Study On Growth Performance And Rumen Function In Finishing Hu Lambs With Different Residual Feed Intakes

Raising low residual feed intake(RFI)livestock can decrease the feed cost and improve the economic profit,but the biological mechanism for RFI is still unclear.Feeding high-concentrate diet is a common strategy in the intensive feeding system.While,in doing so,the rumen health can be affected negatively.Investigating the rumen function between high and low RFI finishing Hu lambs offered a high-concentrate diet can provide some references to RFI variability and feeding management for the low RFI finishing Hu lambs in the future.We recorded the dry matter intake(DMI)and average daily gain(ADG)of 60 finishing male Hu lambs during 42 days,then we used the residual feed intake(RFI)calculation model to select10 Hu lambs with high and low RFI,respectively.After finishing RFI selection,we sampled the rumen fluid and blood on d 10 and d 20 from the lambs with high and low RFI.Rumen fluid was used for measuring volatile fatty acid(VFA)and extracting genomic DNA.The blood was used for measuring metabolites related with glucose metabolism and liver function.The slaughter experiment was conducted on d 75 after we began our experiment.Rumen epithelium and liver tissues,which were used for total RNA extraction,were collected from the lambs with high and low RFI.In this study,rumen fermentation variables,blood variables,rumen microorganisms,gene expressions associated with short chain fatty acid(SCFA)absorption and metabolism,and rumen morphology were measured.The major results of the experiment are as follows:1.The DMI of low RFI group was significantly lower than its counterpart(P < 0.05).However,no difference was observed in final live body weight(P > 0.05).2.The concentration of glucose for high RFI group was significantly higher than low RFI group(P < 0.05).RFI had a significant effect on glutamyl transpeptidase(GGT)(P < 0.05).Furthermore,the concentration of GGT for finishing Hu lambs on d 20 was higher than that on d10(P < 0.05).3.The concentration of propionate in low RFI group was significantly higher than high RFIgroup(P < 0.05),but both acetate to propionate ratio and the concentration of butyrate were significantly lower than high RFI group(P < 0.05).4.The relative abundance of Butyrivibrio fibrisolvens in low RFI group was significantly lower compared with the high RFI group(P < 0.05).5.No difference was detected in gene expressions associated with SCFA absorption between high and low RFI groups(P > 0.05).In addition,no difference was found between high and lowRFI groups in the size of rumen papillae(P > 0.05).To sum up,in the current study,no difference was found between high and low RFI finishing Hu lambs in final body weight and ADG,but low RFI finishing lamb had higher feed conversion efficiency.Feeding high-concentrate diet could increase the concentration of GGT for both high and low RFI lambs over time and the concentration of GGT for the high RFI group is higher than low RFI group.Low RFI finishing Hu lamb tended to have a propionic-type fermentation.There was no difference between high and low RFI finishing Hu lambs' rumen epithelium in gene expression associated with SCFA transorption and the morphology of rumen papillae.