Variations in meat quality in live halothane heterozygotes identified by biopsy samples of M. longissimus dorsi

The meat quality of halothane heterozygotes (Nn) was investigated using British Landrace (n = 18) and Landrace × Large White pigs (n = 67). Normal and PSE meat were identified in both breeds using M. longissimus dorsi (LD). In Landrace × Large White Nn pigs, the potential meat quality identified using small biopsy LD samples (500 mg) showed a wide spectrum in water-holding capacity (WHC), ranging from normal (43%) to PSE (57%). Predictions of meat quality in live pigs were confirmed from post-mortem assessments of LD samples based on pH(1) and fibre optic probe measurements. Our results show that Nn pigs have the propensity to produce a higher proportion of PSE than normal carcasses. The predictive meat quality test performed on small biopsy LD samples offers an opportunity not currently available to the pig industry, to select Nn pigs with the potential to produce pork of superior WHC.     

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.     

Halothane genotype and pork quality. 1. Carcass and meat quality characteristics of three halothane genotypes

The carcass and meat quality characteristics of three halothane genotypes in pigs were evaluated. Sixty crossbred Landrace×Large White pigs (NN=25, Nn=19, nn=16) of ±86 kg live weight were slaughtered, the carcasses chilled for 24 h at 2°C, certain carcass and meat quality traits determined and the shoulder and leg cuts deboned and cut into primal cuts. Dressing percentage of the Nn pigs was higher (P<0.05) than that of the NN and nn pigs. Carcass length was the longest (P<0.05) for the nn pigs. Midline fat measurements as well as measurements at the 2nd-3rd last rib (45 mm from the midline) indicated that the nn pigs had less fat (P<0.05) and a larger eye muscle width (P<0.05), depth (P<0.001) and area (P<0.001) than the NN or Nn pigs. This resulted in the nn pigs having the highest (P<0.05) percentage predicted carcass lean content. Fat, bone and lean yield of the shoulder identified the nn pigs with the least bone (P<0.05) and fat (P<0.001) and the highest lean yield (P<0.05), expressed as a percentage of total shoulder weight. Yield from the legs identified the nn pigs as having the lowest fat (P<0.001) and highest lean (P<0.05), expressed as a percentage of total leg weight. The primal lean cuts (topside, silverside, thickflank and rump) from the legs showed that the nn pigs had the highest values (P<0.05) for lean as a fraction of cold carcass weight. This resulted from the higher weight of these cuts (P<0.05) in the nn pigs. Calculation of bone yield in the legs showed that the femur weights were highest (P<0.05) for the Nn pigs, also when expressed as percentage of leg weight (P<0.05) and as a fraction of cold carcass weight (P<0.05). Comparison of meat quality traits show that the nn pigs had poor quality with regard to pH(45) (P<0.001), pH(24) (P<0.05), drip loss (P<0.001) and reflectance values (P<0.05).     

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively?- means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.     

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.     

Effect of dietary vitamin E, fishmeal and wood and liquid smoke on the oxidative stability of bacon during 16 weeks' frozen storage

Twelve (Large White×Landrace) gilts were randomly allotted in a 2×2 factorial design with the respective factor being dietary vitamin E (10 or 200 mg/kg feed) and dietary fishmeal (0 or 5%). Bacon was manufactured from the meat obtained from the animals after slaughter using wood smoke only or a combination of liquid and wood smoke. The oxidative stability of the bacon was examined over 16 weeks of frozen storage. Lipid oxidation in the product was measured by means of thiobarbituric acid reactive substances (TBARS) and fluorescence shift. Dietary fishmeal supplementation increased lipid oxidation in bacon, while dietary vitamin E supplementation reduced lipid oxidation in the product. Lipid oxidation in frozen bacon was successfully reduced when bacon was manufactured from pigs fed a diet supplemented with or without 200 mg of α-tocopherol per kilogram of feed and processed with a combination of liquid and wood smoke. It is concluded that bacon processed with a combination of liquid and wood smoke was significantly less (P<0.001) susceptible to lipid oxidation than bacon processed with wood smoke only.     

