Effects of fumaric acid supplementation on methane production and rumen fermentation in goats fed diets varying in forage and concentrate particle size

Background: In rumen fermentation, fumaric acid(FA) could competitively utilize hydrogen with methanogenesis to enhance propionate production and suppress methane emission, but both effects were diet-dependent. This study aimed to explore the effects of FA supplementation on methanogenesis and rumen fermentation in goats fed diets varying in forage and concentrate particle size.Methods: Four rumen-cannulated goats were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments: low or high ratio of forage particle size: concentrate particle size(Fps:Cps), without or with FA supplementation(24 g/d). Fps:Cps was higher in the diet with chopped alfalfa hay plus ground corn than in that with ground alfalfa hay plus crushed corn.Results: Both increasing dietary Fps:Cps and FA supplementation shifted ruminal volatile fatty acid(VFA) patterns toward more propionate and less acetate in goats. An interaction between dietary Fps:Cps and FA supplementation was observed for the ratio of acetate to propionate(A:P), which was more predominant when FA was supplemented in the low-Fps:Cps diet. Methane production was reduced by FA, and the reduction was larger in the low-Fps:Cps diet(31.72%) than in the high-Fps:Cps diet(17.91%). Fumaric acid decreased ruminal total VFA concentration and increased ruminal p H. No difference was found in ruminal DM degradation of concentrate or alfalfa hay by dietary Fps:Cps or FA. Goats presented a lower ruminal methanogen abundance with FA supplementation and a higher B. fibrisolvens abundance with high dietary Fps:Cps.Conclusions: Adjusting dietary Fps:Cps is an alternative dietary model for studying diet-dependent effects without changing dietary chemical composition. Fumaric acid supplementation in the low-Fps:Cps diet showed greater responses in methane mitigation and propionate increase.

High rumen degradable starch decreased goat milk fat via trans-10,cis-12 conjugated linoleic acid-mediated downregulation of lipogenesis genes,particularly,INSIG1

Background:Starch is an important substance that supplies energy to ruminants.To provide sufficient energy for high-yielding dairy ruminants,they are typically fed starch-enriched diets.However,starch-enriched diets have been proven to increase the risk of milk fat depression(MFD)in dairy cows.The starch present in ruminant diets could be divided into rumen-degradable starch(RDS)and rumen escaped starch(RES)according to their different degradation sites(rumen or intestine).Goats and cows have different sensitivities to MFD.Data regarding the potential roles of RDS in milk fat synthesis in the mammary tissue of dairy goats and in regulating the occurrence of MFD are limited.Results:Eighteen Guanzhong dairy goats(day in milk=185±12 d)with similar parity,weight,and milk yield were selected and randomly assigned to one of three groups(n=6),which were fed an LRDS diet(Low RDS=20.52%),MRDS diet(Medium RDS=22.15%),or HRDS diet(High RDS=24.88%)for 5 weeks.Compared with that of the LRDS group,the milk fat contents in the MRDS and HRDS groups significantly decreased.The yields of short-,mediumand long-chain fatty acids decreased in the HRDS group.Furthermore,increased RDS significantly decreased ruminal B.fibrisolvens and Pseudobutyrivibrio abundances and increased the trans-10,cis-12 conjugated linoleic acid(CLA)and trans-10 C18:1 contents in the rumen fluid.A multiomics study revealed that the HRDS diet affected mammary lipid metabolism down-regulation of ACSS2,MVD,AGPS,SCD5,FADS2,CERCAM,SC5D,HSD17B7,HSD17B12,ATM,TP53RK,GDF1 and LOC102177400.Remarkably,the significant decrease of INSIG1,whose expression was depressed by trans-10,cis-12 CLA,could reduce the activity of SREBP and,consequently,downregulate the downstream gene expression of SREBF1.Conclusions:HRDS-induced goat MFD resulted from the downregulation of genes involved in lipogenesis,particularly,INSIG1.Specifically,even though the total starch content and the concentrate-to-fiber ratio were the same as those of the high-RDS diet,the low and medium RDS diets did not cause MFD in lactating goats.

