Preweaning period is a critical window for rumen microbial regulation of average daily gain in Holstein heifer calves

Background Rumen bacterial groups can affect growth performance,such as average daily gain(ADG),feed intake,and efficiency.The study aimed to investigate the inter-relationship of rumen bacterial composition,rumen fermentation indicators,serum indicators,and growth performance of Holstein heifer calves with different ADG.Twelve calves were chosen from a trail with 60 calves and divided into higher ADG(HADG,high pre-and post-weaning ADG,n=6)and lower ADG(LADG,low pre-and post-weaning ADG,n=6)groups to investigate differences in bacterial composition and functions and host phenotype.Results During the preweaning period,the relative abundances of propionate producers,including g_norank_f_Butyricicoccaceae,g_Pyramidobacter,and g_norank_f_norank_o_Clostridia_vadin BB60_group,were higher in HADG calves(LDA>2,P<0.05).Enrichment of these bacteria resulted in increased levels of propionate,a gluconeogenic precursor,in preweaning HADG calves(adjusted P<0.05),which consequently raised serum glucose concentrations(adjusted P<0.05).In contrast,the relative abundances of rumen bacteria in post-weaning HADG calves did not exert this effect.Moreover,no significant differences were observed in rumen fermentation parameters and serum indices between the two groups.Conclusions The findings of this study revealed that the preweaning period is the window of opportunity for rumen bacteria to regulate the ADG of calves.

Isolation,identification and artificial inoculation of Ustilago esculenta on Zizania latifolia

The smut Ustilago esculenta is an endophytic fungus that invades Zizania latifolia(Jiaobai)and plays an important role in inducing the host stem to form a swollen gall.The aims of this study were to investigate isolation,identification and inoculation methods of U.esculenta from Jiaobai.The spore suspension culturing method was the best method of isolating U.esculenta,and yeast-like fungal strains and septate hyphal strains were obtained.The universal primers ITS1 and ITS4 amplified a ribosomal DNA spacer element from all tested strains,while specific primers for Lam16A gene generated a 442 bp product only with septate hyphae strains.De novo transcriptome assembly results showed that the yeast-like fungal strains did not match Ustilago,and genomic analysis suggested the septate hyphae strains were highly similar to known smut fungi.Therefore,the septate hyphae strains were identified as U.esculenta,which indicated that the ITS primers were not species-specific but that Lam16A-specific primers can distinguish U.esculenta accurately and easily.In vitro,U.esculenta grew quickly on PDA medium at 28°C in darkness.Furthermore,an inoculation method was established to produce swollen stems by injecting a spore suspension of U.esculenta at OD600=2.5 into the basal culm internode of male Jiaobai.