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).     

Prediction of meat quality in live pigs using stress-susceptible and stress-resistant animals

A new in-vivo procedure for predicting the potential meat quality in live pigs was devised using stress-susceptible (halothane positive) and stress-resistant (halothone negative) pigs. The potential meat quality in live pigs was determined using small biopsy samples of M. longissimus dorsi (LD). Meat quality was assessed by the combined measurements of pH and water-holding capacity (WHC) on the 12 000 g supernatant after incubation of 500 mg biopsy LD muscle with an equal volume of 150 mm KCl at 39°C for 45 min. With the LD muscles of halothane positive (n = 37) and halothane negative (n = 55) pigs, high correlations (r = -0·854) were observed between the supernatant (i.e. fluid) pH and WHC of the biopsy samples, between fluid pH of the biopsy samples and 1-h post-mortem (pH(60)) LD muscles (r = 0·951), and between pH(60) and WHC (r = -0·956). The experimental data show that our in-vivo test can differentiate halothane positive from halothane negative pigs and can also predict the potential meat quality in live pigs. The test could be applied to select pigs with differences in WHC to improve meat quality.     

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.     

A comparison of some muscle metabolites in stress susceptible and resistant Landrace gilts after halothane exposure or exercise stress

Sixty-six South African Landrace gilts were used in the experiments. At the age of 21 weeks, 47 of the pigs were challenged with halothane exposure. As a result 17 of the pigs died, and were classified stress susceptible (SS), whereas the 30 survivors were classified stress resistant (SR). The other 19 pigs were subjected to treadmill exercise. Four of the exercised pigs died. The pigs that survived the treadmill exercise were later exposed to halothane. The pigs that died as a result of the halothane exposure (n = 5) or the treadmill exercise (n = 4), were classified SS (n = 9) and the survivors as SR (n = 10). A biopsy of the M. semitendinosus was used for measurement of difference in muscle lactate, ATP, glucose 6-phosphate, phosphocreatine, glucose and glycogen concentrations. The results show that in all pigs exercise resulted in the higher stimulation of glycogenolysis than did halothane exposure. However, SS pigs overall showed a greater stimulation of glycogenolysis and glycolysis and general anaerobic metabolism, compared to SR pigs. Under halothane exposure, glycogenolysis and anaerobic metabolism were stimulated in the SS pigs to a much greater extent than in SR pigs, with significant differences between all the muscle metabolites determined. However, treadmill exercise, although sufficient to cause death in some pigs, resulted only in significantly higher lactate and glucose 6-phosphate concentrations. SR pigs exposed to halothane had significantly higher ATP, phosphocreatine and glycogen concentrations, but a lower glucose concentration than exercised SR pigs, indicating less severe stimulation of glycogenolysis by halothane than exercise. No significant differences were found in the determined muscle metabolites in SS pigs exposed to halothane compared to exercised SS pigs. In conclusion, these differences suggest that different mechanisms of stimulation of metabolism on exposure to halothane and exercise may exist, although both types of stress cause stimulation of glycogenolysis.     

Quality, palatability and weight loss of pork as affected by electrical stimulation

Forty-five swine (n = 15, stress-susceptible pigs, fasted for 18 h; n = 15, normal pigs, fasted for 48, 60 or 72h; n = 15, normal pigs, fasted for 18 h) were slaughtered. One side of each pig was electrically stimulated (ES)-550 V, 2-6 A, seventeen impulses, 1·8 s on and 1·8 s off per impulse-and the opposite side was not stimulated (NS). Ham and loin temperatures were monitored at 12 and 24 hours post mortem. Carcass quality-marbling, loin eye colour, loin eye firmness, subcutaneous fat firmness and belly firmness-was evaluated at 24 hours post mortem. Sides were fabricated into four lean cuts at 48 hours; cuts were placed on open metal racks in a 2°C cooler and weight loss was measured after 24, 48 and 72 hours storage. At 120 hours post mortem, loin chops were cut, frozen (-24°C for 45 days) and subsequently used to determine thaw loss, cooking loss, Warner-Bratzler shear (WBS) force and palatability. Ham temperatures (12 h) were significantly (P < 0·05) lower for the ES sides from the stress-susceptible, short-fast (SSF) group but not for normal, long-fast (NLF) or normal, short-fast (NSF) groups. ES produced lighter coloured, softer loin eyes in the SSF group but darker coloured, firmer loin eyes and firmer subcutaneous fat in the NLF group. No significant differences (P > 0·05) were detected for thaw loss, cooking loss, palatability ratings or WBS values between ES and NS in the SSF group but chops from ES sides of NLF animals had significantly (P < 0·05) higher ratings for muscle fibre tenderness, overall tenderness and overall palatability. Weight losses of the lean cuts from the ES sides were higher (P < 0·05) than those from NS sides in only three of sixty comparisons of cuts from the three groups of swine. These data suggest that ES had very minimal effects on quality, palatability or weight loss of pork.     

