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The effects of halothane sensitivity on carcass composition and meat quality in HAL-1843-normal pigs^1,2

C. P. Allison^*, R. C. Johnson and M. E. Doumit^*,,3

^* Departments of Animal Science and and Food Science and Human Nutrition, Michigan State University, East Lansing 48824; and and Farmland Foods, Denison, IA 51442

	Abstract

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Objectives of this study were to determine the incidence of halothane sensitivity in pigs that are homozygous normal at the ryanodine receptor nucleotide 1843 (HAL-1843-normal) and the relationships between halothane sensitivity and carcass composition or meat quality. In Exp. 1, piglets (Lines A, B, C, and D; n = 168, 170, 168, and 169, respectively) were obtained from mating a HAL-1843-normal sire line to four HAL-1843-normal dam lines. In Exp. 2, piglets from Lines A and B (n = 87 and 90, respectively) were included with piglets (Lines E, F, G, and H; n = 94, 92, 89, and 89, respectively) obtained from mating four HAL-1843-normal sire lines to a single HAL-1843-normal dam line. Pigs were subjected to 3% halothane at approximately 9 wk of age. In Exp. 1, limb rigidity, blotching of the skin, and muscle tremors were visually assessed, and based on these criteria, halothane sensitivity (HS) was observed in 48% of the pigs. To better characterize this response, a scoring system was developed and used in Exp. 2. Using this system, 25, 42, and 33% of the pigs in E and 40, 33, and 27% of the pigs in Line G were categorized as HS-low (HS-L), HS-intermediate (HS-I), and HS-high (HS-H), respectively. In Lines F and H, 13 and 18% of the pigs were HS-I, and 0 and 2% were HS-H, respectively. No consistent effects due to HS were observed in carcass composition or meat quality; however, when a subset of pigs from Exp. 2 were subjected to more extensive handling and transportation before slaughter, ultimate pH was lower and drip loss was higher in LM from HS-H compared with HS-L pigs (P < 0.05; n = 71). These results demonstrate that some pigs are sensitive to halothane anesthesia even in the absence of the known HAL-1843 polymorphism. Additionally, halothane sensitivity may be associated with inferior pork quality under adverse antemortem conditions.

Key Words: Halothane • Pork Quality • Stress Susceptibility • Swine

	Introduction

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Porcine stress syndrome (PSS) is characterized by open-mouth breathing, blotching of the skin, hyperthermia, muscle rigidity, and either loss of mobility or death (Topel et al., 1968). These same characteristics have also been documented in some cases when humans (Denborough et al., 1962) and pigs (Hall et al., 1966; Harrison et al., 1968) are subjected to halothane anesthesia. Because of these similarities, the halothane test was implemented to predict stress susceptibility of swine (Webb and Jordan, 1978).

Fujii et al. (1991) compared the full-length cDNA sequence of the sarcoplasmic reticulum Ca-release channel (ryanodine receptor; RYR1) of a halothane-sensitive (HS) Pietrain and a halothane nonsensitive (HN) Yorkshire. These researchers identified a C1843T polymorphism (HAL-1843), which codes for an AA change of arginine to cysteine at residue 615. Due to the association of the HAL-1843 polymorphism with the incidence of PSS and an increase in frequency of PSE pork, most swine genetics companies eliminated this polymorphism from their herds.

Rempel et al. (1993) demonstrated that 23% of the pigs classified as homozygous normal (C/C) at RYR1 nucleotide 1843 (HAL-1843-normal) responded abnormally to halothane anesthesia. Thus, it seems reasonable to postulate that other mutations may occur in the RYR1 or other proteins involved in Ca regulation that would lead to altered ability to control cytoplasmic calcium concentration. Indeed, 23 other mutations in the human RYR1 have been identified that are linked to halothane sensitivity (Girard et al., 2001). It is unclear what proportion of HAL-1843-normal pigs are HS, and it is unknown whether sensitivity to halothane is associated with PSS or an increase in the frequency of inferior quality pork. Therefore, we hypothesized that some HAL-1843-normal pigs respond abnormally to halothane anesthesia and are more prone to producing inferior quality pork products.

