A survey of pre-slaughter conditions, halothane gene frequency, and carcass and meat quality in five Spanish pig commercial abattoirs

Meat Science 55 (2000) 97±106

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A survey of pre-slaughter conditions, halothane gene frequency, and carcass and meat quality in ®ve Spanish pig commercial abattoirs M. Gispert a, L. Faucitano a,1, M.A. Oliver a, M.D. GuaÁrdia a, C. Coll a, K. Siggens b, K. Harvey b, A. Diestre a,* a IRTA, Centre de Tecnologia de la Carn. Granja Camps i Armet, 17121 Monells, Spain PIC Group, Department of Pathology, University of Cambridge, Cambridge CB2 1P, UK

b

Received 6 March 1999; received in revised form 1 June 1999; accepted 16 September 1999

Abstract A total of 116 deliveries, comprising 15,695 commercial pigs delivered to ®ve abattoirs, were surveyed during winter and summer. Information about on-farm fasting, transport duration and stocking density, and lairage time was collected. Cortisol, creatine phospho-kinase (CPK), and lactate, and DNA for halothane genotype were analysed in a subsample of pigs at exsanguination in every journey. Electrical conductivity (PQM) in semimembranosus muscle (SM) and carcass characteristics (Fat-o-Meater and skin damage) were measured in each carcass. pHu of SM was analysed in the laboratory in a subsample in every journey. Carcasses were identi®ed as PSE or DFD based on PQM and pHu, respectively. The n gene frequency ranged among abattoirs from 54 to 8%. Mean lean content was 58.9% for nn, 57.3% for Nn, and 55.8% for NN pigs, though a di€erence of 2.5% lean was observed between two abattoirs with the same n gene frequency. A straight relationship of the incidence of serious PSE carcasses and n gene frequency was found. The overall incidence of serious PSE and DFD carcasses was 6.5 and 12.5%, respectively. A higher incidence of PSE carcasses was found in summer; in deliveries with <12 h on-farm fasting; with transport stocking densities >0.40 m2/100 kg pig; and in transports of <2 h duration. A higher incidence of DFD carcasses was found in winter; with transport stocking densities <0.40 m2/100 kg pig; transports of >2 h duration; and lairage times >9 h. Cortisol level in blood increased in winter and decreased after 12±18 h fasting time. A rise in the lactate concentration was observed in pigs transported in high stocking density (<0.40 m2/100 kg pig) and for a longer time (>2 h). All blood stress indices increase as increasing lairage time. Carcasses with more skin damage had higher levels of cortisol, CPK and lactate, and higher incidence of DFD meat, compared with non and low skin damage carcasses. # 2000 Elsevier Science Ltd. All rights reserved.

1. Introduction Transport, lairage and slaughter conditions are of great importance for ®nal meat quality, because ante mortem short-term or long-term stressors change the normal muscle metabolism and a€ect fresh meat colour, waterholding capacity, shelf-life, and technological yields. In pigs subjected to a short-stress situation, the relationship between the genetic susceptibility to stress and meat quality has been demonstrated to be the main cause of pale, soft and exudative meat (PSE) (Cassens,

* Corresponding author. Tel.: +34-972-630052; fax: +34-972-630373. E-mail address: [email protected] (A. Diestre). 1 Present address: PIC Western Europe, Fy®eld Wick, Abingdon, OX13 5NA, UK.

Maple & Eikelenboom, 1975). The mutation well known as the halothane gene (n), which is responsible for genetic stress-prone pigs, can be detected by a DNA-test (Fujii et al., 1991). Halothane positive pigs (nn) have a superior lean carcass content and conformation compared with pigs free of this mutation (NN). Jensen and Barton-Gade (1985) and more recently GueÂblez et al. (1995) found that heterozygous pigs (Nn) produced carcasses with lower backfat thickness and higher loin muscle area when compared with normal NN pigs. Therefore, some countries have a great demand for slaughter pigs carrying that mutant allele. Nevertheless, McPhee and Trout (1995) and Garcia-Macias et al. (1996) found that the n allele has very little e€ect on carcass traits. However, PSE meat can be also detected in pigs from halothane-free populations subjected to acute pre-slaughter stressors immediately prior to slaughter (Honkavaara,

0309-1740/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(99)00130-8

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M. Gispert et al. / Meat Science 55 (2000) 97±106

