Gerd Nürnberg

Phenotypic variations of muscle fibre and intramuscular fat traits in Longissimus muscle of F2 population Duroc×Berlin Miniature Pig and relationships to meat quality

In Longissimus muscle from a F(2) population of Duroc×Berlin Miniature Pigs, micro-structural fibre traits and fatty acid composition were investigated to calculate correlation coefficients between these traits and meat quality. The animals of the F(2) population exhibited low carcass weight (55.7±11.2 kg), low meat percentage (35.0±8.4%) but a relatively high intramuscular fat content (3.52±1.44%) compared to pure bred animals (F(0)). No unacceptable meat quality was observed. The variation coefficients of carcass composition, muscle fibre traits, and fat traits were high enough to allow the analysis of candidate genes which influence the growth of muscle fibres, fat cells, and meat quality. Phenotypic correlation coefficients between muscle fibre characteristics and meat quality traits were low whereas fatty acid composition and meat quality were more closely related. The correlation coefficients between muscle fibre traits and fatty acid composition ranged from 0.10 to 0.40. The relationship between a low quotient of n-6/n-3 fatty acids in muscle and greater fibre sizes, higher percentages of the oxidative fibre type and higher capillary density was noteworthy indicating good conditions for muscle growth and meat quality.

POST MORTEM CHANGES IN CA2+ TRANSPORTING PROTEINS OF SARCOPLASMIC RETICULUM IN DEPENDENCE ON MALIGNANT HYPERTHERMIA STATUS IN PIGS

Meat quality of pigs is dependent on biochemical and biophysical processes in the time course post mortem (p.m.) and is associated with the intracellular Ca2+ homeostasis. However, there is little known about changes in the Ca2+ transporting proteins controlling the Ca2+ uptake of sarcoplasmic reticulum (SR) in the time course p.m. In this study changes in the Ca2+ transporting proteins were investigated in homogenates of longissimus muscles of 4 malignant hyperthermia susceptible (MHS) and 6 malignant hyperthermia resistant (MHR) Pietrain pigs. Muscle samples were obtained at different time intervals: biopsy 2 h prior slaughtering and from the carcass immediately after exsanguination (0 h), 45 min, 4 h, and 22 h p.m. The SR Ca2+ uptake rate was measured immediately after homogenization with closed calcium release channel (CRC), with opened CRC and without manipulation of CRC. Additionally the SR Ca2+ ATPase activity was determined.The results show: (i) The ability of SR to sequester Ca2+ declined to about 60% in the first 45 min p.m. in MHS samples irrespective of CRC state, whereas in MHR samples this decline was about 5%; (ii) Ca2+ uptake and Ca2+ ATPase activity were not different between the biopsy and 0 h samples, i.e. the stress of slaughter was of no immediate influence; (iii) The Ca2+ ATPase activity of the SR declined at about the same rate as the Ca2+ uptake in both MHS and MHR pig samples in the course of time p.m.; (iv) In samples, taken immediately after exsanguination, the Ca2+ ATPase activity of MHS pigs was higher than that of MHR pigs. However, in samples taken 4 h p.m. Ca2+ ATPase activity of MHS pigs has declined to about 30% of the value at 0 h; (v) The CRC can be closed and opened in all samples up to 22 h p.m. and seems to be fully functional at all sampling times; (vi) The CRC of MHS pigs is almost fully open, whereas the CRC of MHR pigs is only partially open at all sampling times; (vii) The permeability of the SR membrane to Ca2+ (determined as the ratio of SR Ca2+ ATPase with and without ionophore A23187) is the same in both MHS and MHR and did not change with ongoing time; (viii) No uncoupling of uptake from ATP hydrolysis occurred up to 4 h p.m., but the coupling differed between MHS and MHR for all time intervals with lower values for MHS pigs. The results suggest that the decreasing Ca2+ uptake rate of homogenates, sampled at different times p.m., is essentially caused by changes in the Ca2+ pump and not by changes in the CRC or an increased phospholipid membrane permeability to Ca2+.

Influence of dietary n-3 fatty acids on the membrane properties of skeletal muscle in pigs

The aim of the experiment was the in vivo modification of long-chain fatty acids in phospholipids and to investigate the impact on Ca 2+ transport of sarcoplasmic reticulum (SR). Ten pigs were fed daily a diet containing 1.3g n-3 fatty acids/kg diet (control), and ten pigs were fed a diet containing 14g n-3 fatty acids/kg diet (n-3 diet) during the growing-finishing period. The intake of dietary n-3 fatty acids increased the percentages of these fatty acids in the phospholipids of skeletal muscle sarcoplasmic reticulum (21.6% n-3 fatty acids) and in the polar fraction of total muscle homogenates (30.7% n-3 fatty acids) significantly, compared with control (3.0% and 3.9% n-3 fatty acids, respectively), while the n-6 fatty acid concentration was reduced. In phosphatidylethanolamine of skeletal muscle polar lipids eicosapentaenoic (EPA) and docosahexaenoic acids (DPA) were increased seven times compared with control. There were no differences in the maximal rate of Ca 2+ uptake in skeletal muscle SR between the groups. However, the activity of Ca 2+ -ATPase of skeletal muscle SR as elevated in the n-3 diet group. It is suggested, that n-3 fatty acid enriched diet can change the complex membrane composition dependent on experimental conditions and animal species leading to different effects on membrane protein activities.

Androgen profiling in males of two high-fertility mouse models does not reveal a distinct phenotype but provides new reference values for androgens in mice

Background: Animal models are valuable tools in fertility research. Worldwide, there are more than 1000 transgenic or knockout mouse models available showing a reproductive phenotype; almost all of them exhibit an infertile or at least subfertile phenotype. By contrast, animal models revealing an improved fertility phenotype are barely described. We developed two outbred mouse models exhibiting a ‘high-fertility’ phenotype. These mouse lines were generated via selection over a time period of more than 40 years and 170 generations. By now both mouse lines doubled the number of offspring as well as the total birth weight per litter.