Identification and characterization of pigs prone to producing 'RSE' (reddish-pink, soft and exudative) meat in normal pigs

RSE (reddish-pink, soft and exudative) meat was investigated using pigs of three different halothane genotypes. A significantly lower pH_1h, value was observed in RSE compared with that of RFN (red, firm and non-exudative) -meat, both of which have values higher than 6.0 at 1 hr post-mortem. Drip loss (%) in RSE-meat was ≥7%, which was twice that of RFN-meat. Normal values for fibre optic probe and Minolta L and a were observed for RSE-meat. RSE-meat could be derived from NN and Nn pigs, and its formation could be induced from RFN-prone pigs by poor post-slaughter management. Pigs expected to produce RSE-meat were identified using small biopsy samples of M. longissimus dorsi (LD). Predicted RSE-meat in live pigs was confirmed by post-mortem assessments of meat quality using LD muscle. With NN Landrace-Yorkshire × Duroc pigs, 15.6% were identified to be RSE-prone in live pigs, and a further 6.7% RSE was induced after slaughter from RFN pigs. The rate of glycolysis determined from biopsy LD samples and at 1 hr post-mortem (pH_1h) were significantly (p < 0.001) faster in RSE than in RFN-prone pigs, but significantly slower than those of PSE-prone pigs. Good correlations (p < 0.001) were observed between biopsy fluid (F) values, an indicator of water-holding capacity (WHC), and drip loss (r = 0.652) from post-mortem LD muscle, and between biopsy pH (F), an indicator for the rate of glycolysis, and F (r = −0.828). These results show that the skeletal muscle test using biopsy LD muscle could be employed to reduce the incidence of RSE-meat.     

Effects of halothane genotype and pre-slaughter treatment on pig meat quality. Part 1. Post mortem metabolism, meat quality indicators and sensory traits of m. Longissimus lumborum

Forty-eight castrated F₂ offspring of Piétrain and Large White pigs were allocated to a 3 × 2 factorial design in order to study the interactive effect of halothane genotype (NN, Nn and nn) and pre-slaughter treatment [referred to as ‘Experimental’ (EXP) and ‘Commercial-like’ (COL) conditions; the latter combining short transportation, mixing unfamiliar pigs and slaughtering shortly after transport] on muscle post mortem changes and meat quality. The pigs were slaughtered over 4 days. Pre-slaughter glycogen depletion in M. longissimus lumborum (LL) was greater in the nn pigs, compared with the two other genotypes. Lactate accumulation post mortem in LL muscle was greater and the pH value at 40 min post mortem was lower in nn compared with NN pigs. Nn pigs were close to nn pigs for lactate accumulation and showed intermediate pH values in the LL muscle. In the M. semimembranosus (SM), NN and Nn pigs showed the same rate of post mortem changes, as evidenced by similar glycogen, lactate, creatine phosphate and ATP levels, and pH values at 40 min post mortem. Pre-slaughter treatment did not affect the rate of post mortem changes in both muscles and no interactive effect with halothane genotype was found. The pigs slaughtered under the ‘COL’ conditions had a significantly higher ultimate pH in the LL and SM muscles than those slaughtered under the ‘EXP’ conditions. The LL muscle from nn pigs was paler (higher L*) than that of NN and Nn pigs. In SM muscle, Nn pigs showed a significantly higher L* value than NN pigs. Drip loss of the LL muscle was significantly higher in nn compared with NN pigs, the heterozygous pigs being intermediate. Sensory evaluation of the LL muscle showed that nn pigs had a lower colour intensity and colour homogeneity of raw meat than NN and Nn pigs. Tenderness was significantly lower in nn compared with NN pigs, the Nn pigs being intermediate. Pre-slaughter treatment significantly increased ultimate pH in both muscles (LL and SM) but did not affect significantly the rate of pH fall (pH₄₀). It did not affect any of the meat quality traits and no interactive effect with halothane genotype was found. These results confirmed the influence of the halothane gene on the kinetics of muscle post mortem changes and related meat quality traits. They also confirmed the intermediate position of heterozygous pigs in terms of meat quality.     

