J. Wegner

Differences in muscle and fat accretion in Japanese Black and European cattle.

The development of different muscles and adipose tissues during growth was investigated in commercial Japanese Black (JB) cattle and compared with breeds of the largest variation to be found in Europe. Animals, reared under typical conditions for Japanese and European beef production systems, gained similar body weights but different carcass composition at 24months of age. The carcass of JB contained more adipose tissue and the least proportion of muscle. The longissimus muscle of JB developed extraordinary amounts of 23.3% intramuscular fat (IMF) at 24months of age, compared from 0.6% to 4.7% in European breeds. The relationships between IMF content in the longissimus muscle and different adipose tissue weights indicate that a large amount of waste fat is accreted with every percent of IMF. However in JB, the good ability of IMF deposition is associated with relatively least development of waste fat, as a result of unique breed characteristics combined with special feeding system.

Cellular conditions for intramuscular fat deposition in Japanese Black and Holstein steers

The experiment was conducted to study the development of intramuscular fat in Japanese Black (JB) compared to Holstein (HS) steers and to find breed differences for fat depot development and distribution in the carcass under equal feeding conditions. Additional to slaughter samples, biopsy samples of longissimus muscle (LM) and subcutaneous fat, taken at 10, 14, 18, and 22 months of age, were used for histological and molecular investigations. Japanese Black steers stored about 14% more fat in the LM (P = 0.001), resulting in larger marbling flecks (P < 0.001). Muscle fibers and intramuscular adipocytes in both breeds responded to the high energy feeding with significant enlargement, which was faster in JB. Histograms of intramuscular adipocytes size showed a shift toward larger cells during growth, but also the abundance of small, developing adipocytes. This development was accompanied by a correlated up-regulation of adipogenic genes until 22 months of age.

How do n-3 fatty acid (short-time restricted vs unrestricted) and n-6 fatty acid enriched diets affect the fatty acid profile in different tissues of German Simmental bulls?

This study investigated the effect of n-6 (control group) and n-3 polyunsaturated fatty acids (PUFA) supply (treatment group unrestricted) and a short-time feed restriction for n-3 PUFA supply (treatment group restricted) on intramuscular fat content and the total fatty acid composition in different tissues (muscle, subcutaneous fat, liver, serum and erythrocytes) and lipid classes of intramuscular fat of German Simmental bulls (n=25). Exogenous n-3 PUFA caused a higher concentration of the sum of all single n-3 and n-3 long-chain polyunsaturated fatty acids (LC PUFA) in all analysed tissues. Feed restriction compared to control feeding induced a significant decrease of C18:1cis-9 in the phospholipid fraction of longissimus muscle and in subcutaneous fat. The concentration of C18:3n-3 in liver of treatment groups was between 34 and 44% higher compared to control. PUFA in serum and the sum of n-3 PUFA in erythrocytes were significantly higher in both treatment groups compared to control. The synthesis and deposition of n-3 LC PUFA seems to be tissue dependent according to different relative amounts.

Technical note: Determination of cell-specific gene expression in bovine skeletal muscle tissue using laser microdissection and reverse-transcription quantitative polymerase chain reaction1

Skeletal muscle is a very heterogeneous tissue consisting of diverse cell types with specific transcription profiles. Therefore, the measured mRNA abundance of a certain cell type marker is influenced by the transcriptional activity as well as by the usually unknown number of contributing cells in the sample. In studies on the transcriptional activity of adipogenic genes, as indicators for the development of intramuscular adipocytes, an altered number of adipocytes or respective progenitor cells can mask changes in transcriptional activity. To overcome this problem, we started to use laser microdissection to isolate RNA of adipocytes and muscle fibers separately for downstream analysis. Even muscle fiber types can be collected and analyzed separately. Laser microdissection in combination with biopsy techniques enables gene expression studies of particular cell types during the life cycle of an animal. First experiences using laser microdissection for adipogenic gene expression studies in bovine skeletal muscle are described, and the influence of sample preparation and future challenges are discussed.

Perilipin, C/EBPα, and C/EBPβ mRNA abundance in longissimus muscle and different adipose tissues of Holstein and Charolais cattle.

Possible regulators of intramuscular fat deposition were investigated in longissimus muscle (LM) and adipose tissues of 18months old Holstein and Charolais bulls. The mRNA abundance of perilipin and transcription factors C/EBPα and C/EBPβ was analyzed by real-time RT-PCR. Carcass traits and marbling traits were recorded and relationships among adipogenic genes and tissue traits were determined. Charolais cattle were heavier (P<0.001) and had less body fat (P<0.001). Holstein bulls accumulated more fat in the LM (P=0.02), but the number and size of marbling flecks did not differ (P>0.7) between breeds. Perilipin, C/EBPα, and C/EBPβ mRNA abundance was influenced by tissue but not by breed. Relationships between mRNA abundance and marbling traits could not be confirmed, however relationships among adipogenic genes. The transcriptional activity of adipogenic genes in LM suggests that intramuscular adipose tissue is still developing and differentiation still occurs.

