Strategic finishing feeding as a tool in the control of pork quality

A standard diet and two finishing feeding strategies known to reduce muscle glycogen stores were investigated in combination with exercise immediately prior to slaughter in pigs. The objective was to determine the influence of muscle glycogen at slaughter on temperature and pH in post-mortem muscle, the colour, drip loss and Warner–Bratzler shear force of the meat. The muscle glycogen stores were reduced by strategic finishing feeding. In general, pH_{45 min} was higher in muscles from strategically fed pigs compared with control pigs. Exercise also resulted in higher pH_{45 min} in control pigs compared to non-exercised control pigs, while the opposite was seen in muscles from strategically fed pigs. Exercise resulted in higher muscle temperatures in the carcasses irrespective of feeding strategy. pH_{24 h} were higher in M. biceps femoris and M. semimembranosus from exercised, strategically fed pigs compared with the corresponding controls. In contrast, irrespective of feeding strategy no difference in pH_{24 h} was registered in the meat of non-exercised pigs. Drip loss was lower in meat of strategically fed pigs compared with meat of control pigs. Moreover the drip loss was lowest in the meat of non-exercised pigs. The present study shows that strategic finishing feeding has high potential for the control of pork quality.     

Comparison of different dietary magnesium supplements on pork quality

Forty-eight crossbred (Large White×Landrace) boars were used to compare the effect of dietary magnesium aspartate (MgAsp), magnesium sulphate (MgSO(4)) and magnesium chloride (MgCl(2)) on muscle glycogenolysis and pork quality. The pigs were fed finisher feed supplemented with either MgAsp, MgSO(4) and MgCl(2) for 5 days prior to slaughter. At the abattoir, all pigs received 15 electric shocks from an electric goad 5min prior to slaughter. Pigs fed the diet supplemented with MgSO(4) had the highest plasma Mg concentrations at slaughter in comparison with pigs fed the MgAsp and MgCl(2) supplemented diets. There were no differences in plasma adrenaline and noradrenaline concentrations at slaughter between the different diets. Pigs fed the Mg diets had higher muscle glycogen concentrations in the Longissimus thoracis (LT) muscle at 5min and at 40min (except MgCl(2)) post-slaughter compared to pigs fed the control diet. Also pigs fed the Mg diets had lower muscle lactic acid concentrations in the LT at 5min post-slaughter and lower drip loss at 24hr post-slaughter compared to pigs fed the control diet. These results indicate that cheaper magnesium sources, MgSO(4) and MgCl(2), are as efficacious as MgAsp in reducing drip loss and improving pork quality.     

The effect of dietary magnesium oxide supplementation on postmortem (31)P NMR spectroscopy parameters, rate of Ca(2+) uptake and ATPase activity of M. longissimus dorsi and meat quality of heterozygous and normal on malignant hyperthermia pigs

Twenty four crossbred (Large White, White Meaty, Pietrain, Hampshire) pigs were tested by DNA probe for a mutation on the ryanodine receptor RYR1 (malignant hyperthermia-MH). An equal number of pigs heterozygote (monomutant-MON) and normal on MH (nonmutant-NON) were used in the experiment. The pigs were fed finisher feed (control group) or finisher feed supplemented with magnesium (3.6 g MgO per pig per day; MgO group) for 5 days prior to slaughter. Pigs fed the diet supplemented with MgO had higher plasma Mg concentrations. Phosphorus nuclear magnetic resonance ((31)P NMR) measurements on postmortem (15 min) muscle samples (longissimus muscle) showed the highest phosphocreatine levels in normal pigs fed MgO (P<0.05). The MgO supplementation caused increased Ca(2+) uptake and Ca(2+) ATPase activity only in normal (NON) pigs. ATPase activity was lowest (P<0.05) in heterozygote control pigs. Pigs fed MgO supplemented diet had higher pH (45 min postmortem). A significant lower pH (P<0.05) was obtained in heterozygous (MON) control pigs. Also pigs fed with MgO had lower percentage of drip losses and significant differences (P<0.05) were obtained between heterozygous (MON) pigs. The results indicate that dietary MgO supplementation can improve parameters of muscle energetic metabolism, Ca(2+) uptake and meat quality (pH, drip loss).     