Meat quality characteristics of springbok (Antidorcas marsupialis). 1: Physical meat attributes as influenced by age, gender and production region

Springbok is the most extensively cropped game species in South Africa. The effects of age (adult, sub-adult, lamb), gender and production region on the physical attributes (pH₂₄, cooking and drip loss, Warner Bratzler shear force and colour) were determined using samples of the M. longissimus dorsi (LD) muscles of 166 springbok. Stressed animals had a higher (P < 0.05) pH₂₄ (6.3 ± 0.07), as observed in the meat originating from the Caledon region. This meat had lower (P < 0.05) cooking loss (27.2 ± 0.62%) and drip loss (1.8 ± 0.08%) values in comparison to meat originating from the other regions. Inverse correlations were noted between pH₂₄ and drip loss (r = −0.26, P < 0.01) and cooking loss (r = −0.42, P < 0.001). Shear force values (kg/1.27 cm diameter) correlated positively (r = 0.25, P < 0.01) with pH₂₄. Age-related effects on tenderness were small in comparison with pH₂₄ effects. CIELab colorimetric values were typical of game meat and venison (L^* < 40, high a^* and low b^* values). It was noted that pH₂₄ correlated negatively (r = −0.51, P < 0.001) and positively (r = 0.33, P < 0.001) with the hue-angle and the chroma value of colour, respectively. Springbok originating from Caledon had a significantly (P < 0.05) higher a^* value, indicating meat to be more red with higher colour saturation.     

Thermal inactivation of lectins (PHA) isolated from Phaseolus vulgaris

The influence of the thermal process on the loss of ability to bind a carbohydrate target was studied on lectins (PHA) purified from Phaseolus vulgaris seeds. Thermal inactivation of aqueous solutions of pure PHA occurred according to a biphasic first-order mechanism, the thermodynamic parameters, at pH 7·3, being as follows: ΔH*₁ = ΔH*₂ = 86·2 kcal mole⁻¹, ΔS*₁ = − 54·04 cal deg⁻¹ and ΔS*₂ = − 56·71 cal deg⁻¹. The first-order rate constants appeared to be dependent on pH (minimal around 7) and divalent cations. All different subunits constituting the whole PHA were inactivated at the same rate. The biphasic nature of this process is independent of the presence of 10 m Ca⁺⁺ or Mg⁺⁺ and appeared to indicate a discrete aggregation of PHA molecules.     

Prediction of fluid losses from pork using subjective and objective paleness

Meat paleness in pork Longissimus dorsi (LD) 1 day post-mortem (p-m) was measured subjectively using Japanese Pork Colour Scores (JPCS) and objectively using a Colormet fibre-optic (FO) meat probe (400–700 nm). Water-holding capacity (WHC), fluid loss during thin-slicing, and drip loss were measured in unfrozen and in frozen and thawed (FT) samples. FT caused a decrease in WHC, and an increase in slicing and drip loss (P < 0·001). FO interactance (i) was correlated (P < 0·01) with unfrozen WHC (R = 0·55), with FT WHC (r = −0·45 at 440 nm), with FT slicing loss (R = 0·81), with unfrozen drip loss (R = 0·66), and with FT drip loss (R = 0·61). Objective measurements proved that the development of pork paleness takes several days p-m and that paleness is increased by FT. Where fluid losses were predictable from paleness, the FO probe was superior to subjective evaluation by JPCS.     

Effects of halothane genotype and pre-slaughter treatment on pig meat quality. Part 2. Physico-chemical traits of cured-cooked ham and sensory traits of cured-cooked and dry-cured hams

