Dietary crude protein and protein solubility manipulation enhances intestinal nitrogen absorption and mitigates reactive nitrogen emissions through gut microbiota and metabolome reprogramming in sheep

Dietary nutrient manipulation(e.g.protein fractions)could lower the environmental footprints of ruminants,especially reactive nitrogen(N).This study investigated the impacts of dietary soluble protein(SP)levels with decreased crude protein(CP)on intestinal N absorption,hindgut N metabolism,fecal microbiota and metabolites,and their linkage with N metabolism phenotype.Thirty-two male Hu sheep,with an age of six months and an initial BW of 40.37±1.18 kg,were randomly assigned to four dietary groups.The control diet(CON),aligning with NRC standards,maintained a CP content of 16.7%on a dry matter basis.Conversely,the experimental diets(LPA,LPB,and LPC)featured a 10%reduction in CP compared with CON,accompanied by SP adjustments to 21.2%,25.9%,and 29.4%of CP,respectively.Our results showed that low-protein diets led to significant reductions in the concentrations of plasma creatinine,ammonia,urea N,and fecal total short-chain fatty acids(SCFA)(P<0.05).Notably,LPB and LPC exhibited increased total SCFA and propionate concentrations compared with LPA(P<0.05).The enrichment of the Prevotella genus in fecal microbiota associated with energy metabolism and amino acid(AA)biosynthesis pathways was evident with SP levels in low-protein diets of approximately 25%to 30%.Moreover,LPB and LPC diets demonstrated a decrease in fecal NHþ4 eN and NO2 eN contents as well as urease activity,compared with CON(P<0.05).Concomitantly,reductions in fecal glutamic acid dehydrogenase gene(gdh),nitrite reductase gene(nirS),and nitric oxide reductase gene(norB)abundances were observed(P<0.05),pointing towards a potential reduction in reactive N production at the source.Of significance,the up-regulation of mRNA abundance of AA and peptide transporters in the small intestine(duodenum,jejunum,and ileum)and the elevated concentration of plasma AA(e.g.arginine,methionine,aspartate,glutamate,etc.)underscored the enhancement of N absorption and N efficiency.In summary,a 10%reduction in CP,coupled with an SP level of approximately 25%to 30%,demonstrated the potential to curtail reactive N emissions through fecal Prevotella enrichment and improve intestinal energy and N utilization efficiency.

Sodium butyrate promotes gastrointestinal development of preweaning bull calves via inhibiting inflammation,balancing nutrient metabolism,and optimizing microbial community functions

Butyrate promotes the growth and gastrointestinal development of calves.But,the mechanisms behind its effects on signaling pathways of the gastrointestinal tract and rumen microbiome is unclear.This study aimed to reveal transcriptomic pathways of gastrointestinal epithelium and microbial community in response to butyrate supplementation in calves fed a high fiber starter.Fourteen Holstein bull calves(39.9±3.7 kg,14 d of age)were assigned to 2 groups(sodium butyrate group,SB;control group,Ctrl).The SB group received 0.5%SB supplementation.At d 51,the calves were slaughtered to obtain samples for analysis of the transcriptome of the rumen and jejunum epithelium as well as ruminal microbial metagenome.Sodium butyrate supplementation resulted in a higher performance in average daily gain and development of jejunum and rumen papillae.In both the rumen and jejunum epithelium,SB downregulated pathways related to inflammation including NF-κB(PPKCB,CXCL8,CXCL12),interleukin-17(IL17A,IL17B,MMP9),and chemokine(CXCL12,CCL4,CCL8)and up-regulated immune pathways including the intestinal immune network for immunoglobulin A(IgA)production(CD28).Meanwhile,in the jejunum epithelium,SB regulated pathways related to nutritional metabolism including nitrogen metabolism(CA1,CA2,CA3),synthesis and degradation of ketone bodies(HMGCS2,BDH1,LOC100295719),fat digestion and absorption(PLA2G2F,APOA1,APOA4),and the PPAR signaling pathway(FABP4,FABP6,CYP4A11).The metagenome showed that SB greatly increased the relative abundance of Bacillus subtilis and Eubacterium limosum,activated ruminal microbial carbohydrate metabolism pathways and increased the abundance of carbohydrate hydrolysis enzymes.In conclusion,butyrate exhibited promoting effects on growth and gastrointestinal development by inhibiting inflammation,enhancing immunity and energy harvesting,and activating microbial carbohydrate metabolism.These findings provide new insights into the potential mechanisms behind the beneficial effects of butyrate in calf nutrition.

A mathematical model to describe the diurnal pattern of enteric methane emissions from non-lactating dairy cows post-feeding

Enteric methane emission is not only a source of energy loss in ruminants, but also a potent contributor to greenhouse gas production. To identify the nature and timing of interventions to reduce methane emissions requires knowledge of temporal kinetics of methane emissions during animal husbandry.Accordingly, a mathematical model was developed to investigate the pattern of enteric methane emissions after feeding in dairy cows. The model facilitated estimation of total enteric methane emissions（V,g） produced by the residual substrate（V1, g） and newly ingested feed（V2, g）. The model was fitted to the10 h methane emission patterns after morning feeding of 16 non-lactating dairy cows with various body weights（BW）, and the obtained parameters were used to predict the kinetics of 24 h methane emission for each animal. The rate of methane emission（g/h） reached a maximum within 1 to 2 h after feeding,followed by a gradual post-prandial decline to a basal value before the next feeding. The model satisfactorily fitted curves for each cow according to the criterion of goodness-of-fit, and provided biological descriptions for fluctuations in methane emissions based on basal V1 and feeding V2 in response to the changes in BW and dry matter intake（DMI） of different dairy cows. The basal V1 and feeding V2 are probably maintained by slow-and readily-degradable substrates, respectively. The former contributed at least 0.6 of methane production. In summary, the model provides a means to separate basal V1 and feeding V2 within V, and can be used to predict 24 h emission from a single feeding period.

Sheep numbers required for dry matter digestibility evaluations when fed fresh perennial ryegrass or forage rape

Research trials with fresh forages often require accurate and precise measurement of digestibility and variation in digestion between individuals, and the duration of measurement periods needs to be established to ensure reliable data are obtained. The variation is likely to be greater when freshly harvested feeds are given, such as perennial ryegrass(Lolium perenne L.) and forage rape(Brassica napus L.),because the nutrient composition changes over time and in response to weather conditions. Daily feed intake and faeces output data from a digestibility trial with these forages were used to calculate the effects of differing lengths of the measurement period and differing numbers of sheep, on the precision of digestibility, with a view towards development of a protocol. Sixteen lambs aged 8 months and weighing 33 kg at the commencement of the trial were fed either perennial ryegrass or forage rape(8/treatment group) over 2 periods with 35 d between measurements. They had been acclimatised to the diets, having grazed them for 42 d prior to 11 days of indoor measurements. The sheep numbers required for a digestibility trial with different combinations of acclimatisation and measurement period lengths were subsequently calculated for 3 levels of imposed precision upon the estimate of mean dry matter(DM) digestibility. It is recommended that if the standard error of the mean for digestibility is equal to or higher than 5 g/kg DM, and if sheep are already used to a fresh perennial ryegrass or forage rape diet,then a minimum of 6 animals are needed and 4 acclimatisation days being fed individually in metabolic crates followed by 7 days of measurement.