1989). Long-term stress conditions, i.e. low environmental temperatures, ®ghting when mixing, long transport and lairage times, and prolonged rough handling cause muscle fatigue and reduce the muscle glycogen concentration at slaughter, producing dark, ®rm and dry meat (DFD). An ultimate pH (pHu) higher than 6 is indicative of DFD meat, causing bacteriological spoilage in fresh meat and important technological problems in dry-cured products. The aim of this survey was to evaluate, under commercial conditions, the presence of PSE and DFD meat, to examine the current pre-slaughter conditions from delivery on the farm until slaughter, as well as to determine the frequency of the halothane gene in slaughtered pigs. 2. Material and methods 2.1. Animals A total of 116 deliveries comprising an overall random sample of 15,695 animals transported into ®ve pig commercial abattoirs (referred to as A±E) were surveyed during the winter and summer of 1995. The average number of pigs for each journey was 148 ranging from 62 to 235. Pre-slaughter conditions, on-line measurements, and tissue sampling for further analysis were recorded during 3±5 visits to each abattoir during 1 week in both seasons. The proportion of non-castrated males and females (including castrated males) was 3 and 97% in A; 48 and 52% in B; 36 and 64% in C; 44 and 56% in D; and 58 and 42% in E, respectively. 2.2. Pre-slaughter conditions The deliveries were carried out using 20 lorries and deliveries data have been provided by the drivers after completing a questionnaire with information concerning the transport conditions. The lorries used had natural ventilation and hydraulic lifts for loading and unloading. On-farm fasting time was divided into three periods (<12, 12±18, and >18 h). Stocking density during transport and transport time were divided into two intervals (<0.40 and >0.40 m2/100 kg pig and <2 and >2 h, respectively). Lairage time, obtained by calculating the time elapsing between the arrival time of the animals at the abattoir and the time of slaughter, was divided into three intervals (<3, 3±9 and >9 h). The distribution of the deliveries studied within abattoirs according to the di€erent pre-slaughter conditions is shown in Table 1. Abattoirs C and D did not mix unfamiliar animals during transport; and abattoir B indicated not to mix animals in 60% transports. Abattoirs A and E did not mix animals in 26 and 33%, and 16 and 25% of the transports during winter and summer, respectively. However, all animals were mixed during lairage.

Table 1 Distribution of the deliveries studied according to season, on-farm fasting, stocking densities, transport and lairage time in the ®ve abattoirs studied Abattoirs

Total

A

B

C

D

E

2849

2036

4206

3214

3390

15,695

107

129

188

169

146

148

Season summer winter

12 15

7 9

10 14

9 14

8 18

46 70

On-farm fasting time (h) <12 12±18 >18

3 12 12

5 9 2

14 2 8

12 8 3

13 10 2

47 41 27

Stocking density (m2/100 kg pig) <0.40 >0.40

13 14

14 2

19 5

22 1

14 12

82 34

Transport time (h) <2 >2

22 5

12 4

4 20

7 16

2 24

47 69

Lairage time (h) <3 3±9 >9

4 20 3

1 13 2

1 4 19

4 18 1

11 5 10

21 60 35

Number of pigs Average pigs/delivery

2.3. Abattoirs The ®ve abattoirs were located in di€erent geographical areas in order to cover a wide range of ante mortem conditions and di€erent sources of animals. The description of the lairage pens and stunning methods used at the abattoirs during this survey is provided in Table 2. Abattoir E had the smallest lairage pens (7.50 m2) and the highest lairage stocking density (0.28 m2/100 kg pig), while abattoir D had the largest lairage pens (41.04 m2) keeping 100 pigs by pen (0.41 m2/100 kg pig). Only abattoir A used metal tubes to divide the pens, and only in abattoir E drinking water was not available during lairage. All the abattoirs showered the pigs in lairage. Abattoir A used carbon dioxide stunning (83% CO2 Butina, APS, Copenhagen) while 3 abattoirs used head-only automatic electrical stunning device (B with 500 V, and D and E with 700 V,) combined with Vtype restrainers (Valhalla1, Stork). Abattoir E replaced this stunning system with an automatic head-to-heart electrical system combined with a chest belt restrainer (Midas1, Stork) during summer. The same novel stunning system was also installed during the summer in abattoir C replacing the manual electrical stunning system (250 V) used during winter. The two abattoirs in which the

M. Gispert et al. / Meat Science 55 (2000) 97±106 Table 2 Lairage and stunning facilities in the abattoirs surveyed Abattoirs A Annual slaughtering Lairage pens Area (m2) Pigs per pen Density (m2/100 kg pig) Solid walls Drinking water

B

C

D

E

418,252 271,021 525,000 442,717 886,398 13.25 26 0.51

20.00 30 0.67

11.25 22 0.51

41.04 100 0.41

7.50 27 0.28

± Yes

Yes Yes

Yes Yes

Yes Yes

Yes ±

Stunning methods Restrainer V-type Restrainer chest belt Electric manual Electric automatic Electric head-to-heart CO2

