Dietary manipulation offers an effective strategy for modifying rumen microbiota to reduce methane emissions. The study assessed the influence of sorghum-based diets on the ruminal methanogenic archaeal community in Mashona goats. The diets were formulated as follows; PS:50-50% (plain or untreated sorghum); SS:75-75% (soaked sorghum at 75% inclusion); FS:25-25% (fermented sorghum at 25% inclusion); MS:100-100% (malted sorghum at 100% inclusion); M:100-(100% maize-based) and CC-a commercial concentrate as the control. A total of 48 Mashona goats blocked by sex were randomly allocated into six treatments of eight animals each in a randomized block design (RBD). Selection of experimental animals was based on breed characteristics. The selected goats had an initial age range of approximately 12 months and an average initial body weight of 16–17 kg. A total of 16 rumen samples were collected from the experimental animals after a 15-week feeding trial for DNA extraction and microbiota analysis. Results obtained revealed that diet significantly influenced archaeal composition, with the phylum Euryarchaeota and genus Methanobrevibacter dominating across all dietary treatments. The FS:25 diet exhibited a 99.4% dominance of Euryarchaeota while the MS:100 diet had a representation of 55% Euryarchaeota and 45% Candidatus Thermoplasmatota. The phylum Candidatus Thermoplasmatota represented by genus Methanomethylophilus was observed in low abundance across treatments. While diet did not significantly influence microbial diversity ( p 0.05), a numerical trend was observed, with the MS:100 diet showing the highest Shannon diversity index (1.66 ± 0.11) and the commercial concentrate exhibiting the lowest (1.13 ± 0.40) numerical diversity. The study concluded that the methanogenic archaea responded differently to every dietary treatment. Notably, the Bray–Curtis PCoA identified FS:25 and CC diets as distinct outliers with Methanosarcina and Methanomicrobium exclusively observed in FS:25 and CC, respectively. Future research could be designed toward in vivo methane emission quantification for the MS:100 diet to confirm its mitigation potential and optimal dietary status. The diversity in the methanogenic community in MS:100 reflects an integrated rumen ecosystem function. Direct quantification of enteric methane emissions through in vivo measurements is necessary to validate whether this favorable microbial balance translates into measurable reductions in methane output.
Rugwete et al. (Wed,) studied this question.