Effects of Dietary Digestible Energy Levels on Milk Performance, Rumen Fermentation, and Rumen Microbiota in Lactating Bactrian Camels from Southern Xinjiang

This study aimed to investigate the effects of different dietary digestible energy (DE) levels on lactation performance, rumen fermentation, and rumen microbiota in lactating Bactrian camels in southern Xinjiang. Twenty-four mid-lactation Bactrian camels were randomly assigned to four groups, with six camels per group, and were fed diets containing DE levels of 12.25 (CK), 12.49 (LE), 12.74 (ME), and 12.99 MJ/kg (HE), respectively. The experiment lasted 60 days, including a 15-day adaptation period and a 45-day experimental period. Metagenomic sequencing was performed to characterize the composition and functional gene profiles of the rumen microbiota. The results showed that increasing dietary DE significantly increased milk yield, milk fat yield, and lactose yield (p < 0.05), while decreasing ruminal NH3-N concentration. Propionate and butyrate concentrations were significantly higher in the HE group (p < 0.05). No significant differences were detected in rumen pH or the concentrations of acetate, valerate, and total volatile fatty acids among treatments (p > 0.05). No significant differences were detected in rumen microbial α-diversity or overall community structure among dietary DE treatments, although several bacterial genera showed differential enrichment. No significant differences were detected in the relative abundances of genes assigned to the major KEGG pathways or CAZy families among dietary treatments. In conclusion, within the dietary range examined in this study, higher DE was associated with greater lactation performance and changes in rumen fermentation, while no significant differences were detected in the overall rumen microbial community structure or the relative abundances of genes assigned to the major KEGG pathways and CAZy families.