Taurine is a sulfur-containing nonproteinogenic amino acid.Recent studies have shown that taurine can improve rumen microbial crude protein(MCP)synthesis.This experiment aimed to investigate the action mechanisms of t...Taurine is a sulfur-containing nonproteinogenic amino acid.Recent studies have shown that taurine can improve rumen microbial crude protein(MCP)synthesis.This experiment aimed to investigate the action mechanisms of taurine on rumen MCP synthesis and nitrogen(N)metabolism in beef steers using sodium sulfate(Na_(2)SO_(4))as a contrast.Six steers(bodyweight 506±17 kg)were assigned to three experimental groups including a basal diet(control),the basal diet supplemented with 45 g taurine/d or 50 g Na_(2)SO_(4)/d,and were allocated in a replicated 3×3 Latin square design.The amounts of sulfur from taurine and Na_(2)SO_(4)were equal(11.38 g/d).The results showed that,compared with the control group,both taurine and Na_(2)SO_(4)increased ruminal MCP concentration(P<0.05)by 37.50%and 29.17%,respectively,and increased ruminal sulfide(S2−)concentration(P<0.001).Both taurine and Na_(2)SO_(4)increased neutral detergent fiber digestibility(P<0.05).Taurine tended to increase(P=0.087)while Na_(2)SO_(4)decreased(P=0.049)plasma urea concentration,while the taurine group exhibiting higher plasma urea concentration than the Na_(2)SO_(4)group(P=0.003).Compared with the control group,taurine did not affect urinary urea excretion(P=0.246)whereas Na_(2)SO_(4)decreased urinary urea excretion(P=0.002)and both taurine and Na_(2)SO_(4)increased urinary allantoin excretion(P<0.05),total purine derivatives excretion(P<0.05),and estimated rumen microbial N flow(P<0.05).The urinary urea excretion of the taurine group was higher than the Na_(2)SO_(4)group(P=0.019).Compared with the control group,taurine did not affect N excretion,N retention(NR)or N utilization efficiency(NUE)(P>0.10),but Na_(2)SO_(4)decreased urinary N excretion(P=0.018)and total N excretion(P=0.024),and increased NR(P=0.024)and NUE(P=0.022).No differences were found in NR and NUE between the taurine and Na_(2)SO_(4)groups(P>0.10).Taurine improved ruminal MCP synthesis by enriching the pathways associated with sulfur and amino acid metabolism while Na_(2)SO_(4)improved ruminal MCP synthesis by enriching pathways related to nucleotide and purine metabolism.In conclusion,both taurine and Na_(2)SO_(4)improved ruminal MCP synthesis by modulating different pathways.Taurine was less effective in decreasing total N excretion than Na_(2)SO_(4)but no differences in NR and NUE were found between the two treatments.展开更多
基金the National Natural Science Foundation of China for financial support(grant No.32172748)to the research.
文摘Taurine is a sulfur-containing nonproteinogenic amino acid.Recent studies have shown that taurine can improve rumen microbial crude protein(MCP)synthesis.This experiment aimed to investigate the action mechanisms of taurine on rumen MCP synthesis and nitrogen(N)metabolism in beef steers using sodium sulfate(Na_(2)SO_(4))as a contrast.Six steers(bodyweight 506±17 kg)were assigned to three experimental groups including a basal diet(control),the basal diet supplemented with 45 g taurine/d or 50 g Na_(2)SO_(4)/d,and were allocated in a replicated 3×3 Latin square design.The amounts of sulfur from taurine and Na_(2)SO_(4)were equal(11.38 g/d).The results showed that,compared with the control group,both taurine and Na_(2)SO_(4)increased ruminal MCP concentration(P<0.05)by 37.50%and 29.17%,respectively,and increased ruminal sulfide(S2−)concentration(P<0.001).Both taurine and Na_(2)SO_(4)increased neutral detergent fiber digestibility(P<0.05).Taurine tended to increase(P=0.087)while Na_(2)SO_(4)decreased(P=0.049)plasma urea concentration,while the taurine group exhibiting higher plasma urea concentration than the Na_(2)SO_(4)group(P=0.003).Compared with the control group,taurine did not affect urinary urea excretion(P=0.246)whereas Na_(2)SO_(4)decreased urinary urea excretion(P=0.002)and both taurine and Na_(2)SO_(4)increased urinary allantoin excretion(P<0.05),total purine derivatives excretion(P<0.05),and estimated rumen microbial N flow(P<0.05).The urinary urea excretion of the taurine group was higher than the Na_(2)SO_(4)group(P=0.019).Compared with the control group,taurine did not affect N excretion,N retention(NR)or N utilization efficiency(NUE)(P>0.10),but Na_(2)SO_(4)decreased urinary N excretion(P=0.018)and total N excretion(P=0.024),and increased NR(P=0.024)and NUE(P=0.022).No differences were found in NR and NUE between the taurine and Na_(2)SO_(4)groups(P>0.10).Taurine improved ruminal MCP synthesis by enriching the pathways associated with sulfur and amino acid metabolism while Na_(2)SO_(4)improved ruminal MCP synthesis by enriching pathways related to nucleotide and purine metabolism.In conclusion,both taurine and Na_(2)SO_(4)improved ruminal MCP synthesis by modulating different pathways.Taurine was less effective in decreasing total N excretion than Na_(2)SO_(4)but no differences in NR and NUE were found between the two treatments.
