Variation In Pork Quality Research Articles

Combined effects of weather conditions, transportation time and loading density on carcass damages and meat quality of market-weight pigs.

This study investigated the interactive effects of weather conditions, transportation time and loading density on carcass damages and meat quality traits of market-weight pigs under commercial conditions. The following pork quality parameters were measured: pH and temperature; colour; drip, thawing and cooking loss; and textural traits. Pigs were assigned to one of eight groups arranged in a 2 2 2 factorial design according to the weather conditions (hot and cold), transportation time (short and long) and loading density (high and low). A three-way ANOVA and Tukey's post-test (multiple comparisons) were performed to assess the differences between groups in examined pork quality traits. Pigs exposed to short transportation ( 20 ) at high loading density (0.29 ) during hot weather conditions produced meat with the lowest initial and ultimate meat pH value and sensory colour scores, and the highest initial temperature and the occurrence of pale, soft and exudative pork. The occurrence of pale, soft and exudative pork was reduced 5-fold during hot weather conditions when pigs were exposed to longer transportation ( 210 ) and low loading density (0.53 ). Pigs exposed to short transportation ( 20 ) at high loading density (0.41 ) during cold weather conditions produced the highest quality pork (the highest percentage of red, firm and non-exudative pork) characterised by lowest drip loss and value and the highest sensory colour scores. The highest percentages of carcass damages were recorded in pigs exposed to both low (0.50 ) and high (0.33 ) loading density during long transportation ( 210 ) in cold weather conditions. In conclusion, weather conditions and loading density are of greater importance for the occurrence of carcass damages and pork quality variation than transportation time.

Identifying Physiological Stress Biomarkers for Prediction of Pork Quality Variation.

Simple SummaryPrediction of technological and sensory pork quality—during a pig’s life or quickly after slaughter—is increasingly required by the pork industry in order to classify carcasses or primary cuts of carcasses for different production lines. Therefore, there is increasing demand for the development of accurate, reliable, time-efficient, non-invasive, real-time tools for predicting pork and carcass quality characteristics. Based on this, the aim of this study was to assess the potential use of various physiological stress biomarkers as indicators of carcass and meat quality traits in slaughter pigs subjected to the standard marketing conditions and to minimal stressful preslaughter handling. According to the results of this investigation, lactate dehydrogenase can be considered as a useful predictor of pork quality, while cortisol, alanine amino transferase, and albumin could be useful in prediction of carcass quality.This study assessed the potential use of various physiological stress biomarkers as indicators of carcass and meat quality traits in 240 pigs subjected to the standard marketing conditions and minimal stressful antemortem handling using Pearson correlations. The most important pork quality traits (pH and temperature, water holding capacity, and color) had limited correlations with stress metabolites (lactate, glucose), stress hormones (cortisol, adrenocorticotropic hormone), stress enzymes (creatine kinase, aspartate amino transferase, alanine amino transferase), electrolytes (sodium, chloride), and acute-phase proteins (haptoglobin, C-reactive protein, albumin), indicating poor reliability in predicting pork quality. Albumin level was moderately positively correlated with live weight, hot carcass weight, cold carcass weight, and back fat thickness. Alanine amino transferase level was moderately positively correlated with live weight, hot carcass weight, and cold carcass weight. Cortisol level was moderately positively correlated with live weight, hot carcass weight, cold carcass weight, and back fat thickness, and moderately negatively correlated with the lean carcass content. Increased lactate dehydrogenase level was moderately correlated with decreased drip and cooking loss. In conclusion, lactate dehydrogenase could help pork producers predict pork quality variation, while cortisol, alanine amino transferase, and albumin could be useful in prediction of carcass quality.

Characterization of variability in pork carcass composition and primal quality,.