Sensory and functional meat quality characteristics of pork derived from three halothane genotypes

The effect of the halothane gene in pigs on the meat and sensory qualities thereof were determined. Meat derived from 60 Landrace×Large White pigs of three halothane genotypes was used. The sensory qualities, cooking loss, colour, shear value and proximate analysis of the cooked pork loin roasts were determined. The three genotypes did not differ significantly (P>0.05) with regard to the colour of the cooked meat, percentage cooking loss and percentage moisture. There were significant differences (P<0.05) between the genotypes in the percentage protein, ash and fat. Meat from the three genotypes also differed significantly (P<0.05) in juiciness, an analytical sensory panel scored the juiciness of meat from the NN-genotype the highest with a value of 71.3 when using a structured line scale. Meat from the nn-genotype had the lowest score for juiciness (62.8). Meat from the three genotypes did not differ significantly (P>0.05) with regard to tenderness, pork flavour and no mealiness. Correlation values showed a positive correlation (r=0.46, P<0.05) between juiciness and tenderness. These results indicate that the inclusion of the halothane gene in pig production programmes results in meat with an inferior quality and it can be recommended to exclude the halothane positive genotype from any pig production system where fresh pork quality is considered a primary goal.     

Intramuscular fat and muscle fibre lipid contents in halothane-gene-free pigs fed high or low protein diets and its relation to meat quality

Immediately after exsanguination, samples were taken from M. longissimus dorsi (LD) and M. biceps fermorsi (BF) of halothane-gene-free Swedish Yorkshire pigs (entire males and gilts) fed a high-protein (18·5% crude protein, 0·96% lysine; n = 20) or a low-protein diet (13·1% crude protein, 0·64% lysine; n = 20). The lipid content, measured as triglyceride (TG), was analysed after the samples had been freeze-dried and dissected free from blood, fat and connective tissue. Fibre type composition (type I, IIA, IIB, IIC) was analysed by histochemical staining on all samples. In 14 samples of LD, representing the entire variation of the intramuscular fat content (IMF) among the 40 animals, fibre areas, lipid content and oxidative capacity within the fibre types were evaluated. IMF, meat colour and drip loss were measured in both muscles. Shear force was measured on cooked meat samples from LD. IMF was higher in both LD (2·5%) and BF (2·0%) from pigs on the low-protein diet compared with LD (1·5%) and BF (1·3%) from pigs on the high-protein diet. TG content did not differ between diets in BF but was higher in LD from pigs on low- vis-à-vis high protein diet. A significant correlation was seen in LD between IMF and TG content (r = 0·57; P < 0·001). Fibre type composition did not differ between pigs on the two diets. BF had a higher proportion of type I and IIA fibres and a lower proportion of IIB fibres, compared with LD. TG content in muscle was not correlated with fibre type composition or staining intensity for lipids and oxidative capacity. High staining intensity for lipid in LD was seen in all type I fibres and in some type IIA fibres. Meat quality parameters did not differ between groups except shear force, which was higher in pigs fed the high- vis-à-vis low-protein diet (4·7 and 4·0 kg/cm(2), respectively). Shear force was correlated significantly with TG content (r = -0·42; P < 0·01) and IMF (r = -0·43; P < 0·01) in LD. The results of this study show that lipids are stored mainly in type I fibres and in some type IIA fibres. Intracellular triglycerides account for only a small fraction of IMF. The results indicate that IMF and TG content in muscle fibres may be related to shear force.     