± ± ± ± ± Yes

Yes ± ± 500V ± ±

Yes Yes 250V ± 250V ±

Yes ± ± 700V ± ±

Yes Yes ± 700V 250V ±

Bleeding-out position Hoisted Lying

Yes ±

Yes ±

Yes Yes

Yes ±

Yes Yes

Line speed (pigs/h)

240

150

250

350

550

novel electrical stunning system (C and E) was installed, also started bleeding the pigs in the lying position at the same time. Line speed ranged from 150 (B) to 550 pigs/h (E). At all abattoirs, except abattoir A, carcasses went through a chilling tunnel and were kept in refrigeration for di€erent times (B 105; C 120; D 35; E 50 min). Abattoir A was equipped with a conventional chilling system. 2.4. Measurements of carcass and meat quality The carcass weight (kg) was recorded for each carcass. Carcass grading was carried out by using the Fat-o-Meater grading probe (FOM). Carcass lean percentage was estimated from backfat and loin muscle thickness (Gispert & Diestre, 1994). Meat quality was assessed by measuring electrical conductivity with the Pork Quality Meter (PQM-IINTEK, Gmbh, Germany) in the semimembranosus muscle (SM) 1±2 h post mortem in 14,370 carcasses (2536 in A; 1740 in B; 4182 in C; 2883 in D; and 3029 in E). Ultimate pH (pHu) was measured in 3075 random samples taken from the SM at 1 h post mortem. An average of 25.4 carcasses per journey were sampled, except in one of the deliveries studied (731 in A; 427 in B; 729 in C; 629 in D; and 559 in E). The samples were kept in refrigeration (3±4 C) for 24 h and then frozen (ÿ20 C) and pHu was measured after thawing (CRISON, micro pH 2001) in the laboratory (Solomon, 1987). Carcasses showing PQM values between 4 and 6 m s were classi®ed as moderate PSE and those >6 as serious PSE, whereas the carcasses presenting pHu values

99

between 6 and 6.2 were classi®ed as moderate DFD and those >6.2 as serious DFD. Meat was considered as being of normal quality when PQM was <4 and pHu <6 for PSE and DFD respectively. Skin damage was scored in each carcass by using a photographic scale ranging from 1 (no damages) to 5 (severe damages) (Meat and Livestock Commission, 1985). 2.5. Blood indices of stress and halothane genotype A random blood sample was collected at exsanguination in approximately 20% of the pigs of each of the deliveries to determine cortisol, creatine phospho-kinase (CPK), lactate, and the halothane genotype. Immediately, 2 ml of blood were put in an eppendorf tube containing 40 ml of ¯uoride/EDTA solution (Boehring, Manheim) and within 30 min, 2 ml of the liquid phase of the settled blood were put in eppendorf tubes and centrifuged at full speed (10,000 RPM) for the analysis of cortisol and CPK. Finally, the serum and plasma obtained were put into cryotubes of 1 ml and frozen in liquid nitrogen for the transportation and stored at ÿ20 C until analysis. Cortisol concentration was measured in 1567 samples (378 in A; 212 in B; 336 in C; 333 in D; and 308 in E) by competitive radioimmunoassay (Incstar ref. Ca-1549) and expressed as mg/100 ml. An average of 13.5 pigs per journey ranging from 5 to 18 pigs were available to determine cortisol. The CPK and lactate concentrations were assessed by enzyme kits (Gernon ref. 43125 and Boehring ref. 256773 respectively) and expressed as log UI/l and mg/100 ml, respectively. With the analysis of CPK, a previous dilution of the samples was necessary to guarantee the linearity of the values obtained. CPK and lactate were determined in 2875 (701 in A; 389 in B; 662 in C; 642 in D; and 481 in E) and 2958 (747 in A; 395 in B; 672 in C; 655 in D; and 489 in E) samples respectively, with an average of 24.8 pigs per delivery in the case of CPK and 25.5 pigs per delivery in the case of lactate. A minimum of 6 pigs and a maximum of 32 pigs per delivery were sampled to determine the concentration of both blood stress indicators. DNA was prepared from 1331 blood samples for halothane genotype analysis. The HAL 1843 genotype (homozygous nn and NN and the heterozygous Nn) was determined by PCR ampli®cation and digestion with restriction enzymes as described previously by Fujii et al. (1991). (The HAL-1843 trademark is licensed from Innovations Foundation, Toronto, Canada). An average of 11.5 pigs per journey was analysed. No halothane genotyping was available in two deliveries. The distribution of the number of samples by genotypes and abattoirs is presented in Table 3. 2.6. Data analysis A Chi Square test was applied to compare the distribution of the frequencies of PSE and DFD classes

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Table 3 Number, mean values and standard deviation (SD) of carcass and meat quality traits, blood indices of stress, and halothane genotype and gene frequency in the abattoirs surveyed Number