The objective was to characterize the factors and production practices that contribute to variation in pork composition and quality. It is possible the variation in pork quality traits, such as color, marbling, and tenderness, contributes to reduced customer confidence in the predictability of finished product quality and, therefore, pork products becoming less competitive for consumer dollars. Pigs raised in 8 different barns representing 2 seasons (hot and cold) and 2 production focuses (lean and quality) were used in this study. Pigs were marketed in 3 groups from each barn and marketing procedures followed commercial marketing procedures. Data were collected on a total of 7,684 pigs. The mivque0 option of the VARCOMP procedure in SAS was used to evaluate the proportion of variation each independent variable (season, production focus, marketing group, sex, and random variation) contributed to total variance. Random variation including inherent biological differences, as well as factors not controlled in this study, contributed the greatest proportion to total variation for each carcass composition and quality trait. Pig and other factors contributed to 93.5% of the variation in HCW, and marketing group, sex, season, and production focus accounted for 4.1, 1.4, 0.8, and 0.3%, respectively. Variation in percent carcass lean was attributed to production focus (36.4%), sex (15.8%), and season (10.2%). Pig and other factors contributed the greatest percentage of total variation (39.4%). Loin weight variation was attributed to production focus (21.4%), sex (5.4%), season (2.7%), marketing group (1.8%), and pig (68.7%). Belly weight variation was attributed to pig (88.9%), sex (4.1%), marketing group (3.8%), production focus (3.0%), and season (0.1%). Variation in ham weight was attributed to pig and other factors (93.9%), marketing group (2.8%), production focus (2.2%), and season (1.1%). Ultimate pH variation was attributed to pig (88.5%), season (6.2%), production focus (2.4%), marketing group (2.2%), and sex (0.7%). Aside from pig (71.9%), production focus (14.0%) was the next largest contributor to variation in iodine value followed by sex (13.2%) and marketing group (0.9%). Variation in carcass quality and composition could be accounted for, but the greatest percentage of variation was due to factors not accounted for in normal marketing practices.

Variability of U.S. Pork Primal Quality

ObjectivesIt is possible variation in pork quality contributes to reduced customer confidence in the predictability of finished product quality, and therefore, may lead to pork products being less competitive for U.S. consumer dollars. The objective of this study was to quantify the amount of variability attributable to pork primal quality by sex, season, marketing group (MG), production focus (PF), and random variation (pig).Materials and MethodsPigs (N = 8,042) were raised in 8 different barns (cental U.S.) representing 2 seasons (hot and cold) and 2 production focuses (lean and quality). Pigs were marketed in 3 groups from each barn. Data were collected on a total of 7,684 pigs. Variance of each pork quality trait was calculated using the MEANS procedure. The mivque0 option of the VARCOMP procedure (SAS v. 9.4) was used to evaluate the proportion of variability that sex, season of production, PF, and MG, contributed to total variance. Variance remaining was referred to as pig and includes biological variation between pigs as well as other factors not accounted for in this study.ResultsVariances for carcass composition traits were: HCW (s2 = 88.13 kg), backfat thickness (15.96 mm), loin depth (72.62 mm), percent lean (7.63%), and iodine value (13.17g/100g Fatty Acid Methyl Esters). Pig contributed 93.5% of the variation in HCW, and MG, sex, season, and PF accounted for 4.1, 1.4, 0.8, and 0.3%, respectively. Variability that was present in percent lean could be attributed to pig (39.4%), PF (36.4%), sex (15.8%), and season (10.2%). Pig contributed 71.9% of the variability in iodine value; remaining variation was accounted for by PF (14.0%), sex (13.2%), and MG (0.9%). Variances for loin traits were: boneless weight (s2 = 0.24 kg), L* (6.21), a* (1.32), b* (1.08), ultimate pH (0.02), slice shear force (30.24 kg), and marbling score (0.85). Loin weight variability was attributed to 68.7% by pig, 21.4% by PF, 5.4% by sex, 2.7% by season, and 1.8% by MG. Pig accounted for 70.5% of the variability in loin L*, season 17.2%, PF 9.1%, and sex 3.3%. Ultimate pH variability was accounted for by pig (88.5%), season (6.2%), PF (2.4%), MG (2.2%), and sex (0.7%). Pig accounted for 62.7% of the variability in slice shear force, with remaining variability accounted for by season (23.4%), PF (11.2%), and sex (2.8%). Variability in marbling score was impacted by pig (48.9%), PF (39.0%), and sex (12.0%). Variances for belly traits were: weight (s2 = 1.32 kg), length (18.59 cm), width (5.98 cm), average depth (0.18 cm), and flop (0.70). Belly weight variability was due to 88.9% pig, 4.1% sex, 3.8% MG, 3.0% PF, and 0.1% season. Variability in belly flop was attributed to pig (74.6%), PF (13.6%), sex (11.3%), and MG (0.5%). Variances for ham traits were: weight (s2 = 1.20 kg), semimembranosus (SM) pH (0.08), SM L* (9.83), SM a* (3.47), and SM b* (2.42). Ham weight variability was accounted for by pig (93.9%), MG (2.8%), PF (2.2%), and season (1.1%). Variability of SM L* was due to pig (95.3%), season (3.0%), MG (0.8%), sex (0.6%), and PF (0.3%).ConclusionAlthough variability of carcass composition and quality traits can be accounted for by sex, season, PF, and MG, the greatest portion of variability cannot be attributed to those factors. Therefore, other factors, including inherent variation of pigs, contribute to variability in pork quality and carcass characteristics. This project was funded, in part, by The Pork Checkoff.

