Ann-Charlotte Enfält

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.

Comparison of non-carriers and heterozygous carriers of the RN− allele for carcass composition, muscle distribution and technological meat quality in Hampshire-sired pigs

Abstract The aim of this experiment was to compare non-carriers and heterozygous carriers of the dominant RN − allele (Rendement Napole) for carcass composition, muscle distribution and technological meat quality in pigs. Crossbred slaughter pigs ( n = 79), from Hampshire sires, heterozygous for the RN − allele, and Swedish Yorkshire X Swedish Landrace dams were used. The animals were classified into RN − genotype according to the estimated glycogen level at slaughter (glycolytic potential) in the longissimus dorsi muscle. Carriers of the RN − allele had higher daily gain, fewer days on test and produced carcasses with higher lean meat content, and a larger proportion of ham. The major ham muscles were larger in the RN − carriers than in the non-carriers. The proportions between the individual muscles were changed due to the RN − allele, with a greater content of glycolytic ham muscles ( M. semimembranosus et adductor, M. biceps femoris, M. gluteus ) and a smaller content of M. quadriceps femoris in RN − carriers. RN − carriers had lower values for ultimate pH, Napole yield (yield after curing and cooking), crude protein, and dry matter, and higher values for glycolytic potential, drip losses, filter paper wetness, internal reflectance and ash content. No effect of the RN − allele was found regarding lactate and surface reflectances.

Sensory and technological meat quality in carriers and non-carriers of the RN(-) allele in Hampshire crosses and in purebred Yorkshire pigs.

The effect of the dominant RN(-) allele on technological and sensory meat quality of loin and ham from pigs, crossbred from Landrace × Yorkshire sows and one Hampshire sire heterozygous for the RN(-) allele was studied. The non-carriers of the RN(-) allele and the purebred Yorkshire pigs were similar regarding most of the technological traits. In comparison with the RN(-) carriers, they had higher values for pH(u), Napole yield, dry matter and protein content, but lower values for drip loss, filter paper wetness, cooking loss, internal reflectance, residual glycogen and glycolytic potential. The three groups did not differ concerning lactate content, intramuscular fat or ash content. Shear-force values did not differ between the two RN genotypes, but both genotypes had lower shear-force values than the purebred Yorkshire pigs. Non-carriers had higher processing yield for cured cooked ham than RN(-) carriers. The RN(-) allele had little effect on the sensory attributes, as assessed by a trained panel using a descriptive test, but there was a tendency to lower chewing time for meat from the crossbreds compared to the purebred Swedish Yorkshire. RN(-) carriers produced more acidic fresh loin than non-carriers and purebred Yorkshire pigs, and juicier cured cooked ham than non-carriers.

A second mutant allele (V199I) at the PRKAG3 (RN) locus - I. : Effect on technological meat quality of pork loin.

The effect of three alleles (RN(-), rn(+) and a second mutant allele V199I, denoted rn*) at the PRKAG3 (RN) locus on such meat quality traits as pH, internal reflectance (FOP), Warner-Bratzler shear force, water-holding capacity and cooking loss were studied. M. longissimus dorsi (LD) from a total of 334 crossbreed pigs, entire males and females, Hampshire (H) and Finnish Landrace (L) of three combinations H × LH, LH × H and LH × LH, were used. The PRKAG3 alleles were identified with a DNA test and all possible RN genotypes, RN(-)/RN(-) (23%), RN(-)/rn(+) (24%), RN(-)/rn* (33%), rn(+)/rn(+) (8%), rn(+)/rn* (9%) and rn*/rn* (2%), were found. Water, intramuscular fat, protein and glycogen contents were determined. All the three alleles at the RN locus affected the studied technological meat quality traits of pork loin, except for the internal reflectance 24 h post mortem and the shear force. The RN(-) allele was dominant over the other two alleles, rn(+) and rn*, in LD with regard to ultimate pH, water-holding capacity and cooking loss, giving lower ultimate pH and water-holding capacity and higher cooking loss. The rn* allele affected ultimate pH in LD of non-carriers of the RN(-) allele, giving higher ultimate pH. The RN(-) allele was also dominant over the other two alleles in residual glycogen content in entire male pigs, but not in female pigs, where the rn* allele had a glycogen-lowering effect. The water content was higher and the protein content lower in LD of all RN(-)/- animals compared with the other genotypes, while no significant differences were found with regard to IMF content. Water-holding capacity, cooking loss and shear force were higher in LD of entire males compared with females.

