http://directory.umm.ac.id/Data%20Elmu/jurnal/L/Livestock%20Production%20Science/Vol66.Issue2.Oct2000/1947.pdf

Myogenesis and postnatal skeletal muscle cell growth as influenced by selection

Quantitative (muscle fibre number and cross-sectional areas) and qualitative (myosin isoforms and metabolic enzyme activities) characteristics of two muscles, M. pectoralis major and M. anterior latissimus dorsi, were compared among male chickens of two lines during growth from hatching to adulthood. The lines were derived from a divergent selection based on growth rate. The two muscles were chosen on the basis of their histochemical profile. Pectoralis major muscle contains only fast contracting muscle fibres whereas anterior latissimus dorsi muscle is almost entirely made up with slow contracting fibres. At both ages, the two lines showed similar fibre type distributions. At hatching, fibre cross-sectional areas were equivalent in the two lines, but after the first week, animals from the fast growing line exhibited wider fibre areas, whatever the muscle, than animals from the slow growing line. The total number of fibres in a muscle was found greater in the fast growing line, irrespective of whether it was exactly determined (anterior latissimus dorsi muscle, +20%) or only estimated (pectoralis major muscle). This number remains constant in the two lines throughout the growth. Myosin isoform profiles and metabolic enzyme activities were similar in the two lines, at both ages, and were in good agreement with the histochemical muscle fibre profiles.

Selection for rapid growth increases the number and the size of muscle fibres without changing their typing in chickens.

Publisher Summary Cell size, the nucleocytoplasmic ratio, and the DNA content of the nucleus are mutually interdependent. It is, therefore, justifiable to use the data on one of these features for the approximate determination of the other two. In the evolutionary process, every factor that favors a change in one of these characters influences the state of the other two. For vertebrates, the primitive DNA content was probably not very different from the actual state in Latimeria , many elasmobranchs, and some anurans. It is moderately reduced in mammals. In Dipnoi and Urodela , DNA content and cell size are greatly increased. A reduction in both these features occurred in reptiles, birds, and the majority of teleosts. Regularities occur in the cell size of passerine birds, which suggest that they are indispensable for a high metabolism. The diverse levels of cell-size variability in other vertebrates demonstrate that natural selection may be indifferent to changes in cell size unless they are fairly pronounced. Natural selection could have decreased cell size and DNA content when it favored a decrease in overall size of the organism, speed of development, high metabolism, and rejection of unused genetic information. An increase in DNA content and in cell size could be favored as a means of economizing in structural material with an enlargement of the body and a reduction in maintenance costs. It could confer a greater resistance of cells to changes in the composition of body intercellular fluids.

Cell Size and Nuclear DNA Content in Vertebrates

An experiment was conducted in 1995 in order to examine muscle growth, muscle histochemical properties, muscle metabolism and meat quality of two types of Danish Landrace pigs representing the growth potential of years 1976 and 1995, respectively. Danish Landrace pigs representing 1976 (slow-growing, SG) originated from a breeding station where the population was maintained without being selected for production traits such as daily gain, food conversion ratio and meat content. Pigs representing Danish Landrace of 1995 (fast-growing, FG) were bought from certified Danish pig breeders. The pigs were simultaneously tested for performance from 40 to 95 kg live weight. The daily gain, food conversion ratio and meat content of the carcass were improved proportionately by 0·43, 0·24 and 0·03 in FG pigs compared with SG pigs. In m. longissimus dorsi (LD), the cross-sectional area of muscle fibres was smaller in FG pigs compared with SG pigs indicating increased muscle fibre number. Data further suggest increased satellite cell proliferation in muscles of FG pigs. Serum from FG pigs stimulated the proliferation of C2C12 muscle cells to a greater extent than serum from SG pigs, although the serum level of insulin-like growth factor 1 did not differ between pig types. The effect of serum on protein turn-over of C2C12 myotubes did not depend on pig type. The glycogen concentration in the LD did not differ significantly between pig types, while the activity of citrate synthase, 3-OH-acyl-CoA-dehydrogenase, and lactate dehydrogenase were higher in the LD of SG pigs compared with FG pigs. Pork chop colour of FG pigs was proportionately 0·09 lighter (L⋆) and 0·13 less red (a⋆) than pork chops of SG pigs. The total muscle pigment concentration in the LD, m. biceps femoris and m. vastus intermedius was proportionately reduced by 0·17, 0·19 and 0·11, respectively, in FG pigs compared with SG pigs. In the LD, the concentration of myoglobin was proportionately reduced by 0·17 in FG pigs. The chemical composition of the LD differed between pig types such that the water content was higher and protein content lower in LD from FG pigs compared with SG pigs. The pH of the LD measured 45 min and 24 h post mortem, drip loss and thawing loss were similar for both pig types. Meat tenderness of conditioned pork chops of FG pigs was slightly reduced in accordance with a decreased intensity of the 31 kDa peptide band and increased cooking loss. The present study suggests that increased muscle fibre number and rate of muscle DNA deposition (satellite cell proliferation) have contributed to the increased muscle growth as a result of selection for performance in pigs under Danish conditions. However, the increase in growth performance was accompanied by deterioration in muscle colour and slightly reduced tenderness.

Long-term changes in performance and meat quality of Danish Landrace pigs: a study on a current compared with an unimproved genotype

1. Histochemical (fibre type distribution and areas) and biochemical (myosin isoforms) characteristics of three muscles, M. anterior latissimus dorsi, M. pectoralis major and M. sartorius, were compared among male chickens of two lines at 11 and 55 weeks of age. 2. The lines were derived from a divergent selection based on growth rate. Cockerels from the Fast Growing Line (FGL) were 2‐3 times heavier than those from the Slow Growing line (SGL) when 11 weeks old and 1–7 times at 55 weeks of age. The latter age was chosen as representative of the adult stage and the 11‐week age because, at this time, FGL cocks weighed as much as SGL cockerels at 55 weeks. 3. At both ages, the two lines showed similar fibre type distributions, but the total number in the ALD muscle, and the size (cross‐sectional areas) of fibres in each muscle were higher in the FGL compared with the SGL (14–6% and 33% more at 11 and 55 weeks of age respectively in favour of the FGL birds). 4. The two lines displayed similar myosin ...

Effects of divergent selection for body weight on three skeletal muscles characteristics in the chicken.

The effects of selection for increased or decreased body weight in mice, at 5 or 10 weeks of age, on the fibre number, fibre diameter and weight of the m. sternomastoideus and m. anterior tibialis muscles were studied. Unselected control mice were also included. Significant effects were detected in the case of each of the traits. However, the magnitude of any particular correlated response to selection varied between muscles and between selection ages in an unsystematic fashion. Most of the changes in muscle weight resulting from selection were attributable to positively correlated changes in fibre number but they were also accompanied by changes in fibre diameter in some cases. The correlated responses described indicate the difficulty of predicting how selection for body weight changes will influence cellular structure of any given muscle. Phenotypic correlations between muscle fibre number and diameter were essentially zero. The phenotypic correlations between muscle weight and fibre number and fibre diameter were positive. Sex had no effect on fibre number but had an effect on fibre diameter which depended on the particular muscle and the age of the animal.

A. C. Hooper

Papers

Effects of divergent selection for body weight on fibre number and diameter in two mouse muscles