Meat Science and Muscle Biology Symposium: in utero nutrition related to fetal development, postnatal performance, and meat quality of pork.

Intrauterine growth restriction (IUGR) occurs naturally in pigs and leads to low birth weight of piglets due to undernutrition caused by placental insufficiency. For 2 main reasons, low birth weight causes economic loss. First, low birth weight pigs have a greater mortality and increasing the litter size causes more low birth weight piglets within litters. Second, surviving low birth weight piglets have reduced performance (i.e., ADG, feed conversion rate, and percentage meat). To develop dietary strategies for preventing IUGR, knowledge of the biological basis of IUGR is required. Muscle fiber number, formed during myogenesis, is correlated positively with performance traits and has been shown in several studies to be reduced in low birth weight pigs. Postnatal muscle hypertrophy is due to satellite cell number per fiber at birth and their rate of proliferation as well as protein deposition (i.e., protein synthesis and degradation). Previous studies and some recent ones indicate that low birth weight littermates in mice are born with fewer satellite cells and studies on pigs show that the rate of satellite cell proliferation may vary within litters. Proteomics studies show that protein synthesis and degradation is downregulated in IUGR pigs and low birth weight pigs also produce meat with less tenderness. Alternative maternal feeding strategies to prevent IUGR have been examined. Increasing maternal global nutrition had no beneficial effect on performance and muscle growth traits in several studies. Feeding excess maternal dietary protein also did not influence muscle growth traits whereas moderately decreased maternal dietary protein may decrease muscle fiber number and performance. On the other hand, addition of L-carnitine to the maternal gestation or lactation diet may increase birth and weaning weights or the muscle fiber number, respectively, in low birth weight pig offspring. Finally, promising data have been obtained on reproductive traits in pigs after addition of functional AA, such as arginine and glutamine, to the gestational diet. Although much is known about the biological basis of IUGR, we still need to learn much more about the mode of action before maternal dietary strategies can be developed to prevent IUGR.

Proteomic and peptidomic study of proteolysis in quarter milk after infusion with lipoteichoic acid from Staphylococcus aureus.

Mastitic milk is associated with increased bovine protease activity, such as that from plasmin and somatic cell enzymes, which cause proteolysis of the caseins and may reduce cheese yield and quality. The aim of this work was to characterize the peptide profile resulting from proteolysis in a model mastitis system and to identify the proteases responsible. One quarter of each of 2 cows (A and B) was infused with lipoteichoic acid from Staphylococcus aureus. The somatic cell counts of the infused quarters reached a peak 6h after infusion, whereas plasmin activity of those quarters also increased, reaching a peak after 48 and 12h for cow A and B, respectively. Urea-polyacrylamide gel electrophoretograms of milk samples of cow A and B obtained at different time points after infusion and incubated for up to 7 d showed almost full hydrolysis of ß- and α(S1)-casein during incubation of milk samples at peak somatic cell counts, with that of ß-casein being faster than that of α(S1)-casein. Two-dimensional gel electrophoretograms of milk 6h after infusion with the toxin confirmed hydrolysis of ß- and α(S1)-casein and the appearance of lower-molecular-weight products. Peptides were subsequently separated by reversed-phase HPLC and handmade nanoscale C(18) columns, and identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. Twenty different peptides were identified and shown to originate from α(s1)- and ß-casein. Plasmin, cathepsin B and D, elastase, and amino- and carboxypeptidases were suggested as possible responsible proteases based on the peptide cleavage sites. The presumptive activity of amino- and carboxypeptidases is surprising and may indicate the activity of cathepsin H, which has not been reported in milk previously.

Effect of minor milk proteins in chymosin separated whey and casein fractions on cheese yield as determined by proteomics and multivariate data analysis.

The objective of this work was to find regressions between minor milk proteins or protein fragments in the casein or sweet whey fraction and cheese yield because the effect of major milk proteins was evaluated in a previous study. Proteomic methods involving 2-dimensional gel electrophoresis and mass spectrometry in combination with multivariate data analysis were used to study the effect of variations in milk protein composition in chymosin separated whey and casein fractions on cheese yield. By mass spectrometry, a range of proteins significant for the cheese yield was identified. Among others, a C-terminal fragment of beta-casein had a positive effect on the cheese yield expressed as grams of cheese per 100 g of milk, whereas several other minor fragments of beta-, alpha(s1)-, and alpha(s2)-casein had positive effects on the transfer of protein from milk to cheese. However, the individual effect of each identified protein was relatively low. Therefore, further studies of the relations between different proteins/peptides in the rennet casein or sweet whey fractions and cheese yield are needed for advanced understanding and prediction of cheese yield.

