The impact of feeding diets of high or low energy concentration on carcass measurements and the weight of primal and subprimal lean cuts.

Pigs from four sire lines were allocated to a series of low energy (LE, 3.15 to 3.21 Mcal ME/kg) corn-soybean meal-based diets with 16% wheat midds or high energy diets (HE, 3.41 to 3.45 Mcal ME/kg) with 4.5 to 4.95% choice white grease. All diets contained 6% DDGS. The HE and LE diets of each of the four phases were formulated to have equal lysine:Mcal ME ratios. Barrows (N = 2,178) and gilts (N = 2,274) were fed either high energy (HE) or low energy (LE) diets from 27 kg BW to target BWs of 118, 127, 131.5 and 140.6 kg. Carcass primal and subprimal cut weights were collected. The cut weights and carcass measurements were fitted to allometric functions (Y = A CW(B)) of carcass weight. The significance of diet, sex or sire line with A and B was evaluated by linearizing the equations by log to log transformation. The effect of diet on A and B did not interact with sex or sire line. Thus, the final model was (B)) where Diet = -0.5 for the LE and 0.5 for HE diets and A and B are sire line-sex specific parameters. cut weight = (1+bD(Diet)) A(CW Diet had no affect on loin, Boston butt, picnic, baby back rib, or sparerib weights (p>0.10, bD = -0.003, -0.0029, 0.0002, 0.0047, -0.0025, respectively). Diet affected ham weight (bD = -0.0046, p = 0.01), belly weight (bD = 0.0188, p = 0.001) three-muscle ham weight (bD = -0.014, p = 0.001), boneless loin weight (bD = -0.010, p = 0.001), tenderloin weight (bD = -0.023, p = 0.001), sirloin weight (bD = -0.009, p = 0.034), and fat-free lean mass (bD = -0.0145, p = 0.001). Overall, feeding the LE diets had little impact on primal cut weight except to decrease belly weight. Feeding LE diets increased the weight of lean trimmed cuts by 1 to 2 percent at the same carcass weight.

Progress in reducing the pale, soft and exudative (PSE) problem in pork and poultry meat.

Research in the area of the pale, soft and exudative (PSE) pork and poultry meat is reviewed in this article with an emphasis on genetic, biochemical and metabolic factors contributing to the problem. Over the past five decades, there has been much more work in the pork meat area where a few genetic markers have been identified, and are currently used to remove susceptible animals from the herd. Some of the markers are linked to aberrant calcium regulation in the early postmortem muscle. The poultry industry is still not at the point of using genetic marker(s); however, some recent work has revealed several potential markers. The review also discusses environmental factors such as antemortem stress and early postmortem processing practices (e.g. chilling rate) that can influence the development and severity of the PSE phenomenon. Some of these factors are known to cause protein denaturation at the early stage of postmortem and directly contribute to poor water-holding capacity and inferior texture in fresh meat and later in processed products. A newer hypothesis suggesting that variation in protein oxidation, in response to antemortem stress and early postmortem tissue environment, can contribute to development of PSE pork is also discussed. Finally, a few recommendations for future work are proposed.

Relationships between carcass quality parameters and genetic types.

It is important for the meat industry, including pig farmers and breeding companies, to know the composition of the carcass including the proportions of the different commercial cuts when making decisions on the type of pigs to be produced and marketed. Carcass composition is influenced significantly by the genotype of the animals. The aim of this work was to characterise carcasses from five different pig genotypes, by means of the quantification and comparison of their physical composition. Carcasses from 500 gilts from five different genetic types were studied. These lines were based on the following breeds: Large White, Landrace, Duroc, Piétrain and a Meishan synthetic population developed from a cross with a Large White based line. Measurements were taken in the carcasses directly with a ruler and with the Fat-O-Meat'er. The carcasses were cut following the European reference method and the four main joints were dissected. Carcasses from the Piétrain based line, which was halothane negative, presented the highest killing-out (83.34%) and were the shortest (81.81cm). The Piétrain based line was also the leanest and the Meishan based line the fattest. The highest proportion of ham (270.9g/kg) and the lowest proportion of belly (97.97g/kg) were found in the Piétrain line. The proportion of lean in all of the dissected cuts was higher in carcasses from this line while the Meishan line presented the highest proportions of intermuscular fat in all of the pieces. Carcasses came from the Piétrain line received the highest conformation scores and they were leaner and with better ham yield.