Influence of porcine stress on blood composition and early post-mortem meat quality in pigs of different halothane genotypes

The purpose of this study was to investigate porcine stress, blood serum values and early post-mortem (pm) meat quality in pigs of unknown and known halothane genotype. Collection, transportation and slaughtering of the pigs were studied from the farm up to the carcass chilling (45 min pm). Reactors (nn) had the highest creative kinase (CK) activity. CK activity increased most prominently during transport in reactors, and at the abattoir in non-reactors (Nn or NN). The content of serum glucose was highest in non-reactors and lowest in non-carriers (NN, P<0·01). Serum glycerol level was highest in reactors and lowest in carriers (Nn, P < 0·05). Differences in serum lactate and pH values were not significant. Carriers had the highest and non-reactors the lowest carcass temperature, 0 min pm (P = 0·001). Temperature of non-reactors increased most rapidly (9·4%) and that of carriers increased most slowly (0·9%) during scalding. Reactors had the most rapid (3·1%) and carriers the slowest (0·3%) fall in carcass temperature between scalding and chilling. No significant differences were found between halothane genotypes in the rate of glycogen breakdown and lactate formation, 45 min pm. PSE (pH(1) ≤ 5·8) frequencies of reactors, non-reactors, non-carriers and carriers were 100·0, 14·3, 13·0 and 12·5, respectively.     

The effects of breed and halothane sensitivity on pig meat quality

The effects of halothane sensitivity and breed (Belgian Landrace BL and Landrace L), and their interactions on carcass and meat quality were analysed. Also the effect of breed (Pietrain P, BL, L, Large White LW and Duroc D) on carcass and meat quality was studied in a sample of 153 gilts. Each of the half-carcasses was cut and fully dissected to obtain lean percentage. The following measurements of meat quality were carried out: muscle pH, electrical conductivity (QM) and light scattering (POP). Muscle reflectance (GOFO value), muscle protein solubility (MPS) and intramuscular fat content were also determined. The results obtained in this study revealed the effect of halothane gene on all of the traits studied. The halothane-positive animals showed less fat thickness and more lean percentage in the carcass. The P and BL breeds had more lean percentage in the carcass and a better lean-to-bone ratio compared with L, LW and D. The L breed was intermediate. Stress sensitivity is an important factor affecting the inverse relationship between carcass quality and meat quality. Those breeds free of the halothane gene (LW and D) had the best meat quality. The L breed was in an intermediate position, but more similar to halothane-negative breeds. The Duroc breed had significantly higher intra-muscular fat (>2·0%), required for optimum fresh meat quality and for the production of Spanish dry-cured ham of high quality.     

屠宰应激对宰后猪肉保水性的影响

本文研究了电击晕和二氧化碳致晕对杜大长三元杂交猪和三门峡黑猪的应激效应及宰后肌肉保水性的影响。结果表明:与电击晕相比,二氧化碳致晕使得杜长大三元杂交猪和三门峡黑猪血液中的乳酸(LAC)、乳酸脱氢酶(LDH)、肌酸激酶(CK)、肌酐(CRE)、皮质醇(COR)含量显著降低(P0.05);且杜长大三元杂交猪和三门峡黑猪宰后p H45min值较高,差异显著(P0.05),宰后24 h汁液损失率(降低1.17%和0.59%)、蒸煮损失率(降低3.09%和3.56%)及解冻损失率(降低0.55%和0.29%)显著降低(P0.05);剪切力显著降低0.71 kg及0.66 kg(P0.05)。此外,杜长大三元杂交猪的抗应激能力较差,其宰后肌肉保水性显著低于三门峡黑猪(P0.05)。LF-NMR研究表明,二氧化碳致晕能够显著降低解冻后肌肉中的自由水含量(降低32.24%和28.92%),抑制了不易流动水向自由水的"态变"。因此,在实际生产中采用二氧化碳致晕能降低生猪屠宰应激,提高肌肉保水性。     

Influence of temperature variation on the metabolism of pig muscle in situ and after excision