Carcass weight (kg) 3/4 last rib backfat (mm) 3/4 loin depth (mm) Estimated carcass lean (%) PQM (ms) pHu Skin damage Cortisol (mg/100 ml) CPK (logUI/1) Lactate (mg/100 ml) Halothane genotype Number nn (%) Nn (%) NN (%) Frequency n gene (%)

15,695 14,064 14,064 14,064 14,370 3075 15,535 1567 2875 2958 1331 82 688 561 32.0

A

B

C

D

E

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Mean

SD

76.6 14.4 58.5 58.1 4.7 5.7 1.9 8.3 3.9 107.2

9.16 4.07 6.31 3.78 2.99 0.26 0.54 2.79 0.35 29.93

76.2 15.7 55.4 56.5 4.0 5.8 2.5 7.7 3.9 122.5

8.45 4.19 5.83 3.84 1.22 0.29 0.69 2.62 0.42 37.41

82.6 15.8 55.0 56.3 4.4 5.9 2.1 9.1 3.8 131.9

9.59 4.04 6.18 3.66 0.85 0.30 0.34 2.96 0.39 30.90

76.2 15.9 54.0 56.0 4.2 5.9 2.2 8.3 3.7 129.3

9.77 4.25 6.06 3.88 1.31 0.33 0.54 2.61 0.40 31.06

78.3 15.1 61.1 57.9 4.2 5.6 1.8 6.5 3.6 101.3

9.77 3.95 7.48 3.71 1.67 0.26 0.66 2.91 0.45 30.07

348 14.9 78.2 6.9 54.0

246 3.3 52.0 44.7 29.3

262 ± 16.0 84.0 8.0

236 5.5 44.1 50.4 27.5

239 3.8 59.3 36.8 33.5

(normal, moderate, and serious), according to the intervals or periods stipulated within each of the preslaughter conditions collected. This information is presented in Table 5. No further statistical analysis was performed due to the number of independent variables this survey has included, as well as to the extensive variability that may exist among the numerous uncontrolled factors. Therefore, the rest of the ®gures and tables were made using the mean values and their standard deviations.

densities >0.40 m2/100 kg pig less variation was observed in E (from 0.34 to 0.55 m2/100 kg pig). The lairage time was extremely variable among the abattoirs (from less than 1 up to 15 h). On average, abattoir D had a shorter (between 3 and 4 h) and less variable (from 2 to 9 h) lairage times compared with the others. Contrarily, extremely long lairage periods were recorded at abattoir C in winter, where each delivery was held in lairage for over 9 h.

3. Results and discussion

The abattoirs A and E had lower backfat and higher loin depth and consequently more estimated lean content (58.1 and 57.9%, respectively) compared with abattoirs B, C and D (56.5, 56.3 and 56.0%, respectively) (Table 3). These last abattoirs had lesser lean content than the national average (57.8%) (Diestre & Gispert, 1997). The highest PQM mean was found in abattoir A (4.7) followed by C (4.4); D and E (4.2) and B (4.0). The pHu mean was higher in abattoirs C and D (5.9) followed by B (5.8), A (5.7) and E (5.6). Abattoir B had higher skin damage mean score (2.5), especially when compared to A and E which had mean scores lower than 2. The means of cortisol and lactate were 6.5 mg/100 ml and 101.3 mg/100 ml in pigs slaughtered in abattoir E respectively, while means for cortisol ranging from 7.7 to 9.1 mg/100 ml and for lactate from 107.2 to 131.9 mg/100 ml in the rest of the abattoirs. CPK level was lower in abattoir E (3.6 log UI/l) than in A and B (3.9 log UI/l). In general, abattoir E was less noisy and the pigs were easy to drive to the stunning point. These observations are con®rmed by the transport plus lairage mortality (0.07%) recorded at this abattoir (Guardia, Gispert & Diestre, 1996), which was signi®cantly lower

3.1. Pre-slaughter animal handling As shown in Fig. 1, on-farm fasting mean time was around 12 h during summer and winter in abattoirs B, D and E, as well as during summer in abattoir C. The longest on-farm fasting mean time was found during the winter deliveries to abattoir C (19 h), having the most extreme period of feed withdrawal registered (34 h). The pigs studied in the deliveries to abattoir A were also subjected to relative long fasting periods (around 16 h). On average the abattoirs A and B had the shortest transport times (<2 h). The mean duration of transport time for abattoir C was intermediate (between 2 and 3 h). Abattoirs D and E subjected pigs to long transport times (>3 h) with maximum duration higher than 6 h. During transports to abattoirs A and E pigs had more space available (0.40 and 0.42 m2/100 kg pig respectively), compared to B and D (0.28 and 0.34 m2/100 kg pig respectively), being the average stocking density intermediate in the deliveries to abattoir C (0.39 m2/100 kg pig). When comparing the two abattoirs with stocking