Quality pork genes and meat production.

Functional genomics, including analysis of the transcriptome and proteome, provides new opportunities for understanding the molecular processes in muscle and how these influence its conversion to meat. The Quality Pork Genes project was established to identify genes associated with variation in different aspects of raw material (muscle) quality and to then develop genetic tools that could be utilized to improve this quality. DNA polymorphisms identified in the porcine PRKAG3 and CAST genes illustrate the impact that such tools can have in improving meat quality. The resources developed in Quality Pork Genes provide the basis for identifying more of these tools.

Histochemical and molecular determination of fiber types in chemically skinned single equine skeletal muscle fibers.

Until now, there has been no reliable method for histochemical determination of fiber types of single skinned muscle fibers. The major problem arises from the fact that most histochemical techniques use cross-sections of a large group of fibers and compare a given fiber with those surrounding it. This is not possible with a single skinned fiber which has been separated from a bundle to be used for mechanical analysis. A further problem is that the skinning procedure itself may alter the staining pattern. We have developed a procedure by which multiple cross-sections of single skinned fibers can be exposed to various histochemical reactions and the staining patterns compared on the same slide to those of frozen muscle and skinned bundles. By this procedure, three fiber types were distinguished by both Ca2+-ATPase and SDH reactions. The fiber typings determined from both enzyme systems correlated well with each other. Although we were able to differentiate only between slow and fast fibers by SDS-PAGE, these results corroborated the histochemical classification. This procedure will clearly be useful in skinned single muscle fiber mechanics experiments performed to determine functional differences among fiber types.

Histopathological observation of stress myopathy in M. longissimus in the pig and relationships with meat quality, fattening and slaughter traits.

The characteristic myopathic features revealed by histological observations included strong proliferation of connective and fatty tissue, perivascular infiltrations and necrosis of muscle fibers with phagocytosis to the lesser extent. In the myopathic muscle, as well as in giant fibers, histochemical techniques showed a reduction in succinate dehydrogenase and lactate dehydrogenase activity in type beta R (slow-twitch, oxidative) and alpha R (fast-twitch, oxidative and glycolytic). Magnesium-activated adenosine triphosphatase reaction ranged from diffuse to negative in beta R, alpha R and alpha W (fast-twitch, glycolytic) fiber types. Diffuse reaction for acid phosphatase and total loss of glycogen content were observed. The micrographs of the myopathic muscle indicated enlarged mitochondria with atrophy or complete destruction of cristae. Many myofibrils were hypercontracted. Giant fibers possessed mitochondria enlarged to an even greater extent and many of the myofibrils had loss of continuity, were narrow, depleted and were also hypercontracted. Significant differences between myopathic and normal groups were found in number of beta R fibers (lower in the myopathic group), number of alpha R fibers and percent of alpha R and alpha W fibers (higher in the myopathic group). Differences (P less than .01) existed between meat pH1 value in the myopathic group (mean value of 5.95) and the normal group (mean value of 6.29). Meat from the myopathic group of pigs also had a lower (P less than .01) pH24 value and reduced water-holding capacity (P less than .01) relative to the meat of the normal pigs. The lack of difference of fattening and slaughter traits between the groups suggested that the White Zlotnicka pigs is of particular value because it is possible to improve the production traits without increasing the incidence of these syndromes within the breed. Negative correlations (P less than .05) between number of giant fibers and percent of alpha W fibers, and between percent of giant fibers and percent of alpha W fibers indicate that alpha W fibers can undergo degeneration and be transformed into giant fibers. Therefore, it it suggested that giant fibers should be treated as muscular, pathological results of past stresses and not as an additional type of normal muscle cells.