Forty-eight castrated F₂ offspring of Piétrain and Large White pigs were allocated to a 3×2 factorial design in order to study the interactive effect of halothane genotype (NN, Nn and nn) and pre-slaughter treatment (referred to as ’Experimental’ (EXP) and ’Commercial-like’ (COL) conditions; the latter involving short transportation, mixing unfamiliar pigs and slaughtering shortly after transport) on the qualities of cured-cooked and dry-cured hams. At 24 h post mortem, the hams were collected and assigned to cured-cooked (right ham) and dry-cured (left ham) ham processing. A sample of M. semimembranosus (SM) was collected before cooked ham processing, was used for chemical composition analysis, cured and then cooked at various temperatures. Cooking losses and compression tests were carried out after cooking on these SM samples. The water and collagen content of SM muscle was significantly higher in nn pigs compared with the two other genotypes. At all cooking temperatures (60, 65 and 70 °C), SM muscles from nn pigs showed higher cooking losses and instrumentally assessed toughness than the other genotypes, the heterozygous pigs being intermediate. The technological yield of cured-cooked ham processing was lower in nn, compared with NN and Nn animals. Cooked hams from nn pigs were drier, tougher, stringier and less smooth than NN and Nn pigs. The heterozygous pigs were similar to normal pigs for all texture characteristics with the exception of toughness for which they got a significantly higher score than NN pigs. The pigs slaughtered under the COL conditions had a better slice cohesiveness and a significantly lower dryness, than pigs slaughtered under the EXP conditions. The effect of HAL genotype on slice cohesiveness was significant only when pigs were slaughtered under the EXP conditions. Dry-cured hams from nn pigs showed significantly more visual defects, but were less tough, smoother and more fondant (softer) than NN and Nn pigs. The dry-cured hams from pigs slaughtered under the COL conditions had a better cohesiveness between muscles and a more intense yellow colour of fat than those from pigs slaughtered under the EXP conditions. COL pigs were also judged significantly less tough, smoother and more fondant than EXP ones. Overall, the effects of pre-slaughter treatment were small compared with those of the HAL genotype. The effects of HAL genotype on the sensory traits of cured-cooked ham were similar to those reported for fresh meat. However, the good textural characteristics of dry-cured ham processed from HAL positive pigs are somewhat surprising and need to be confirmed.     

A comparison of halothane homozygous negative and positive pietrain sire lines in relation to carcass and meat quality, and welfare traits

Barrows (n=164) and gilts (n=249) from crosses of a Pietrain homozygous halothane recessive (Pi nn) and two Pietrain homozygous dominant (Pi NN-a and Pi NN-b) sire lines with Landrace×Large White NN sows, were used to study the effect of terminal sire and pre-slaughter treatment on meat quality and animal welfare. The pigs from each of the two farms where they were finished were delivered to the abattoir in two batches differing in the pre-slaughter conditions. A total of 90 pigs (54 NN and 36 Nn) were assigned to a long pre-slaughter treatment (6 h transport and 14.5 h lairage) and 89 (57 NN and 33 Nn) to a short pre-slaughter treatment (4.5 h transport and 2.5 h lairage) in Farm 1, and 118 (65 NN and 53 Nn) to the long (7 h transport and 14 h lairage) and 114 (66 NN and 48 Nn) to the short pre-slaughter treatment (1.5 h transport and 2 h lairage) in Farm 2. In Farm 1, heart rate of 3 NN and 3 Nn gilts was recorded throughout loading and transport and blood samples from 5 NN and 5 Nn were collected before loading and after transport to measure cortisol, creatine phosphokinase (CPK) and lactate dehydrogenase (LDH). Carcasses were classified and commercial cutting was carried out. At 24 h, meat quality was assessed on the Longissimus thoracis muscle by measuring electrical conductivity (PQM), colour (Minolta CR 200 and Japanese scale), pHu and drip losses. Halothane carriers showed a higher mean heart rate and higher increase in CPK levels (P<0.05) after transport in the short pre-slaughter treatment than halothane free pigs. No effect was observed in cortisol or LDH values. Pi NN-a sired pigs had a higher live and carcass weight (P<0.001) and loin depth (P<0.05), but lower killing out percentage (P<0.01) and leg yield (P<0.01) compared with the progeny of the other two terminal sires. Gilts were leaner (P<0.001), had a higher killing out percentage (P<0.001) and higher yields of primal cuts (P<0.001) compared with barrows. Pi nn sired pigs had poorer meat quality (higher PQM values in both farms, P<0.01) than Pi NN-a sired pigs. Long pre-slaughter treatment resulted in darker meat (P<0.01) in both farms and in higher pHu (P<0.001) in Farm 1 than short pre-slaughter treatment. Conversely, pigs subjected to the short pre-slaughter treatment showed higher PQM values (P<0.01) in Farm 1 and higher PSE percentage (P<0.05) in both farms compared to the ones subjected to the long pre-slaughter treatment. These results suggest that Pietrain halothane free sire lines could produce similar results on carcass quality to halothane carriers, without compromising meat quality and welfare.     