Can the monitoring of animal welfare parameters predict pork meat quality variation through the supply chain (from farm to slaughter)?

The objective of this study was to assess the relationship between the animal welfare conditions evaluated through the supply chain and pork quality variation. A total of 4,680 pigs from 12 farms-5 animal welfare improved raising system (AWIRS) and 7 conventional raising system (CON) farms-were assessed from farm to slaughter through a comprehensive audit protocol merging the European Welfare Quality, the Canadian Animal Care Assessment, and American Meat Institute audit guide criteria. At the abattoir, a subsample of 1,440 pigs (120 pigs/farm) was randomly chosen out of 24 loads (2 farms per wk) transported by 2 drivers (driver A and driver B) for the assessment of stunning effectiveness, carcass bruises, blood lactate levels, and meat quality traits. Meat quality was assessed in the longissimus lumborum (LL) muscle 24 h postmortem by measuring ultimate pH (pHu), color (L*, a*, and b*), and drip loss. Data were analyzed by the MIXED, GLIMMIX, and NAPAR1WAY procedures of SAS. Spearman correlations were calculated to determine the relationship between audit scores and meat quality traits. Better animal welfare conditions, as showed by greater final scores for good housing (GHo; = 0.001) and good health ( = 0.006) principles, were recorded at AWIRS farms. Pigs from AWIRS farms handled by driver B displayed a greater percentage of turning back ( = 0.01) and slips ( < 0.001) during unloading and a greater ( = 0.02) frequency of falls in the stunning chute. A greater ( = 0.02) reluctance to move at loading was found in CON pigs loaded by driver A compared with driver B, whereas a greater ( < 0.001) reluctance to move was found in these pigs at unloading when they were unloaded by driver B. Drip loss was higher ( = 0.003) and pale, soft, and exudative pork percentage was greater ( < 0.001) in the LL muscle of the heavier AWIRS pigs. The GHO principle was best correlated with pHu ( = -0.75, = 0.01) and Minolta L* value ( = 0.87, < 0.001) of the LL muscle. Overall, drip loss variation in the LL muscle was correlated with the frequency of slips at unloading ( = 0.63, = 0.001) and in the restrainer area ( = 0.74, < 0.001). The results of this study showed that the quality of the raising system and truck driver skills as assessed by animal welfare audit protocols are important sources of variation in the behavioral response of pigs to preslaughter handling and may affect pork quality variation. However, the different live weight between CON and AWIRS pigs may have biased the meat quality results in this study.

