An analysis of factors influencing post-natal growth and development of the muscle fibre

摘要: 1. An investigation is described in which the effect of both technical and physiological factors on muscle fibre size was examined. Size determined by measuring cross-diameter 16,450 individual fibres means an ocular micrometer. In cases where animal represented a single sample, 100 were measured, otherwise fifty measurements recorded per sample. 2. The material consisted samples always taken from same position along length immediately afterwards fixed for varying periods time 10% formalin. Samples obtained various sources, principally experiments conducted past at School Agriculture, Cambridge, but also slaughterhouses contemporary investigations. These latter treated manner to ensure consistency. 3. From results formalin fixation diameter, carried out mature buck rabbit, it tentatively concluded that although shrinkage does occur only slight; difference between fresh compared with being non-significant statistically. Shrinkage apparently ceased as soon fixative had penetrated since no further changes could be detected after prolonged fixation. 4. used study heat. Application heat (boiling) matter seconds caused immediate, highly significant, shrinkage.of fibres, continued heattreatment resulted changes. Though lose its characteristic striated appearance, there signs disintegrating or sarcolemma becoming detached protoplasmic contents. 5. previous investigations deduced measurement sample provides reliable mean value representative indication dispersion given muscle, age. Results present demonstrated slight tendency larger measured period observation proceeds, factor should guarded against. 6. species diameter examined comparing m. gastrocnemius pig, sheep cattle birth maturity. Only male animals included comparison. It shown relation exists body either At rabbit rather similar-sized while those pig respectively smaller diameter. maturity largest followed decreasing order sheep. accounted degree post-natal development weight particular species. 7. breed studied two groups steers, one consisting Dairy Shorthorns Shorthorn-crosses, other Friesians Friesian-crosses. available longissimus dorsi each thirty-four animals: their crosses significantly thicker than pure- cross-bred Shorthorn steers. differences existed respective pure-bred animals; Friesian × Angus Angus, Hereford Hereford, though fairly distinct, were, however, not statistically significant. 8. age investigated group forty-one lambs different nutritional status sex, ranging 290 days. Muscle increase general age, consistent decline coefficient variation regarded indicative fact muscular growth during life occurs essentially hypertrophy number birth. 9. Correlating corresponding weight, indicated primarily function strictly chronological significant correlations established carcass weights, strongest correlation exist former variate weight. However, even higher square attempted, linear regressions, indicate contribution increments need is, apparent; insufficient data made impossible elucidate this point altogether. relationships confirmed analysis twenty breed, all slaughtered 112 days age; heavier lighter counterparts, very nearly proportional muscle. 10. Sex basis alone 13·6 kg. high-plane wethers slightly female despite musculature. This ascribed (as bone measurements), composition chemical analyses presented prove muscles contain greater amounts intra-muscular (chemical) fat, hence apparent increases component fibres. 11. nutrition ewes influence appreciably ages. differences, favour lambs, statistically, probably due small numbers groups. supermaintenance diet increased proportion total submaintenance opposite found. appeared continuation treatment would have little additional prolongation considerable 12. absolute relative dorsi, rectus femoris gastrocnemius. possessed smallest. On whole, situated late maturing part body, showed greatest life, gastrocnemius, earlier latest. average, maturity, smallest measure. Comparing develop under high low planes nutrition, low-plane days, resembled 60-day-old counterparts anatomical development. animals, early benefit most initially diet; later stages experiment, increases, ration, reduced rate muscles. Individual variation, extremely difficult generalize subsequent stages. 13. width depth (or ‘eye muscle’) junction thoracic lumbar vertebrae, dimension less affected depth. found depth, more strongly correlated thickness 14. has been suggested work nature might provide suitable estimating amount tissue carcass; such relationship great assistance students meat physiology who resort laborious dissection techniques composition. obvious, species, possibly considered attempt establish kind. Furthermore, test demand consideration, influenced degrees nutrition. A furnish criterion; light evidence produced study, sampled regions suitable.