3.2. Stress indicators, carcass and meat quality by abattoir

M. Gispert et al. / Meat Science 55 (2000) 97±106

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Fig. 1. Means, maximum and minimum values for on-farm fasting times, stocking density, transport and lairage times of the deliveries during summer & and winter & in the ®ve abbatoirs studied.

than the mortality found in abattoirs D, C, A, and B (0.16, 0.30, 0.46 and 0.55% respectively). The highest frequency of the halothane gene (n) was obtained in abattoir A (54%), with a total of 14.9% homozygous stress susceptible pigs (nn). Only in abattoir C no nn pigs were found having the lowest gene frequency (8%). The ranking of genetic stress susceptibility of the abattoir from high to low was the following: A, E, B, D and C (Table 3). 3.3. Halothane gene e€ect As shown in Table 4, the carcass characteristics from Nn were between both homozygotes. In fact, their estimated lean content was 1.5% higher and lower when compared to NN and nn, respectively. The scienti®c literature is controversial about the advantage on fatness and muscularity of the carcasses from heterozygous pigs. Jensen and Barton-Gade (1985) and more recently GueÂblez et al. (1995) found that Nn pigs had lower backfat thickness and higher loin area than NN pigs. However, McPhee and Trout (1995) and GarcõÂa-MacõÂas et al. (1996) found that the halothane gene had no signi®cant e€ect on fatness and very little e€ect on muscularity. These ®ndings are supported by O'Brien, Ball and Maclennan (1994) indicating that the expression of the mutation is modi®ed by the breed. In fact, abattoirs D and E had 2.5% di€erence in carcass lean percentage with approximately the same frequency of the n gene, suggesting that other factors are also determining this trait. However, some relationship between the n gene frequency and carcass lean content (R2=0.45) was found (Fig. 2).

PQM mean from Nn and NN pigs was similar (4.2) and lower with respect to nn ones (6.5). It is more clear that objective meat quality measurements of PSE are closely related to the halothane genotype, although the position of the heterozygous pigs is still uncertain and controversial. Wolf-Schwering and Kallweit (1991) showed Nn to be closer to NN pigs; Rundgren, Lundstrom, Edfords-Lilja and Juneja (1990) indicated that heterozygotes were intermediate; and Pommier and Houde (1993) found they were closer to nn pigs. A strong positive association between the serious PSE carcasses and the frequency of the halothane gene (R2=0.87) was found (Fig. 2). Abattoir A with the highest frequency of the n gene had 13.2% and abattoir C with the lowest frequency of the gene had 3 of serious PSE. Ultimate pH (pHu) was higher in NN carcasses (5.9) compared with Nn and nn (5.7). The highest pHu found in NN carcasses can be caused by the longest preslaughter treatment of pigs slaughtered in abattoir C with the lowest frequency of the n gene (8%). In 79% of the deliveries to abattoir C pigs were kept in the lairage pens >9 h. Additionally, the most extreme on-farm fasting time (34 h) was recorded in this abattoir. The halothane gene does not seem to have any in¯uence on the levels of lactate and pHu, as pigs slaughtered at abattoir D with a relatively high frequency of the gene (27.5%), showed levels of lactate (129.3 mg/100 ml) and pHu (5.9) as high as those killed at abattoir C. This can be attributed to the longer transport time and higher stocking density during transit to abattoir D. In fact, 16 out of a total of 23 deliveries studied had transports of

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Table 4 Means and standard deviation (SD) of the carcass quality, meat quality and blood indices in the di€erent halothane gene status Halothane genotype Overall

Carcass weight (kg) 3/4 last rib backfat (mm) 3/4 last rib loin depth (mm) Estimated lean content (%) Skin damage PQM (ms) pHu Cortisol (mg/100 ml) CPK (logUI/l) Lactate (mg/100 ml)

