jokanović, Petrović, Tomović, Tasić, Ikonić, Sumić, Sojić, Skaljac and Sošo (2013) (43.4% and 56.6%, respectively). 3.3. Handling procedure Table 6 shows frequencies of pig handling and pig's behavior parameters according to which pigs were assigned to the categories of gentle or rough handling. The group with gentle handling, in which none of the mentioned pig handling or behavior parameters was observed, contained 66% of pigs, while the remaining 34% of pigs were categorized into the group with rough handling. Occurrences of slipping, falling or being electrically prodded are negative to the animal's well-being (Grandin, 2010) and therefore should be minimized during handling. In our study, the use of a stick or electric prod in 17% of pigs led to their slipping, falling and high-pitched vocalization, but also to their jumping on pigs in front, which then exhibited a similar behavior. Similarly, Correa et al. (2010) observed that the use of an electric prod caused a higher incidence of slipping, falling and vocalization in pigs. Greater heart rates and cortisol and lactate concentrations in blood of pigs handled with an electric prod have been reported in several studies (Brundige, Oleas, Doumit, & Zanella, 1998; Correa et al., 2010; Hemsworth et al., 2002), confirming the higher degree of stress. Slipping and falling caused stress in animals (Cockram & Corley, 1991; Grandin, 1998), and therefore, in the current study, pigs that slipped (14%) or fell (13%) experienced a stressful procedure. Furthermore,

high-pitched vocalization can be an indicator of stress and negative emotional states in pigs (Dupjan, Tuchscherer, Langbein, Schon, Manteuffel & Puppe, 2011; Manteuffel, Puppe, & Schön, 2004; Reimert, Bolhuis, Kemp, & Rodenburg, 2013), so the 15% of pigs in our study with such high-pitched vocalization may have done this in response to stress. Table 6 shows stress and meat quality parameters in relation to the handling procedure. Blood lactate content was significantly higher (p b 0.001) after rough handling (13.61 mmol/l) compared to after gentle handling (8.21 mmol/l). The impact of rough procedures on increase of blood lactate was also determined by Hambrecht et al. (2004) and Hambrecht, Eissen, Newman, Smits, den Hartog, et al. (2005). Inadequate pre-slaughter handling operations often elevate blood cortisol levels (Bradshaw et al., 1996). However, no significant differences were found in blood cortisol between the two handling procedures in the current study. Effects of lairage time and handling procedure on blood lactate and cortisol content are shown in Figs. 1 and 2. Significantly higher (p b 0.05) lactate values were measured after rough handling compared to gentle handling, regardless of lairage duration. In terms of blood cortisol, there were no significant differences between the compared groups. After pigs were gently handled prior to slaughter, the initial meat pH value (6.37) was significantly higher (p b 0.01) compared to that of meat from pigs exposed to rough handling (6.26), which is in accordance with the results of most authors (Hambrecht, Eissen, Newman, Smits, Verstegen & den Hartog, 2005; Hambrecht et al., 2004; Rabaste et al., 2007; Stoier, Aaslyng, Olsen, & Henckel, 2001). In fact, rough treatment immediately prior to slaughter causes release of stress hormones that speed up metabolism in muscles and post-mortem glycogen degradation which leads to lower initial pH values of meat (Lambooij, 2000). This is confirmed by significantly higher (p b 0.001) meat temperature after rough handling (38.92 °C) compared to that after gentle handling (38.40 °C). In the current study, ultimate pH values did not differ after rough (5.55) or gentle handling (5.54), while other authors found higher ultimate pH values after rough handling compared to after gentle handling (Carr, Newman, Rentfrow, Keisler, & Berg, 2008; Hambrecht, Eissen, Newman, Smits, Verstegen, et.al., 2005; Hambrecht et al., 2004). Contrary to the findings of most authors who measured darker meat color after rough handling (Hambrecht, Eissen, Newman, Smits, Verstegen, et.al., 2005; Stoier et al., 2001; Terlouw & Rybarczyk, 2008), in the current study, no significant difference was found in the color of meat from pigs handled gently compared to those handled roughly. No significant differences were found between the two handling procedures in the incidences

Table 6 Stress and meat quality parameters in relation to the handling procedure. Parameter

Gentle handling (n = 66) X  SD

Blood lactate (mmol/l) Plasma cortisol (nmol/l) pH60 min pH24h T60 min (°C) Rigor mortis (°) Skin damage score Drip loss (%) CIE L* value CIE a* value CIE b* value Sensory color

8.21α ± 57.08 ± 6.37x ± 5.54 ± 38.40α ± 125.00 ± 6.82 ± 6.41 ± 49.91 ± 7.67 ± 4.19 ± 2.45 ±

4.25 58.64 0.18 0.14 0.67 4.54 2.23 1.41 2.92 1.17 0.84 0.54

Rough handling (n = 34) Min.

Max.

X  SD

1.3 3 6.01 5.26 37.1 115.1 3 3.01 35.11 4.15 2.23 1.0

17.5 248 6.81 5.93 39.9 136.6 12 9.49 55.19 10.62 6.78 4.0

13.61β 63.53 6.26y 5.55 38.92β 124.40 7.47 6.08 50.78 7.80 4.24 2.39

± ± ± ± ± ± ± ± ± ± ± ±

5.84 56.94 0.23 0.13 0.76 4.83 2.48 1.38 3.17 1.43 1.18 0.54

Min.

Max.

2.8 4 5.64 5.32 37.5 116.3 3 3.73 46.64 6.03 2.70 1.0

24.6 221 6.67 5.77 40.3 135.4 12 8.82 60.22 11.83 7.41 3.5

pH60 min and pH24 h — pH values measured 60 min and 24 h post-mortem; T60 min — meat temperature measured 60 min post-mortem; L* — lightness; a* — redness; and b* — yellowness; within a row different letters indicate a significant difference between groups (x,y — p b 0.01; α, β — p b 0.001).

M. Dokmanović et al. / Meat Science 98 (2014) 220–226 Table 7 The effect of handling procedure on incidences of meat quality classes (n = 100). Handling

Gentle Rough Total

Total

PSE

RSE

RFN

PFN

DFD

n

%

n

%

n

%

n

%

n

%

n

%

66 34 100

100 100 100

30 15 45

45.45 44.12 45

25 10 35

37.88 29.41 35

10 5 15

15.15 14.71 15

1 3 4

1.52 8.82 4

0 1 1

0 2.94 1

PSE — pale, soft and exudative; RSE — reddish-pink, soft, exudative; RFN — red, firm and non-exudative; PFN — pale, firm, non-exudative; and DFD — dark, firm and dry meat.

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