Evaluation of halothane sensitivity and prediction of post-mortem muscle metabolism in pigs from a muscle biopsy using (31)P NMR spectroscopy

Phosphorus nuclear magnetic resonance (³¹P NMR) measurements were made on biopsy samples from pig muscles. Two experiments were performed, one in France and one in Czechoslovakia. In experiment 1, the muscle samples were obtained by surgery from the Biceps femoris muscle of 10 pigs with various genetic types (5 Large White, 1 Large White × Landrace, 4 Pietrains). In experiment 2, the muscle samples were obtained by shot biopsy from the Longissimus dorsi muscle of 11 Belgian Landrace × Duroc pigs, of which 6 were halothane-negative and 5 halothane-positive. The pigs were slaughtered by electrostunning and exsanguination respectively 3 weeks and 1 week after the biopsy, and meat quality traits (pH₁, reflectance and water holding capacity) were determined. The changes in adenosine triphosphate (ATP), creatine phosphate (CP), inorganic phosphate (P_i) and pH, as deduced from NMR, were faster in Pietrains than in Large Whites, and in halothane-positive than in halothane-negative pigs. The value of the CP/P_i ratio at 40 min after taking biopsy allowed discrimination between halothane-positive and halothane-negative pigs. The values of pH, creatine phosphate and adenosine triphosphate, as measured at definite times on the biopsies, were correlated with the rate of post-mortem metabolism (r approx 0·8) and with meat quality traits. ³¹P NMR measurements combined with a rapid and efficient biopsy technique appear as an alternative tool for assessment of both halothane sensitivity and prediction of meat quality in 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).     

Effect of different dietary levels of natural-source vitamin E in grow-finish pigs on pork quality and shelf life

Improving pork quality and shelf life is important in today’s swine industry because higher levels of DDGS are incorporated into pig diets. Relatively high level of poly-unsaturated fatty acids (PUFA) in DDGS may increase pork susceptibility to lipid oxidation and thus reduce pork shelf life. Antioxidants such as vitamin E may delay the onset of pork lipid oxidation when used as an ingredient in the diet. This experiment examined carcass characteristics, meat quality, shelf life, and color stability in pork from pigs (n = 150) fed five levels of a natural vitamin E (Nova-E) and one level of synthetic vitamin E. Natural vitamin E and synthetic vitamin E had no effect on carcass characteristics or meat quality. Increasing dietary natural vitamin E from 10 to 200 mg/kg decreased lipid oxidation. Lipid oxidation of pork chops and ground pork was similar between pigs fed 40 mg/kg and higher levels of natural vitamin E, indicating no additional benefits from supplementing beyond 40 mg/kg natural vitamin E. Supplementing 200 mg/kg synthetic vitamin E decreased pork lipid oxidation when compared to supplementing 10 mg/kg natural vitamin E. High levels of natural vitamin E or synthetic vitamin E, however, did not prevent discoloration of loin chops. These data indicate that natural vitamin E was effective to help reduce lipid oxidation and the effective minimal level of dietary supplementation appeared to be 40 mg/kg.     

In vitro (31)P NMR studies on biopsy skeletal muscle samples compared with meat quality of normal and heterozygous malignant hyperthermia pigs

Phosphorus nuclear magnetic resonance ((31)P NMR) measurements were made to determine muscle energetic metabolism on muscle biopsy samples of heterozygote malignant hyperthermia (Nn) and normal (NN) pigs DNA tested on occurrence of mutation in RYR 1 gene. Biopsy samples (approx. 1 g) were obtained by spring-loaded biopsy instrument (Biotech, Slovakia) from Longissimus dorsi (LD) muscle at 80 kg live weight. The spectra were recorded at 121 MHz on a VXR 300 (Varian) spectrometer in 10 mm diameter tube (maintained at 39?°C) for 50 min. pH of bioptates after NMR measurements were also measured at 60 min. The changes in inorganic phosphate (Pi), phosophocreatine (PCr) and adenosine triphosphate (ATP) were faster in heterozygote malignant hyperthermia (MH; 29 crossbred White Meaty×Pietrain) than in normal (13 Duroc, Yorkshire and White Meaty). The values of PCr at 20 min and pH at 60 min after taking biopsy allowed discrimination between NN and Nn pigs and significant (P<0.05) differences were also found between two subgroups in heterozygote MH pigs with different rate of post mortem muscle metabolism. The values of PCr and pH as measured at definite time on the biopsies, were significantly (P<0.05) correlated with the rate of post mortem metabolism (pH) and with meat quality traits (r approx. 0.4-0.6). The (31)P NMR measurements pointed to impaired muscle energetic metabolism connected with the occurrence of mutation on the RYR 1 gene in heterozygote MH pigs.     