Effect of rapid rigor mortis processes on protein functionality in pectoralis major muscle of domestic turkeys.

The pale, soft, exudative (PSE) phenomenon in turkey pectoralis major (breast) muscle was studied using a combination of biochemical, meat quality, microscopic, and gel electrophoresis techniques. Breast muscle samples were collected from turkeys characterized by slow vs fast postmortem glycolysis assessed by muscle pH at 20 min after death. The PSE group was characterized by lower muscle ATP (P < .05) and higher lactate levels (P < .05) compared with the normal group. Excess water-holding capacity and cooking yield were significantly lower (P < .05) in the PSE group than in normal turkeys. Breast muscle of the PSE group was also lighter (P < .05) than that in the normal group as determined by Minolta L* values. The SDS-PAGE, Western blotting, and immunofluorescence microscopy revealed that phosphorylase, a soluble enzyme, became tightly associated with the myofibrils in muscle from the PSE group. Also, less myosin could be solubilized from PSE vs normal myofibril samples. The results indicate that irreversible myosin insolubility due to low pH and high-temperature conditions is decisive in the development of PSE turkey breast muscle.

The effect of pig genetics on palatability, color and physical characteristics of fresh pork loin chops.

The objective of this study was to characterize the quality attributes of pork derived from pigs of the following backgrounds: Duroc, Pietrain (Halothane negative, NN), Pietrain (Halothane positive, nn), Berkshire, Hampshire (rn+), Hampshire (RN-), and a synthetic line. A 10-member panel was trained to evaluate visual appearance of uncooked lean and fat, and flavor and texture of cooked chops. Hunter L*, a*, and b* values, hue angle, cookloss and Warner-Bratzler shear force were also determined. Visual color differences occurred due to genetic background. Chops from Duroc, Berkshire, Pietrain-nn, and the synthetic line were least pink. Chops from Berkshire carcasses appeared to have the most marbling in the lean and those from Pietrain-nn pigs appeared to have the least. Chops from Pietrain-nn and Hampshire-rn+ carcasses had the highest a* values while chops from Duroc, Pietrain-NN, and Hampshire-RN- carcasses had the lowest. Cook loss from chops from Duroc carcasses was lower than that from Hampshire rn+, Pietrain-NN and synthetic line carcasses. Shear force was highest for chops from Pietrain-nn and Hampshire-rn+ carcasses. Chops from Hampshire-RN- carcasses were most juicy followed by those from Hampshire-rn+, Pietrain-NN, Berkshire and Duroc carcasses. Shear force was positively correlated with abnormal flavor intensity, metallic taste, and chewiness (r=0.72, 0.94, and 0.69, respectively), and negatively correlated with sweetness (r=-0.73). Overall, genetic background had significant effects on many of the quality characteristics evaluated.

The role of major genes and DNA technology in selection for meat quality in pigs.

The aim of this paper is to discuss the role of major genes and DNA technology in selection for meat quality in modern breeding schemes. An overview of major genes, including genes that affect water-binding, colour, marbling, boar taint and tenderness, is given. Two different approaches for the development of DNA tests as selection tools are described: (1) localization of relevant genes on the genome map using DNA markers, and (2) research on mutations in targeted functional genes (candidate genes). It is concluded that major genes for meat quality provide excellent opportunities, not only for increasing the level of meat quality, but also for decreasing variability. Furthermore, major genes can be exploited for differentiation for specific markets. It is stressed that phenotypic data on culled nucleus animals provide an important basis for the development of DNA tests for selection for meat quality. More fundamental research is recommended to understand the interactions of genes with each other and with environmental factors.

Metachromatic procedure for fiber typing in chicken skeletal muscle.

