| Muscle fibers is the basic unit of muscle, its characteristics had directly effect on quality of meat products. To improve the meat quality, lots of researches were focused on adjusting the type of muscle fiber composition and muscle fiber size nowadays. The variety of muscle fiber characteristics(fiber type composition, total number of fibers, diameter and cross-sectional area of different types)affected by the change of growth months, meat sample collecting spot, gene and weight of bamei sheep in different age and weight were studied in this project, to reveal the effect of characteristics of muscle fiber and glycolytic potential on meat quality traits, and provide basic theory and data for better quality control on bamei sheep raising in the future. The result showed as followed:Bamei sheep of 4,5,6,8 and 12 months old was picked to study the muscle fiber characteristics, which showed that as the growing months increased, muscle fiber diameter increased in the different parts of the sheep, muscle fiber density decreased, oxidation type fiber proportion reduced, glyco lysis type fiber proportion increased. Concluded from the change trend of muscle fiber characteristics from different growth stages, The change slowed after 8 months old, but proportion of type Ⅰ muscle fibers was still high, which were 8.46%,18.79% and 18.31% in longissimus doris, biceps femoris and triceps brachii respectively, so bamei sheep of 8 months old have better mutton quality from the perspective of muscle fiber type distribution.Comparing the muscle fiber characteristics of bamei sheep, small tail han sheep and sunite sheep of the same months old, the results showed that muscle fiber density of bamei sheep was higher than the small tail han sheep (p< 0.05), number proportion of type Ⅰ in biceps femoris of bamei sheep was 18.79%, significantly higher than sunite sheep and small tail han sheep (p< 0.05), area proportion of type Ⅰ was 11.84%, significantly higher than sunite sheep (p< 0.05), diameter of type Ⅰ was 44.03μm, cross-sectional area was1504.74μm2, significantly higher than sunite sheep (p< 0.05). Number proportion of type ⅡA was 10.14%, significantly higher than the small tail han sheep (p< 0.05). Number proportion of type ⅡB was 72.18%, significantly less than sunite sheep and small tail han sheep (p< 0.05), diameter of type ⅡB was 55.83μm, cross-sectional area was 2485.38μm2, significantly higer than the sunite sheep and small tail han sheep (p < 0.05). So bamei sheep had higher yiled production potential with a higher proportion of oxidative fiber.Two ways to study different weight of the mutton sheep muscle fiber characteristics were proceeded in this research project, which were ATP enzyme staining and MyHC mRNA method. The results showed that with the increasing of body weight, the diameter of all kinds of muscle fiber grew bigger, muscle fiber density decreased, number proportion of oxidation fiber reduced, glycolysis fiber increased, but growth slowed down after bamei sheep grew up to 40～50 kg. The number percent of type Ⅰ was 4.10%, 14.58% in the Longissimus doris, triceps brachii respectively collected from 40～50 kg weight bamei sheep, significantly higher than from 50～60 kg body weight (p< 0.05), which meant that bamei sheep with moderate weight has a higher proportion of oxidative fiber than bamei sheep with high weight. It was also confirmed that the both of two methods mentioned above can effectively reflect the characteristics of muscle fiber and showed similar patterns.Postmortem glycolysis is the first selection to reveal the internal relations between muscle fiber type composition and meat quality. Glycolytic potential affected by growth months, breed, body parts, body weight, etc. The influence from gene and the body part was larger, the influence of glycolytic potential value lined as:Longissimus dorsi> biceps femoris> triceps brachii. Glycolytic potential value of different varieties lined as:bamei sheep> sunite sheep> small tail han sheep, the difference was significant (p< 0.05).There were close connection amongst muscle fiber characteristics, potential glycolysis and meat quality, muscle fiber density and shear force value negatively correlated (p< 0.05), and the area proportion of type Ⅰ in biceps femoris and triceps brachii of bamei sheep positively correlated with degree of red a* value (p< 0.05). Cross-sectional area of type Ⅰ and rib eye area were positively correlated (p< 0.05), number percent of type Ⅱ B was positively correlated with carcass weight (p< 0.05)in longissimus doris and biceps femoris muscle. Proportion of type Ⅱ B in different body parts were negatively correlated with pH24(p< 0.05), positively correlated shear force value(p< 0.05), and were positively correlated with glycolytic potential(p< 0.05).This study creatively apply two methods which were the ATP ase staining and MyHC mRNA expression on analyzing muscle fiber characteristics of sheep, proposed the possibility to manipulate the constitution of muscle fiber type at the last stage of raising sheep, and was the first one in meat science to elaborate the key factor of determine mutton quality in the field of histology and physiology after slaughter. The entire conclusion could be used as scientific support on local resource utilization and high quality mutton production. |
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