Influence of dietary vitamin E and selenium on muscle fatty acid composition in pigs

A total of 28 female pigs were fed a basal diet containing a low amount of α-tocopherol (10.3 mg/kg; control), and diets supplemented with 0.3 mg selenium/kg (group Se) or with 200 mg α-tocopherol/kg (group V) at the growing-finishing period. Increasing dietary level of vitamin E resulted in higher concentration of α-tocopherol in plasma and muscle immediately after slaughter and 4 h later (P⩽0.05). The fatty acid composition of muscle microsomes and mitochondria was slightly affected by the diet. Corresponding to the minor changes of the membrane fatty acid composition the fluidity was unaffected by the diet. A positive relationship was observed between the resistance to in vitro stimulation of peroxidation and the vitamin E content of the muscle samples. Supplementation with selenium did not reduce the lipid oxidation after stimulation. In conclusion, even though the effect was minor, vitamin E improved the antioxidative status in pork.     

Short-term feeding strategies and pork quality

Two experiments were done to determine whether short-term supplementation (5 days pre-slaughter) with magnesium acetate, or a combination of magnesium acetate, tryptophan, vitamin E and vitamin C would improve pork quality. In the first experiment the pigs (Pietrain×Yorkshire, n=96) were fed a standard feed or a magnesium supplemented feed for 5 days prior to slaughter. As a possible stress factor half of the animals were slaughtered upon arrival at the slaughterplant whereas the remaining animals were allowed two hours of rest in lairage before slaughter. Magnesium supplementation did not result in an increase in plasma magnesium concentration at slaughter. Omission of lairage resulted in higher plasma glucose concentrations, but plasma lactate concentrations were not affected. Drip loss and ultimate pH were not affected by diet or omission of lairage. Omission of lairage resulted in poorer color characteristics. This effect was prevented by supplementation with magnesium. In the second experiment the pigs (Pietrain×Yorkshire, n=92) were fed a standard feed or this standard feed supplemented with magnesium acetate, tryptophan, vitamin E and vitamin C for 5 days prior to slaughter. Supplementation with vitamin E did not increase muscle vitamin E concentration. Inclusion of supplements in the diet failed to improve water-holding capacity or color characteristics. These results indicate that short-term supplementation with magnesium acetate, tryptophan, vitamin E and vitamin C is of little value in improving pork quality when pigs are not stressed beyond levels associated with routine slaughter procedures.     

Effect of halothane genotype on muscle metabolism at slaughter and its relationship with meat quality: A within-litter comparison

The effects of halothane genotype on muscle metabolism at slaughter and its relationship with meat quality were studied within 16 litters. Heterozygous boars and sows were mated and the offspring were halothane tested and bloodtyped to reveal the halothane (Hal) genotype of the 120 animals used (NN, Nn or nn).

Following slaughter at 100kg live weight, muscle samples from M. longissimus dorsi (LD) and M. quadriceps (Qu) were taken immediately after exsanguination and analysed for glycogen, glucose-6-phosphate, lactate, creatine phosphate (CP), and adenosine triphosphate (ATP), as well as for enzyme activities representing both the oxidative and glycolytic pathways. The enzyme activities were similar for all genotypes. All muscle metabolites differed significantly between samples from NN and nn animals, with higher lactate and glucose-6-phosphate and lower glycogen, CP and ATP in the nn muscles. The heterozygote animals were intermediate or close to either of the homozygotes.

Meat quality characteristics (drip loss, surface and internal reflectance and dielectric loss factor) were studied only in the LD muscle. Meat quality of the muscle from the heterozygote (Nn) animals was inferior to that from NN animals (no difference for internal reflectance) but better than that from nn animals. When reflectance and drip loss were combined into an index, very few values from the nn-animals were better than the total mean. Indexes from the dominant homozygotes were generally better than the mean and those of heterozygotes were approximately normally distributed around the mean.     