Metachromatic staining of anterior latissimus dorsi, posterior latissimus dorsi, and sartorius muscles of domestic chicken with azure A and toluidine blue produced differentiation of muscle fiber types. The procedure is rapid, with optimum results obtained after 2 to 5 min incubation and 5 to 10 s of staining. Reaction of serial sections for myosin Ca++-adenosine triphosphatase with the usual procedure showed that the same fibers were typed similarly with both methods.

Determination of fiber types of chicken skeletal muscles based on reaction for actomyosin, calcium+2, magnesium+2-dependent adenosine triphosphatase.

Muscle fiber subtypes, determined with the actomyosin Ca+2,Mg+2-adenosine triphosphatase (ATPase) reaction in chicken anterior latissimus dorsi and posterior latissimus dorsi muscles, were demonstrated only after acid or alkaline preincubation followed by a 60-min enzyme incubation. In contrast, subtypes were demonstrated in the sartorius muscle either with or without preincubation. A single-step procedure was therefore possible with this muscle. The results were generally similar to those obtained previously with the mycosin Ca+2-ATPase procedure. Both methods revealed corresponding muscle fiber subtypes, with the exceptions noted below. The actomyosin Ca+2,Mg+2-ATPase procedure, following preincubation at pH 9.4 and 10.3, resulted in a similar reaction intensity in all fiber types. With the myosin Ca+2-ATPase procedure, the IRA (slow) type in anterior latissimus dorsi and sartorius muscles and the I (slow), IIR (fast oxidative-glycolytic), and IIW (fast glycolytic) types in posterior latissimus dorsi muscle had a higher reaction intensity following preincubation at pH 9.4 than at pH 10.3. Fiber Types IIR and IIW in sartorius muscle were easily distinguished with the actomyosin Ca+2,Mg+2-ATPase procedure.

Relationship between muscle growth and poultry meat quality.

For a number of years, poultry selection has concentrated on growth velocity in meat lines, producing improvements in growth that have not been without consequence for muscle structure, metabolism, and meat quality. Higher growth rates may induce morphological abnormalities, induce larger fiber diameters and a higher proportion of glycolytic fibers, and a lower proteolytic potential in the muscles. After death, the faster development of rigor mortis increases the likelihood of paler color and reduced water holding capacity and poorer quality of further processed products. Reduced proteolytic potential is likely to increase toughness of poultry meats.

Histopathological and ultrastructural alterations of turkey skeletal muscle.

The pectoralis thoracicus and biceps femoris muscles were obtained from 30 18-wk-old Large White turkey males at the time of slaughter. The birds had no observable mobility or postural problems, and the meat appeared normal. Samples were processed for histology, histochemistry, and electron microscopy. Degenerative features were found in muscle from 10 of the 30 birds. Four of the 10 had alterations in both muscles. The degenerative changes included scattered focal necrosis, hypercontraction of muscle fibers, infiltration by mononuclear cells, formation of fibrous tissue scars, and Z-band streaming. These structural alterations appear to be related to muscle ischemia.

Distribution of capillaries in normal and ischemic turkey skeletal muscle.

Capillary to fiber relationship was studied in musculi biceps femoris and musculi pectoralis thoracicus from 20 normal and 10 ischemic turkeys. Capillary density, the number of capillaries surrounding a fiber, capillary to fiber ratio, intercapillary distance, and fiber area were measured. The muscles from the ischemic group had significantly lower (P less than .05) values for capillary density and capillary to fiber ratio and significantly higher intercapillary distance than those from the normal group. There was no evidence of larger muscle fiber size in the ischemic versus normal birds. It is suggested that the occurrence of muscle ischemia in the domestic turkey is due to alterations in capillarity and reduced vasodilatation, resulting from lack of exercise.

High glycolytic potential does not predict low ultimate pH in pork.