The experiment involved six halothane-positive (HP) and six halothane-negative (HN) pigs of about 100 kg liveweight. Under general anaesthesia the tibialis cranialis was exposed. The temperature of the muscle was maintained at either 35 or 40°C (in situ). The muscle was stimulated via the peroneal nerve at 0·1 Hz for 10 min then 1 Hz for 10 further min. Twitch contractions were recorded throughout the stimulation, after which the muscle was excised and split into two parts which were kept in paraffin oil at either 35 or 40°C (post-excision temperature) for 2 h. Samples were taken just before and after the 20 min stimulation period, and at 1 and 2 h after muscle excision for determination of pH and concentrations of PC, ATP, IMP, glycogen, G-6-P and lactate. As soon as one muscle was removed, the operation was repeated on the other leg. Both temperatures (35 and 40°C) were applied to each animal in a balanced design. However data were obtained from only 11 pigs at 40°C as one HP pig died accidentally at the beginning of the 40°C experiment. Halothane sensitivity influenced the pH value and the levels of PC, G-6-P and lactate of the muscle in situ (P < 0·01 in all cases). Temperature affected contrction time (P < 0·01). Both halothane sensitivity and Post-excision temperature affected the pH values and the levels of PC, ATP, IMP, G-6-P and lactate (P < 0·01 in all cases) in the excised muscle. By contrast, the in situ temperature treatments did not affect any of the muscle traits measured after excision. It was concluded that the effects of the various treatments on the rate of metabolism in the excised muscle were wholly explainable in terms of temperature from the time of excision, and that the in situ temperature treatments may not be responsible for the differences after excision.     

Influence of dietary fat and α-tocopherol supplementation on lipid oxidation in pork

Sixty-four pigs, approximately 3 weeks old, were fed diets containing 3% beef tallow or 3% soya oil with either a basal (10-50 mg/kg diet) or supplemented (200 mg/kg diet) level of α-tocopheral acetate. In pigs fed the soya oil diet the neutral and polar lipid fractions of muscle tissue and the total lipid fraction of adipose tissue had significantly (P < 0·05) higher C18:2/C18:1 ratios when compared to pigs fed the tallow diet. Muscle from pigs fed the soya oil diet was significantly more susceptible (P < 0·05) to lipid oxidation than muscle from pigs fed the tallow diet. In pigs receiving the α-tocopherol supplemented diet, α-tocopherol levels were approximately 3·3, 2·8 and 2-times higher in plasma, muscle and adipose tissue, respectively, when compared to pigs fed the basal level of α-tocopherol acetate. α-Tocopherol supplementation significantly increased (P < 0·05) the oxidative stability of muscle from pigs fed both the tallow and soya oil diets.     

Relationships between bacon grade schedules and carcass characteristics

A computer model was used to compare alternative bacon grade schedules in terms of the carcass composition, joint proportions and simple meat quality characteristics (muscle pH and light reflectance) of pigs in different grades. The data used were for 350 side-dissected carcasses from years 6 to 8 of the Meat and Livestock Commission's Commercial Pig Evaluation. Analyses were carried out separately for restricted-fed and ad libitum-fed pigs. Overall means and standard deviations for carcass weight and lean percentage were 64·4 ± 3·19 and 51·5 ± 3·98 (restricted) and 65·1 ± 3·57 and 49·9 ± 4·09 (ad libitum). Alternative schedules were compared against a base schedule, typical of commercial practice in Great Britain and involving the following requirements for the principal grade: a maximum P(2) measurement (taken laterally over the M. longissimus) of 15 mm, maximum mid-line fat measurements (shoulder/loin) of 42 22 mm and a minimum side length of 770 mm. Removal of the shoulder/loin and length requirements increased the proportion of pigs in the principal grade by seven percentage units with little effect on the mean carcass characteristics of pigs in the grade. An extreme tightening of the maximum shoulder/loin measurements to 35 15 mm removed half the pigs from the principal grade and increased the mean carcass lean content and the lean content of individual joints for pigs in the grade by one to two percentage units. Introduction of a minimum muscle thickness measurement of 55 mm had a similar effect. In both cases the effect was partially mediated through a general reduction in fatness and could be achieved by tightening the maximum P(2) fat thickness. None of the changes in grade schedules examined materially altered the mean meat quality characteristics of pigs in the principal grade. The analysis illustrates the complexities involved in using grade thresholds based on a number of correlated measurements. The use of a multiple regression approach, in which carcass lean content and commercial value are estimated from measurements known to contribute significantly to the regression, would simplify the situation considerably.     

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.     