Halothane genotype and pork quality. 3. Comminuted meat products derived from the three halothane genotypes

The effect of the halothane gene on cured meat products was investigated using the meat from 60 Landrace×Large White pigs of known halothane genotype (NN=25, Nn=19, nn=16). Results for the two types of fresh sausage manufactured (with and without rusk) indicated that the NN pigs (15.7%) had lower total moisture losses (P<0.05) compared to the nn pigs (18.9%), with Nn being intermediate (17.4%) for the sausage without rusk. Where rusk was added, there were no significant differences between genotypes for moisture losses (NN=12.6%, Nn=13. 0%, nn=14.2%). Taste panel evaluations of the fresh sausages made without rusk indicated no genotypic influence for juiciness, however the sausage made with the rusk was judged the juiciest for the nn genotype, with Nn being intermediate and NN the least juiciest. The smoking and cooking losses during manufacturing of the emulsion product (vienna) indicated that the nn genotype (12.5%) had significantly (P<0.05) higher total losses than the Nn genotype (11. 3%), with NN being intermediate (12.4%).     

Halothane genotype and pork quality. 2. Cured meat products of three halothane genotypes

The effect of the halothane gene on cured meat products was investigated using the meat from 60 Landrace×Large White pigs of known halothane genotype (NN=25, Nn=19, nn=16). The backs and hams were used to prepare cured, smoked bacon and canned hams. Initial bacon gain in pumped weight was significantly higher (P<0.001) for the NN (15.2%) and Nn (14.9%) compared to the nn pigs (8.9%). Similarly, the total gain in bacon yield was the highest for the Nn (11.5%) and NN pigs (10.0%), and significantly higher (P<0.05) than the bacon from nn pigs (3.4%). Differences between sexes were not significant. Canned hams (no phosphate) from the NN genotype had a significantly (P<0.001) lower percentage cooking loss (27.9%) compared to the Nn (30.1%) and nn pigs (31.1%), which did not differ statistically. Although addition of phosphates (0.3% on final product) led to a decrease in percentage cooking loss, the genotypes gave a similar response, with the NN genotype having 13.8% cooking loss, significantly lower (P<0.001) than the Nn (16.9%) and nn genotypes (17.7%). The results indicate reduced product quality with the inclusion of the halothane gene.     

The influence of RN genotype, including the new V199I allele, on the eating quality of pork loin

