Comparative Analysis of Fecal Microbiota and Metabolomic Profiles in Male and Female Leizhou Goats Offered a 10% Crude Protein Diet Among Four Energy Levels

The gut microbiota plays a crucial role in maintaining the host’s metabolism and can influence the host’s productivity. Both dietary composition and gender have distinct effects on the composition of the gut microbiota. Therefore, to investigate the differences in the structure and function of the gut microbiota between female and male goats, we analyzed their fecal microbiota and metabolites when fed a 10% crude protein diet at four different energy levels—7.01, 8.33, 9.66, and 10.98 MJ/kg DM. Four non-pregnant female and four male Leizhou goats (all 8 months of age) were used in the experiment, with an average body weight of 10.3 ± 0.8 kg for females and 13.6 ± 1.1 kg for males (mean ± SD). The animals were assigned to two separate 4 × 4 Latin square designs according to their gender, each consisting of four treatments and four 28-day periods, including 25 days of a dietary adaptation period and 3 days of fecal sample collection per period. The data were analyzed using the SAS statistical package and Pearson’s correlation analysis. The dominant phyla for all samples were Firmicutes and Bacteroidota, regardless of dietary energy levels or gender. Among fecal bacteria, <i>unclassified_f_Lachnospiraceae</i> was the dominant genus in the female goats, and <i>Oscillospiraceae_UCG-005</i> was the dominant genus in the male goats. The relative abundance of <i>unclassified_f_Lachnospiraceae</i> (<i>p</i> < 0.001), <i>Bacteroides</i> (<i>p</i> = 0.007), <i>norank_f_Ruminococcaceae</i> (<i>p</i> = 0.024), <i>Mediterraneibacter</i> (<i>p</i> = 0.001), and <i>norank_f_Muribaculaceae</i> (<i>p</i> = 0.008) was greater in the female goats than in the male goats. In contrast, the relative abundance of <i>Oscillospiraceae</i>_UCG-005 (<i>p</i> < 0.001), <i>Ruminococcus</i> (<i>p</i> = 0.035), <i>Monoglobus</i> (<i>p</i> = 0.006), <i>Oscillospiraceae-NK4A214_group</i> (<i>p</i> = 0.008), <i>norank_f_F082</i> (<i>p</i> < 0.001), and <i>Prevotellaceae_UCG-003</i> (<i>p</i> < 0.001) was lower in the female goats than in the male goats. The volcano plot showed that there were 153, 171, 171, and 183 differential metabolites between the female and male goats at dietary energy levels of 7.01, 8.33, 9.66, and 10.98 MJ/kg DM, respectively. Numerous correlations were observed between differential metabolites and microflora genera. We concluded that the non-pregnant female and male goats exhibited distinct metabolic abilities when consuming a 10% crude protein diet at four different energy levels. Interestingly, in the female and male goats, the fecal microbiota also showed some differing responses to the energy levels. These results provide a gender-based reference for formulating low-protein dietary strategies for 8-month-old Leizhou goats.