Bovine muscle glycogen concentration in relation to finishing diet, slaughter and ultimate pH

The aim of this study was to investigate the effects of a high-energy diet provided for a rather short time prior to transportation to slaughter on muscle glycogen concentration on farm, after transportation and after refrigeration of the carcasses. The experiment involved 60 Ayrshire bulls which were fed either a low energy diet of 100% grass silage or a compound feed based diet providing 10.8 and 12.9 MJ of metabolizable energy per kg of dry matter, respectively. Identical setup of 30 bulls was carried out in spring and in summer. Three muscle samples were obtained from the longissimus dorsi and gluteus medius muscles: a biopsy prior to initiation of experimental feeding (B1); another biopsy after 14 days on diet (B2); a post mortem sample at 48 h after slaughter (3) (also M. semimembranosus). Initial resting muscle glycogen concentration affected the responsiveness of glycogen to diet. The more glycogen there was initially the less glycogen increased (r=-0.678, p<0.0001). However, compared to the low energy diet the high energy diet seemed to protect cattle from potentially glycogen-depleting stressors such as high temperatures and transportation. The cattle on high energy lost 7±4.0 (se) mmol/kg and 23±3.9 mmol/kg during transportation in spring (cool weather) and in summer (hot weather), respectively, whereas the cattle on low energy diet lost 16±3.8 mmol/kg in spring and 33±4.1 mmol/kg in summer. The overall protective effect of high energy diet corresponded to 0.65 pH units. The effects of diet were reflected all the way to ultimate pH values [5.69±0.03 (high energy); 5.93±0.03 (low energy)] (p<0.0001) and residual glycogen concentrations (p<0.0001). It seems indeed that providing a diet high in energy for a couple of weeks prior to transportation to slaughter is one of the many appropriate measures to take in the fight against bovine dark-cutting.     

Effect of dietary vitamin E supplementation on pork quality

The purpose of this experiment was to examine the effect of dietary vitamin E supplementation on pork quality, and in particular on colour stability. Crossbred pigs (n = 72) at a mean weight of 44 kg were assigned to one of two treatments. One group received, during a period of 84 days prior to slaughter, a tapioca based diet, which contained 8 mg vitamin E per kg feed. The other group received during this period the same diet, except it was supplemented with 200 mg vitamin E per kg feed. Muscle samples of longissimus thoracis and lumborum (LL) and psoas (PM) were collected at 24 hr post mortem and meat quality was assessed: pH, drip and cooking loss, shear force and intramuscular fat content. Colour stability was evaluated in fresh muscle (LL and PM) and after freezing (LL only) by measuring redness (a(?)-values) during 6 days of storage at 7 °C. TBA-values and microbiological counts were also determined during storage. Results showed that extra dietary vitamin E had no effect on pig performance (daily gain, feed efficiency, lean meat percentage) nor on meat quality traits. The vitamin E levels were five times higher in the muscles of the treated group than the control group. In comparison with fresh LL muscle, colour stability was lower in PM and after freezing. In both muscles, the vitamin E treatment reduced TBA-values, in particular after frozen storage. No effect was found on microbiological counts. Colour stability was improved in LL after 6 days of storage, but not in PM. The effect in LL is too late to be of practical significance, since pork is usually sold well before that time in The Netherlands. It is suggested that variation in feedstuff composition of the diet may possibly explain part of the variable results reported in literature for the effect of vitamin E supplementation on colour stability of pork.     

Effects of Dietary Rape Seed Oil, Copper(II) Sulphate and Vitamin E on Drip Loss, Colour and Lipid Oxidation of Chilled Pork Chops Packed in Atmospheric Air or in a High Oxygen Atmosphere