Fibre optic probe measurements in landrace pigs of different halothane phenotypes

Fibre Optic Probe (FOP) measurements were made in the longissimus dorsi muscle of 70 halothane-positive (HP) and 70 halothane negative (HN) pigs of a synthetic Landrace strain at 45 min (FOP(1)), 3 h (FOP(3)) and 17h (FOP(17)) post mortem. Measurements of pH, rigor and temperature were also made in the slaughterline. Carcasses were sampled (longissimus dorsi, 2-4 lumbar vertebrae) at 18h post mortem and meat quality objectively assessed. The incidence of slight PSE (visual score) was 49% in HP and 10% in HN pigs, while the incidence of serious PSE was 20% and 4%, respectively. Yet, the percentage drip loss during 48 h storage in HN/PSE pigs was higher than in HP/PSE pigs (10·2 vs 7·5%), which was associated with a lower ultimate pH (5·25 vs 5·44). Therefore, it is suggested that the remaining PSE problem in HN Landrace pigs, although less in frequency, might be more serious. In the whole population, of all FOP measurements taken correlations with colour (Hunter L(?)-value) and percentage drip loss were highest for the FOP(17) measurements (r = 0·82 and 0·69, respectively). FOP(1) was better related than pH(1) to colour, while the relationships with drip loss were of a similar magnitude. Differences in FOP values between HP and HN pigs were larger for FOP(1) (148 vs 108) than for FOP(3) (148 vs 125) or FOP(17) (153 vs 130). The relationship between FOP1 and ultimate meat colour (L(?)-value) appeared to be higher in HP (0·60) than in HN (0·48) pigs, while for the relationship between FOP(1) and percentage drip loss the reverse was true (0·48 and 0·60, respectively). The effect of halothane phenotype on the relationships found, may partially explain the different results of reflectance measurements reported in the literature as to their predictive value for ultimate meat quality. The results suggest that the measurement of reflectance in the slaughterline offers opportunities for identifying (potential) PSE carcasses. The large genetic influence of halothane phenotype on this parameter, may eventually justify its use as a base for payment for meat quality to the producer.     

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.     

Predicting the weight of lean meat in lamb carcasses and the suitability of this characteristic as a basis for valuing carcasses

The carcasses of 138 lambs were dissected into fat, muscle and bone as the basis for developing a model to estimate the weight of lean meat (muscle and intramuscular fat). The lambs represented two sexes (70 wethers, 68 ewes) and three sire genotypes (67 Poll Dorset, 39 Suffolk, 32 Wiltshire Horn) all from Border Leicester × Polwarth × Booroola type ewes. Hot carcass weight (HWT) was found to explain the majority of the variation in the weight of lean meat. When measures of subcutaneous fat depth at different sites were used as predictors in addition to HWT, the accuracy with which lean meat yield could be estimated was found to increase by a small amount. There was, however, little difference in their individual value as predictors. The area of the M. longissimus thoracis et lumborum at the twelfth-thirteenth rib was found to account for the significant breed type difference between Poll Dorset and Suffolk sired lambs when included in a multiple regression with HWT and the GR measurement (tissue thickness at the twelfth rib 110 mm from the midline). The final model produced an R(2) = 0·92 and an RSD = 0·45 kg for the 106 lambs. Using the model for the 106 lambs, the estimated (from the model) and actual values of lean meat for the Wiltshire Horn sired lambs were compared. The correlation coefficient between the values was r = 0·97 and the RSD was 0·31 kg. This shows that for second cross lambs as used in this study the fitted model exhibits a degree of general validity and stability. An overall model for the 138 lambs produced an R(2) = 0·92 an RSD = 0·43 kg. The potential for pricing meat on the basis of lean meat yield is discussed, with particular emphasis on the current developments in assessment of lamb carcasses in Australia.     

Effect of dietary Vitamin E on the stability of raw and cooked pork

Experiments were designed to investigate the effects of dietary α-tocopherol supplementation for 2 weeks prior to slaughter on plasma and muscle α-tocopherol levels and on the oxidative stability of raw and cooked pig muscle during refrigerated storage at 4°C. Plasma and muscle α-tocopherol levels of the pigs on the α-tocopherol supplemented diet (200 mg α-tocopherol acetate/kg feed) were ～2·5-fold higher than those of the pigs on the control diet (30 mg α-tocopherol acetate/kg feed). Dietary supplementation with α-tocopherol significantly (p < 0·01) improved the oxidative stability of both raw and cooked muscle after storage at 4°C for up to 8 days. α-Tocopherol stabilized the membrane-bound lipids against metmyoglobin/H(2)O(2)-initiated oxidation and also significantly (p < 0·05) improved the oxidative stability of rendered fat.     

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.     

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.