Klaus Ender

Myogenesis and postnatal skeletal muscle cell growth as influenced by selection

Abstract The major component of a given muscle is the constituent muscle fibres. Lean growth and ultimate muscle mass are therefore largely determined by the number of muscle fibres and the size of those fibres. During myogenesis, myoblasts develop from mesenchymal precursor cells by proliferation and myogenic commitment. Myoblasts subsequently fuse to form multinucleated myofibres. Postnatal growth of skeletal muscle is mainly realised through increases in length and girth of the muscle fibres, but not by increases in muscle fibre number. Postnatal fibre hypertrophy, associated with accumulation of myonuclei (satellite cell proliferation) and muscle-specific proteins, is inversely correlated with the number of prenatally formed muscle fibres. On the other hand, both fibre number and fibre thickness are positively correlated with muscle mass and lean meat percentage. Both fibre number and fibre size are influenced by selection as shown by differences between breeds and correlated responses to (lean) growth selection. Increases in muscle mass solely by fibre hypertrophy, as observed particularly in meat-type pigs and chickens, may be associated with problems in stress adaptability and ultimate meat quality. Genetic variability and heritability of muscle fibre number and size are sufficiently high to include these traits in farm animal selection in addition to commonly used selection criteria for improving lean meat content and meat quality.

Factors influencing fat composition in muscle and adipose tissue of farm animals

Abstract Fat deposition can be characterized chemically by continual accretion of lipids, primarily in the form of triacylglycerols, and morphologically by adipocyte differentiation and hypertrophy. The relative proportion of nutrients and the fatty acid composition are influenced by numerous factors including diet, fatness, age/body weight, gender, breed, environmental temperature, depot site, maintenance and hormones. Deposition of body fat can be modulated by nutritional and hormonal means. The level of food intake and the composition of food regulates the rate of fatty tissue growth and the composition of lipids. Exogenous endocrine substances have effects on adipose tissue metabolism. For example, porcine somatotropin reduces lipid deposition by decreasing lipogenesis. There is a correlation between the amount of fatty tissue and the fatty acid composition. The differences between animals of different gender are partially due to the amount of fat deposited. Finally, the potential for dietary variation of lipid composition in monogastric animals is much greater than in ruminants. In young sheep and cattle, there is a limited possibility to influence fatty acid content.

Effects of dietary olive and linseed oil on lipid composition, meat quality, sensory characteristics and muscle structure in pigs

The aim of this study was to alter the fatty acid composition of porcine tissue by accumulating essential fatty acids without adversely affecting carcass composition, muscle structure or meat eating quality. A total of 13 female and 12 castrated Pietrain×German Landrace pigs were fed a basal concentrate diet supplemented with 5% olive oil or 5% linseed oil during the growing-finishing period. Carcass composition and meat quality were not affected by the diet. Feeding linseed oil to pigs significantly increased the relative content of linolenic acid and long chain n-3 fatty acids in lipids of muscle, backfat and heart at the expense of arachidonic acid. Oleic acid was accumulated in muscle, backfat and heart lipids by feeding olive oil. The overall flavour of combined meat/backfat samples from castrates was negatively influenced by linseed oil supplementation compared to supplementation with olive oil. The oxidative stability of muscle lipids was lower in linseed oil-fed pigs compared to olive oil fed pigs. The greater cross section areas of the longissimus muscle of females were caused by an increased diameter of red, intermediate and white fibres.

