Growth performance, rumen fermentation, bacteria composition, and gene expressions involved in intracellular pH regulation of rumen epithelium in finishing Hu lambs differing in residual feed intake phenotype

The objective of this study was to evaluate the effect of residual feed intake (RFI) on rumen function in finishing lambs. A total of 60 male Hu lambs (average initial BW = 25.2 +/- 2.5kg) were used and were offered a pelleted high-concentrate diet, of which the forage to concentrate ratio was 25:75. Individual feed intake was recorded over a period of 42 d, then 10 lambs with the lowest RFI and the highest RFI were selected, respectively. The rumen fluid used for fermentation variables and relative abundance of bacteria measurement was obtained on d 10 and 20 after RFI measurement. At the end of this experiment, the selected lambs were slaughtered and rumen epithelium and liver tissues were collected for RNA extraction. Low-RFI lambs had lower (P 0.05). Additionally, RFI was positively (r = 0.57; P 0.05) were not affected by RFI classification. Nonetheless, low-RFI group lambs had a greater (P 0.05) on gene expression associated with intracellular pH regulation (PAT1, AE2, DRA, NHE2, NHE3, MCT1, MCT4, and ATPase) in rumen epithelium and alpha-hydroxybutyrate metabolism (HMGCS2) in both rumen epithelium and liver tissues. In conclusion, even though lowRFI lambs had lower DMI, however, the number of B. fibrisolvens was lower. Additionally, there was no difference in gene expressions level associated with intracellular pH regulation in rumen epithelium between RFI groups.