The eating quality of M. longissimus dorsi (LD) from RN⁻ homozygotes, RN⁻ heterozygotes and RN⁻ non-carriers was investigated in a Swedish Hampshire×Finnish Landrace pig population. The recently identified new allele (V199I, here denoted rn*) at the RN locus was also detected among the pigs selected and included in the sensory evaluation. The number of animals varied from 10 to 15 in the five genotype groups; RN⁻/RN⁻, RN⁻/rn+, RN⁻/rn*, rn+/rn+ and rn+/rn* (in total 59 pigs). In addition, one pig was determined to be rn*/rn* but was excluded from the analysis. The three genotypes in which the RN⁻ allele was represented (RN⁻/RN⁻, RN⁻/rn+ and RN⁻/rn*) had higher glycogen and lower protein contents as well as lower ultimate pH (measured 48 h post-mortem) in LD than the non-carriers (rn+/rn+ and rn+rn*). Of the sensory parameters evaluated (tenderness, chewing time, chewing residual, juiciness, meat flavour and acidity), the five RN genotypes only affected acidity significantly; the RN⁻ allele contributing to a more acid taste in LD. The influence of the rn* allele resembled that of rn+ on the sensory parameters. When the material was divided into three groups (homozygous, heterozygous and non-carriers of the RN⁻ allele) the juiciness was found to be significantly influenced by RN genotype, and LD from animals that were homozygous and heterozygous with respect to the RN⁻ allele exhibited a higher juiciness than LD from non-carriers. The RN⁻ allele also tended to contribute to greater tenderness, which was significantly higher in LD from heterozygous carriers than from non-carriers of the RN⁻ allele. A more rapid decline in pH (measured as pH at 45 min and 3 h post-mortem) contributed to a greater tenderness in LD (according to a trained panel and Warner-Bratzler shear force). In addition to the RN genotype, the decline in pH was influenced by carcass weight, which varied between 71 and 97 kg, and by stunning procedure, which changed during the course of the study from individual to group stunning with CO₂. The individual stunning procedure contributed to a lower pH in the initial post-mortem phase (pH₄₅), whereas a higher carcass weight and the RN⁻ allele lowered the pH in the mid-post-mortem region (pH_3h and pH_24h), significantly (P0.05). The pH continued to decline after 24 h post-mortem and the ultimate pH was not reached until 48 h post-mortem. The cooking loss, juiciness and acidity were related to the specific characteristics of the RN⁻ carriers, such as higher glycogen content, lower protein content and lower ultimate pH (pH_48h).     

Sensory properties of hot-deboned ostrich (Struthio camelus var. domesticus) Muscularis gastrocnemius, pars interna

Cold-deboning is currently practiced in South African ostrich abattoirs. However, the advantages of hot-deboning include the reduction of costs and time, but there is always the risk of cold-shortening. The effects of hot-deboning of ostrich M. gastrocnemius, pars interna on meat sensory attributes were investigated. The data showed that the hot-deboned muscles’ pH₄₈ (6.57 ± 0.18) was significantly negatively correlated (r = −0.7813; P < 0.038) to the mean Warner–Bratzler shear force values (71.28 ± 18.62 N, 12.7 mm⁻¹ diameter) and positively correlated (r = 0.789; P < 0.035) to the mean scores for taste panel tenderness (66.39 ± 15.45). After storage for 48 h post-mortem, the hot-deboned muscles were found to be less juicy (P < 0.004) and, according to both sensory tenderness scores and Warner–Bratzler shear force values, tougher (P < 0.0001) than the cold-deboned muscles.     

Beef tenderness and sarcomere length

A wide range of muscle glycolytic rates was produced in 60 beef carcasses by applying different forms and periods of electrical stimulation immediately after decapitation; a further seven carcasses were not stimulated. The sides were subjected to normal chilling, and at 48 h one short loin per carcass was taken for tenderness evaluation and determination of sarcomere length (SL).

In the 19 relatively slow-glycolysing loins—those of 3-h pH (pH₃) above 6·3—tenderness extended over almost five panel units on a 1–8 scale, and included both the tenderest two and the toughest 10 muscles of the entire study. In the 48 loins of pH₃ below 6·3, on the other hand, tenderness ranged over only 2·5 units, and on average was a full panel unit higher than that of the high-pH₃ muscles. The most striking difference between the two groups, however, was in the relationship between toughness and shortening; the correlation of panel tenderness on SL was remarkably high in the slow glycolysers (r = 0·84), but negligible in those of faster pH decline (r = 0·16). Thus although shortening occurred to about the same extent and over the same range in both groups, it influenced tenderness and tenderness variability only when glycolysis was quite slow. A loin pH₃ of below 6·3, however, is unusual in non-stimulated carcasses, so slow glycolysis and the very wide tenderness diversity accompanying it must be expected in commercial operations that do not use electrical stimulation.     