Low rumen degradable starch promotes the growth performance of goats by increasing protein synthesis in skeletal muscle via the AMPK-mTOR pathway

Since starch digestion in the small intestine provides more energy than digestion in the rumen of ru-minants,reducing dietary rumen degradable starch(RDS)content is beneficial for improving energy utilization of starch in ruminants.The present study tested whether the reduction of rumen degradable starch by restricting dietary corn processing for growing goats could improve growth performance,and further investigated the possible underlying mechanism.In this study,twenty-four 12-wk-old goats were selected and randomly allocated to receive either a high RDS diet(HRDS,crushed corn-based concen-trate,the mean of particle sizes of corn grain=1.64 mm,n=12)or a low RDS diet(LRDS,non-processed corn-based concentrate,the mean of particle sizes of corn grain>8 mm,n=12).Growth performance,carcass traits,plasma biochemical indices,gene expression of glucose and amino acid transporters,and protein expression of the AMPK-mTOR pathway were measured.Compared to the HRDS,LRDS tended to increase the average daily gain(ADG,P=0.054)and decreased the feed-to-gain ratio(F/G,P<0.05).Furthermore,LRDS increased the net lean tissue rate(P<0.01),protein content(P<0.05)and total free amino acids(P<0.05)in the biceps femoris(BF)muscle of goats.LRDS increased the glucose concen-tration(P<0.01),but reduced total amino acid concentration(P<0.05)and tended to reduce blood urea nitrogen(BUN)concentration(P=0.062)in plasma of goats.The mRNA expression of insulin receptors(INSR),glucose transporter 4(GLUT4),L-type amino acid transporter 1(LAT1)and 4F2 heavy chain(4F2hc)in BF muscle,and sodium-glucose cotransporters 1(SGLT1)and glucose transporter 2(GLUT2)in the small intestine were significantly increased(P<0.05)in LRDS goats.LRDS also led to marked activation of p70-S6 kinase(S6K)(P<0.05),but lower activation of AMP-activated protein kinase(AMPK)(P<0.05)and eukaryotic initiation factor 2a(P<0.01).Our findings suggested that reducing the content of dietary RDS enhanced postruminal starch digestion and increased plasma glucose,thereby improving amino acid utilization and promoting protein synthesis in the skeletal muscle of goats via the AMPK-mTOR pathway.These changes may contribute to improvement in growth performance and carcass traits in LRDS goats.

High rumen degradable starch diet induced blood bile acids profile changes and hepatic inflammatory response in dairy goats

The objective of this study was to reveal the effect of rumen degradable starch(RDS)on bile acid metabolism and liver transcription in dairy goats using metabolomics and transcriptomics.Eighteen Guanzhong dairy goats of a similar weight and production level(body weight=45.8±1.54 kg,milk yield=1.75±0.08 kg,and second parity)were randomly assigned to 3 treatment groups where they were fed a low RDS(LRDS,RDS=20.52%DM)diet,medium RDS(MRDS,RDS=22.15%DM)diet,or high RDS(HRDS,RDS=24.88%DM)diet,respectively.The goats were fed with the experimental diets for 5weeks.On the last day of the experiment,all goats were anesthetized,and peripheral blood and liver tissue samples were collected.The peripheral blood samples were used in metabolomic analysis and white blood cell(WBC)count,whereas the liver tissue samples were used in transcriptomic analysis.Based on the metabolomics results,the relative abundances of primary bile acids in the peripheral blood were significantly reduced in the group that was fed the HRDS diet(P<0.05).The WBC count was significantly increased in the HRDS group compared with that in the LRDS and MRDS groups(P<0.01),indicating that there was inflammation in the HRDS group.Transcriptomic analysis showed that 4 genes related to bile acid secretion(genes:MDR1,RXRa,AE2,SULT2A1)were significantly downregulated in the HRDS group.In addition,genes related to the immune response were upregulated in the HRDS group,suggesting the HRDS diet induced a hepatic inflammatory response mediated by lipopolysaccharides(LPS)(gene:LBP),activated the Toll-like receptor 4 binding(genes:S100A8,S100A9)and the NF-kappa B signaling pathway(genes:LOC106503980,LOC108638497,CD40,LOC102180880,LOC102170970,LOC102175177,LBP,LOC102168903,LOC102185461,LY96 and CXCL8),triggered inflammation and complement responses(genes:C1QB,C1QC,and CFD).The HRDS diet induced a hepatic inflammatory response may be mediated by activating the Toll-like receptor 4 binding and NF-kappa B signaling pathway after free LPS entered the liver.The changes of bile acids profile in blood and the downregulation of 4 key genes(MDR1,RXRa,AE2,SULT2A1)involved in bile secretion in liver are probably related to liver inflammation.