Early supplementary feeding of lambs before weaning is important to meet their nutritional needs, promote the development of rumen and improve performance. To study the effect of early supplementary feeding on rumen development and the microbiota of lambs, 22 Hu lambs were randomly divided into two groups: one group was fed with milk replacer (group C), and the other group was fed with milk replacer and starter (group S). At 28 days, six lambs in each group were slaughtered, and the rumen content and tissue samples were collected for detection and analysis. The starter significantly promoted the length of rumen papilla (P = 0.03), the concentration of acetate, propionate, butyrate and total volatile fatty acids (TVFA) (P < 0.01), which were higher in group S compared with group C. Group C had a higher rumen microbial diversity than group S. The dominant bacteria in the two groups were the same (Bacteroidetes, Firmicutes and Proteobacteria); however, they differed notably at the genus level. The microbial abundance of the two groups was significantly different for 22 species. In group C, the first three dominant bacteria were Bacteroides, Porphyromonas, and Campylobacter, while in group S they were Succinivibrio, unidentified_Prevotellaceae, and unidentified_Lachnospiraceae. Spearman correlation analysis showed that some ruminal bacteria were closely related to internal environmental factors, e.g., the relative abundances of unidentified_Bacteria, Euryarchaeota, Fusobacteria, and Gracilibacteria correlated negatively with acetate, propionate, butyrate, and TVFA (P < 0.05), while the relative abundances of Firmicutes correlated positively with acetate, propionate, butyrate and TVFA (P < 0.05). Bacteroidetes correlated negatively with propionate, butyrate, and TVFA (P < 0.05); Synergistetes correlated negatively with acetate, propionate, and butyrate (P < 0.05); Deinococcus-Thermus correlated negatively with propionate, butyrate, and TVFA (P < 0.05); Spirochaetes correlated negatively with propionate and TVFA (P < 0.05); and Elusimicrobia correlated negatively with propionate and butyrate (P < 0.05). Actinobacteria and Verrucomicrobia correlated positively correlated with NH3-N. In conclusion, supplementary feeding of lambs before weaning promoted the development of rumen tissue morphology and rumen microorganisms.
Aims To increase enduracidin production in Streptomyces fungicidicus ATCC 31731 by overexpressing positive regulators in enduracidin biosynthesis. Methods and Results Genes orf22 and orf42 were knocked out by in‐frame deletion based on CRISPR/Cas9 strategy, while the orf41 gene was inactivated by replacing it with the apramycin resistance gene cassette aac(3)IV using a fast screening blue/white system. The integrative plasmid pSET152ermE was used for the overexpression of orf22, orf41 and orf42 individually. The constructed plasmids were transformed into wild‐type strain Streptomyces fungicidicus ATCC 31731. Three gene inactivation mutants Δorf22, Δorf41 and Δorf42 and three recombinant strains overexpressing orf22, orf41 and orf42 were all fermented and the enduracidin production of each strain was detected and compared by HPLC analysis. Two resulting engineered strains were generated through overexpression of gene orf22 and orf42 in Streptomyces fungicidicus, respectively, and in these strains the enduracidins titres were increased by approximately 4·0‐fold and 2·3‐fold higher than that of the wild‐type strain. Conclusions The functions of three regulatory genes orf22, orf41 and orf42 in the enduracidin gene cluster in Streptomyces fungicidicus ATCC 31731 were examined. The orf22 gene, encoding a SARP family protein, was proposed to act in a positive manner. The proteins encoded by genes orf41 and orf42 were proposed to compose a two‐component regulation system, in which the response protein Orf41 was characterized as a repressor, and the kinase Orf42 was shown to be an activator. The production of enduracidins was improved considerably by overexpression of the two positive regulatory genes orf22 and orf42 respectively. Significance and Impact of the Study The production of enduracidins was successfully improved by manipulating the regulatory genes involving in enduracidin biosynthesis, providing an efficient approach to improve enduracidin production further for fermentation industry and synthetic biological research.
Starch and NDF are the main components in the diets of ruminants worldwide and are the main energy source for rumen microorganisms and hosts. The purpose of this study was to investigate the effects of different NDF/starch ratios on rumen fermentation parameters, rumen development and rumen microbes in lambs and to predict the function of rumen microbes by metagenomic techniques. In this study, 30 lambs with birth weights of (3.0 ± 0.5) kg were selected. The lambs of Hu sheep were randomly divided into two groups, fed starter with an NDF/starch ratio of 0.5 (group A) or 1.0 (group C). Samples of the rumen tissue and contents were collected after slaughter. The results showed that the ADG and ADFI of group A were significantly higher than those of group C (P < 0.05), but there was no significant difference in the FCR (P > 0.05). Therefore, from the perspective of feed-related economic benefits, group C showed greater economic value; the A/P of group C was significantly lower than that of group A (0.05 < P < 0.1), and the TVFA showed no significant difference (P > 0.05); The lengths of the rumen papillae of group C was significantly higher than that of group A (0.05 < P < 0.1). There was no significant difference in the abundance of the top 10 species at the phylum level and genus level (P > 0.05). CAZymes gene enrichment was observed in the rumen microbial community of lambs in group C (P < 0.05). In conclusion, group C, fed with starter with a higher NDF/starch ratio, had a higher feeding value. This study provides comprehensive insights into the composition of NDF and starch in lamb starter.
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