Extent of postmortem pH decline influences meat quality development. To better understand physiological determination of ultimate pH (pHu), we utilized female and castrated male pigs from a line whose selection index includes differentiated pHu. All genotypes of AMP-activated protein kinase γ3 subunit (AMPKγ3) V199I site were present. The mutant 199II genotype increased pHu, but only in castrated males. Genotype affected glycolytic potential (GP), but GP was weakly associated with pHu. A subset of animals was selected based on low (-Gly) and high (+Gly) residual glycogen content, and compared with AMPKγ3 200Q, which is associated with low pHu. Both +Gly and 200Q muscle contained glycolytic substrate at 24h; however, 200Q muscle generated low pHu and greater lactate compared to +Gly. Additionally,-Gly and +Gly groups exhibited similar pHu despite a large difference in GP. In conclusion, high GP does not appear to directly impact the extent of postmortem pH decline.

The effects of pre-slaughter pig management from the farm to the processing plant on pork quality.

Two experiments (Exp.1, n=80; Exp.2, n=144) were conducted to determine the effects of pre-slaughter pig management on pork quality by monitoring blood lactate concentration ([LAC]) during marketing. [LAC] was measured at: (1) baseline at farm, (2) post-loading on truck, (3) pre-unloading after transport, (4) post-unloading at plant, (5) post-lairage, (6) post-movement to stun, and (7) exsanguination. Pearson correlations were used to determine relationships between [LAC] and meat quality. Higher [LAC] post-loading or a greater change in [LAC] during loading resulted in increased 24h pH (P=0.002, P=0.0006, Exp.1; P=0.0001, P=0.01, Exp.2, respectively), decreased L* (P=0.03, P=0.04; P=0.001, P=0.01) and decreased drip loss (P=0.02, P=0.12; P=0.002, P=0.01). Even though improved handling during loading is important to animal well-being, it will not necessarily translate into improved pork quality.

Use of exsanguination blood lactate to assess the quality of pre-slaughter pig handling.

The objective of these studies (Exp.1, n=76; Exp.2, n=140) was to characterize the relationship of pre-slaughter animal-handling events to exsanguination blood lactate concentration ([LAC]) in a commercial pork processing plant. Pearson correlations indicated relationships (P<0.05) between [LAC] and the number of times a pig jammed, backed up and reared (Exp.1), and [LAC] was correlated (P<0.05) with electric prod use and vocalization in response to prod use in the crowd pen, as well as jamming in the single-file chute (Exp. 2). Single degree of freedom contrasts indicated that pigs experiencing one or more events (i.e., jamming, rearing and/or backing up) while moving through a single-file chute had greater (P<0.03) [LAC] than pigs that did not experience these events in both experiments, whereas pigs prodded in the crowd pen had greater (P=0.03) [LAC] than pigs that were not prodded (Exp. 2). This study provides data demonstrating that specific pre-slaughter animal-handling events are related to post-slaughter [LAC] in a commercial setting.

The influence of temperature on mechanics of red muscle in carp.