Genomic Selection, a New Era for Pork Quality Improvement

Traditional breeding approaches apply sophisticated statistical tools such as best linear unbiased prediction (BLUP) to evaluate the genetic potential of animals for economically important traits using phenotype and pedigree information observed on the animal. However, the genetic gain achieved is relatively slow for traits with low-to-moderate heritability, or expensive to measure traits, such as those determined post-mortem e.g., pork quality. Nowadays, the availability of dense panels of DNA markers covering the whole genome along with powerful statistical tools has made genomic selection (GS) feasible in pigs. The large number of single nucleotide polymorphisms generated by high-throughput technologies can be used in GS to select superior animals with better meat quality. Many quantitative trait loci (QTL) affecting meat quality traits have been detected in pigs demonstrating the potential for this improvement. Genomic selection uses genome-wide markers so that all QTL are likely to be in linkage disequilibrium with at least one marker. Genomic selection sums the effects of markers covering the whole genome so that potentially all the genetic variance associated with the traits and explained by the markers are considered. This can greatly improve selection accuracy to accelerate genetic gain for pork quality traits. In this review, we discuss the genetic component underlying pork quality variation, statistical approaches for pork quality genomic prediction, and present recent highlights for their application in swine breeding programs. Firstly, we review how pork quality is integrated into breeding objectives. Secondly, we present approaches for application of molecular genetics in meat quality improvement. Additionally, we discuss the statistical methods for genomic prediction including ridge regression, Bayesian approaches, GBLUP, and combining genomic and traditional information using single-step BLUP. Finally, we review the strategies for their use in swine genetic improvement and management. In particular, we review the strategy for implementing GS in swine breeding programs to improve pork quality.

Estimation of pork quality traits using exsanguination blood and postmortem muscle metabolites.

The current study was designed to estimate the pork quality traits using metabolites from exsanguination blood and postmortem muscle simultaneously under the Korean standard pre- and post-slaughter conditions. A total of 111 Yorkshire (pure breed and castrated male) pigs were evaluated under the Korean standard conditions. Measurements were taken of the levels of blood glucose and lactate at exsanguination, and muscle glycogen and lactate content at 45 min and 24 h postmortem. Certain pork quality traits were also evaluated. Correlation analysis and multiple regression analysis including stepwise regression were performed. Exsanguination blood glucose and lactate levels were positively correlated with each other, negatively related to postmortem muscle glycogen content and positively associated with postmortem muscle lactate content. A rapid and extended postmortem glycolysis was associated with high levels of blood glucose and lactate, with high muscle lactate content, and with low muscle glycogen content during postmortem. In addition, these were also correlated with paler meat color and reduced water holding capacity. The results of multiple regression analyses also showed that metabolites in exsanguination blood and postmortem muscle explained variations in pork quality traits. Especially, levels of blood glucose and lactate and content of muscle glycogen at early postmortem were significantly associated with an elevated early glycolytic rate. Furthermore, muscle lactate content at 24 h postmortem alone accounted for a considerable portion of the variation in pork quality traits. Based on these results, the current study confirmed that the main factor influencing pork quality traits is the ultimate lactate content in muscle via postmortem glycolysis, and that levels of blood glucose and lactate at exsanguination and contents of muscle glycogen and lactate at postmortem can explain a large portion of the variation in pork quality even under the standard slaughter conditions.

