Kerstin Lundström

A paternally expressed QTL affecting skeletal and cardiac muscle mass in pigs maps to the IGF2 locus.

A paternally expressed QTL affecting skeletal and cardiac muscle mass in pigs maps to the IGF2 locus

Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs

The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed Hampshire, Swedish Landrace and Swedish Yorkshire pigs was studied. The contribution of the pigment content, the myoglobin forms deoxymyoglobin (Mb), oxymyoglobin (MbO) and metmyoglobin (MetMb) and the internal reflectance to the colour of pork of normal meat quality was evaluated using partial least squares regression (PLS). The colour of LD and BF from the Hampshire breed was more red and yellow and more saturated than the colour of the same muscles from the Swedish Landrace and the Swedish Yorkshire breeds. Furthermore, BF from Hampshire was darker than BF from the other two breeds. These differences in colour were related to the lower pH in Hampshire, resulting in more blooming and in higher internal reflectance, and to the higher pigment content. The colour of BF was darker and more red than the colour of LD within each breed. No colour difference was found between gilts and castrates within each breed. Most of the variation (86-90%) in lightness (L* value), redness (a* value) and yellowness (b* value), chroma (saturation) and hue angle of pork of normal meat quality was explained by the pigment content, myoglobin forms and internal reflectance. The L* value, a* value, chroma and hue angle were influenced by both the pigment content and by the myoglobin forms to almost the same extent, while the internal reflectance was of no significance to these colour parameters. The b* value was influenced most by the myoglobin forms, less by the internal reflectance and almost not at all by the pigment content.

Effects of outdoor rearing and sire breed (Duroc or Yorkshire) on carcass composition and sensory and technological meat quality

The effects of outdoor rearing and sire breed on carcass composition and technological and sensory meat quality in pigs were studied in a trial with 102 crossbred slaughter pigs (Yorkshire, or Yorkshire × Landrace sows and Duroc or Yorkshire as terminal sire). Half of each litter were reared conventionally indoors, while the remainder were reared outdoors in a 50 000 m(2) area, as a single group. All pigs were fed ad libitum. Yorkshire sired pigs had significantly leaner carcasses and meat with lower IMF content and marbling scores, and higher shear force and water content. The sire breeds did not differ regarding pH(u), water-holding capacity, or colour. Meat from the Yorkshire crosses was more acid, less tender and gained lower overall acceptance scores in the sensory test. The outdoor-reared pigs had lower daily gain values and leaner carcasses. They produced meat with lower pH(u), higher drip loss, higher shear force values and higher internal reflectances. Their meat contained more lactate and crude protein and had a higher glycolytic potential, less IMF and less water. Regarding the sensory qualities, outdoor rearing impaired tenderness, juiciness and overall acceptance.

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.

Effect of the RN gene on technological and sensory meat quality in crossbred pigs with Hampshire as terminal sire

The effect of the dominant RN gene (Rendement Napole) was studied in Hampshire crosses (Hampshire sires × Swedish Landrace-Swedish Yorkshire dams). The present material comprised 107 entire male and 52 female pigs slaughtered at 106 kg live weight. Carriers and non-carriers of the RN gene were distinguished on the basis of the glycolytic potential (GP) in post-mortem longissimus muscle, or with the Napole yield (yield after curing and cooking). Compared with the glycolytic potential classification, Napole classification gave 16% misclassified samples. In comparison with non-carriers of the RN gene, gene carriers showed the following significant differences in m. longissimus dorsi meat quality traits: lower pH, higher surface and internal reflectance values, lower protein extractability, lower water-holding capacity, lower Napole yield and greater cooking loss. The high correlation (r = -0.73; p < 0.001) which was found between GP and Napole yield in the total material, was absent in muscle from individuals carrying the RN gene. In addition to the detrimental effect on meat quality, the RN gene also had beneficial effects. Thus RN carriers had a lower (p = 0.02) shear force value (Warner-Bratzler) and, at sensory testing, a stronger taste and smell and greater acidity (9-member untrained panel). No difference was found in sensory evaluated tenderness.

Free range rearing of pigs with access to pasture grazing — effect on fatty acid composition and lipid oxidation products