Variation in post-mortem rate of glycolyis does not necessarily affect drip loss of non-stimulated veal

In this study the effect of the rate of post mortem pH fall on the water-holding capacity of meat from moderately chilled veal carcasses was investigated. Also the relationship between muscle protein denaturation and drip loss of veal was examined. Three groups of 10 Friesian Holstein male veal calves each were selected on the basis of their pH in M. longissimus thoracis et lumborum (LTL) at 3 hr post mortem (pH₃): (1) fast pH-fall, pH₃ < 6.2; (2) intermediate pH-fall, 6.5 < pH₃ < 6.6; (3) slow pH-fall, pH₃ > 6.7. After 48 hr of chilling the LTL was excised from the carcass and sampled for determination of drip loss, filter paper wetness, sarcomere length, protein solubility and transmission value. Differences in pH₃ were not associated with differences in drip loss, filter paper wetness or differences in protein denaturation. It is suggested that at the relatively high veal carcass chilling rate the effect of rate of pH-fall on protein denaturation and thus on drip loss is negligible. Drip loss of veal was highly correlated with both solubility of sarcoplasmic (r = −0.67; p < 0.001) and total muscle protein (r = −0.54; p < 0.01) and with transmission values (r = 0.66; p < 0.001). These results indicate that protein denaturation measurements may be a good predictor for drip loss of veal.     

The effect of ractopamine on myofibre distribution and morphology and their relation to meat quality in swine

One hundred and twenty-eight purebred Lacombe pigs (equal number of barrows and gilts) were assigned to one of four treatments at 64 kg and fed a commercial grower-finisher diet ad libitum to which ractopamine (RAC) was incorporated (0, 10, 15 or 20 mg kg⁻¹). Pigs were slaughtered at 100 kg. Histological samples were collected from the semimembranosus (SM) and the psoas major (PM) muscles from the 0 and 20 mg kg⁻¹ RAC groups. Meat quality and muscle composition data were collected for all pigs. A significant 3-way interaction for muscle weight involving treatment, muscle and gender (P = 0·01) indicated that for the SM, gilts appeared to respond to RAC at a lower level of incorporation (10 mg kg⁻¹) than barrows. Despite these differences in response at the gross muscle level, responses were similar at the cellular level for both muscles. The proportion of red fibres did not change (P = 0·21), the proportion of intermediate fibres decreased (P = 0·01) and the proportion of white muscle fibres increased (P = 0·02) in the mg kg⁻¹ RAC group compared to the controls. In addition, when compared to controls, average fibre diameters in the 20 mg kg⁻¹ RAC group remained constant in the red fibres, and increased significantly in both the intermediate and white fibres (P = 0·01 and 0·02, respectively). Over both muscles Kramer Press values were significantly higher (P = 0·030 in the RAC-fed pigs than in the controls. Incorporation of RAC into the diet did not result in any changes to crude protein or total and soluble hydroxyproline levels. Crude fat tended to increase in the 15 mg kg⁻¹ RAC treatment in the SM and decreased in the 20 mg kg⁻¹ RAC treatment in the PM. The shift in fibre type, and the associated changes in fibre size, may contribute to the increased shear values found in RAC-fed pigs.     

Muscle glycogen level and meat quality in pigs of different halothane genotypes

The halothane genotype of 22 Polish landrace pigs was determined using halothane test and blood typing. Eight homozygous normal (NN), eight hetero-zygotes (Nn) and six homozygous recessive (nn) were identified. The levels of glycogen and lactate were measured in biopsy samples taken from the longissimus lumborum using a shot biopsy technique. pH (pH(1)) and IMP/ATP ratio (R) were determined at 30 min after slaughter, while pH, meat colour and water holding capacity were determined on the day after slaughter. The halothane genotype did not affect intra vitam glycogen level. The nn pigs had a higher R value and lower pH(1) than both Nn and NN animals. Heterozygous animals were intermediate between both homo-zygotes for biopsy lactate level and meat colour. The lactate content of biopsy samples was significantly correlated with pH(1) (r = -0·68; P < 0·01), R (r = 0·68; P < 0·01), meat colour (r = 0·57; P < 0·01) and water holding capacity (r = 0·45; P · 0·05).     

