STRUCTURAL DIFFERENCES BETWEEN WHITE AND RED MUSCLES OF BIRDS

Histochemical parameters of white breast muscles of turkeys and chicke ns and of red breast muscles of goose and pigeons as well as of red le g muscles of these species were analyzed and compared in our work. Mus cle fiber types were determined in m, pectoralis major (MPM) and in m. semimembranosus (MSM) based on the reaction on succinate dehydrogenas e (SDH) and on histochemical reaction to the myoglobin content, glycog en was determined by PAS reaction and lipids were stained by using oil -red O and Sudan III-IV. We confirmed the significantly higher frequen cy of white fibers in MPM of turkey and chicken (97% and 95%, respecti vely) when compared with corresponding muscles of goose and pigeon (47 % and 18%, respectively). We found that so called red muscles represen ted by MSM also contain relatively high percentage of the white fibers , as high as 70% in the turkey and 71% in the chicken, 59% in the goos e and 61% in the pigeon (Fig. 1). Average thickness of muscle fibers i n turkeys and chickens is high, ranging from 78.5 to 95.4 mu m, while in the muscles of goose and pigeon it is about 31.5 and 58.8 mu m, res pectively (Tab. I). Higher occurrence of myoglobin in red fibers was c onfirmed by histochemical methods. The distribution of glycogen obtain ed by histochemistry fluctuates, probably as a result of its depletion during the slaughtering of the animals. Intensity of this reaction, c ontrary to the myoglobin, is also different in the muscle fibers of th e same type. The size of the lipid cells is about the same in differen t muscles of the same species and also in all investigated animal spec ies, with the exception of the pigeon. In MPM it ranges from 33.8 to 4 1.5 mu m, in MSM from 32.8 to 45.3 mu m, white in the pigeon their siz e is 30.0 or 28.1 mu m (Tab. II). The lipid droplets are histochemical ly well provable in goose red muscles. We also determined the approxim ate numbers of capillaries surrounding the single fibers on the slices stained by hematoxylin eosine and Masson trichrom. The number of capi llaries surrounding the red fibers is higher by 46% when compared with the number of capillaries surrounding the white fibers. The differenc es in the occurrence of muscle fiber types of investigated birds influ ence qualitative parameters of meat. In our work we discuss these diff erences, especially in relation to the anaerobic metabolism of white f ibers and the oxidative metabolism of red fibers and their influence o n the meat quality.