| Hulun buir sheep is a meat-type breed of Mongolian grassland in China after a long period of natural and artificial selection,with growth and development fast,walking feeding,strong ability to sink fat and good quality meat and other characteristics.It can be divided into two strains(the baer hu strain is semi-elliptical tail and the short-tailed strain is small peach tail)according to its tail features.Among them,the tail of the baer hu strain was significantly larger than that of the short-tailed strain.The difference in tail type is mainly caused by tail fat deposition,but the dynamics of fat deposition and its mechanism is not clear.Here,21 of the 4 to 5-month-old Hulun buir sheep were selected under the same feeding and management conditions(including 11 baer hu sheep,6 raws,5 ewes,10 short-tailed sheep,5 rams,5 ewes).The body weight,body size and tail trait were measured,and the population genetic differentiation index(FST)was analyzed according to the D-loop sequence of mtDNA.After the slaughter,the adipose tissue of eight different parts(shoulder,intramuscular,abdomen,waist,omental,tail,rump and renal)were selected and analyzed.The morphological differences of adipocytes were analyzed by tissue biopsies.The content of triglycerides in different fat tissue of the two strains were compared.The mRNA expression of PPAR?,ATGL,CEBP/? and SREBP were detected by qRT-PCR in different adipose tissue.The main research results were as follows.1.The results of variance analysis showed that the body weight,body size and tail traits(tail weight,tail length,tail width and tail circumference)of the baer hu strain was significantly higher than those of the short-tailed strain(P<0.01),and there were significant differences in body weight,body size and tail traits between the two strains.The effect of gender on body weight and body size was significant among the two trains(P<0.05).2.The genetic differentiation index(FST)of different strains showed that the FSTvalues between the two strains of Hulun buir sheep and the other breeds were greater than 0.25,indicating that there were great genetic differentiation between Hulun buir sheep and other breeds.The FST in the two strains of Hulun buir sheep was 0.042,indicating a certain degree of differentiation in the two strains.3.Adipocytes morphology analysis showed that the diameter,area and volume of visceral and tail adipocytes in different sex of the two strains were higher than those in the subcutaneous adipose adipocytes,so it indicatated that in the early growth of sheep fat was mainly pull down in visceral peripheral deposition.There were significant differences in the diameter,area and volume of adipocytes between the Hulun buir Baer hu strain and the short-tailed strain(P<0.05).There were significant differences in the area and volume of adipocytes between different locations(P<0.05),but there was no significant difference in gender(P>0.05).4.Determination of triglyceride(TG)in different parts of fat tissues,the results showed that the two strains of Hulun buir sheep triglyceride relative content in the omental fat,subcutaneous fat,liver and tail fat were significantly difference(P<0.05).In baer hu strain of hulun buir sheep,the content of triglyceride was higher in the perirenal,omental and tail fat,and the content of triglyceride was lower in the liver and longissimus dorsi.In the short-tailed strain,the content of triglyceride was higher in the subcutaneous adipose tissue,liver and longissimus dorsi were lower.5.qRT-PCR showed that in baer hu and short-tailed strains of hulun buir sheep,ATGL gene mRNA expression level in perirenal fat,subcutaneous fat,omental fat and liver fat was significant difference or extremely significant difference(P<0.05 or P<0.01),and the expression level of PPARy mRNA in omental fat,intramuscular fat,tail fat and liver was significantly difference(P<0.05 or P<0.01).The C/EBP? gene was significantly difference in perirenal fat,subcutaneous fat,omental fat and tail fat(P<0.05).The mRNA expression of SREBP gene in the perirenal fat,omental fat,intramuscular fat and liver were significantly difference(P<0.05).The four genes were not significant in the longissimus dorsi.6.Correlation analysis of PPAR?,C/EBP?,ATGL and SREBP mRNA expression and TG content in the adipose tissue indicated that the expression of ATGL in adipose tissue was negatively correlated or weakly positively correlated with TG,but there is a significant positive correlation(P<0.05)in longissiimus dorsi.PPAR? gene expression in perirenal fat was positively correlated with TG(P<0.05),and the PPARy expression in tail fat and liver is positively correlated with TG.The C/EBPa expression in intramuscular fat,tail fat,and longissimus dorsi is positively associated with TG,and there was a significant positive correlation(P<0.05)between the longissimus dorsi and TG in the baer hu strain(P<0.05),and a significant negative correlation(P<0.05)in the subcutaneous fat(P<0.05);The expression of,SREBP gene was significantly positively correlated with TG(P<0.05)between in baer hu strain and short-tailed strain. |
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