1. We measured the influence of temperature on maximum velocity of shortening (Vmax) of red muscle in carp in order to better understand the influence of temperature on locomotory performance. 2. A stable red muscle bundle preparation containing about 100 muscle fibres was developed. The bundles could not be activated directly by electrical stimulation, but rather contained sufficient nervous tissue so that acetylcholine released from the nerve terminals caused activation of the muscle. A high level of activation was achieved (116 kN/m2) by adding a combination of a 1 mM-caffeine and 10(-5) g/ml eserine to physiological Ringer solution and electrically stimulating the preparation. 3. Force-velocity characteristics were determined at 10 and 20 degrees C by the force clamp method. The data were well fitted by a hyperbola not constrained to pass through P0 = 1 (where P0 is the isometric force). The mean Vmax at 10 degrees C was 3.55 +/- 0.26 muscle lengths/s (ML/s) (n = 6) and at 20 degrees C, 5.71 +/- 0.29 ML/s (n = 6). The mean Q10 for Vmax was 1.63 +/- 0.07 (n = 6). The a/P0* (Hill constant) and Po* (where P0* is the extrapolated load at zero velocity) were 0.49 +/- 0.06 (n = 6) and 1.19 +/- 0.04 (n = 6) respectively at 10 degrees C and 0.29 +/- 0.06 (n = 6) and 1.51 +/- 0.20 (n = 6) respectively at 20 degrees C. 4. The mean Q10 for maximum isometric tension was 1.13 +/- 0.02 (n = 6). The maximal power generation was 59.7 +/- 2.3 W/kg (n = 6) at 10 degrees C and 94.3 +/- 3.2 W/kg (n = 6) at 20 degrees C representing a Q10 of 1.58. The Q10 is less than the product of Q10s for P0 and Vmax because of the greater curvature of the force-velocity curve at 20 degrees C. 5. The 1.63-fold higher Vmax at 20 degrees C than at 10 degrees C enables fish to swim with a 1.6-fold faster muscle shortening velocity, V, at the higher temperature. Thus at both 10 and 20 degrees C, red muscle is used only over the same narrow range of V/Vmax (0.18-0.36), where isolated muscle experiments suggest that power and efficiency are maximal. Thus V/Vmax appears to be an effective design constraint which limits the range of velocities over which muscle is used in vivo at different temperatures.

Myofilament overlap in swimming carp. II. Sarcomere length changes during swimming.

This study was performed to determine myofilament overlap during swimming in carp. By using frozen sections, we found that sarcomere lengths of the red and white muscle could be related to the curvature of the backbone. Sarcomere length (SL) during swimming was calculated from an analysis of backbone curvature in high-speed motion pictures. Because carp have the same myofilament lengths as frogs, we related force generation to SL using the frog SL-tension curve. At slow swimming speeds, the red fibers are used at a SL of 1.91-2.22 microns, where force generation is calculated to be no less than 96% maximal. If the red fibers powered the escape response they would have to shorten to 1.45-1.55 microns, where force generation would be reduced to approximately 50% maximal and the fibers damaged. Instead, the white muscle fibers are recruited and because of their helical orientation (resulting in a higher gear ratio), they shorten to only 1.75 microns, where they generate no less than 85% maximal tension. Thus, by recruitment of fiber types with different orientations, the full range of movements is powered by fibers operating at nearly maximal overlap. This suggests that myofilament overlap is an important design constraint of muscular systems.

The influence of temperature on muscle function in the fast swimming scup. II. The mechanics of red muscle.

To understand better how scup can swim twice as fast as carp with its red muscle, we measured the mechanical properties of red muscle bundles in scup. The values of the mean maximum velocity of shortening (Vmax) at 10 degrees C (3.32 muscle lengths s-1) and at 20 degrees C (5.55 muscle lengths s-1; Q10 = 1.69) were nearly the same as those in carp. Isometric force, however, was approximately 50% greater (183 kN m-2; Q10 = 1.08). The maximal power generation was correspondingly about 50% greater in scup than in carp (71 W kg-1 at 10 degrees C and 134 W kg-1 at 20 degrees C; Q10 = 1.88). The larger power output of its muscle may be important in the faster swimming of the scup. In addition, the fact that scup use a less undulatory style of swimming means that, when they are swimming twice as fast, their red muscle shortens at the same velocity (V) and with the same V/Vmax (0.37, i.e. where maximum power is generated) as that of carp. The importance of V/Vmax is further shown by the comparison of scup swimming at different temperatures. The 1.69-fold higher Vmax at 20 degrees C than at 10 degrees C enables scup to swim with a 1.67-fold faster V at 20 degrees C. Thus, at both 10 degrees C and 20 degrees C, red muscle is used only over the same narrow range of V/Vmax (0.17-0.37), where experiments on isolated muscle suggest that power and efficiency are maximal. Therefore, V/Vmax appears to be an important design constraint that limits the range of velocities over which muscle is used in vivo, both at different temperatures and in fast- and slow-locomoting species.