Abstract
Our previous research revealed the advantages of separate feeding (SF) systems compared to total mixed ration (TMR) in terms of ruminal methane (CH4) production. The purpose of this experiment was to confirm the advantage of SF as a nutritional strategy for CH4 mitigation, and to determine the effects of different feeding systems (TMR and SF) on the rumen microbiome and associated metagenome of two different breeds and on CH4 emissions. We randomly allocated four Holstein (305 ± 29 kg) and four Hanwoo steers (292 ± 24 kg) to two groups; the steers were fed a commercial concentrate with tall fescue (75:25) as TMR or SF, in a crossover design (two successive 22-day periods). Neither feeding systems nor cattle breeds had an effect on the total tract digestibility of nutrients. The TMR feeding system and Hanwoo steers generated significantly more CH4 (P < 0.05) and had a higher yield [g/d and g/kg dry matter intake (DMI)] compared to the SF system and Holstein steers. A larger rumen acetate:propionate ratio was observed for the TMR than the SF diet (P < 0.05), and for Hanwoo than Holstein steers (P < 0.001), clearly reflecting a shift in the ruminal H2 sink toward CH4 production. The linear discriminant analysis (LDA) effect size (LEfSe) revealed a greater abundance (α < 0.05 and LDA > 2.0) of operational taxonomic units (OTUs) related to methanogenesis for Hanwoo steers compared to Holstein steers. Kendall’s correlation analysis revealed wide variation of microbial co-occurrence patterns between feeding systems, indicating differential H2 thermodynamics in the rumen. A metagenome analysis of rumen microbes revealed the presence of 430 differentially expressed genes, among which 17 and 27 genes exhibited positive and negative associations with CH4 production, respectively (P < 0.001). A strong interaction between feeding system and breed was observed for microbial and metagenomic abundance. Overall, these results suggest that the TMR feeding system produces more CH4, and that Hanwoo cattle are higher CH4 emitters than SF diet and Holstein cattle, respectively. Interestingly, host-associated microbial interactions differed within each breed depending on the feeding system, which indicated that breed-specific feeding systems should be taken into account for farm management.
Highlights
Some dietary interventions have the potential to reduce ruminal CH4 emissions with little negative impact on the animals
There was no effect on apparent total tract nutrient digestibility (P > 0.05; Table 3), total mixed ration (TMR) feeding resulted in greater CH4 production (g/day) and CH4 yield per unit of organic matter (OM), neutral detergent fibre and gross energy (GE) intake than the separate feeding (SF) diet in both Holstein and Hanwoo steers (P < 0.05; Table 4)
We described the rumen microbial community and its associated functions in Holstein and Hanwoo steers provided with the same diet, under the same management conditions, to identify compositional changes that might underlie the marked differences in CH4 production between these breeds
Summary
Some dietary interventions have the potential to reduce ruminal CH4 emissions with little negative impact on the animals. The practice of TMR feeding in beef cattle production has increased gradually, and is used in about 20% of beef cattle farms in Korea. This has led to an increase in research on its effects on ruminal fermentation, animal performance and carcass quality in Hanwoo (Korean native cattle) steers (Lee et al, 2010; Kim et al, 2011; Chung et al, 2017). The effects of the TMR and SF systems on ruminal CH4 mitigation have not been studied extensively in either dairy or beef cattle. Further studies are needed to validate the effects of these feeding systems on CH4 production in beef cattle
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
