Comparative ruminal study of buffalo (Bubalus bubalis) and cattle (Bos taurus), and their response to maize grain grown on mycorrhized soil

Arbuscular mycorrhizal fungi (AMF) form symbiotic relations with most terrestrial plants, and can reduce the need for crop fertilization, pest control, weed control and water input. Several studies have analyzed the effect of AMF inoculation on forage yield; however, it is unclear whether AMF treatment of maize crops affect grain usage as a ruminant feed. Therefore, the effect of maize grain grown on soil with and without AMF on ruminal fermentation, and the associated rumen microbiota was investigated. Both Holstein-Friesian dairy cows and Mediterranean buffaloes were studied because of known differences in their ruminal fermentation and microbiota. For each host type, rumen cannulated non-lactating animals were fed the two diets in a cross-over design. Diet did not affect any of the assessed ruminal fermentation parameters, microbial concentrations or the prokaryotic barcoded 16S rRNA gene amplicon sequencing based community composition analysis. In contrast, host type had numerous effects. Protozoal counts, lactic acid, volatile fatty acids and the molar proportion of isobutyric acid were all higher in buffaloes compared to dairy cows. Conversely, the molar proportion of butyric acid was lower in buffaloes than the dairy cows. Host type also explained 9.3% of the total variation in the prokaryotic community composition, and several amplicon sequence variants could be associated with host type. These findings indicate that AMF treatment of maize crops has no detrimental impact on the value of the resulting maize grains as a ruminant feed, and provide additional insight into the ruminal based differences between dairy cows and buffaloes.