Effects Of Surgical Tail Removal In Fat-tail Sheep On Carcass Traits, Fat Deposition, And Liver Transcriptome Differential Gene Expression

Fat-tailed sheep have adapted to nutritional environments that vary in energy throughout the year by developing a tail capable of storing energy as fat in times of good nutrition and mobilizing that energy in times of poor nutrition. To evaluate the effects of tail docking in fat-tail sheep on carcass traits and fat deposition, 18 Lanzhou fat-tailed lambs and 18 Mongolian ram lambs were included in the trial. Nine lambs of each breed were randomly selected for tail docking(treatment group) and 9 sheep of each breed were left with intact tails(control group). All sheep in the trial were harvested at the age of 15 months. The carcass merit of each sheep was evaluated, and fat from different fat depots was excised and weighed. The longissimus dorsi muscle was also sampled and analyzed to estimate meat quality in the sheep. Liver tissue of Lanzhou fat-tailed sheep was sampled at harvest to validate the differential gene expression of transcriptomes by using real-time quantitative polymerase chain reaction method(RT-q PCR), which were screened using RNA-Seq technology by our team. The association analysis between differential gene expression and carcass fat weight was also studied. The results and conclusions obtained in the trial were as follows:(1) There was a significant trend on the backfat weight and GR value in Lanzhou fat-tailed sheep with tail removal(P<0.10), and no significant effect on the slaughter performance of the Mongolian sheep. We drew a conclusion that there was an obvious difference on slaughter performance between Lanzhou fat-tailed sheep and Mongolian sheep.(2) There was a significant trend on the pressing loss and shear force, which were significantly decreased, the p H1 value was increased in Lanzhou fat-tailed sheep with tail removal(P<0.10), and no significant effect on the meat quality of the Mongolian sheep. The pressing loss and shear force in Lanzhou fat-tailed sheep were significantly lesser than the Mongolian sheep(P <0.05). What’s more, the cooked meat rate and p H1 value were significantly greater than the Mongolian sheep(P <0.05), which indicated the meat quality in Lanzhou fat- tail sheep was better than the Mongolian sheep.(3) The weight of rump fat, testicular fat, omental and mesenteric fat and internal fat were significantly increased in Lanzhou fat-tailed sheep with tail removal(P <0.05), but the total fat weight of sheep with tail was significantly greater than the sheep with tail removal(P <0.05). The total fat weight of Mongolian sheep was significantly decreased with tail removal(P <0.05), and no significant difference among other fat tissues. Lanzhou fat-tailed sheep and Mongolian sheep have distinct specificity on fat deposition.(4) The gene expression of SLC38A11 and SMIM24 genes in Lanzhou fat-tailed sheep with tail removal were significantly increased(P <0.05), while the ETTA2 and TGM3 genes were decreased significantly(P <0.05), there was a significant decreasing tendency on the TYMS gene(P <0.10), and no significant difference on the PIM1 gene.(5) There was a highly significant correlation between the gene expression of SLC38A11 gene and the weight of omental and mesenteric fat and internal fat in Lanzhou fat-tailed sheep with tail(P <0.01), the tail and rump fat weight and perirenal fat weight were significantly positively correlated in Lanzhou fat-tailed sheep with tail(P <0.05); The correlation between gene expression of SMIM24 gene and the weight of testicular fat and perirenal fat were significantly positive in Lanzhou fat-tailed sheep with tail removal(P <0.05); The gene expression of EAAT2 gene and tail fat weight,tail and rump fat weight significantly positively correlated in Lanzhou fat-tailed sheep with tail removal(P <0.05); There also showed a significantly positive correlation between gene expression of PIM1 gene and tail fat weight in Lanzhou fat-tailed sheep with tail removal(P <0.05).