The influence of free-range rearing, RN genotype and sex on different pig meat quality traits, including intramuscular fatty acid composition and levels of lipid oxidation products, were studied. A total of 60 Hampshire crossbred pigs were reared outdoors for two months with access to green feed, while 60 others were kept indoors, in a 120-m(2)-large pen, throughout the rearing period. From these 120 animals a subsample of 44 animals was chosen for meat quality analysis. Of the three factors studied, the RN genotype had the largest influence on basic technological meat quality traits, whereas the rearing conditions and sex had limited effects. However, outdoor rearing resulted in higher levels of polyunsaturated fatty acids in the intramuscular fat (P=0.026) and in an increased level of vitamin E (P=0.030) compared with the pigs that had been reared indoors. The sex and RN genotype of the animals also had an effect on the fatty acid profile: females had higher levels of unsaturated fatty acids (P=0.003) as well as lower levels of saturated fatty acids (P=0.011) than castrated males. Carriers of the RN(-) allele expressed a higher sum of omega-3 fatty acids (P=0.047) and C22:5 (P=0.012) than did the non-carriers. In a storage study where meat from free-range and indoor reared pigs was stored for 3 months at-20°C, it was shown that the lipid oxidation product malondialdehyde was formed at increased levels in animals that had a higher lean meat percentage than others, i.e. females that were carriers of the RN(-) gene and that were reared outdoors.

Effect of a Gonadotropin-releasing Hormone Vaccine (ImprovacTM) on Steroid Hormones, Boar Taint Compounds and Performance in Entire Male Pigs

The objective of this study, comprising two trials, was to evaluate the effect of a gonadotropin-releasing hormone (GnRH [corrected] vaccine Improvac; Pfizer Ltd) in a sample of the Swedish pig population. The pigs (n = 120) were assigned to three groups: control (entire male pigs), surgical castration and immunization against GnRH. Surgically castrated pigs did not express detectable levels of either testosterone or estrone sulphate (E1S) in plasma, or androstenone in fat and had lower skatole and indole levels in fat than entire male pigs. Immunization significantly reduced testes weight and bulbourethral gland length, plasma levels of the testicular hormones testosterone and E1S, and fat levels of androstenone, skatole and indole. Skatole levels in plasma were significantly lower than in entire male pigs in the second trial, but not in the first due to overall low skatole levels. All immunized pigs and surgically castrated pigs expressed skatole concentrations in fat below the level of 0.2 microg/g, above which meat is regarded as tainted. In contrast, eight entire male pigs exceeded this level. Indole levels in plasma from immunized pigs were lower than those from entire male pigs. Surgical castration caused lower daily weight gain in the suckling period compared with piglets raised intact, whereas in the post-weaning period no difference was observed. Immunization resulted in higher feed intake and daily weight gain after the second injection. The estimated lean meat content was improved in comparison with the castrated pigs, but was lower than for entire male pigs. Dressing percentage was lower in immunized pigs than in surgically castrated and entire male pigs. The frequency of skin damage did not differ between immunized and entire male pigs or between immunized and surgically castrated pigs.

Effect of freezing on sensory quality, shear force and water loss in beef M. longissimus dorsi

The objective of this study was to determine how sensory quality, shear force and water loss differ between beef stored either chilled or frozen before cooking. Meat tenderness was analysed instrumentally and sensorially using both a consumer panel and a semi-trained panel. Both M. longissimus dorsi (LD) from eight young Holstein bulls were cut into eight samples, weighed, vacuum packed and aged at 4°C for 2, 7 or 14 days. After ageing, the frozen samples were kept at -20°C prior to heat treatment. Water holding capacity was recorded as purge or thawing loss and cooking loss or as combined loss. Sensory analyses were performed on samples aged 7 days. Peak force values declined with ageing time and freezing. Frozen meat aged 2 days had the same peak force values as chilled meat aged 7 days. Total energy was the same for both treatments at day 2 and 7, whereas at day 14 frozen samples showed significantly higher values than chilled samples. The sensory panel experienced the chilled meat to be more tender, juicier and having a more intense meat taste than the frozen meat, whereas the consumers could not find any significant difference in degree of liking. Water holding capacity was lower for the frozen samples. The results indicate that conclusions from studies concerning sensory quality of beef will depend on whether the meat has been kept chilled or frozen before testing.

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.

Variation in light scattering and water-holding capacity along the porcine Longissimus dorsi muscle

The meat quality of M. longissimus muscle was evaluated in 851 pigs by using the Fibre Optic Probe (FOP) at three sites in the muscle and in both halves of the carcass. A systematic difference between sites was found, with the lowest light scattering (indicating the best meat quality) in the mid-part of the muscle and higher light scattering in the anterior and posterior parts. A non-systematic variation was also observed, with the opposite pattern in some animals, even though it was not frequent. A negative influence of the shackling was found, yielding higher FOP values in the shackled half. Drip loss measurements in the Longissimus muscle, taken from another 100 pig carcasses, were evaluated using three methods. Drip loss, too, showed a considerable variation along the Longissimus muscle, with minimum losses around the last rib. Repeatability estimates, calculated from two non-consecutive pieces of the Longissimus dorsi muscle from each carcass, varied from 0·4 when keeping samples vacuum packed for 2 days, to 0·5 when the samples were either kept in plain plastic bags for 2 days or in a meat container with a squared inset for 1 or 2 days.