	Materials and Methods

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Animals and Halothane Challenge Test
The Michigan State University Animal Use and Care Committee approved the protocol for animal handling and halothane administration (No. 04/02-057-00). One thousand two hundred sixteen (1,216) cross-bred pigs were subjected to a halothane challenge test in two separate experiments. In Exp. 1, piglets (Lines A, B, C, and D; Table 1) were randomly selected from progeny generated by inseminating four commercially available, HAL-1843-normal dam lines (Lines D1, D2, D3, and D4, respectively) with pooled semen from a commercially available, HAL-1843-normal sire line (S1). Piglets used in Exp. 2 (Lines E, F, G, and H; Table 1) were randomly selected from progeny generated by inseminating a single, commercially available HAL-1843-normal dam line (D5) with pooled semen from four commercially available HAL-1843-normal sire lines (S1, S2, S3, and S4). Two lines from Exp. 1 (A and B) were also included in Exp. 2. In both experiments, sire and dam lines were assumed to be HAL-1843-normal based on selection against the detrimental allele in these lines of pig for many generations. All piglets were shipped to the New Ulm Test Station in New Ulm, MN, at approximately 17 d of age and individually identified on arrival.

Pigs weighed an average of 15.7 ± 2.8 kg and were 8 wk old in Exp. 1, whereas pigs in Exp. 2 were 22.8 ± 3.4 kg and were 9 wk of age, when halothane testing was performed. This is similar to the age shown by Carden and Webb (1984) to elicit the highest probability of an abnormal response. The halothane test was administered similarly to that described by Webb and Jordan (1978). Pigs were exposed to 3% halothane in a closed system, with a delivery rate of 2 L/min for a total of 4 (Exp. 1) or 3 (Exp. 2) min. Pigs were placed in a sitting position on an elevated platform and a mask was applied to the snout of each pig. Care was taken to ensure that the mask fully covered the mouth of the pig to maximize inhalation of halothane. At approximately 1 min into the test, the pigs were unconscious and were placed flat on their backs. Limb rigidity, blotching of the skin, and muscle tremors were documented. Animals exhibiting any of these symptoms were considered to be HS.

To more precisely characterize the response to halothane in Exp. 2, a scoring system was developed. Each limb was individually evaluated for rigidity and scored on a scale of 1 to 4 (1 = no stiffness; 2 = minor stiffness with some straightening of limb; 3 = stiffness with no flexion at knee, hock, or pastern; and 4 = stiffness with no flexion at knee, hock, or pastern, and shoulder or hip immobile). Blotching was scored on a scale of 1 to 3 over the entire belly of the pig (1 = no discoloration; 2 = minor blotching or pinking; and 3 = severe blotching or purple). Tremors were often observed from the middle to end of the testing period in the front limbs and shoulder, and were scored on a scale of 1 to 3 (1 = no tremors; 2 = minor tremors; and 3 = severe tremors). The average limb rigidity score was added to the blotching and tremor scores to calculate the halothane response. The cumulative halothane score was more highly correlated to phenotypic traits of interest than any individual or combination of responses observed. Pigs were then categorized into three groups based on their cumulative score: HS-low (HS-L; 3.00 to 4.00), HS-intermediate (HS-I; 4.01 to 5.49), and HS-high (HS-H; >5.49).

To determine the probability of misclassifying a pig’s response to halothane on one test, 177 pigs from Lines A and B (Exp. 2) were subjected to halothane on 2 d, with 1 d of rest between evaluations. Different evaluators scored the response to halothane on each day, but all other procedures were as previously described.

Animal Handling Model
Eighty pigs from Lines E and G were used in an animal-handling model described by Marr et al. (2004). Briefly, 10 groups of eight pigs each were briskly moved through a 36.6-m-long aisle that was 2.1 m wide at each end and 0.6 m wide in the middle 18.3 m. Each group was moved down and back four times with each pig receiving a minimum of one electrical prod per pass (eight prods per pig). Following the model, four of these pigs were euthanized because they were deemed to be in distress by an attending veterinarian. The remaining pigs were allowed 8 h of rest and then transported to one of two slaughter facilities. All procedures for the animal-handling model were approved by the Elanco Animal Health (Greenfield, IN) Animal Use and Care Committee (No. 03033).