Hand-held lactate analyzer as a tool for the real-time measurement of physical fatigue before slaughter and pork quality prediction

The objectives of this study were to assess the relationship between blood lactate variation measured at the plant, and pork quality variation on a large sample size and under commercial preslaughter handling conditions. A total of 600 pigs were randomly chosen on arrival at a commercial slaughter plant and blood samples taken from the ear vein at unloading (UN), after lairage (LA), in the restrainer (RE; before stunning) and at exsanguination (EX) were analysed for lactate content using a Lactate Scout Analyzer (LSA). In order to have a large range of measures, pigs were distributed into two groups; one kept in lairage overnight (G1) and the other for 2 to 3 h (G2) before slaughter. Meat quality was assessed in the Longissimus thoracis (LT), Semimembranosus (SM) and Adductor (AD) muscles by measuring the pH 30 min postmortem (pH1) and at 24 h postmortem (pHu), the colour and the drip loss. Blood lactate levels did not differ between G1 and G2 (P>0.05). A reduced muscle lactate and glucose contents (P=0.02 and P=0.004, respectively) resulting in a lower (P<0.001) glycolytic potential (GP) was observed in the LT muscle of G1 pigs when compared with G2 loins. In the LT muscle of G1 pigs, the lower GP resulted in an increased pHu (r=−0.67; P<0.001), decreased drip loss (r=0.57; P<0.001) and darker colour (r=0.50; P<0.001) compared with G2. In both G1 and G2 pigs, the lower GP was correlated to higher pHu value in the SM and AD muscles (r=−0.73; P<0.001). The greatest correlation was observed in G2 between blood lactate levels at LA and pHu value of the SM and AD muscles (r=0.46 and r=0.44, respectively; P<0.001 for both muscles). The second greatest correlation was found between blood lactate levels at EX and pH1 value in the SM muscle in both groups (r=−0.37 and r=−0.41, respectively; P<0.001 for both groups). Based on the results of this study, it appears that blood lactate levels, as measured by the LSA, reliably reflect the physiological response of pigs to perimortem stress and may help explain the variation in pork quality.

Use of infrared ocular thermography to assess physiological conditions of pigs prior to slaughter and predict pork quality variation

Infrared thermography (IRT) body temperature readings were taken in the ocular region of 258 pigs immediately before slaughter. Levels of lactate were measured in blood taken in the restrainer. Meat quality was assessed in the longissimus dorsi (LD), semimembranosus (SM), and adductor muscles. Ocular IRT (IROT) temperature was correlated with blood lactate levels (r=0.20; P=0.001), with pH taken 1hour postmortem (pH1: r=−0.18; P=0.03) and drip loss (r=0.20; P=0.02) in the LD muscle, and with pH1 in the SM muscle (r=−0.20; P=0.02). Potentially, IROT may be a useful tool to assess the physiological conditions of pigs at slaughter and predict the variation of important meat quality traits. However, the magnitude of the correlations is rather low, so a further development of image capture technique and further studies under more variable preslaughter conditions ensuring a larger pork quality variation are needed.

Welfare and carcass and meat quality of pigs being transported for two hours using two vehicle types during two seasons of the year

Correa, J. A., Gonyou, H. W., Torrey, S., Widowski, T., Bergeron, R., Crowe, T. G., Laforest, J. P. and Faucitano, L. 2013. Welfare and carcass and meat quality of pigs being transported for two hours using two vehicle types during two seasons of the year. Can. J. Anim. Sci. 93: 43–55. A total of 3756 pigs were transported for 2 h in summer and winter using a “pot-belly” trailer (PB) and a hydraulic double-decked truck (DD) in order to assess the effect of vehicle design on animal welfare and carcass and meat quality. Animal welfare was assessed in randomly selected barrows by measuring heart rate of pigs and lactate and creatine phospho-kinase (CPK) concentrations in exsanguination blood. Skin damage was scored and meat quality was evaluated in the longissimus dorsi (LD), semimembranosus (SM) and adductor (AD) muscles. Heart rates in winter were higher (P&lt; 0.01) during transport, at unloading and in lairage. Blood CPK and lactate concentrations at slaughter were higher (P&lt;0.05 and P&lt;0.01, respectively) in pigs transported on the PB trailer. Bruises increased in winter (P&lt;0.001) and in pigs from the DD truck (P&lt;0.05). The pHu was higher (P&lt; 0.01) in all muscles and L* value was lower (P&lt;0.05) in the LD muscle from pigs transported in the PB trailer. Overall, the results of this study indicate that the type of vehicle, animal location in the truck and the season affect the welfare of pigs during transport with clear consequences on skin bruises and pork quality variation.

