Study On The Developmental Characteristics Of Skeletal Muscle Tissue In Sheep Fetal

With the rapid development of sheep industry,people pay more and more attention to the quality of mutton.There are many factors affecting meat quality.The histological structure of skeletal muscle fiber is one of the key factors to determine meat quality.Fetal period is the key period to determine the performance of meat production,the number and diameter of muscle fiber in the fetal period affect the growth and development of skeletal muscle for a lifetime,and fiber type and proportion has formed in the fetal period.Present studies on fetal skeletal muscle development foused on mice and pigs,less on ruminant animal.To clear the developmental characteristics of skeletal muscle in fetal sheep,will play an important role of scientific theoretical guidance on meat performance and improvement of meat quality.In order to comprehend the formative and developmental pattern of fetal muscle fibers,this study explored the developmental characteristics of histological structure between sheep breeds and under the restrictive maternal nutrition condition.This study selecting the critical pregnancy stage of fetal development measured fetal body size and took samples of fetal longissimus muscle to perform histological analysis by tissue paraffin embedded method and H.E.staining.The fetal muscle fiber number,diameter and density of different developmental stages were calculated from imaging pictures and the fast and slow muscle fiber number and density of the longissimus muscle were identified using immunohistochemical method.The results of this study are as follows:(1)This study indicated that the formation of primary muscle fibers between Chinese merino sheep is about 32 d-55.55-85 d fetal skeletal muscle development is mainly manifested in the increase in the number of muscle fibers,and the development of fetal skeletal muscle after 85 d period is mainly manifested in the increase in muscle fiber diameter.The primary fiber diameter decreases with the increase of days,while the secondary fiber diameter increased with the increase of the number of days of pregnancy increased,and the secondary fiber diameter was positively correlated with fetal carcass weight.The early development of the muscle fiber types in China and the United States was mainly slow muscle(type I muscle fiber).(2)The results of this study show that the German Merino sheep fetal sheep 75 d muscle activities behind the Chinese Merino sheep fetal muscle fiber,the number reached a peak in the 105 d stage,the number of muscle fibers to 105 d constant.At 135 d,the sheep muscle fiber density was significantly better than that of Chinese Merino,muscle fibers are closely and evenly arranged.75 d and 135 d's sheep and Chinese Merino per unit area,the number of muscle fibres had extremely significant difference(P < 0.01),105 d and 135 d in German Merino sheep and Chinese Merino unit area of muscle fiber diameter significantly(P < 0.01).The German Merino sheep fetal sheep muscle fiber development model and Chinese Merino sheep are different,the difference on this model development may cause the meat production performance level.The sheep and Chinese Merino in different developmental stages of fast skeletal muscle number had extremely significant difference(P < 0.01),that there are differences in muscle fiber type variation between different varieties.(3)The experimental results show that the maternal pregnancy nutrition restriction will cause serious impact on fetal development of muscle fiber,resulting in fetal muscle fiber diameter decreased significantly(P < 0.01),late pregnancy were no obvious differences in maternal nutrition restriction.The results showed that maternal nutrition restriction at different stages had different effects on muscle development.In the middle stage of pregnancy,the rapid development of the fetal fast muscle was delayed by maternal nutrition restriction.The number of slow muscle decreased with the number of days of pregnancy.The results showed that maternal nutritional level had some influence on the type of fetal muscle fiber.