Transcriptomic analysis reveals the molecular mechanisms of rumen wall morphological and functional development induced by different solid diet introduction in a lamb model

Background:This study aimed to elucidate the molecular mechanisms of solid diet introduction initiating the cellular growth and maturation of rumen tissues and characterize the shared and unique biological processes upon different solid diet regimes.Methods:Twenty-four Hu lambs were randomly allocated to three groups fed following diets:goat milk powder only(M,n=8),goat milk powder+alfalfa hay(MH,n=8),and goat milk powder+concentrate starter(MC,n=8).At 42 days of age,the lambs were slaughtered.Ruminal fluid sample was collected for analysis of concentration of volatile fatty acid(VFA)and microbial crude protein(MCP).The sample of the rumen wall from the ventral sac was collected for analysis of rumen papilla morphology and transcriptomics.Results:Compared with the M group,MH and MC group had a higher concentration of VFA,MCP,rumen weight,and rumen papilla area.The transcriptomic results of rumen wall showed that there were 312 shared differentially expressed genes(DEGs)between in“MH vs.M”and“MC vs.M”,and 232 or 796 unique DEGs observed in“MH vs.M”or“MC vs.M”,respectively.The shared DEGs were most enriched in VFA absorption and metabolism,such as peroxisome proliferator-activated receptor(PPAR)signaling pathway,butanoate metabolism,and synthesis and degradation of ketone bodies.Additionally,a weighted gene co-expression network analysis identified M16(2,052 genes)and M18(579 genes)modules were positively correlated with VFA and rumen wall morphology.The M16 module was mainly related to metabolism pathway,while the M18 module was mainly associated with signaling transport.Moreover,hay specifically depressed expression of genes involved in cytokine production,immune response,and immunocyte activation,and concentrate starter mainly altered nutrient transport and metabolism,especially ion transport,amino acid,and fatty acid metabolism.Conclusions:The energy production during VFA metabolism may drive the rumen wall development directly.The hay introduction facilitated establishment of immune function,while the concentrate starter enhanced nutrient transport and metabolism,which are important biological processes required for rumen development.

Alterations in nutrient digestion and utilization associated with different residual feed intake in Hu sheep

Improving feed efficiency is crucial to the animal industry.Residual feed intake(RFI)is now regarded as an index of feed efficiency evaluation and is independent of growth characteristics.Our study aims to explore the alterations in growth performance and nutrient digestion in Hu sheep with different RFI phenotypes.Sixty-four male Hu sheep(body weight=24.39±1.12 kg;postnatal days=90±7.9)were selected for the study.After an evaluation period of 56 days and power analysis,samples were collected from 14 low RFI(L-RFI group,power=0.95)and 14 high RFI sheep(H-RFI group,power=0.95).The L-RFI sheep yielded a lower(P<0.05)feed conversion ratio and dry matter intake;however,both groups exhibited similar average daily gain(P>0.05).The acid detergent fiber,neutral detergent fiber,organic matter,and crude protein apparent digestibility were higher(P<0.05)in L-RFI sheep.N intake and fecal N output(%of N intake)were lower(P<0.05)and N retention(%of N intake)was higher(P<0.05)in L-RFI sheep,whereas no difference(P>0.05)was found in urine N output(%of N intake)between the 2 groups.Furthermore,L-RFI sheep gave lower(P<0.05)serum glucose concentrations and higher(P<0.05)non-esterified fatty acid concentrations.Meanwhile,a lower ruminal acetate molar proportion(P<0.05)and higher propionate molar proportion(P<0.05)were observed in L-RFI sheep.In summary,these results revealed that despite having lower dry matter intake,L-RFI sheep possess higher nutrient digestibility,N retention,ruminal propionate production and serum glucose utilization,in order to meet energy demands.Selection for low RFI sheep could reduce feed costs,which in turn provides economic benefits to the sheep industry.