nn

Nn

NN

Mean

SD

Mean

SD

Mean

SD

Mean

SD

78.1 15.4 56.9 57.0 2.01 4.3 5.8 8.2 3.8 118.7

9.91 4.12 7.00 3.85 0.58 1.72 0.31 3.08 0.43 34.32

75.4 13.8 60.4 58.9 1.9 6.5 5.7 8.1 4.2 122.1

8.16 4.00 8.48 3.89 0.44 4.35 0.28 2.86 0.39 34.47

77.9 15.2 58.2 57.3 2.1 4.2 5.7 8.1 3.9 115.1

9.05 4.08 6.52 3.83 0.60 1.52 0.29 2.82 0.38 33.76

79.7 16.4 54.7 55.8 2.2 4.2 5.9 8.1 3.7 120.6

9.32 4.47 6.30 4.09 0.53 1.16 0.32 3.04 0.40 34.03

>2 h and 22 out of a total 23 deliveries had a stocking density <0.40 m2/100 kg pig. These results are in agreement with previous works showing that the n allele had no signi®cant e€ect on ultimate muscle pH (Jensen and Barton-Gade, 1985; GarcõÂa-MacõÂas et al., 1996; Larzul et al., 1997). In agreement with previous studies (Nyberg, Lundstrom, Edfors-Lilja & Rundgren 1988; Shaw, Trout & McPhee, 1995), the level of cortisol obtained does not seem to be in¯uenced by the halothane gene. However, con®rming the results of the literature (Honkavaara, 1988), CPK level was higher in nn (4.2 log UI/l), and lower in NN (3.7 log UI/l) being the levels of Nn intermediate (3.9 log UI/l). In relation to lactate concentration, higher level was obtained in NN pigs (120.6 mg/100 ml) and nn pigs (122.1 mg/100 ml) compared with Nn ones (115.1 mg/ 100 ml). The increase of the lactate concentration in the free-halothane carcasses could be explained by the e€ects of the above-mentioned long-term stress in the deliveries studied to abattoir C, which had the highest proportion of NN pigs studied (84%). 3.4. PSE and DFD incidence The distribution of the frequencies of the various PSE and DFD groupings was signi®cantly di€erent (p<0.001) between the intervals or periods within each of the pre-slaughter conditions studied using a Chi square test. Serious PSE and DFD incidence ranged widely from 3 to 13.2% and 3.6 to 19.8% respectively among abattoirs (Table 5). The highest incidence of serious PSE carcasses was observed in pigs slaughtered at the abattoir A, where the highest n gene frequency was found. It seems clear that the high percentage of nn pigs (14.9%) triggers the incidence of serious PSE carcasses in this abattoir. On the other hand, abattoir C with no nn pigs showed the lowest incidence of serious PSE carcasses, but had higher incidence of moderate PSE meat (67.3%) and less normal meat (29.7%) according to the PQM deter-

minations, compared with the other abattoirs. This con®rms the evidence that the PSE myopathy (i.e. moderate) can be also triggered out by environmental factors. Indeed, abattoir C had the highest incidence of very DFD carcasses (19.8%) indicating the stressful conditions experienced by animals before slaughter. During summer, the incidence of serious PSE and particularly moderate PSE were higher than in winter (8.5 vs 5.2% and 58.5 vs 39.9% respectively), while the incidence of serious DFD carcasses was higher during winter than summer (13.4 vs 8.4%). The higher incidence of DFD meat in winter is explained by higher muscle glycogen depletion under colder climatic conditions as already observed by Gallwey and Tarrant (1978) and more recently by Homer and Matthews (1998). On the other hand, the increase of temperature during summer is followed by higher incidence of PSE meat (Cassens et al., 1975; Santos, Almeida, Matias, Franqueza, Roseiro & Sardinha, 1997). A lower PSE incidence was observed when pigs are subjected to on farm fasting periods from 12 to 18 h compared with shorter on farm fasting times. These results support the recommendation of Chevillon (1994) concerning the application of 12±18 h on-farm fasting time in order to reduce meat quality problems. On the other hand, a higher proportion of moderate DFD carcasses (15.4%) was observed in >18 h fasting times compared to shorter fasting periods. When animals are subjected to short on-farm fasting periods (<12 h) a higher proportion of normal meat (pHu <6) is observed (Table 5). In relation to the PSE groupings, less normal meat (45.1%) and particularly more moderate PSE (48.6%) were observed when transports with stocking densities >0.40 m2/100 kg pig were used. More serious DFD (12.3%) and moderate DFD (13.6%) carcasses were found in transports with stocking densities <0.40 m2/ 100 kg pig, compared with stocking densities >0.40 m2/ 100 kg pig (8.7 and 9.6%, respectively). The EC Directive on the protection of animals during transport (O€.

M. Gispert et al. / Meat Science 55 (2000) 97±106

103

decrease. It is well known that longer transport times may deplete glycogen content in muscle increasing the incidence of DFD meat, especially when associated with long fasting period (Warriss & Bevis, 1987). In this survey, the short deliveries can provoke acute stress when glycogen levels are still high causing more potentially serious PSE meat. The time intervals pigs spent in lairage pens clearly a€ected the DFD meat categories. In fact, as lairage time increased, the proportion of moderate and serious DFD carcasses increased. In the case of PSE categories, long lairage time (>9 h) reduced the proportion of carcasses with normal meat. The increased DFD percentage is due to the long-term e€ect of lairage on muscle glycogen exhaustion. 3.5. Blood stress indicators

Fig. 2. The relationship between n gene frequency and estimated carcass lean and serious PSE (PQM>6).