Meat Quality Data Collection
Meat quality data were collected on 281 pigs in Exp. 1 and on 293 pigs in Exp. 2. Pigs were marketed over a 6-wk timeframe in Exp. 1 (September to October), with the heaviest pigs in each pen being shipped at 2-wk intervals. In Exp. 2, all pigs were marketed during the month of January, with Lines A and B marketed on 2 d and Lines E through H marketed on 3 d. To maintain a balanced design, pigs were matched for line, gender, and halothane response whenever possible. Pigs were transported (approximately 580 km) to a commercial slaughter facility, and held in lairage for a minimum of 2 h before slaughter. Pigs were rendered unconscious via carbon dioxide stunning (Plant A). Pigs subjected to the animal-handling model had an initial transport of approximately 1,000 km (n = 80), with a final transportation distance of approximately 484 km (n = 76) to one of two commercial slaughter facilities that both use electrical stunning (n = 52 and 24 at Plants B and C, respectively) and allowed at least 2 h of rest before slaughter. Pigs representing each of the three halothane categories and both sire lines were transported to Plant C to obtain an early postmortem tissue sample for further biochemical analyses. The remaining pigs were transported to Plant B due to the proximity of the slaughter facility to the testing facility. Data from five pigs were lost at Plant B. Hot carcass weight, Fat-O-Meat’er (SFK Technology A/S, Herlev, Denmark) fat depth, and LM depth were collected before carcasses entering the cooler (Plants A and B), and HCW, fat depth, and LM area were measured at Plant C. Carcass composition data from Plants A and B were used to calculate lean percent with the following equation: 58.86 – (0.61 x fat depth) + (0.12 x LM depth), whereas lean percent for pigs slaughtered at Plant C was calculated using the current fat-free lean yield equation (NPPC, 2000). At approximately 1 h postmortem, pH was measured in the ham (Exp. 1) and in the LM between the 5th and 6th ribs (Exp. 1 and 2). Following a 22-h chill, ultimate pH of the LM was measured between the 5th and 6th ribs, and body wall thickness was determined on the hanging carcass in the geometric center of the right side belly. Following carcass fabrication, loins were collected and L*, a*, and b* values were taken at the 5th-/6th-rib interface using a ColorTec PCM (Clinton, NJ) with a 10° observer and 16-mm orifice using D₆₅ illuminant. Subjective color, firmness, and marbling were also evaluated on the LM at the same interface (NPPC, 2000). Forty-gram samples were removed from each LM at the 5th/6th rib, trimmed of external fat, placed in a funnel, and stored in an airtight container until 7 d postmortem. Following storage, samples were reweighed to determine drip loss. Similar traits were measured on pigs slaughtered at Plant C, with pH (45 min and 22 h) and color (d 1) being measured at the last rib. Drip loss was measured by suspending duplicate 2.54-cm-thick chops for 7 d in sealed bags at 4°C. The difference between initial and final weights was used to calculate fluid loss.

Statistical Analyses
Differences within halothane sensitivity across lines of pigs were analyzed using the GENMOD procedure of SAS (SAS Inst., Inc., Cary, NC). The statistical model included the dependent variable halothane category and the independent effect of sire line. Differences in Lines A and B between experiments also were estimated using the GENMOD procedure. The HS-I and HS-H numbers were pooled to compare to the HS percent observed in Exp. 1. The probability (p) of misclassifying a pig on one test was calculated from the proportion of disagreement (d) between the outcomes of the two tests, where d = 2p(1 – p) (Webb and Smith, 1976).

Least squares means of meat quality traits were compared using mixed-model ANOVA procedures. The model statement included the fixed effects of line, gender, halothane class, and all possible two-way interactions, with slaughter day included as a random effect. The only significant (P < 0.05) two-way interaction was line x halothane class. Thus, means are reported separately for each halothane class within line. Although not significant (P > 0.10), all other two-way interactions were left in the statistical model, as they accounted for some of the variation observed in the traits of interest. In Exp. 2, meat quality data of Lines A and B were evaluated separately from Lines E through H because Lines A and B were slaughtered on separate days. Carcass composition models included HCW within line x gender as a covariate and the same fixed and random effects were used for meat quality traits. Meat quality data from different slaughter facilities were analyzed separately from each other using Proc Mixed of SAS, with the fixed effects of line, gender, and halothane class. Carcass composition models included HCW as a covariate, and all least squares means were compared using a protected LSD test (Freud and Wilson, 1997).

	Results and Discussion

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Mating schemes and halothane responses for both experiments are shown in Table 1. In Exp. 1, progeny were generated using a single commercially available, HAL-1843-normal sire line to inseminate four different commercially available, HAL-1843-normal dam lines. All the lines tested had >30% incidence of HS pigs. Two of the lines tested exhibited a higher frequency of sensitivity to halothane than the other two lines (B and D > A and C; P < 0.01). This result indicates a significant contribution to the observed halothane response from the dam line.