N-3 fatty acids and conjugated linoleic acids of longissimus muscle in beef cattle

The objective of the experiment with cattle was to produce high quality beef under different feeding conditions and to increase the concentration of essential fatty acids in muscle. In total 10 German Simmental (GS) bulls and 9 German Holstein (GH) steers were kept either on pasture (grass feeding) or in stable (concentrate feeding). Despite biohydrogenation in the rumen, linolenic acid (C18:3n-3) contained in grass was absorbed and deposited into the lipids of muscle. This led to a significantly (p ≤ 0.05) higher content of n-3 fatty acids in the muscle lipids of grazing cattle. The relative amount of total n-3 fatty acids increased from 1.4 g/100 g fatty acid methyl ester (%FAME) in the intensively fed Simmental bulls to 5.5 %FAME in grass fed cattle. The n-6/n-3 ratio of pasture grazing GS bulls was 1.3 in contrast to 13.7 of the animals kept in the byre. The total n-3 fatty acid concentration in beef muscle increased from 24.6 mg (concentrate) to 108.6 mg/100 g wet weight (grazing). In GH steers the total n-3 fatty acid concentration was significantly (p ≤ 0.05) increased up to 86.3 mg/100 g wet weight in pasture grazing steers compared to 28.8 mg/100 g wet weight in animals fed the concentrate. The relative content (%FAME) of CLAcis-9, trans-11 (0.6 vs 0.56 %FAME in GS; 0.55 vs 0.52 %FAME in GH) in muscle was not significantly increased by grazing on pasture in comparison to concentrate feeding neither in GS bulls nor in GH steers, respectively.

Effect of pasture vs. concentrate diet on CLA isomer distribution in different tissue lipids of beef cattle

This study examined the effects of feeding pasture vs. concentrate on the distribution of CLA isomers in the lipids of longissimus and semitendinosus muscle, liver and heart muscle, and subcutaneous fat in beef bulls. Sixty-four German Holstein and German Simmental bulls were randomly allocated to either an indoor concentrate system or periods of pasture feeding followed by a finishing period on a concentrate containing linseed to enhance their beef content of n−3 PUFA and CLA. The concentrations of CLA isomers in the different tissues were determined by GC and silver ion HPLC. The diet affected the distribution of individual CLA isomers in the lipids of the different tissues. The concentration (mg/100 g fresh tissue) of the most prominent isomer, cis-9,trans-11 18∶2, was increased up to 1.5 times in liver and heart tissue of bulls fed on pasture as compared with concentrate. However, no diet effect was observed for cis-9,trans-11 18∶2 in the lipids of longissimus muscle and subcutaneous fat. In all tissues, the second-most abundant CLA isomer in concentratefed bulls was trans-7,cis-9 18∶2. In contrast, trans-11,cis-13 18∶2 was the second-most abundant CLA isomer in all investigated tissue lipids of pasture-fed bulls. The concentration of the trans-11,cis-13 18∶2 isomer was up to 15 times higher in tissues of pasture-fed bulls as compared with concentrate-fed animals. Furthermone, diet affected the concentrations of the CLA trans,trans 18∶2 isomers. Pasture feeding significantly increased the concentrations of some trans,trans 18∶2 isomers as compared with concentrate, predominantly trans-12,trans-14 18∶2 and trans-11,trans-13 18∶2. Overall, pasture feeding resulted in significantly increased concentrations of the sum of CLA isomers in the lipids of longissimus, muscle, subcutaneous fat, heart and liver muscle of German Holstein and German Simmental bulls, but not in semitendinosus muscle.

Structural and functional characteristics of muscle fibres in pigs with different malignant hyperthermia susceptibility (MHS) and different meat quality

In pigs, intensive growth of the musculature is often accompanied by malignant hyperthermia susceptibility (MHS; n gene) and poorer meat quality. Using histological and histochemical methods, different fibre characteristics in the Longissimus muscle were found in Pietrain×German Landrace pigs with this gene defect. Compared to MHS homozygous negative pigs, groups with the n gene had increased diameters of the mean fibre types and increased glycolytic metabolic potential, as shown by a higher frequency of the fast twitch glycolytic type and a lower frequency of the slow twitch oxidative fibre type. Differences between the groups were also found in the number of angular and giant fibre types. Furthermore, a positive correlation was found between the frequency of oxidative fibres and the relative enzyme activity of NADH tetrazolium reductase. The changes correlated with lower pH and higher drip loss in meat from the MHS homozygous positive group. In conclusion, the different muscle fibre characteristics can be interpreted as endogenous factors which influence the physiological condition in the muscle of the live animal and meat quality post mortem.