Augmented postmortem glycolysis does not occur early postmortem in AMPKγ3-mutated porcine muscle of halothane positive pigs

The objective of this study was to determine the effects of the halothane (HAL) and Rendement Napole (RN) genes on the rate-limiting reactions of glycolysis and their relationship to pork quality development. Samples were collected from the longissimus muscle at 0, 30, 60, and 120 min and 24 h postmortem from homozygous HAL and RN pigs (NN/rn⁺rn⁺, NN/RN⁻RN⁻, nn/rn⁺rn⁺, nn/RN⁻RN⁻). Muscle pH was recorded at 0, 15, and 45 min, and 24 h postmortem. HAL mutants, compared with HAL normal, had lower (P < 0.05) ATP concentrations at 0 and 30 min, lower (P < 0.05) pH at 45 min, and hastened glycogen degradation and lactate accumulation in the first 120 min postmortem (HAL × time, P < 0.0001). RN mutants had greater (P < 0.0001) glycolytic potentials than RN normal, and lower (P < 0.05) 24 h pH compared with the normal genotype, but not the HAL mutant genotype. The HAL mutation negatively affected (P < 0.05) L*, b* and color scores whereas both HAL and RN mutations independently decreased (P < 0.05) firmness, marbling and water holding capacity. RN mutant genotypes had higher (P < 0.0001) phosphocreatine concentrations than other genotypes at 0 min. Compared with HAL normal, HAL mutants had elevated (P < 0.05) muscle glucose concentrations at 30, 60, and 120 min, and 24 h. RN mutants had higher (P < 0.05) glucose levels than RN normal after 60 min. Glucose-6-phosphate (G6P) concentrations decreased (P < 0.05) during the first hour postmortem except in HAL/RN mutants, which had higher (P < 0.01) G6P concentrations than all other genotypes at 30 min. From 60 min to 24 h postmortem, G6P increased (P < 0.05) in HAL normal genotypes. Altogether, these data show that elevated muscle glycogen content does not further aggravate rapid early postmortem metabolism.     

Stunning and shackling influences on quality of porcine Longissimus dorsi and Semimembranosus muscles

Seventy-one barrows of three porcine genotypes (nn, Nn and NN genotypes with respect to halothane) were electrically stunned on the right side and randomly assigned to one of three treatments during the bleeding process (prone, PR; shackled left, SL; or shackled right, SR) to investigate the influence of both shackling and stunning on ultimate meat quality. PR carcasses had less side-to-side variation in 40 min pH than either SL or SR carcasses. Shackling contributed to a decreased 40 min pH in the semimembranosus (SM) and posterior longissimus dorsi (PL). The effects of stunning appeared to be additive when combined with shackling, tending to lower pH in the mid-longissimus dorsi (ML; P <- 0·10). The ‘free’ side of the shackled carcass also had significantly lower 40 min pH in the ML, PL and SM locations when compared to PR sides. Genotype had no influence on shackling since there was no treatment by genotype interactions. Despite significant effects on post-mortem metabolism (indicated by the differences in 40 min pH) shackling alone had little influence on overall ultimate meat quality of the carcass. Depending on the sampling location, soluble protein and L^* and b^* values varied among treatments. Shear force and a^* values were similar among treatments, but PR and SL carcasses had significantly lower expressible juice and drip loss compared to SR carcasses. These results suggest that, although shackling alone has little effect on meat quality, in combination with electrical stunning, shackling can lead to a decrease in meat quality.     

Development of backfat and individual fat layers in the pig and its relationship with carcass lean

The development of backfat (total and individual layers) was monitored in 140 Yorkshire pigs (71 castrates and 69 gilts) during a growing period extending from 14·5 kg to 137·0 kg live weight using a serial slaughter procedure. The allometric coefficient (b) for fat thickness was calculated at several locations extending from the shoulder to the M. gluteus medius at the mid-line and lateral to the mid-line. The relationships between backfat (total and individual layers) and the yield of trimmed boneless meat were also obtained from 80 carcasses.

