The Alpha diversity indices of the Boschveld indigenous chickens’ microbial communities at days 60 and 90 of collection, according to the three different sorghum varieties fed.
In the current study, the differences between the species communities were presented according to the Observed, Shannon, and Simpson indexes at days 60 and 90 of sample collections, as reflected in Fig. 1 (A). The Observed and Shannon diversity indexes, known to demonstrate the abundance of bacterial species present, revealed all three sorghum varieties to have more bacteria varieties on day 90 than on day 60. Regardless of the sorghum variety offered to chickens, the two measures gradually increased from days 60 to 90, suggesting that the diversity of bacteria in each sample grows as the chickens get older. However, the summary of the Simpson diversity index, which measures the species diversity considering the number of species present, showed more bacterial species on day 90 than 60. This pattern was noted in chickens fed any of the three sorghum varieties.
Alpha diversity was also calculated at different inclusion levels of the sorghum varieties (presented in Fig. 1 (B)), where bacteria were in abundance in the group of chickens offered feed with a 50% (level 3) inclusion of red and white sorghum varieties at observed, Shannon and Simpson diversity indexes. The group of chickens that was offered 25% (level 2) of the red and white sorghum varieties inclusion had the lowest bacterial counts at observed and Shannon indexes. However, the bacteria abundance and diversity of the chickens fed brown sorghum variety was highest in chickens offered feed with a 25% (level 2) inclusion across all diversity indexes. At 25% (level 2) of red and white sorghum inclusion, the lowest level of bacterial abundance and diversity on the was recorded while in brown sorghum had their lowest diversity at 50% (level 3) inclusion.
Microbial community diversity amongst Boschveld indigenous chickens fed different sorghum-based diets at different inclusion levels, including three sorghum varieties.
Figure 2 shows the microbial profiles of Boschveld chickens on the days of collection. Sorghum varieties with five inclusion levels were used when formulating the trial diets, and these are represented using the Principal Coordinates Analysis (PCoA). The PCoA plots clustered the bacterial diversity according to the sorghum varieties offered during the trials of the current study. Also, they illustrated the microbial succession when chickens were 60 and 90 days old. The microbial profiles from Boschveld chicken guts had a statistical difference (P < 0.05) in the species diversity at days 60 and 90 of the collection, shown in Fig. 2 (A). The bacteria in the chicken’s gut at days 60 and 90 clustered far from each other, although there were very few bacteria that clustered together during these collection periods.
The bacterial diversity from the guts of the chickens, when divided according to the three sorghum varieties (red, brown, and white) and as presented in Fig. 2 (B), were significantly different (P < 0.05). Microbial communities found in the gut of Boschveld chickens offered the control diet, red and white sorghum varieties clustered closely together. The group that was fed the brown sorghum variety had few bacteria clustering close to the other varieties. Still, it also had some bacteria that were unique and clustered separately. The inclusion level's effect on the chickens’ guts – regardless of the sorghum varieties included, as shown in Figure S2 were not significantly different (P > 0.05). However, the bacterial diversity at different inclusion levels was similar at all levels, although there were outliers noted from levels 1,2,3 and 5, which clustered closely together.
The phylogenetic analysis results, which present the bacterial similarities between the chickens’ guts from all studied treatments as of the days of sample collection, are shown in Fig. 3. The phylogenetic results corroborated the PCoA results, which indicated the significant difference in the diversity of the bacterial communities found in the guts of chickens at days 60 and 90. However, amazingly, the microbiome community of chickens offered feed formulated with the sorghum brown variety at inclusion of 100% (level 5) at collection day 60 was similar to the group of chickens fed the diet with the inclusion of the sorghum white variety at 75% (level 4) at day 90 (Fig. 3).
The gut microbial diversities and community composition among Boschveld indigenous chickens fed different sorghum-based diets at the Phylum level.