The effect of addition of rapeseed oil (canola), CuSO(4) and vitamin E (all-rac-α-tocopheryl acetate) to pig diets on pork meat quality (lipid oxidation, colour and drip loss) was studied. Pigs were reared on ten different diets, either a control diet (no supplementation of rapeseed oil, CuSO(4) or vitamin E) or 6% rapeseed oil diets supplemented with CuSO(4) (0, 35 or 175mg/kg) and vitamin E (0, 100 or 200mg all-rac-α-tocopheryl acetate/kg). The natural content of vitamin E originating from feed ingredients amounted to 9-23mg vitamin E (α-tocopherol) per kg feed. Muscle vitamin E levels reflected the dietary intake and pigs fed the control diet had significantly lower levels than pigs fed rapeseed oil diets. The quality of fresh pork chops packed in air or in 80% O(2):20% CO(2) was followed during chill storage for 8 and 13 days, respectively. Colour, as measured by tristimulus colorimetry of pork chops packed in 80% oxygen atmosphere, was significantly improved with respect to redness when compared to chops packed in air, regardless of dietary treatment. The low vitamin E content in pigs fed the control feed significantly decreased a values and the oxidative stability of pork chops during chill storage compared to the other feeding groups. Packing of chops in a high-oxygen atmosphere increased lipid oxidation, especially in chops with low levels of vitamin E. Supplementation of rapeseed oil diets with 100 or 200mg vitamin E significantly decreased lipid oxidation of chill stored chops. Supplementation with CuSO(4) did not influence meat quality attributes (drip loss, colour stability and lipid oxidation) for any of the storage conditions.     

Effect of dietary vitamin E supplementation for one week before slaughter on drip, colour and lipid stability during display in Japanese Black steer beef

Effects of dietary vitamin E supplementation for one week on drip, colour and lipid stability in raw beef steaks were studied. Four Japanese Black steers were fed no supplemental vitamin E and four were supplemented with 5000 mg of dl-α-tocopherol per animal daily for one week before slaughter. Steak samples from psoas major and longissimus thoracis muscles were over-wrapped with PVC film and displayed under fluorescent lights at 4 °C for 10 days. Drip loss percentages, L(?), a(?) and b(?) values, metmyoglobin percentages, and 2-thiobarbituric acid reactive substances values were determined at day 1, 4, 7 and 10. Dietary vitamin E supplementation increased (p < 0.01) α-tocopherol concentration in the plasma, liver and muscles. Vitamin E supplementation reduced (p < 0.001) drip loss compared to the control. Vitamin E supplementation maintained (p < 0.001) redness and retarded (p < 0.01) metmyoglobin formation in beef steak from day 4 to day 10 of display compared to the control. Vitamin E supplementation delayed (p < 0.001) lipid oxidation during 10 days of display compared to the control. The data indicated that dietary vitamin E supplementation for one week prior to slaughter improved lipid stability better than drip and colour stability in beef steak during 10 days of display.     

STORAGE STABILITY OF PORK FROM BERKSHIRE AND HAMPSHIRE SIRED PIGS FOLLOWING DIETARY SUPPLEMENTATION WITH VITAMIN E

Effects of vitamin E supplementation on pork quality of two genotypes were evaluated using 240 pigs (initial body weight was 87 0.35 kg). Berkshire or Hampshire sired pigs were fed either 12, 55, 99, 174, and 351 IU/kg of vitamin E for 6 weeks prior to slaughter. Loins from Hampshire sired pigs had increased (P < 0.001) levels of drip loss, were paler, more red, and more yellow than loins from Berkshire sired pigs following refrigerated display storage for up to 8 days or vacuum packaged storage for up to 55 days. Vitamin E supplementation did not improve fresh pork quality in either genotype. However, results indicate that vitamin E supplementation improved oxidative stability of pork chops during refrigerated display storage and this effect was more pronounced in the leaner Hampshire sired pigs. Therefore, vitamin E supplementation could be strategically applied to improve storage stability in select genotypes.     

