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Four muscles (m. semispinalis capitis, m. semimembranosus,m. longissimus thoracis, m. psoas major) of 51 German Landrace castrated male pigs were examined for total intramuscular fat and for intramuscular adipose tissue. The pigs had been selected through 8 generations for high (E+- line) and low (E--line) levels of NADPH-generating Dehydrogenases in subcutaneous adipose tissue. Pigs of control line (K°) without selection for enzyme activity were fed parallel on an energy level of 0,9 IME and 1,3 IME.From body weight 60kg up to 100kg feeding experiments with different levels of dietary energy, 0,9 and 1,3 IME, and ad libitum regime respectively, were arranged. In addition, piglets of 25kg and hogs of 135kg body weight (K°) were also examined.1. Results of ether extraction:A) Muscletyoes. The average fat content of m. semispinalis capitis was 11%, of m. semimembranosus 1,7%, of m. longissimus thoracis 1,4%, of m. psoas major 1,8%.B) Age and body weight, Young pigs had significant less intramuscular fat than mature pigs. There were no differences between influence of age and influence of body weight.C) Breeding lines. Intramuscular fat content of the E+-line was about 16% higher compared with the E--line (statistical significance by m. longissimus thoracis). Intramuscular fat content of K°-line was calculated significantly 58% higher than E--line as well as 44% higher than E+-line.D) Feeding. Intramuscular fat showed the tendency to increase with higher levels of dietary energy, exceptionally for the ad libitum fed E--line.2. A method of planimetry was developed empirically for determination of marbling proportions. Photographs of histological sections (cryostat-cut, 25Nm, Sudan black stained) were measured. Planimetric results of 3 muscles showed 6 - 36% higher values than those of ether extraction; the recognized inverse tendency of m. semimembranosus (12% lower) is suggested to be due to an especially high rate of intrafibrillar fat droplets. High significant correlations were found between etherextracted and planimetric values (r = 0,55 - 0,86).The influences of muscle type, age, body weight, breeding lines and feeding, which were registrated by analysing the ether extract values, were essentially found by analysing the planimetrical values, too.Additionally, imm thick cross-sections of m. psoas major were measured. There was neither improvement nor crucial correction of the previous results from histological sections.3. Histological muscle preparations were also scored for marbling patterns. There were distinct differences in marbling due to age of the animals and muscle type, yet to a much lesser extend to feeding regime or breeding line. A) Muscle types. Marbling of m. semispinalis capitis was structured extremely coarse and distributed greatly unsymmetrically. Adipose tissue of m. semimembranosus and m. longissimus thoracis showed comparatively finer structures, which were distributed symmetrically as well as asymmetrically. Marbling of m. psoas major had finest structures and was distributed almost perfect, with certain exceptions for cranial localisations.B) Age and body weight. Marbling of young pigs was distinctly the finest, compared to all other pigs examined. C) Breeding lines. Marbling of control group (K°) showed a greater tendency to coarser and more asymmetrical structures than marbling of either E*- or E--line.D) Feeding. Generally, pigs fed higher energy levels had coarser marbled muscles.Cross-sections of m. psoas major showed very uniform structures of marbling. They were therefore graded into "thickness of fat islets" combined with "density of network". The resulting serial range showed a close correspondence to those of the planimetrical values not proving any additional statements.Photographs illustrating some of the marbling patterns are included.4. Correlations of intramuscular fat with specific data of pigs and traits of fat content in the carcass indicated that during growth period fat content in these muscles increases with fat content in the carcass (r = 0,52 - 0,62) and also with backfat thickness (r = 0,35 - 0,45), especially with respect to the part of the inner layer of subcutaneous adipose tissue (r = 0,36 - 0,51). 5. Using the data of the heavier pigs (100 - 135kg) correlations of intramuscular fat with specific measurements of rib eye muscle (planimetry, m. longiss., 13. rib) and dimensions of m. psoas major indicated: the thicker the muscle the less the intramuscular fat content. Contrary tendencies were found with respect to age, however.80% of the pigs had the highest fat content in the middle section of m. psoas major compared with the cranial and caudal localisation.