Difference Analysis of Blood Biochemistry, Slaughter Performance and Gastrointestinal Microbiota in Small-Tailed Han Sheep of Different Sexes

This study explored the differences in slaughter performance, blood biochemical indices, and ruminal and colonic microbiota between 6-month-old male and female Small-tailed Han sheep, a typical meat-wool dual-purpose breed in China. Twenty weaned lambs (10 males and 10 females) with uniform body condition were reared under unified feeding management until 6 months of age, followed by slaughter sampling and microbial sequencing detection. Results showed that male lambs had significantly higher pre-slaughter live weight, carcass weight and serum ALP content than females (p < 0.05), with lower BUN and β-BHBA levels (p < 0.05). High-throughput sequencing of the 16S rDNA gene in rumen fluid and colon contents revealed that microbial alpha diversity in the rumen was extremely significantly higher than that in the colon (p < 0.01), and their microbial community structures were distinctly separated (p = 0.001). Sex had no significant effect on overall microbial diversity, but altered specific flora and functional pathways: male rumen had higher Actinobacteriota abundance, while female colon had enriched galactose metabolism and male colon had enhanced folate-mediated one-carbon pool pathway. These findings clarify the tissue specificity of gastrointestinal microbiota and sex-related phenotypic differences, providing a theoretical basis for sex-specific feeding of Small-tailed Han sheep.