Texture and rheological properties of meat from pigs of different halothane genotypes

The effects of halothane genotype (NN, Nn and nn) in pigs on meat texture, rheological properties, fibre diameter, area of intramuscular fat, pH, colour, drip loss, cooking loss and yield of cooked and of smoked loin were examined. Cooked and smoked meat of NN pigs exhibited lower hardness, gumminess, chewiness, elasticity moduli, greater cohesiveness and a longer relaxation time compared to meat from pigs with genotype Nn or nn. Meat from pigs of the nn genotype exhibited the greatest hardness and elasticity, the shortest relaxation time and the lowest viscosity and cohesiveness, while meat from genotype Nn was intermediate regarding these parameters. Significant correlations were found between parameters of texture, and rheological properties and pH, structure, drip and cooking loss. © 1998 SCI.     

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.     

Dietary vitamin A concentration alters fatty acid composition in pigs

This experiment was conducted to study the effect of vitamin A concentration in the diet on fatty acid composition in pigs. One-hundred and twenty eight Duroc × (Large White × Landrace) castrated male pigs were used. Pigs were randomly distributed and located in cages of four pigs each to the following treatment: vitamin A-enriched diet (100,000IU/kg) (n=16) and control diet with a basal level (7500IU/kg) (n=16). The pigs were slaughtered at an average weight of 125.9kg. No effect of diet vitamin A level on performance, carcass traits and intramuscular fat percentage was observed. The retinol concentration in subcutaneous backfat and retinol and retinol palmitate contents in liver were higher in the pigs that were given the vitamin A enriched diet than in those receiving the control diet. However the vitamin A supplementation did not increase the retinol content in the muscle. Pigs receiving the vitamin A enriched diet showed a higher C16:0 and ∑SFA proportions in the outer layer and C18:0 and ∑SFA proportions in the inner layer. Moreover, the diet rich in vitamin A led to a reduction of C18:1 n-9 and ∑MUFA proportions in subcutaneous backfat inner layer. Dietary vitamin A concentration had not influence on main fatty acids composition of intramuscular lipids. Dietary vitamin A enrichment lead to a higher C16:0, ∑SFA concentration in liver lipids.     

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.     

Carcass and meat quality of selected final hybrids of pigs in the Czech Republic

The objective of this work was to compare the quality of carcass and meat in the selected crossbred pigs used in the Czech Republic. A total of 200 pigs that arose from four crossbreeding was studied; the dam line was in all combination of hybrids represented by Czech Large White × Landrace. Sire line included Large White × Belgian Landrace (I), Hampshire × Pietrain (II), Duroc × Pietrain (III) and Czech meat pig (IV). Influence of crossbreeding on lean meat percentage and muscle depth was statistically highly significant (P<0.001), influence on fat depth was evident (P<0.05). Differences in pH(1) value among the individual final hybrids were not statistically significant but variance of pH(24) value was highly notable (P<0.001). All colour parameters (L(?), a(?), b(?) values), drip loss and exudate also were influenced by hybrid combination (P<0.001). Influence of crossbreeding on intramuscular fat content was not statistically significant (P=0.067). Higher content of intramuscular fat was determined in the hybrids with Duroc breed in sire line. In the whole group, 8.5% pig with PSE defect was found. By comparison of all the various hybridisation, positive influence of Hampshire breed on the carcass quality and negative influence on meat quality was confirmed. On the other hand, meat quality is positively influenced Duroc and Czech meat pig breeds.     

Effect of different dietary levels of natural-source vitamin E in grow-finish pigs on pork quality and shelf life

