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Simple Summary: The study described the effects of Myostatin gene editing on cattle to improve the growth and muscle development of hybrid cattle offspring. We focused on the Myostatin gene, which plays a crucial role in regulating muscle development. Gene editing could be able to enhance the size and performance of the crossbred cattle. The results showed that the Myostatin gene-edited cattle offspring displayed improved body size parameters, particularly body weight, cross height, and hip height, indicating the significant development of the hindquarters. The edited cattle have "double-muscled" forequarters and hindquarters with clear muscle masses, and their coat color reverted back to the original yellow. The study also found differences in blood glucose, calcium, and low-density lipoprotein levels, as well as a decrease in serum insulin levels in the edited cattle. Overall, the findings suggest that breeding with these Myostatin gene-edited bulls improve growth and performance in crossbred cattle, benefiting both farmers and consumers. (1) Background: Myostatin (MSTN) is a protein that regulates skeletal muscle development and plays a crucial role in maintaining animal body composition and muscle structure. The loss-of-function mutation of MSTN gene can induce the muscle hypertrophic phenotype. (2) Methods: Growth indexes and blood parameters of the cattle of different months were analyzed via multiple linear regression. (3) Results: Compared with the control group, the body shape parameters of F2 cattle were improved, especially the body weight, cross height, and hip height, representing significant development of hindquarters, and the coat color of the F2 generation returned to the yellow of Luxi cattle. As adults, MSTN gene-edited bulls have a tall, wide acromion and a deep, wide chest. Both the forequarters and hindquarters are double-muscled with clear muscle masses. The multiple linear regression demonstrates that MSTN gene-edited hybrid beef cattle gained weight due to the higher height of the hindquarters. Significant differences in blood glucose, calcium, and low-density lipoprotein. Serum insulin levels decreased significantly at 24 months of age. MSTN gene editing improves the adaptability of cattle. (4) Conclusions: Our findings suggest that breeding with MSTN gene-edited Luxi bulls can improve the growth and performance of hybrid cattle, with potential benefits for both farmers and consumers. [ABSTRACT FROM AUTHOR]

Simple Summary: Myostatin (MSTN) gene knockout can increase lean muscle mass and has been widely used in livestock breeding. MSTN deficiency also regulates various metabolic processes. However, the effect of MSTN knockout on the liver, the largest metabolic organ, has not been reported. In this study, physiological and biochemical parameters of serum, untargeted and targeted metabolomics of MSTN+/− and WT cattle were studied, and we found that the knockout of MSTN could regulate liver metabolism and promote bile acid metabolism. This may be due to the enhanced expression of bile acid synthesis genes in MSTN+/− bovine livers. In conclusion, MSTN knockout regulated bile acid metabolism via enhanced bile acid synthesis. Myostatin (MSTN) is a major negative regulator of skeletal muscle mass and causes a variety of metabolic changes. However, the effect of MSTN knockout on bile acid metabolism has rarely been reported. In this study, the physiological and biochemical alterations of serum in MSTN+/− and wild type (WT) cattle were investigated. There were no significant changes in liver and kidney biochemical indexes. However, compared with the WT cattle, lactate dehydrogenase, total bile acid (TBA), cholesterol, and high-density lipoprotein (HDL) in the MSTN+/− cattle were significantly increased, and glucose, low-density lipoprotein (LDL), and triglycerides (TG) were significantly decreased, indicating that MSTN knockout affected glucose and lipid metabolism and total bile acids content. Targeted metabolomic analysis of the bile acids and their derivatives was performed on serum samples and found that bile acids were significantly increased in the MSTN+/− cattle compared with the WT cattle. As the only bile acid synthesis organ in the body, we performed metabolomic analysis on the liver to study the effect of MSTN knockout on hepatic metabolism. Metabolic pathway enrichment analysis of differential metabolites showed significant enrichment of the primary bile acid biosynthesis and bile secretion pathway in the MSTN+/− cattle. Targeted metabolomics data further showed that MSTN knockout significantly increased bile acid content in the liver, which may have resulted from enhanced bile acid synthesis due to the expression of bile acid synthesis genes, cholesterol 7 alpha-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1), and upregulation in the liver of the MSTN+/− cattle. These results indicate that MSTN knockout does not adversely affect bovine fitness but regulates bile acid metabolism via enhanced bile acid synthesis. This further suggests a role of MSTN in regulating metabolism. [ABSTRACT FROM AUTHOR]