To determine whether the observed halothane sensitivity was unique to the sire line used in Exp. 1, progeny from four commercially available HAL-1843-normal sire lines mated to a single commercially available HAL-1843-normal dam line were evaluated in Exp. 2, along with the progeny from two of the lines from Exp. 1. Additionally, the magnitude of the halothane response was characterized by assigning numerical scores to classify the visually observed responses. Based on this scoring system, Lines F and H had more pigs classified as HS-L and fewer HS-I than the other genotypes tested (P < 0.05; Table 1). Line E had the fewest HS-L pigs (P < 0.05), and Lines E and G had more pigs classified as HS-H than the other lines tested (P < 0.05). In both experiments, no differences were observed in the halothane response between barrows and gilts (P > 0.30). This is in agreement with the results of Sather and Murray (1989), who demonstrated that the distribution of halothane-sensitive pigs was unaffected by the gender of the animal.

In contrast to the results in Exp. 1, no differences in halothane response were observed in Exp. 2 between Lines A and B (P > 0.70; Table 1). The percentage of pigs classified as HS (HS-I and HS-H for Exp. 2) in Line A was similar in both experiments (P = 0.12). In Exp. 2, Line B had fewer HS-I and HS-H pigs compared with the percentage of HS pigs in Exp. 1 (43 vs. 58%, respectively; P < 0.05). This observation may be due to differences in time of year, within-line variation in the halothane response, or the implementation of a scoring system in Exp. 2. Similar to the results in Exp. 1, the response to halothane differed among progeny from a single sire line in Exp. 2 depending on the dam line (A vs. B vs. E). Line E had fewer HS-L and more HS-H responses than Lines A and B (P < 0.05). Based on the results from Exp. 2, the halothane response of progeny seems to be influenced by both sire and dam line.

In the previous repeatability studies, pigs that did not show a definitive response were classified as "doubtful" and were pooled with nonresponders (Webb and Smith, 1976; Webb and Jordan, 1978). In our study, HS-I and HS-H were considered to be HS, whereas HS-L pigs were considered to be halothane normal (HN). Thirteen percent of the pigs were positive on the first test day only, whereas 23% were positive on the second test day only. Using these percentages, the frequency of disagreements between the first and second tests was 36%, and the probability of misclassifying a pig on one test was estimated to be 24%. Disagreements between halothane responses on separate test days have been reported. Webb and Smith (1976) tested 335 pigs 28 d apart and observed a 10% disagreement between the two tests. In a second study, Webb and Jordan (1978) showed a 9% disagreement when 394 pigs were tested 21 d apart. The probability of misclassifying a pig on one test in these two studies was calculated to be 6 and 5%, respectively. The higher probability of misclassifying a pig in Exp. 2 is most likely due to a different evaluator scoring the response on the second day. In fact, when a single evaluator scored the response of HAL-1843-normal crossbred pigs subjected to three halothane tests every other day in a 5-d period, the probability of misclassifying a pig on one test was calculated to be 10.5% (unpublished observations). This evaluator’s classification (d 1) was used to determine the relationship between HS and carcass composition or meat quality for all pigs in Exp. 2. It is also possible that the high frequency of disagreements was a result of considering pigs that exhibited a "mild" response to be more similar to the HS group than the HN group as previously described. When disagreements are only considered between HS-H pigs in Exp. 2, the probability of misclassifying a pig on one test would be 14%. The probability of misclassifying a pig in the current study may also be greater than that in previous reports due to the lack of pigs with the HAL-1843 polymorphism, which exhibited a more severe response to halothane in previous studies.

Pigs that are HS are typically leaner and more heavily muscled, equating to a greater total quantity of lean tissue (Monin et al., 1980). However, the increased propensity toward stress-related death (O’Brien and MacLennan, 1992) and poor-quality pork negate the benefit of more lean muscle tissue. Pigs that are classified as HS generally have lower initial pH, higher muscle temperature, lighter color, and poorer water-holding properties (Klont et al., 1993; Sather et al., 1991; Warriss and Listen, 1982). In the current experiments, no consistent differences were observed between halothane response and carcass composition or meat quality in HAL-1843-normal pigs. Means for carcass composition and meat quality data for Lines A through D collected at Plant A are reported by line and halothane status in Table 2. In Exp. 1, Line A pigs that were HS had a lighter final live weight that resulted in a lighter HCW than HN pigs (P < 0.05); however, this difference was not (P > 0.25) observed in any other lines. Ham pH, measured at 22 h postmortem, was higher in HS pigs from Lines B and D (P < 0.05) compared with HN pigs in the respective lines. No differences were observed in loin pH or drip loss between groups of pigs with different sensitivity to halothane (P > 0.20). Loins from HS pigs of Line D were darker and firmer, based on subjective scores, than loins from HN pigs (P < 0.05). When the halothane response for Lines A and B was scored (Exp. 2), no differences were observed between halothane sensitivity and carcass composition or meat quality (Table 3; P > 0.30).