The phylum ranks below the kingdom and above the class in taxonomy, and scientists generally use the term phylum for bacteria and animals. The results found in the current study at the phylum level (Fig. 4) showed Firmicutes dominating the bacterial communities in the chicken's gut from all groups followed by Proteobacteria, Bacteroidota, and Actinobacteria at day 60. The groups of chickens fed diets with the brown sorghum variety included during formulation, regardless of the inclusion level, had bacterial community patterns similar to those of chickens offered diets with the white variety infused. However, when fed the brown variety, chickens had an abundance of Firmicutes in their guts, followed by Proteobacteria.
Furthermore, chickens offered the control diet, which included 0% sorghum, had more Firmicutes at day 60 and more Proteobacteria at day 90. However, findings from chickens fed diets formulated with the inclusion of the red sorghum varieties had an overall abundance of Firmicutes, followed by Proteobacteria, Actinobacteria, and Bacteroidota (Fig. 5).The influence of the inclusion levels on the bacterial diversity of Boschveld chickens is presented in Fig. 6. The group of chickens offered diets formulated with the inclusion of 25% (level 2) of the sorghum red variety had more Firmicutes present, followed by the group that provided the red sorghum variety with a 75% (level 4) inclusion level. At day 90 of sample collection, however, Proteobacteria were abundant compared to other bacterial compositions. These bacteria were noted mainly in the gut of chickens fed diets formulated with sorghum white included at 25% (level 2), followed by the group offered sorghum brown included at 50% (level 3). Overall, the bacterial community found in abundance were Firmicutes at all levels (0, 25, 50, 75, and 100%), followed by Proteobacteria, Desulfobacterota, Bacteroidota, and Actinobacteria.
The microbiome composition of Boschveld chicken gut at the genus level. The Krona plot in Fig. 7 showed the presence of bacteria at the age of collection (60 and 90 days). At day 60 (A), Lactobacillus aviarius was the most dominant group at 18%, followed by the Comamoduceae at 12% and uncultured bacterium at 7%. On day 90 (B), Comamonadaceae was the most dominant (23%), followed by Methylobacterium – Methylorubrum (8%) and Escherichia – Shingella (6%).
The effect of sorghum varieties at the genus level is presented in the Krona plot in Fig. 8. The brown sorghum variety (A) inclusion revealed the Comamonadoceae (11%) followed by Uncultured bacterium (10%) and Methylobacterium – Methylorubrum (7%), although the group offered a diet with the red sorghum variety (B) was dominated by Lactobacillus – Aviarius (35%), Comamozadaceae (7%) and Escherichia – Shigella (4%). The inclusion of the white sorghum variety (C) impacted the gut of Boschveld chickens and was dominated by Comomadaceae (24%), Methylobacterium – Methylorubum (9%) and Lactobacillus – Aviarius (6%). Furthermore, chickens fed diets with the white variety included had 6% Streptococcus, which was present only in the guts of this group and not in those of their counterparts.
Microbial taxa associated with different sorghum-based diets in Boschveld indigenous chickens.
The core taxa Venn diagram (Fig. 9 (A)) demonstrates the bacterial similarities found in the Boschveld chicken's gut-fed diets formulated with the three sorghum varieties (brown, red, and white) at days 60 and 90. A total of 902 bacterial communities were noted during the whole trial. However, from the recorded bacterial communities, about 187 species were reported only on day 60 and about 274 on day 90. Meanwhile, 441 common bacterial species were observed on both day 60 and day 90 of the collection.
The core taxa Venn diagram (Fig. 9 (B)) illustrates the bacterial similarities found in the Boschveld gut-fed chicken formulated with the three sorghum varieties. The bacterial varieties found between chickens fed the control diets, and those fed the brown variety had 15 common bacterial species. However, the group of Boschveld chickens offered the control diet, and those fed with the inclusion of the white variety had 18 common bacterial communities across the entire trial. In contrast, control x red had 18 common bacteria. The brown and red groups had only 36 bacteria in common. The white x red had 97 common bacterial communities. Furthermore, brown x white had 197 common bacteria across the entire study, which was the most when compared to the groups fed other varieties.