Effects of the season of the year, truck type and location on truck on skin bruises and meat quality in pigs

The purpose of this study was to evaluate the effect of the season of the year (summer vs winter), type of truck (A: single decker vs B: double-decker) and pig location on the truck (front, middle, rear) on the incidence of skin bruising and pork quality variation. For this purpose, 2660 gilts of an average weight of 126.7 (± 6.6) kg originating from 19 different farms were used. No interaction between season of the year, type of truck and location on truck was observed. A higher number of bruises on the body at unloading and slaughter (P < 0.0001) and a higher number of bruises on the carcass (P < 0.01) were observed in winter. At unloading a higher number of bruises on the body and on the carcass after slaughter was observed in pigs transported on Truck A (P = 0.004 and P = 0.05). A higher, although not significant, number of bruises was found on the body of pigs transported in the rear compartment of both trucks. Higher paleness value was found in the longissimus and semimembranosus muscles in summer (P = 0.0001) than in winter. Cold and heat stress have a negative influence on skin bruises and meat quality, respectively. Poor vehicle design increases the incidence of bruised carcasses without detracting from pork quality regardless of the climate conditions tested and location of the animal in the truck.

Perspective of NIRS measurements early post mortem for prediction of pork quality

The potential of near-infrared spectroscopy (NIRS) measurements early post mortem was investigated to predict ultimate drip loss, colour, tenderness and intra-muscular fat of pork. Three locations (M. longissimus thoracis, M. longissimus lumborum and M. semimembranosus) in 102 pig carcasses were tested at the end of the slaughter line. A priori variation in pork quality was introduced using an experimental design covering: genotype, lairage time, pre-slaughter handling and day of slaughter. At 1 h post mortem a diode array VIS/NIR instrument (Zeiss MCS 511/522, 380–1700 nm) equipped with a surface fibre optic probe was used and at 1 day post mortem ultimate pH, drip loss, colour and shear force was measured on similar locations. Results indicated that it was possible to predict intra-muscular fat content (correlation (R2 of 0.35 with multiple linear regression), standard error of prediction (SEP)=3.6 g/kg), but the configuration has to be refined for on-line application (bigger aperture). For drip loss no correlation was achieved with the PLS method. Even extremes (low drip loss (<2.5%) or high drip loss (>4.5%)) in drip loss were not discriminated. Predicting drip loss with NIRS early post mortem is not successful, although NIRS in the slaughter line has potential as a fast predictor of intra-muscular fat. Possibilities for using the NIRS technique to get to know more about muscle metabolism and post mortem changes are promising.

Myosin heavy chain isoforms account for variation in pork quality

The objective of this study was to determine the impact of myosin heavy chain (MyHC) isoforms (I, IIB, IIA and IIX) on pork quality traits of halothane (HAL)-negative (NN) and halothane-carrier (Nn) pigs. Gilts ( n=32) were assigned to a 2×2 factorial of genetic population (GP) and slaughter weight (WT; 120 and 135 kg). Classical meat quality characteristics were collected and MyHC content was determined on muscle samples. Regression equations for pork quality and carcass composition traits were determined. Only I/IIB accounted for variation in drip loss of NN gilts ( R 2=0.18), while GP related to drip loss in Nn gilts ( R 2=0.70). Type I MyHC content explained variation in ultimate (24 h) muscle pH of NN gilts ( R 2=0.09), while I/IIB, I/IIX and IIB/IIX were significant for Nn gilts ( R 2=0.99). I/IIA, I/IIX, IIB/IIX and GP accounted for variation in Hunter Color a (redness) values of NN gilts ( R 2=0.69), while IIB, IIA, IIB/IIA and GP were significant for Nn gilts ( R 2=0.97). Overall, fiber type composition accounts for a larger proportion of variation in the quality traits of Nn compared to NN gilts.