The influence of porcine growth hormone on muscle fibre characteristics, metabolic potential and meat quality

Treatment of lean female pigs with porcine growth hormone (placebo or 80 μg pGH per kg body weight per day) for 6 weeks from 50 kg to 86 kg body weight did not change the frequency and the percentage area of muscle fibre types (ST, FTa and FTb fibres) and muscle capillarity of M. longissimus dorsi, M. gluteus medius and M. psoas major. The mean fibre cross-sectional area increased 5·3%, albeit nonsignificantly, corresponding to a 6·6% increase in carcass meat. The muscles contained slightly less dry matter and protein, and the lipid content of M. longissimus dorsi decreased 19% after pGH treatment. In the backfat the fatty acid composition changed towards a higher ratio of polyunsaturated to saturated fatty acids. The pH_u of M. longissimus dorsi was unaltered, while the pH₄₅ was reduced by pGH. The muscle glycogen level and the activity of lactate dehydrogenase (LDH), citrate synthetase (CS), and 3-OH-acyl-CoA-dehydrogenase (HAD) of M. longissimus dorsi were unchanged by pGH. The haem pigment, shear force, sarcomere length and eating quality of loin chops, were unaffected by pGH treatment. The results show that pGH treatment did not change the muscle characteristics in a way that affects the meat quality of M. longissimus dorsi in lean female pigs.     

Effects of feeding in free-range conditions or in confinement with different dietary MUFA/PUFA ratios and α-tocopheryl acetate, on antioxidants accumulation and oxidative stability in Iberian pigs

The experiment was undertaken to provide information of the influence of feeding either free-range or in confinement with different dietary MUFA/PUFA ratios and α-tocopheryl acetate supplementation (40 vs. 200 mg/kg) on tocopherol content and susceptibility to lipid oxidation of muscle and microsomes in Iberian pigs. The grass provided to the pigs had a similar α-tocopherol concentration to that observed for diets supplemented with 200 mg/kg α-tocopheryl acetate, and acorns supplied fourfold higher content of γ-tocopherol than the experimental diets. The α- and γ-tocopherol contents of muscle reflected the tocopherol concentration of the diets. Mono and Medium diets produced a similar MUFA/PUFA ratio in neutral and polar lipids of pig muscle to those fed outdoors. The lowest TBARS numbers were found in muscle samples from pigs fed a MUFA-enriched diet in confinement. No significant influence of free-range feeding or dietary fat on drip loss was found. However, α-tocopheryl acetate supplementation reduced (P<0.05) drip loss. Dietary vitamin E supplementation decreased the membrane lipid oxidation by 18% after 120 min. However, free-range feeding decreased the extent of microsome oxidation by 20%, 56% and 82% after 120 min when compared with those groups fed in confinement with high, medium and low MUFA/PUFA ratios, respectively. The hexanal concentration of muscle showed a similar trend to that observed for microsome induced-oxidation, suggesting, that hexanal determination is a more accurate method to measure lipid oxidation in iberian pig muscle than the thiobarbituric acid test.     

Application of constant current, low voltage electrical stimulation systems to pig carcasses and its effects on pork quality

This study examined the effectiveness of a constant current, low voltage electrical stimulation system on improving pork quality when applied to pigs at 2 min post-exsanguination. A total of 48 female Duroc×Large White/Landrace pigs of 85–90 kg liveweight were randomly allocated immediately prior to slaughter to one of four constant current electrical stimulation treatments: control (no electrical stimulation), 50, 200 and 400 mA. Stimulation was applied to pig carcasses at 2 min post-exsanguination for 30 s. No differences (P>0.05) in WB shear force values, muscle lightness or PSE incidence of pork M. longissimus lumborum (LL) was found due to electrical stimulation treatment. Muscle pH of the LL muscle was lower (P<0.001) in carcasses in the 200 and 400 mA treatments compared to those from carcasses in both the 50 mA and control treatment groups, when measured at the various time points from 40 min to 8 h post-slaughter. Although carcasses stimulated with 200 and 400 mA had higher percentage drip loss (P<0.05) and purge (P<0.001), this was not found to impact WB shear force values, muscle lightness or PSE incidence.     