J. Europ. Comm. No. L340/17) states that pigs should be transported using a minimum stocking density of 0.425 m2/100 kg pig or 235 kg/m2, in order to permit pigs to stand and lie down naturally. In our study, we found that deliveries with stocking densities >0.40 m2/ 100 kg pig produce a better proportion of good meat quality (PQM <4 and pHu <6). When comparing the two transport times (<2 and >2 h), a lower proportion of acceptable meat quality according to PQM and pHu is found when pigs were subjected to long transport times compared with short transport times (44.1 vs 51.2% and 72.2 vs 82.0%, respectively). Long transport increased the proportion of moderate and serious DFD and moderate PSE meat, while the proportion of serious PSE meat tended to

The lower summer levels of cortisol (7.7 mg/100 ml) and CPK (3.7 log UI/l) compared with those found during winter (8.5 mg/100 ml and 3.9 log UI/l) indicate that pigs were subjected to less stressful conditions in summer (Table 6). As for cortisol, our results agree with the ®ndings of Baldwin and Stephens (1973) and Dantzer and Mormede (1983) who recorded a higher cortisol secretion under cold temperature due to the higher energy demand to maintain the body temperature. However, the evidence of an increased CPK activity and lactate production in summer (Honkavaara, 1989) is not con®rmed in this study. This is possibly due to the better precautions taken by the handlers in the summer season. The lowest level of cortisol was found in the group of animals fasted on farm from 12 to 18 h (7.5 mg/100 ml). This fasting time allows pigs to better cope with stress when compared to pigs fasted for >18 h (8.8 mg/100 ml) or for <12 h (8.4 mg/100 ml). The elevation of the cortisol levels either in the short or long periods of fasting can be due to the occurrence of travel sickness when pigs are transported on full stomach or can also be caused by the increasing demand for energy supply (von Mickwitz, 1982). The mean values of CPK seem to be less a€ected by on-farm fasting in agreement with Warriss, Brown, Edwards, Anil and Fordham (1992). The high lactate concentration indicates that pigs arrived more exhausted at the exsanguination point when they were transported at higher stocking densities (121.7 vs 111.1 mg/100 ml) and for longer times (122.1 vs 114.2 mg/100 ml). Low transport densities (>0.40 m2/100 kg pig) caused less physical injuries to pigs as shown by the lower lactate concentration, and produced a slightly less psychological stress as indicated by lower cortisol levels in blood. Our results agree with those obtained by Guise and Penny (1989) who concluded that welfare is compromised at stocking densities lower than 0.3 m2/100 kg pig. The variation of the blood parameters according to the three intervals of lairage indicates that the level of stress in pigs increased as increasing lairage time as Honkavaara (1989) found.

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Table 5 Number of carcasses and distribution in percentages of normal pigmeat, moderate and serious PSE and DFD meat by abattoir, season, on-farm fasting time, stocking density, transport and lairage conditions Normalc

Normalf

PSE Moderate

b

a

Serious

DFD Moderatee

Seriousd

Number Overall

6672 46.4

6765 47.1

933 6.5

2345 75.0

384 12.5

346 12.5

Abattoir A B C D E

51.1 60.0 29.7 48.2 56.2

35.7 35.3 67.3 46.8 35.7

13.2 4.7 3.0 5.0 8.1

86.9 79.2 58.9 68.5 91.4

8.3 10.5 21.3 15.1 5.0

4.8 10.3 19.8 16.4 3.6

Season summer winter

33.0 54.9

58.5 39.9

8.5 5.2

79.6 73.7

12.0 12.9

8.4 13.4

On-farm fasting time (h) <12 12±18 >18

50.7 55.1 49.4

42.8 39.1 43.6

6.5 5.8 7.0

78.9 74.8 73.0

11.1 11.9 15.4

10.0 13.3 11.6

Stocking density (m2/100 kg pig) <0.40 >0.40

45.1 50.4

48.6 42.4

6.3 7.2

74.1 81.7

13.6 9.6

12.3 8.7

Transport time (h) <2 >2

51.2 44.1

40.8 50.2

8.0 5.7

82.0 72.2

9.5 14.6

8.5 13.2

Lairage time (h) <3 3±9 >9

53.9 49.3 38.8

40.6 43.5 55.2

5.5 7.2 6.0

86.5 79.1 65.4

10.2 10.9 16.6

3.3 10.0 18.0

a b c d e f

Serious PSE=PQM>6. Moderate PSE=46.2. Moderate DFD=6
3.6. Relationship among meat quality measurements, blood stress indicators and skin damage score In Table 7, meat quality measurements and blood stress indices means according to the subjective scores for skin damage are shown. The extremely severe and very severe damages were pooled in one category (severe) and 1.5% of the carcasses were scored as such. The majority of the carcasses (73.5%) were scored in the moderate skin damage category. No nn pigs were scored as having severe damages. PQM and pHu values were lower in no damaged carcasses (3.95 and 5.64, respectively) and pHu increases as the skin damage severity increases. Animals showing more skin damages had higher levels of cortisol (9.47 mg/100ml), CPK (4.21 log UI/l), and lactate (126.39 mg/

