Comparative analysis of growth performance and rumen microbiota in Hu sheep and its three-way crossbred offspring

This study compared the growth performance, rumen fermentation patterns, and microbial community structure between three-way crossbred (Poll Dorset × Southdown × Hu, TNH) and purebred Hu (HH) sheep. A total of 75 male lambs (HH: n = 35; TNH: n = 40) with comparable birth dates were selected. After a 56-day suckling period, all lambs underwent an 84-day standardized fattening protocol with a uniform diet. Growth indicators were monitored, and rumen fluid was collected using an oral ruminal sampler for the determination of volatile fatty acids (VFAs) and 16S rRNA sequencing. TNH sheep demonstrated significantly superior growth performance, including higher body weight (BW), average daily gain (ADG) and Kleiber ratio (KR). TNH sheep exhibited an acetate-type pattern with higher acetate, butyrate, total VFAs, and acetate/propionate ratio (A/P), whereas HH sheep showed a propionate-type fermentation pattern with higher branched-chain VFAs. Bacteroidetes and Firmicutes were the dominant core microbiota in both the TNH and HH groups. However, the higher species richness and diversity in the TNH sheep was observed, and harbored a distinct community structure featuring Prevotella as the predominant genus. Shuttleworthia, Olsenella, and Syntrophococcus were unique to HH sheep, whereas Prevotellaceae_UCG_003 was specifically enriched in the TNH sheep. Metabolic pathways, carbon metabolism, and glycolysis/gluconeogenesis were predominantly enriched in TNH sheep, whereas biosynthesis of amino acids and ABC transporters were more abundant in HH sheep. These findings demonstrate that crossbreeding can optimize host metabolism and production performance by modulating rumen VFA dynamics and microbiota structure.