Improving pork quality and shelf life is important in today’s swine industry because higher levels of DDGS are incorporated into pig diets. Relatively high level of poly-unsaturated fatty acids (PUFA) in DDGS may increase pork susceptibility to lipid oxidation and thus reduce pork shelf life. Antioxidants such as vitamin E may delay the onset of pork lipid oxidation when used as an ingredient in the diet. This experiment examined carcass characteristics, meat quality, shelf life, and color stability in pork from pigs (n = 150) fed five levels of a natural vitamin E (Nova-E) and one level of synthetic vitamin E. Natural vitamin E and synthetic vitamin E had no effect on carcass characteristics or meat quality. Increasing dietary natural vitamin E from 10 to 200 mg/kg decreased lipid oxidation. Lipid oxidation of pork chops and ground pork was similar between pigs fed 40 mg/kg and higher levels of natural vitamin E, indicating no additional benefits from supplementing beyond 40 mg/kg natural vitamin E. Supplementing 200 mg/kg synthetic vitamin E decreased pork lipid oxidation when compared to supplementing 10 mg/kg natural vitamin E. High levels of natural vitamin E or synthetic vitamin E, however, did not prevent discoloration of loin chops. These data indicate that natural vitamin E was effective to help reduce lipid oxidation and the effective minimal level of dietary supplementation appeared to be 40 mg/kg.     

Effects of halothane gene and pre-slaughter treatment on meat quality and welfare from two pig crosses

Pigs from crosses of a Piétrain (Pi) and a Large White×Piétrain (LwPi) heterozygous (Nn) boar lines with Landrace×Large White homozygous negative (NN) sows, were used to study the effect of halothane gene and pre-slaughter treatment on animal welfare and meat quality. A total of 83 gilts (47 NN and 36 Nn) were assigned to a long treatment (3 h 15 min transport and 12 h lairage) and 73 (39 NN and 34 Nn) to a short treatment (30 min transport and 2 h lairage). Heart rate was recorded throughout loading and transport. Blood samples were collected before loading, after transport, and at exsanguination to measure cortisol, creatine phospho-kinase (CPK) and lactate dehydrogenase (LDH). Carcasses were classified and commercial cutting was carried out. Meat quality was assessed on the Longissimus thoracis muscle by measuring electrical conductivity (PQM), colour (Minolta CR 200 and Japanese scale) and ultimate pH. Loin drip losses were assessed at 24 h. Halothane carriers showed a higher increase in cortisol levels after transport and exsanguination in the long treatment (P<0.05) as well as in LDH and CPK after exsanguination in the short treatment (P<0.05). In this treatment, halothane-free pigs recovered during lairage when comparing LDH and CPK increases after exsanguination to their increases after transport. No effect of the halothane gene on heart rate was observed. Pi sired pigs were leaner and had higher yields of leg and loin compared with LwPi sired pigs (P<0.001), but no differences in meat quality were observed between crosses. Halothane carriers had a higher estimated lean content (P<0.01) and shoulder and leg yields (P<0.01), but poorer meat quality than non-carriers (i.e. higher incidence of PSE meat, P<0.001). Although pre-slaughter treatment and halothane genotype did not significantly affect pHu, significantly higher L*, a* and b* values found in the short treatment and Nn individuals indicated paler meat. These results suggest that for improving meat quality and welfare the halothane gene should be removed from breeding schemes.     

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca²⁺ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca²⁺ specific electrode at 35°C. Significant differences (P < 0·001) in deterioration (%) of Ca²⁺ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice.

Predictions of meat quality in live pigs (n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN (n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn (n = 13). The Nn pigs (n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH₁ and fibre optic probe (FOP) measurements.

The extent of deterioration (%) in Ca²⁺ accumulation showed high correlations with fluid (r = −0·861) and pH (fluid) (r = −0·831) in the biopsy LD samples, and with pH₁ (r = 0·663), FOP (r = −0·812), and drip (%) loss (r = −0·777) in the post-mortem LD samples.     

Influence of dietary fat on pork eating quality

This study compared the influence of dietary fat sources on meat quality, fatty acid composition and sensory attributes in pork. The experiment was conducted with 43 entire male pigs (Pietrain×(Landrace×Large White)) which were fed a basal diet without added fat (control diet) or supplemented with different sources of fat: animal fat (1%, AF1; 3%, AF3), soyabean oil (1%, SBO1) and calcium soaps of palm oil (1%, CaSPO1). Dietary fat supplementation did not significantly affect ultimate pH, colour, Warner-Bratzler shear force values, sensory attributes or SFA. Pigs fed SBO1 had the lowest proportion of MUFA and the highest of PUFA. In conclusion, these dietary fat sources could be recommended for inclusion in diets, at these levels, with no detrimental effect on eating quality. Despite finding no significant differences, the PCA afforded a comprehensive view of the predominating attributes of pork from animals fed the different fats.