Pork quality variation is not explained by glycolytic enzyme capacity

Our objective was to determine if increased glycolytic enzyme capacity accommodates rapid glycolysis, which leads to inferior pork color and water-holding capacity. Progeny from HAL-1843 free Duroc ( n=16) or Pietrain ( n=16) sires were harvested over a 2-week period. Coupled enzyme assays were used to quantify total capacity of pyruvate kinase (PK) and phosphofructokinase (PFK) in the sarcoplasmic fractions and crude homogenates of longissimus muscle (LM), respectively. Capacity of PK was not correlated with LM pH (20, 45, 180 min or 24 h), purge, drip loss, or CIE L* ( P > 0.2). However, PFK capacity was inversely related to fluid loss ( P<0.05). This finding was unexpected, but may result from PFK becoming partially denatured and inactivated by 20 min postmortem in samples that undergo a rapid pH decline. These data indicate that lighter pork color and reduced water-holding capacity are not associated with an increase in the capacity of enzymes that catalyze regulated steps of glycolysis.

Influence of sire line and halothane genotype on growth performance, carcass characteristics, and meat quality in pigs

Progeny of three commercial sire lines mated to the same halothane negative crossbreed dam line were compared for growth, carcass and meat quality characteristics. Sire line A (halothane reactor) produced halothane carrier progeny; line C was halothane negative and produced negative progeny; line B (a cross between lines A and C) was a halothane carrier line that produced both carrier (BNn) and negative (BNN) progeny within the same litter. Line A pigs grew more slowly (P ≤ 0.05) and consumed less feed (P ≤ 0.05) than the progeny of the other lines (885, 1049, 1057 and 1082 g d−1 and 2.37, 2.82, 2.72 and 2.79 kg d−1 for lines a, BNN, BNn and C respectively). However, gain:feed was similar for all lines. Dressing percentage was similar for lines A, BNn and BNN (77.42, 77.62 and 77.00% respectively) but lower for line C (75.31%: P ≤ 0.05). Line differences for linear carcass measurements, lean cut yield and fat-free lean content were relatively small. Line A had higher shear force than the others (4.32, 3.21, 3.57, and 3.30 kg for A, BNN, BNn and C, respectively; P ≤ 0.05) and lines A and BNn had reduced taste panel tenderness and juiciness (P ≤ 0.05) compared with lines BNN and C. This study highlights commercially important differences between sire lines for pork quality traits. the variation in pork quality within this study resulted from the halothane gene and, potentially, other single genes that affect meat quality parameters. Key words: halothane gene, meat quality, sire line, pigs, carcass quality

Causes for variation in pork quality

Research was carried out on 260 pigs that were slaughtered in 12 batches in the slaughter facilities of ID-DLO at Zeist. The practical circumstances were highly standardized. The ‘animals’ meat quality was good with only little variation; 46 animals showed a ‘slightly’ aberrant quality and 6 ‘slight’ DFD. Carcasses within the quality categories ‘PSE’ and ‘slight’ PSE did not occur. Statistically significant effects on meat quality could be shown for the duration of the resting period before slaughter and the muscular contractions occurring while stunning, shackling and exsanguination, despite the minor variation in pork quality under standardization. A longer resting period before slaughter induced significantly lower temperatures in the m. semimembranosus and the loin at 45 min post mortem and a slightly higher ultimate pH, accompanied by a somewhat darker colour (24hr post mortem). A connection between the animal's behaviour at the fattening station and ultimate pork quality could not be shown. The same counts for fighting in the resting pen of the slaughter house and the pig's behaviour in the stunning area. Muscular contractions during and after stunning had a negative effect on pork quality, causing a more rapid drop in pH, a faster development of rigor mortis and a reduced water holding capacity. An imperfect electrical stunning procedure caused an increase in muscular contractions.