The subset of pigs used in the animal-handling model (from Exp. 2) was subjected to two transportations, one before the handling model (approximately 1,000 km) and the other following the handling model to one of two slaughter facilities (approximately 484 km). Following the posthandling transportation, a minimum of 2 h rest was allowed before slaughter. It was anticipated that these pigs would produce pork products that were darker, firmer, and less exudative than normal in appearance as a result of the more extensive transport and handling that these animals endured. Carcass composition and meat quality results of these pigs are shown in Table 5. No differences were observed in initial (45 min and 1 h) LM pH values (P > 0.80); however, LM from HS-H pigs had lower ultimate pH (P < 0.05) at Plant B, and this trend was also observed in pigs slaughtered at Plant C (P = 0.12). This lower ultimate pH was associated with greater fluid loss from HS-H pigs (P < 0.05). Objective color values were similar between HS-L and HS-H pigs, but subjective color scores indicated that LM from HS-H pigs was slightly lighter in color than that of the HS-L pigs (P < 0.05) at Plant B.

Based on these results, we conclude there are HAL-1843-normal pigs that are susceptible to halothane anesthesia. The relationship between halothane sensitivity and carcass composition or meat quality is inconsistent across lines of pigs when transport and handling of pigs is minimized. However, these results suggest that, when subjected to multiple stressors, HS pigs may be more prone to producing inferior pork than HN pigs. More work is needed to better understand the physiological differences that account for variable responses to halothane anesthesia and the influence of the physiological differences on pork carcass composition and meat quality.

	Implications

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The HAL-1843 polymorphism in the skeletal muscle calcium release channel (ryanodine receptor) has been eliminated from most commercial populations. Nevertheless, some pigs continue to exhibit characteristics similar to porcine stress syndrome and are sensitive to halothane anesthesia in the absence of the HAL-1843 polymorphism. The full implications of sensitivity to halothane are unclear; however, halothane-sensitive pigs that are subjected to multiple stressors seem to be more prone to producing inferior quality pork than halothane non-sensitive pigs. These findings support the notion that novel polymorphism might exist in the ryanodine receptor or other proteins involved in Ca homeostasis that may be associated with stress susceptibility and production of inferior quality pork products.

	Footnotes

 
¹ The authors appreciate support from Animal Health Formula Funds administered through the Michigan Agric. Exp. Stn. We thank M. Ritter, N. Berry, E. Helman, N. Hofer, T. Holthaus, and C. Raines for assistance with data collection. We also thank G. Bohart for help with setting up the halothane test, and C. Ernst and N. Raney for assistance with genotyping the animals.

² The HAL-1843 is a registered trademark owned by The Innovations Foundation, Toronto, Ontario, Canada.

³ Correspondence: 3385 Anthony Hall (phone: 517-355-8452, ext. 203; fax: 517-432-0753; e-mail: doumitm{at}msu.edu).

Received for publication January 10, 2004. Accepted for publication November 28, 2004.

	Literature Cited

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Carden, A. E., and A. J. Webb. 1984. The effect of age on halothane susceptibility in pigs. Anim. Prod. 38:469–475.

Channon, H. A., A. M. Payne, and R. D. Warner. 2002. Comparison of CO₂ stunning with manual electrical stunning (50 Hz) of pigs on carcass and meat quality. Meat Sci. 60:63–68.

Denborough, M. A., J. F. Forster, R. R. Lovell, P. Maplestone, and J. D. Villiers. 1962. Anaesthetic deaths in a family. Br. J. Anaesth. 34:395–396.[Abstract/Free Full Text]

Freund, R. J., and W. J. Wilson. 1997. Statistical Methods. 1st rev. ed. Academic Press, San Diego, CA.