Comparing mRNA levels of genes encoding leptin, leptin receptor, and lipoprotein lipase between dairy and beef cattle

Body weight and fat mass vary distinctly between German Holstein (dairy cattle) and Charolais (beef cattle). The aim of this study was to determine whether the expression of the obese (Ob) gene and lipoprotein lipase (LPL) gene in fat tissues and expression of the long isoform leptin receptor (Ob-Rb) gene in the hypothalamus were different between these two cattle breeds. Body weight and the area of longissimus muscle cross-section of German Holstein were lower (P<0.001), while body fat content, as well as the omental and perirenal fat mass were higher (P<0.001), compared to Charolais. Plasma insulin and leptin levels between two cattle breeds were determined by radioimmunoassay. Compared to Charolais, plasma insulin concentrations were significantly higher (P<0.01), and plasma leptin levels were tended to be higher (P<0.1) in German Holstein. Ob mRNA levels in subcutaneous and perirenal fat depots, but not in the omental fat depot, were significantly higher (P<0.05) in German Holstein than in Charolais. LPL mRNA expression in the perirenal fat depot of German Holstein was greater in abundance than that of Charolais. No significantly different LPL mRNA levels were found in subcutaneous and omental fat depots, and Ob-Rb mRNA levels in the hypothalamus between these two cattle breeds (P<0.05). Both Ob and LPL expression was greater in perirenal and omental fat depots than in the subcutaneous fat depot (P<0.05). Data indicated that in bovine the Ob and LPL gene expression levels in perirenal fats are an important index that is associated with body fat content, while Ob-Rb in hypothalamus is not.

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.

Influence of dietary vitamin E and selenium on muscle fatty acid composition in pigs

Abstract A total of 28 female pigs were fed a basal diet containing a low amount of α-tocopherol (10.3 mg/kg; control), and diets supplemented with 0.3 mg selenium/kg (group Se) or with 200 mg α-tocopherol/kg (group V) at the growing-finishing period. Increasing dietary level of vitamin E resulted in higher concentration of α-tocopherol in plasma and muscle immediately after slaughter and 4 h later (P⩽0.05). The fatty acid composition of muscle microsomes and mitochondria was slightly affected by the diet. Corresponding to the minor changes of the membrane fatty acid composition the fluidity was unaffected by the diet. A positive relationship was observed between the resistance to in vitro stimulation of peroxidation and the vitamin E content of the muscle samples. Supplementation with selenium did not reduce the lipid oxidation after stimulation. In conclusion, even though the effect was minor, vitamin E improved the antioxidative status in pork.

Muscle characteristics and corresponding hormone concentrations in different types of cattle

Abstract Ruminants transform feed components preferentially in body mass or milk. The accretion type of cattle are apt in accreting feed as meat and fat, while the secretion type of cattle secrete metabolised feed as milk. The objective of this study was to investigate the growth- and type-related differences in muscle fibers, adipocytes, and hormones in two metabolic types of cattle. Biopsy samples of semitendinosus muscle and blood were taken at 6, 8, 10, 13, and 16 months of age from 13 bulls of each metabolic type (Charolais—CH, German Holstein—H). Postnatal growth was characterized by a nearly 2-fold increase in muscle fiber area, while a constant fiber type frequency was observed. Differences in the growth potential between CH and H bulls were not only found in a higher daily weight gain or higher weight for CH cattle, but were also caused by stronger muscle fiber growth in that cattle type. The higher muscle growth potential of CH was accompanied by lower fat accretion and metabolically linked with lower plasma concentrations of insulin, glucagon, and leptin. The amount of subcutaneous adipose tissue was directly correlated with leptin in CH and with insulin and glucagon in H bulls.