A second mutant allele (V199I) at the PRKAG3 (RN) locus - II. Effect on colour characteristics of pork loin

Three alleles at the PRKAG3 (RN) locus that influence the glycogen content of pork were found to be segregating in Hampshire×Landrace crossbred pigs, RN(-), rn(+) as well as second mutant allele V 199I (here denoted rn*). The effect of these three alleles on ultimate pH, pigment content, internal reflectance (FOP), surface colour measured by tristimulus colorimetry (L*, a*, b*) and fractions of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) of pork loin was studied. Moreover, the effect of sex, entire male versus female pigs, on these traits was also analysed. The three PRKAG3 alleles affected ultimate pH, internal reflectance, colour and distribution of myoglobin derivatives of pork loin, while the pigment content was not influenced. Ultimate pH values of loins from the three genotypes were found to be in the order RN(-)/- genotypes rn(+)/rn(+) genotype=rn(+)/rn* genotype=rn*/rn* genotype. The RN(-) allele was dominant resulting in higher redness (a* value) and yellowness (b* value), while the rn* allele tended to result in lower redness and yellowness compared with the rn* allele. The RN(-) allele was dominant over the rn* allele in lightness (L* value) giving a lighter colour. Surface colour differences were mainly explained by differences in the distribution of the myoglobin derivatives. Finally, surface lightness was higher and pigment content, redness and fraction of MbO(2) lower in loin from entire males compared with females.

Moderate indoor exercise: effect on production and carcass traits, muscle enzyme activities and meat quality in pigs

The effects of moderate indoor exercise (running/walking up to 735 m, 5 days/week) on performance, muscle enzyme activities, carcass traits and technological meat quality were studied in 20 crossbred slaughter pigs during the fattening period. Non-exercised pigs were kept only in their pens and consisted of littermates (no. = 20). Blood samples for lactate analysis and muscle samples from m. longissimus dorsi (LD) and m. biceps femoris (BF) for analyses of the activities of lactate dehydrogenase (LDH), citrate synthase (CS), 3-OH-acyl-CoA dehydrogenase and hexokinase were collected at exsanguination. The initial pH was measured approximately 1 min after exsanguination in LD and BF. The carcasses were partially cut and then the back and ham were dissected into individual muscles. Carcass length and presence of osteochondrosis were recorded. Technological meat quality parameters measured were: surface reflectance, water-holding capacity, intramuscular fat (IMF), crude protein, dry matter, ash content, shear force, ultimate pH, pigment content and extractability of muscle proteins. In comparison with the non-exercised pigs, the exercised pigs had slightly shorter carcasses, paler meat and higher drip loss values in LD and, in BF, a lower proportion of IMF and dry matter and higher pigment content. The CS and LDH activities differed between LD and BF muscles, as also did many of the technological meat quality traits.