Total backfat was the thickest at the shoulder, decreased gradually to the last rib, increased at the maximum loin, decreased to the middle of the M. gluteus medius and then increased posterior to the M. gluteus medius. The development of total backfat relative to weight at slaughter was generally slowest at the shoulder (b = 0·555−0·767), most rapid in the region extending from the 5/6 last rib to the last rib b = 0·729−0·810) and intermediate at the loin and in the region of the M. gluteus medius (b = 0·609−0·834). The development of the middle fat layer (b = 0·609−1·107) was more rapid than that of the outer layer (b = 0·500−0·817), the inner layer being intermediate (b = 0·515−0·966). Consistent with the rate of development observed for the individual fat layers, at light weights, the outer layer was usually more predominant, particularly at positions above the M. longissimus, whereas, at heavier weights, the middle layer became predominant.

It was observed that backfat (total or individual layers) measurements, which were the most precise predictors of yield of trimmed boneless meat, that is, measurements from the 5/6 last rib to the last rib (RSE = 4·6−3·1), also had the most rapid rate of development. Furthermore, the middle layer of backfat which exhibited the fastest rate of development of all three individual layers (b = 0·609−1·107), also contributed the most to the observed precision (RSE = 4·6−3·1).     

The effect of experimental stress on sarcoplasmic reticulum Ca transport and meat quality in pig muscle

Stress before slaughter affects the meat quality of pigs and a disorder in the Ca²⁺ transport of the sarcoplasmic reticulum (SR) results in inferior meat quality. The object of this work was to determine the impact of stress on SR Ca²⁺ transport in pig muscle in animals with no mutation in the Ca²⁺ release channel. At about 80 kg live weight, pigs were stressed either by running for 4 min (n=9) or by a 5 min application of a nose snare (n=7). Immediately before and after the application of the stress, as well as 4 h after the stress, biopsy samples of the longissimus muscle were taken and the Ca²⁺ uptake of the homogenised muscle samples determined. The nose snare stress reduced the rate of Ca²⁺ uptake by 9% (P=0.02) and running by 18% (P=0.06). Uptake in samples taken 4 h after the stress was at initial levels. The pigs were slaughtered at an average live weight of 109 kg. Half the pigs were stressed just before slaughter for 5 min by the use of a nose snare. Immediately after exsanguination longissimus muscle samples were taken, Ca²⁺ uptake measured, and later standard meat quality parameters were determined. Although the stress reduced the Ca²⁺ uptake rate (61.3 vs. 46.4 nM/min per mg protein for control and stressed pigs; P=0.04), the meat quality was not significantly affected.     

A method for simultaneous fluorometry and rheology of connective tissue in bulk meat

A probe tipped with optical fibres was mounted on the load cell of a compression tester and pushed into well-aged beef rib roasts (Canada Grade AAA, n = 6, 33 ± 3.6 days post-mortem). Fluorescence (F; excitation 365 nm, emission >420 nm) and reflectance (R; 365 nm) were measured through single optical fibres. Diffuse R was measured using different fibres for illumination and detection, thus responding to tissue between the two fibres. Replication was by a matrix pattern of penetrations on single roasts. For example, in a typical roast, F was correlated with the force of penetration (mean r = 0.86 ± 0.06, n = 20, all P < 0.001). R was less (P < 0.001) strongly correlated with penetration force (mean r = 0.46 ± 0.10, n = 20, all P < 0.001). F signals from connective tissue contained less peaks than R signals from both connective and adipose tissue (respectively, 2.75 ± 0.43 versus 5.57 ± 0.67 peaks cm⁻¹, P < 0.001, n = 20 pairs) and F peaks were wider than R peaks (respectively, 3.54 ± 0.88 versus 1.38 ± 0.19 mm, P < 0.001, n = 20 pairs). For the spinales dorsi aponeurosis, the depth at which peak force was reached was strongly correlated with the depths at which both peak F and peak R were reached (r = 0.98, P < 0.001, n = 20 for both). Diffuse R was only weakly correlated with penetration force (mean r = 0.29 ± 0.12 with only 5/10 correlations significant P < 0.001). This new method showed the primary resistance to dorso-ventral penetrometry of well-aged beef rib roasts originated from connective tissue.