Identification of myofibrillar substrates for µ-calpain.

To identify myofibrillar substrates of µ-calpain under post-mortem conditions, a combination of SDS-PAGE, two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) was used. Purified myofibrils were incubated with µ-calpain under post-mortem-simulated conditions for two or four days at 4 °C. The resulting protein changes were analyzed by SDS-PAGE and 2DE. The µ-calpain-mediated protein changes were identified by peptide-mass mapping using MALDI-TOF MS and revealed that desmin, actin, myosin heavy chain, myosin light chain I, troponin T, tropomyosin α1, tropomyosin α4, thioredoxin and CapZ are all degraded in vitro by µ-calpain. The findings that actin and myosin heavy chain are substrates of µ-calpain were rather surprising, as it has previously been reported that these proteins are resistant to µ-calpain degradation. However, both actin and myosin heavy chain are poor substrates compared with desmin.

Muscle glycogen stores and meat quality as affected by strategic finishing feeding of slaughter pigs.

The aim of the present study was to investigate whether muscle glycogen stores in slaughter pigs could be decreased through strategic finishing feeding before slaughter. Moreover, preliminary meat quality traits were measured to see whether such a regulation of muscle glycogen stores affected ultimate pH, color, and tenderness in the meat. The strategic finishing feeding was carried out the last 3 wk prior to slaughter. Seven experimental groups with eight animals per group were fed diets low in digestible carbohydrates. A control group with four animals was fed a traditional grower-finishing diet. The muscle glycogen stores were reduced in longissimus muscle (LM) 11 to 26% at the time of slaughter in pigs that were fed the experimental diets compared with the control group. Meat quality measured as ultimate pH and color on LM muscle in half the pigs 24 h postmortem showed that ultimate pH in LM was not affected by the reduction in glycogen stores in the muscles from pigs fed any of the experimental diets. However, the meat from pigs fed the experimental diets was darker than the meat from pigs that were fed the control diet with two of the experimental diets, resulting in significantly lower L* values. Activities of key enzymes in the glycolytic pathway, glycogen phoshorylase a and b, phosphofructokinase, and the fatty acid oxidative pathway, beta-hydrozyacyl-CoA-dehydrogenase, were not affected by the strategic feeding. In contrast, the activity of the proteolytic enzyme calpain as well as its inhibitor calpastatin was influenced by the strategic feeding. Lower activity of mu-calpain and greater activity of calpastatin in the muscle samples from the strategically fed pigs indicate a lesser muscle protein degradation in the muscles compared with muscles of control animals. The present study showed that the muscle glycogen stores in slaughter pigs can be reduced at the time of slaughter through strategic finishing feeding with diets low in digestible carbohydrate without compromising growth rate.

The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis.

Function of the knee and patellofemoral symptoms were correlated with the position of the implant in 101 consecutive patients with 116 posterior stabilized condylar knee prostheses. All of the patients were followed for a minimum of two and a half years with sequential physical examinations, radiographs, and functional evaluation of the knee. In sixteen knees (14 per cent), clicking or catching of the patella in terminal extension or painless crepitation throughout the arc of flexion developed without lowering the functional knee-evaluation score. Pain or mechanical problems, or both, that lowered the functional knee-evaluation score occurred in another fourteen knees (12 per cent), within the first postoperative year. Of these fourteen, eight required revision solely for patellofemoral complaints. Critical analysis of the tibial-patellofemoral mechanical axis identified three surgical variables that were found to markedly affect the functional result of the prosthesis: the distance from the center line of the tibial prosthesis to the center line of the tibial plateau, a change in the position of the joint line of the prosthesis relative to the hip and ankle, and the patellar height, measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis. Functional knee scores, range of motion, patellofemoral pain or mechanical symptoms, the need for revision, and the necessity of manipulation could all be statistically significantly correlated with the three independent variables. In addition, a range of neutral alignment was developed.(ABSTRACT TRUNCATED AT 250 WORDS)