DIETARY EFFECTS ON BEEF COMPOSITION. 4. Processing and Palatability Attributes

SUMMARY– The influence of dietary regimen of 104 half-sib Angus steers allotted to 1 of 13 combinations of hay, corn silage and corn concentrate, and of slaughter weights of 284 vs. 340 kg and 409 vs. 454 kg (live weight) on processing qualities and palatability of beef was studied. Measurements included postmortem glycolytic activity, water- and fat-binding capacity, textural properties, cooking losses, flavor and juiciness of selected muscles. Results showed that feeding regimens had a greater effect than did slaughter weight on qualities studied. Corn silage in the early dietary regimen of cattle weighing 284 and 340 kg resulted in significantly lower pH values (5 and 45 min post-mortem), higher amounts of glycogen at slaughter and greater water- and fat-binding capacity as compared to hay. Similar effects of early diet were noted for 5- and 45-min pH and water-binding capacity in cattle fed to heavier weights (409 and 454 kg); however, in these animals the early-hay diet resulted in greater muscle glycogen deposition than the early-silage diet. Steaks from animals fed corn silage in the early period were determined to be more tender by both shear values and panel scores and were more juicy and flavorful than those from hay-fed animals. These differences in palatability due to early diet were still evident after the cattle had been fed to heavier (409 and 454 kg) weights. When steers weighing 409 and 454 kg were grouped together, the effects of feeding regimen during the intermediate period were considerably less pronounced than those of the early feeding period.     

Effects of age and/or weight at slaughter on longissimus dorsi muscle: Biochemical traits and sensory quality in pigs

The effect of increasing either age alone through feed restriction, or both age and weight at slaughter, on the quality of the longissimus dorsi muscle (LM) was investigated. Starting at 83 days of age and 32 kg, 80 pigs were allotted within litter to four experimental groups. All pigs were free of RYR1 mutated gene. Pigs were fed either ad libitum (A100, A130) or restricted 30% (R100, R130) and slaughtered at either 100 kg (A 100, R100) or 130 kg (A130, R130) body weight. Restricting feed intake in order to increase age at the same weight resulted in slower growth, better feed efficiency and increased leanness, whereas increasing age and weight simultaneously elicited slower growth, reduced feed efficiency and fatter carcasses. Intramuscular fat (IMF) and muscle collagen concentration were reduced by restricted feeding. Increase in both age and weight of pigs resulted in lower water, and higher protein and IMF concentrations. Although pigs were free of RYR1 gene, the PSE condition (defined as pH1 ≤ 5.9) developed in 25 carcasses, with a higher incidence in restricted pigs. PSE animals were excluded from the subsequent analysis of meat quality data. Feed restriction resulted in higher drip loss and lower a^* and c^* (saturation index) values. Longer myofibril fragments in muscle of restricted pigs on day 1 post mortem are indicative of slower maturation, while longer fragments on day 4 in heavier pigs, suggest that the extent of post mortem tenderisation could be negatively affected by the elevation of slaughter weight. Feed restriction had no significant effect on meat sensory quality, whereas increase in both age and weight resulted in lower tenderness, chewiness and mouth coating scores. Our results indicate that increasing age at a given body weight, via feed restriction, reduced IMF and collagen concentrations, and the rate of post mortem proteolysis, however, this had no significant impact on pork quality assessed after 4 days of ageing. On the other hand, increasing both age and weight at slaughter could alter pork texture, in spite of elevated IMF concentration.     

Effect of low voltage electrical stimulation of pig carcasses and ageing on sensory attributes of fresh pork

The effect of electrically stimulating pig carcasses and ageing on sensory attributes of pork was evaluated in this study. A total of 48 female pigs [Duroc×Large White/Landrace (A; n=24) and Large White/Landrace (B; n=24)] were randomly allocated immediately prior to slaughter to one of two low voltage stimulation treatments; no stimulation or 150 mA applied for 30 s at 2 min post-exsanguination. Each side of the carcass was then randomly allocated to an ageing treatment of either 2 or 7 days post-slaughter. Muscle pH of the M. longissimus lumborum was lower (P<0.001) in electrically stimulated carcasses when measured from 40 min to 8 h post-slaughter compared with non-stimulated carcasses. Percentage drip loss, muscle lightness and PSE incidence were not influenced (P>0.05) by electrical stimulation. Electrical stimulation of pig carcasses and ageing pork for 7 days post-slaughter both improved (P<0.001) consumer scores for tenderness, juiciness, overall liking and quality category, however the interaction term of electrical stimulation and ageing was not significant for any of the sensory attributes. Pork from non-stimulated carcasses that was aged for 2 day post-slaughter was less tender (P<0.01) compared with pork in all other treatments. These results indicate that electrical stimulation (150 mA applied for 30 sec at 2 min post-exsanguination) was effective in improving eating quality attributes of pork, particularly when pork was aged for only 2 days post-slaughter, without detrimentally affecting colour or drip loss.     

Effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in porcine skeletal muscle

The aim of this work was to study the effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in pig muscle. Five pigs were subcutaneously injected with adrenaline (0·3 mg/kg) or with a saline solution 4 h, 1 h or 15 min prior to slaughter. pH(1), pH(u) and FOP(u) were measured in Longissimus dorsi (LD) and Biceps femoris (BF) muscles. m.LD samples were taken 20 days before slaughter using biopsy sampling, immediately after bleeding and 45 min post mortem for biochemical analysis. m.LD glycolytic potential (very close to glycogen content) was decreased by the injection of adrenaline 4 h and 1 h prior to slaughter, when comparing values at rest (20 days before slaughter) and values determined immediately after bleeding. The depletion was greater fro the injection performed 4 h before slaughter. In this group pH(u) was higher foe adrenaline-injected pigs (5·69 versus 5·47 for pigs injected with saline solution) but the difference was not significant. Pigs injected with adrenaline 1 h prior to slaughter exhibited higher glucose, glucose-6-phosphate and lactate levels immediately after slaughter, lower pH(1) and higher FOP values in m.LD than control pigs. Since the differences in pH(1) were not explained by differences in the rate of build-up of lactate, it was hypothesized that pigs injected with adrenaline 1 h prior to slaughter had lower muscle pH at slaughter. It was concluded that the rate or the extent of post mortem metabolism in pig muscle may be affected independently, by manipulating the time between adrenaline injection and slaughter.     

The effect of handling pre-slaughter and carcass processing rate post-slaughter on pork quality

Forty-eight male crossbred (Large White—Landrace) pigs were used in a 2×2 factorial design to determine the effect of pre-slaughter handling (minimal and negative handling prior to slaughter) and the rate of carcass processing post-slaughter [normal rate (45 min) and delayed rate (70 min) from time of exsanguination to carcass entering the chiller] on muscle glycolysis and pork quality. Pigs negatively (using an electric goad) handled at the abattoir just prior to slaughter had lower muscle glycogen concentrations in the Longissimus thoracis (LT) and the Biceps femoris (BF) at all times post-slaughter and lower lactic acid at 5, 45 and 70 min post-slaughter compared to pigs minimally (no use of electric goads) handled prior to slaughter. Negative handling of pigs just prior to slaughter also resulted in pork which had higher surface exudate and a higher incidence of PSE compared with pigs minimally handled prior to slaughter. A prolonged rate of carcass processing resulted in reduced muscle glycogen in the LT and BF at all times post-slaughter. Delays in carcass processing rate also affected pork quality, as the meat was paler in comparison with pig carcasses that were processed without any delays. The results from this experiment have indicated that the use of electric goads to move pigs at the abattoir, and delays in carcass processing post-slaughter, can have a detrimental influence on ultimate pork quality.     

Bovine Longissimus dorsi muscle glycogen and color response as affected by dietary regimen and post-mortem electrical stimulation in young bulls

Eighty bulls were assigned to one of two groups and fed a dietary regimen to defer or accelerate growth until slaughter. Bulls fed at an accelerated rate of growth (or high energy regimen) had higher post-mortem pH, and lower muscle glycogen stores, with darker lean color, and improved shear and palatability traits compared to deferred fed animals. Bulls fed at an accelerated rate of growth also had a higher degree of marbling and USDA quality grade. Electrical stimulation did not affect (P > 0·05) ultimate pH, but reduced (P < 0·05) glycogen values at 0 and 2 h post mortem. Electrical stimulation also improved muscle color, lowered cooking losses and improved the palatability of cooked longissimus dorsi steaks.