Transcriptomic and metabolomic insights into the roles of exogenous β-hydroxybutyrate acid for the development of rumen epithelium in young goats

Beta-hydroxybutyric acid(BHBA),as one of the main metabolic ketones in the rumen epithelium,plays critical roles in cellular growth and metabolism.The ketogenic capacity is associated with the maturation of rumen in young ruminants,and the exogenous BHBA in diet may promote the rumen development.However,the effects of exogenous BHBA on rumen remain unknown.This is the first study to investigate the mechanisms of BHBA on gene expression and metabolism of rumen epithelium using young goats as a model through multi-omics techniques.Thirty-two young goats were divided into control,low dose,middle dose,and high dose groups by supplementation of BHBA in starter(0,3,6,and 9 g/day,respectively).Results demonstrated the dietary of BHBA promoted the growth performance of young goats and increased width and length of the rumen papilla(P<0.05).Hub genes in host transcriptome that were positively related to rumen characteristics and BHBA concentration were identified.Several upregulated hub genes including NDUFC1,NDUFB4,NDUFB10,NDUFA11 and NDUFA1 were enriched in the gene ontology(GO)pathway of nicotinamide adenine dinucleotide(NADH)dehydrogenase(ubiquinone)activity,while ATP5ME,ATP5PO and ATP5PF were associated with ATP synthesis.RT-PCR revealed the expression of genes(HMGCS2,BDH1,SLC16A3,etc.)associated with lipolysis increased significantly by BHBA supplementation(P<0.05).Metabolomics indicated that some metabolites such as glucose,palmitic acid,cortisol and capric acid were also increased(P<0.05).This study revealed that BHBA promoted rumen development through altering NADH balance and accelerating lipid metabolism,which provides a theoretical guidance for the strategies of gastrointestinal health and development of young ruminants.

Impact of dietary supplementation of b-hydroxybutyric acid on performance,nutrient digestibility,organ development and serum stress indicators in early-weaned goat kids

The objective of this study was to determine the effect of dietary supplementation of b-hydroxybutyric acid(BHBA)on performance,nutrient digestibility,organ development,and serum composition in earlyweaned goat kids.Sixty-four goat kids at 30 d of age were assigned to 4 treatments in a completely randomized design:1)control(basal diet);2)low(basal diet with 3 g/d per animal BHBA);3)medium(basal diet with 6 g/d per animal BHBA;and 4)high(basal diet with 9 g/d per animal BHBA).Subsequently,48(6 kids per treatment)goat kids were randomly selected and slaughtered at 60 and 90 d of age.Compared with the control group,BHBA at low and high doses increased body weight(P<0.05),average daily gain(P<0.01),and average daily starter intake(P<0.01).The BHBA improved organ development,especially at the lowest dose(P<0.01).The digestibility of dry matter and crude protein increased with age(P<0.05).However,BHBA did not affect nutrient digestibility.Compared with the control group,serum ceruloplasmin increased(P<0.05)with high BHBA level at 90 d of age.However,the serum creatinine(P<0.05)increased over time but was not affected by BHBA.The serum total antioxidant capacity and superoxide dismutase decreased with the high dose of BHBA at 90 d of age(P<0.01).In contrast,the serum glutathione peroxidase and malondialdehyde increased with the high doses of BHBA(P<0.01).Overall,low doses of BHBA were positive for growth performance,organ development,and health status against weaning stress.Whereas high doses of BHBA in the long term could negatively affect antioxidant status.