Prenatal muscle fiber development and bundle structure in beef and dairy cattle

Muscle fiber development during gestation determines the muscle structure at birth and establishes the conditions for muscle development in growing cattle. Differences in muscle structure among beef cattle breeds and between beef and dairy cattle are obvious already shortly after birth. The objective of the study was to investigate the development of muscle fibers and muscle fiber bundle structure in semitendinosus muscle of divergent cattle breeds from 3 mo of gestation until birth. Fetuses of German Angus (GA), Galloway (GW), Belgian Blue (BB), and Holstein Friesian (HF) were harvested at 3, 4.5, 6, or 9 mo of gestation. Muscle sections were analyzed for fiber size and types as well as for bundle structure. The results confirmed that primary muscle fiber development occurs mainly during the first trimester of gestation. All fibers were initially positive for fetal fast myosin. Slow myosin as a marker for fiber maturation was detected in primary fibers at 3 mo of gestation showing a weak immunostaining. During the second trimester, the intensity of immunostaining strongly increased indicating increased slow myosin protein expression. Concurrently, the shape of primary fibers changed from myotubes to myofibers whereas the size stayed nearly constant. The main increase in muscle mass during the second trimester was caused by secondary fiber development. As an example, the ratio between secondary and primary fibers increased in Holstein Friesian fetuses from 5.9 at 4.5 mo of gestation to 21.6 at 6 mo of gestation. Primary and secondary fibers continued to growth during the third trimester. Regional differences in the density of slow muscle fibers were detected leading to greater variation within the muscle than among breeds. Structural organization of muscle fibers in muscle fiber bundles developed early in fetal life. At first, large main bundles were visible. Smaller structural units defined as primary bundles were measurable at 6 mo of gestation when most fibers were developed. The size of primary bundles nearly doubled from 6 mo of gestation to birth in all breeds. In summary, differences among breeds in the early fetal muscle fiber development were detected in contractile differentiation and partly in muscle fiber bundle structure. A prolonged secondary fiber generation and altered contractile differentiation may be involved in breed differences of postnatal muscle development.

Comparison of feeding systems: Feed cost, palatability and environmental impact among hay-fattened beef, consistent grass-only-fed beef and conventional marbled beef in Wagyu (Japanese Black cattle)

The objective of this article is to compare feed cost, palatability and environmental impacts among feeding systems of high concentrate (HC), high hay (HH) and grass-only-fed (Gof) groups. Feed cost was the sum of costs paid for feed intake times the price of feed per kilogram. Palatability was measured by a panel taste test using HH and Gof beef and analyzed for differences. Environmental impacts were calculated based on 1 kg of Japanese beef yield of CO(2) equivalents (eq) and animal end weights at each feeding stage. Results showed that the HH and Gof feeding systems could significantly reduce feed costs by approximately 60% and 78%, respectively, from the HC. In the panel taste test, 50% and 47.50% of panelists indicated that HH beef was extremely delicious and acceptable, respectively, while 15% indicated that Gof beef was extremely delicious; 62.50% indicated that Gof beef was acceptable. Environmental impacts of each feeding system in terms of CO(2) equivalents (eq) were 9.32, 6.10 and 2.04 tonnes of eq for the HC, HH and Gof, respectively. The HH was an economical system that produced moderate impacts on the environment and had impressive taste.

Effect of nutrient intake on intramuscular glucose metabolism during the early growth stage in cross-bred steers (Japanese Black male × Holstein female).

The objective was to investigate the impact of nutrient intake during the early growth period on the expression of glucose metabolism-related genes in skeletal muscle of cross-bred cattle. From 1.5 to 5 months of age, group H (n=7) animals were intensively fed a high-protein and low-fat milk replacer [crude protein (CP) 28%; ether extracts (EE) 18%; max: 2.0 kg, 12 l/day], and group R (n=7) animals were fed a restricted amount of normal milk replacer (CP 25%; EE 23%; max 0.5 kg, 4 l/day). From 6 to 10 months of age, group H cattle were fed a high-nutrition total mixed ration mainly prepared from grain feed, and group R cattle were fed only roughage. Blood samples were taken from each animal at three biopsy times (1.5, 5 and 10 months of age), and the blood plasma concentration of glucose and insulin was analysed. In glucose concentration, there were no significant differences; however, the concentrations of insulin were higher in group H than in group R at 5 and 10 months of age. Muscle samples were taken by biopsy from longissimus thoracis muscle (LT) at 1.5, 5 and 10 months of age. We analysed mRNA expression levels using the quantitative real-time polymerase chain reaction (PCR) assay for glucose transporters (GLUT1 and GLUT4), insulin receptor, phosphatidylinositol 3-kinase (PI-3K), protein kinase B (PKB, also known as Akt), hexokinase 1 (HK1) and tumour necrosis factor alpha (TNFα). Although no differences were detected at 1.5 and 5 months of age, at 10 months of age, GLUT1, HK1 and TNFα mRNA expression levels were significantly higher in group H than in group R. These results suggested Glut1 that affects insulin-independently mediated glucose uptake was more responsive to improved nutrition during early growth stage than GLUT4 that insulin-dependently mediated glucose uptake in LT of cattle.