Effects Of MSTN Mutation On Growth And Carcass Performance In Duroc X Meishan Hybrid Population

There are many varieties of local pigs in China,which have the characteristics of strong resistance,good meat quality and high fecundity,but there are also some defects such as slow growth,easy fattening and low carcass lean meat rate.Due to the change of market demand for lean meat and the progress of livestock breeding technology,lean meat pig breeds gradually occupy a leading position in the world pork production industry.In order to meet the market demand for lean meat,China has introduced a large number of foreign lean pig breeds,such as Duroc,Landrace and so on.Due to the lack of production efficiency and the impact of foreign varieties,the utilization rate of excellent local pig breeds in China is getting lower and lower,the number is getting smaller and smaller,and some breeds are on the brink of extinction.Therefore,it is an urgent task for pig breeders to protect the local pig breeds,scientifically breed and hybridize them to meet the needs of market and modern commercial pig production.Meishan pig is a famous local pig breed in China,with outstanding reproductive performance,which is characterized by early sexual maturity,large number of piglets and obvious heterosis.After crossbreeding with lean boar,Meishan pig has strong disease resistance and fast growth.The dual hybrid sow basically maintains the high-yield characteristics of Meishan pig.In addition,Meishan pig is more and more popular in the market with its unique flavor and bright red meat color.However,the disadvantages of Meishan pig,such as slow growth and low lean meat rate,are difficult to meet the needs of modern commercial pig production,which greatly limits its development.Myostatin(MSTN)is a kind of secretory glycoprotein mainly expressed in the skeletal muscle of animals.It has a negative regulatory effect on the growth and development of skeletal muscle.The absence or mutation of MSTN will lead to multiple growth of muscle and increase of skeletal muscle mass.Its application prospect in animal husbandry is very wide,which is of great significance to control the muscle growth and improve the muscle quality of livestock and poultry.In recent years,some studies have reported that MSTN gene knockout pigs have been successfully obtained by using genome editing technology combined with somatic cell nuclear transfer technology.These MSTN gene knockout pigs have larger body size,obvious double muscle phenomenon can be observed,and the lean meat rate is significantly increased.However,due to the limitation of technology,the number of MSTN double allele knockout pigs(MSTN-/-)is small,and there is no accurate evaluation of carcass traits.Therefore,in this study,Meishan pig,a typical fat type local pig,was used as the research object.By crossing with Duroc boar with MSTN single allele mutation(MSTN+/-),a large number of MSTN mutant Duroc binary pig(MSTN+/+)and wild Duroc binary pig(MSTN+/+)were obtained.The carcass performance of the whole sib or half sib population composed of these two genotypes was measured.The results showed that:1.Effect of MSTN mutation on reproductive performanceThe litter size,live litter size,litter weight and the ratio of male to female of 6 Meishan sows were not abnormal:the total litter size was 73,9-15 per litter,which was normal;the total live litter size was 63,with a live litter rate of about 90%;the ratio of male to female was close to 1:1;the litter weight of Meishan sows also accorded with the characteristics of the first litter weight.After genotyping,wild type and MSTN mutant pigs were screened out.The detection of MSTN expression in muscle of two kinds of pigs showed that the expression of MSTN+/-pig muscle decreased significantly.2.Effect of MSTN mutation on growth performanceThere was no significant difference in body weight,daily gain and back fat thickness between MSTN+/+ and MSTN+/-pigs after 120 days feeding.There was no significant difference in body length,body height,chest circumference,abdominal circumference,tube circumference,hip circumference and other body size characteristics,and no obvious double muscle phenomenon was observed.3.Effect of MSTN mutation on slaughter performanceThe slaughter performance of the two genotype pigs showed that MSTN+/-pigs had better slaughter performance,and the slaughter rate,carcass lean rate,and loin muscle area of MSTN+/-pigs were significantly higher than those of MSTN+/+ pigs.Carcass fat rate,skin rate,bone rate,and average backfat thickness were significantly lower than MSTN+/+ pigs.It is worth mentioning that the carcass lean rate of MSTN+/-pigs is about 55%,an increase of about 7%,indicating that MSTN single allele mutations have greater application prospects in increasing the lean meat yield of local binary pigs.4.Effect of MSTN mutation on meat qualityThere was no significant difference between MSTN+/+ pigs and MSTN+/+pigs in pH,meat color and dripping loss,but MSTN+/+pigs intramuscular fat was significantly lower than MSTN+/+pigs.