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

The eating quality of M. longissimus dorsi (LD) from RN(-) homozygotes, RN(-) heterozygotes and RN(-) non-carriers was investigated in a Swedish Hampshire×Finnish Landrace pig population. The recently identified new allele (V199I, here denoted rn*) at the RN locus was also detected among the pigs selected and included in the sensory evaluation. The number of animals varied from 10 to 15 in the five genotype groups; RN(-)/RN(-), RN(-)/rn+, RN(-)/rn*, rn+/rn+ and rn+/rn* (in total 59 pigs). In addition, one pig was determined to be rn*/rn* but was excluded from the analysis. The three genotypes in which the RN(-) allele was represented (RN(-)/RN(-), RN(-)/rn+ and RN(-)/rn*) had higher glycogen and lower protein contents as well as lower ultimate pH (measured 48 h post-mortem) in LD than the non-carriers (rn+/rn+ and rn+rn*). Of the sensory parameters evaluated (tenderness, chewing time, chewing residual, juiciness, meat flavour and acidity), the five RN genotypes only affected acidity significantly; the RN(-) allele contributing to a more acid taste in LD. The influence of the rn* allele resembled that of rn+ on the sensory parameters. When the material was divided into three groups (homozygous, heterozygous and non-carriers of the RN(-) allele) the juiciness was found to be significantly influenced by RN genotype, and LD from animals that were homozygous and heterozygous with respect to the RN(-) allele exhibited a higher juiciness than LD from non-carriers. The RN(-) allele also tended to contribute to greater tenderness, which was significantly higher in LD from heterozygous carriers than from non-carriers of the RN(-) allele. A more rapid decline in pH (measured as pH at 45 min and 3 h post-mortem) contributed to a greater tenderness in LD (according to a trained panel and Warner-Bratzler shear force). In addition to the RN genotype, the decline in pH was influenced by carcass weight, which varied between 71 and 97 kg, and by stunning procedure, which changed during the course of the study from individual to group stunning with CO(2). The individual stunning procedure contributed to a lower pH in the initial post-mortem phase (pH(45)), whereas a higher carcass weight and the RN(-) allele lowered the pH in the mid-post-mortem region (pH(3h) and pH(24h)), significantly (P⩽0.05). The pH continued to decline after 24 h post-mortem and the ultimate pH was not reached until 48 h post-mortem. The cooking loss, juiciness and acidity were related to the specific characteristics of the RN(-) carriers, such as higher glycogen content, lower protein content and lower ultimate pH (pH(48h)).

Rapid prediction of RN phenotype in pigs by means of meat juice.

The dominant RN(-) allele occuring in the Hampshire pig breed is associated with a high glycogen content in glycolytic muscles. To determine the RN phenotype in meat, certain alternative rapid methods were studied. Instead of using whole muscle, meat juice released from post-mortem longissimus dorsi muscle was used in the analyses. Carriers of the RN(-) allele were distinguished from non-carriers on the basis of the concentration of glucose + glucose-6-phosphate (spectrophotometrically determined), glucose only (determined with a rapid assay for blood glucose in diabetic patients) or the osmolality of meat juice. These results were compared with a classification based on the glycolytic potential or the residual glycogen (sum of [glycogen], [glucose] and [glucose-6-phosphate]) in muscle. Higher levels of glucose, of the sum of glucose and glucose-6-phosphate, and of osmolality were found in meat juice from animals of the RN phenotype. The sum of glucose and glucose-6-phosphate in meat juice seems to be a reliable marker for the determination of the RN phenotype in meat. Glucose or the osmolality of meat juice can also be used, but more as a preliminary method.

Impact of RN genotype and ageing time on colour characteristics of the pork muscles longissimus dorsi and semimembranosus.

The effect of RN genotype on pH decline, ultimate pH, pigment content, blooming and colour stability during 6 days of display at 5°C was studied in two pig muscles, M. longissimus dorsi (LD) and M. semimembranosus (SM), and furthermore the effect of anaerobic storage time (2 days vs. 9 days of ageing) on the same parameters was examined. The postmortem pH decline was faster and the ultimate pH lower in LD and SM of the RN(-) genotype compared with corresponding muscles from the rn(+) genotype. Pork of the RN(-) genotype was initially lighter and more red and yellow than pork of the rn(+) genotype due to a higher degree of blooming, which might be explained by the faster pH decline and/or lower ultimate pH. The level of oxymyoglobin (MbO(2)) was decisive for the redness of both muscles during display in air despite a higher presence of metmyoglobin (MetMb). Pork of the RN(-) genotype was thus redder than that of the rn(+) genotype throughout display in air despite higher oxidation to MetMb. Ageing for 9 days in chill improved the blooming potential in pork of both genotypes compared with 2 days of ageing, resulting in superior meat colour. However, only in pork from the RN(-) genotype, the colour was not negatively affected by ageing time upon display in air.