Fujii, J., K. Ostu, F. Zorzato, S. D. Leon, V. K. Khama, J. E. Weiler, P. J. O’Brien, and D. H. MacLennan. 1991. Identification of a mutation in porcine ryanodine receptor associated with malignant hyperthermia. Science 253:448–451.[Abstract/Free Full Text]

Girard, T., A. Urwyler, K. Censier, C. R. Mueller, F. Zorzato, and S. Treves. 2001. Genotype-phenotype comparison of the Swiss malignant hyperthermia population. Hum. Mutat. 449:1–8.

Hall, L. W., M. Woolf, J. W. P. Bradley, and D. W. Dolly. 1966. Unusual reaction to suxamethonium chloride. Br. Med. J. 2:1305.

Hamm, R. 1986. Functional properties of the myofibrillar system and their measurements. Pages 135–199 in Muscle as a Food. P. Bechtel, ed. Academic Press, New York, NY.

Harrison, G. G., J. F. Biebuyck, J. F. Terblanche, D. M. Dent, R. Hickman, and S. J. Saunders. 1968. Hyperpyrexia during anaesthesia. Br. Med. J. 3:594–595.

Klont, R. E., E. Lambooy, and J. G. van Logtestijn. 1993. Effect of preslaughter anesthesia on muscle metabolism and meat quality of pigs of different halothane genotypes. J. Anim. Sci. 71:1477–1485.[Abstract]

Marr, A. L., C. P. Allison, N. L. Berry, D. B. Anderson, D. J. Ivers, L. F. Richardson, K. Keffaber, R. C. Johnson, and M. E. Doumit. 2004. Impact of halothane sensitivity on mobility status and blood metabolites of HAL-1843-normal pigs following an aggressive handling model. J. Anim. Sci. 82(Suppl. 2):33. (Abstr.)

Monin, G., P. Sellier, L. Ollivier, R. Goutefongea, and J. P. Girard. 1980. Carcass charactersitcs and meat quality of halothane negative and halothane positive Pietrain pigs. Meat Sci. 5:413–423.

NPPC. 2000. Pork Composition and Quality Assessment Procedures. Natl. Pork Prod. Council, Des Moines, IA.

O’Brien, P. J., and D. H. MacLennan. 1992. Application in the swine industry of a DNA-based test for porcine stress syndrome. Proc. of Am. Assoc. of Swine Pract. 433–435.

O’Brien, P. J., H. Shen, C. R. Cory, and X. Zhang. 1993. Use of a DNA-based test for the mutation associated with porcine stress syndrome (malignant hyperthermia) in 10,000 breeding swine. J. Am. Vet Med. Assoc. 203:842–851.[Medline]

Rempel, W. E., M. Lu, S. E. Kandelgy, C. F. H. Kennedy, L. R. Irvin, J. R. Mickelson, and C. F. Louis. 1993. Relative accuracy of the halothane challenge test and a molecular genetic test in detecting the gene for porcine stress syndrome. J. Anim. Sci. 71:1395–1399.[Abstract]

Sather, A. P., and A. C. Murray. 1989. The development of a halothane-sensitive line of pigs. Can. J. Anim. Sci. 69:323–331.

Sather, A. P., A. C. Murray, S. M. Zawadski, and P. Johnson. 1991. The effect of the halothane gene on pork production and meat quality of pigs reared under commercial conditions. Can. J. Anim. Sci. 71:561–574.

Topel, D. G., E. J. Bicknell, K. S. Preston, L. L Christian, and C. Y. Matsushima. 1968. Porcine stress syndrome. Mod. Vet. Pract. 49:40–60.

Velarde, A., M. Gispert, L. Faucitano, P. Alonso, X. Manteca, and A. Diestre. 2001. Effects of the stunning procedure and the halothane genotype on meat quality and incidence of haemorrhages in pigs. Meat Sci. 58:313–319.

Warriss, P. D., and D. Listen. 1982. Improvements of meat quality in pigs by beta-adrenergic blockade. Meat Sci. 7:183–187.

Webb, A. J., and C. H. C. Jordan. 1978. Halothane sensitivity as a field test for stress-susceptibility in the pig. Anim. Prod. 26:157–168.

Webb, A. J., and C. Smith. 1976. Some preliminary observations on the inheritance and application of halothane-induce MHS in pigs. Pages 211–213 in Proc. 3rd Int. Conf. Prod. Dis. Farm Anim., Pudoc, Wageningen.

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