Effects of Concentrate Feeding Sequence on Growth Performance, Nutrient Digestibility, VFA Production, and Fecal Microbiota of Weaned Donkeys

Abstract

In this study, effects on the growth performance, nutrient digestibility, volatile fatty acids (VFA) production, and fecal microbiota of weaned donkeys were observed using different concentrate feeding sequences. Fifteen healthy 6-month-old weaned male donkeys with a body weight of 117.13 ± 10.60 kg were randomly divided into three treatment groups, including group C1 (roughage-then-concentrate), group C2 (concentrate-then-roughage), and group C3 (total mixed ration, TMR). The experiment lasted 35 d. We measured nutrient digestion by the acid-insoluble ash method and analyzed the fecal microbiota of the weaned donkeys by high-throughput sequencing of 16s rRNA genes in the V₃-V₄ region. The results show that group C3 obtained the best growth performance, and the digestibility of crude protein (CP) and crude extract (EE) was significantly higher than that of group C1 (p < 0.05). Acetic acid, isobutyric acid, valeric acid, isovaleric acid, and caproic acid were notably different among all groups (p < 0.05). In addition, we observed that Firmicutes and Bacteroidetes were dominant in the fecal microbes of each group, and Firmicutes was significantly higher in group C3 (p < 0.05). At the genus level, the different genera were Treponema, Rikenellaceae-RC9-gut-group, Unidentified-F082, and Bacteroidales-RF16-group (p < 0.05). The prediction of fecal microbiota function by PICRUSt indicated that different feeding sequences had minimal impact on the function of the fecal microbiota, particularly on the high-abundance pathway. In summary, the concentrate feeding sequence changed the composition of the fecal microbe of weaned donkeys.

Keywords: VFA; acid-insoluble ash; microbial composition; nutrient digestibility; weaned donkeys.

Figure 1

Species relative abundance histogram. (a) Relative abundance of fecal microbial species in weaned donkeys at the phylum level (top 10); (b) relative abundance of fecal microbial species of weaned donkeys at the genus level (top 10).

Figure 2

Microbial community analysis of fecal microbiota. (a) Principal coordinates analysis (PCoA) was carried out based on weighted−unifrac distances with p−values of anosim to highlight the differences in the fecal microbiota communities of the three groups. (b) Linear discriminant analysis (LDA) value−distributed histogram, only taxa meeting an LDA significant threshold > 4 are shown. (c) Cladogram constructed to visualize the microbial community relative abundance data of the three groups.

Figure 3

Functional predictions of the intestinal microbiota using PICRUSt. (a,b) Relative enrichment of KEGG level 1 and level 2 pathways in intestinal microbiota of donkeys with different concentrate feeding sequences. (c,d) Corresponding heatmaps for KEGG level 1 pathways and KEGG level 2 pathways.