100 ml) in their blood at slaughter. In rodents subjected to electric shock, behavioural responses (Natelson, Creighton, McCarty, Tapp, Pitman & Ottenweller 1987), plasma catecholamine levels (Natelson, Tapp, Adamus, Miller & Levin, 1981) and hypothalamicpituitary-adrenocortical axis activation (Wiener & Levine, 1983) increase with the intensity of the stimulation. Therefore, there is a graded psycho-biological response according to the degree of damage. Certainly, the progressive increase in ultimate pH indicates that glycogen has been depleted, leading to potentially more DFD meat (Warriss et al., 1998). In our case, the potentially PSE carcasses were higher in those carcasses with moderate skin damage score, and gradually decreased in very much and severe skin damage carcasses to the same level of non skin damaged carcasses.

M. Gispert et al. / Meat Science 55 (2000) 97±106

105

Table 6 Means and standard deviation (SD) of blood stress indices according to seasons and preslaughter conditions Cortisol (mg/100 ml)

CPK (logUI/l)

Lactate (mg/100 ml)

Mean

SD

Mean

SD

Mean

SD

Season summer winter

7.7 8.5

2.82 3.22

3.7 3.9

0.43 0.40

119.3 118.3

33.51 34.93

On-farm fasting time (h) <12 12±18 >18

8.4 7.5 8.8

2.96 2.97 3.25

3.8 3.8 3.9

0.43 0.42 0.42

123.6 115.3 116.3

34.82 33.83 33.49

Stocking density (m2/100 kg pig) <0.40 >0.40

8.3 8.0

3.01 3.26

3.8 3.8

0.42 0.44

121.7 111.1

34.49 32.68

Transport time (h) <2 >2

8.2 8.2

2.98 3.15

3.8 3.8

0.41 0.43

114.2 122.1

33.0 34.9

Lairage time (h) <3 3±9 >9

7.8 8.2 8.4

3.39 2.88 3.21

3.6 3.8 3.9

0.37 0.41 0.45

112.9 118.2 123.3

36.21 33.11 34.86

Table 7 Means and standard deviations (SD) of meat quality characteristics and blood stress indices according to subjective carcass skin damage scores Number

Average distribution (%) PQM (ms) pHu Cortisol (mg/100 ml) CPK (log UI/l) Lactate (mg/100 ml)

14,202 3060 1578 2803 2977

None

Moderate

Very much

Severe

Mean

SD

Mean

SD

Mean

SD

Mean

SD

10 3.95 5.64 7.63 3.77 105.35

1.81 0.24 3.04 0.38 32.96

73.5 4.40 5.80 8.18 3.95 119.07

1.77 0.30 3.09 0.38 33.98

15.0 4.17 5.87 8.80 4.00 124.87

1.34 0.35 2.98 0.42 34.64

1.5 4.08 5.86 9.47 4.21 126.39

1.24 0.35 4.04 0.39 34.48

The reduction of the early glycolysis rate, typical of PSE meat, in the very much and severe skin damaged carcasses indicates that these animals have depleted their glycogen reserves after experiencing long-term stress conditions. The skin damage score re¯ects the amount of ®ghting which pigs have indulged in during pre-slaughter, which prevents resting behaviour (Barton-Gade, Blaabjerg & Christensen, 1992; Warriss et al., 1998). In fact, we found higher skin damage scores in the carcasses from pigs transported at the highest stocking density (abattoirs B and D). However, Barton-Gade and Christensen (1998) found little e€ect on blood pro®le and meat quality with varying stocking densities between 0.35 and 0.50 m2/100 kg pig. These authors suggest a risk of increased skin damage when more space than 0.35 m2/100 kg pig was given during short transports.

4. Conclusions Some recommendations can be given on the basis of the information obtained in this survey. The presence of an important proportion of nn stress-susceptible pigs can trigger the development of serious PSE meat. Though the halothane gene increases the lean content overall, abattoirs with the same frequency of this gene can have important di€erences in lean content. Therefore, producers should evaluate the bene®ts on carcass composition when including the gene in their crossing schemes. Environmental aspects, such as high stocking density, long transports and lairage periods, reduce the proportion of normal meat quality, independently of the presence of the halothane gene. On-farm fasting periods between 12 and 18 h reduce pre-slaughter stress

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