This study aims to investigate the relationship between serum vitamin A(VA)and mar-bling grade and the effect of different levels of serum VA on slaughter performance and fatty acid composition and related gene expression in the longissimus dorsi muscle of Woking black cattle and Angus cattle.Thirty Woking black cattle and seventeen Angus cattle aged 30 months were ran-domly selected and analyzed for the linear relationship between serum VA and marbling grade af-ter slaughter.The cattle were divided into three groups:the low VA group,medium VA group and high VA group,ranked in order of VA value in both Woking black cattle and Angus cattle.Statisti-cal analysis of the effects of different types and levels of VA on marbling grade,slaughter performance,fatty acid composition,and the effects of different levels of VA on the expression of genes related to intramuscular fat deposition and other genes in Woking black cattle or Angus cat-tle were also analyzed.The results showed that the marbling grade of Woking black cattle increased numerically with increasing serum VA at slaughter(P=0.203),whereas Angus cattle showed a numerical decrease(P=0.139).Analyses of subsequent subgroups showed that Woking black cat-tle had significantly higher marbling grade and oleic acid,monounsaturated/saturated fatty acids ratio in the longissimus dorsi muscle compared to Angus cattle(P＜0.05).As serum VA levels in-creased,DHA was significantly higher and n-6/n-3 fatty acid ratio significantly lower in the longis-simus dorsi muscle of Woking black cattle(P＜0.05).Whereas VA was elevated in Angus cattle,a significant decrease in DHA and a significant increase in n-6/n-3 fatty acids(P＜0.05)were found.Furthermore,a notable up-or down-regulation(P＜0.05)of LPL,FABP4,PPARγ,C APZA2 and Villin 2 was observed in Woking black or Angus cattle,respectively,as VA levels increased.Based on these results,it was suggested that Woking black cattle require an appropriate increase in dieta-ry VA during the late fattening stage,which was found to produce a higher marbling grade and a higher percentage of beneficial fatty acids for human health when serum VA reached 80.7 IU/dL.Whereas Angus cattle still need to be restricted in ration VA content in the late fattening stage,when serum VA is elevated to 73.6 IU/dL,they produce beef that not only has a lower marbling grade but also has a corresponding reduction in fatty acids beneficial to human health.

This study aims to investigate the relationship between serum vitamin A(VA)and mar-bling grade and the effect of different levels of serum VA on slaughter performance and fatty acid composition and related gene expression in the longissimus dorsi muscle of Woking black cattle and Angus cattle.Thirty Woking black cattle and seventeen Angus cattle aged 30 months were ran-domly selected and analyzed for the linear relationship between serum VA and marbling grade af-ter slaughter.The cattle were divided into three groups:the low VA group,medium VA group and high VA group,ranked in order of VA value in both Woking black cattle and Angus cattle.Statisti-cal analysis of the effects of different types and levels of VA on marbling grade,slaughter performance,fatty acid composition,and the effects of different levels of VA on the expression of genes related to intramuscular fat deposition and other genes in Woking black cattle or Angus cat-tle were also analyzed.The results showed that the marbling grade of Woking black cattle increased numerically with increasing serum VA at slaughter(P=0.203),whereas Angus cattle showed a numerical decrease(P=0.139).Analyses of subsequent subgroups showed that Woking black cat-tle had significantly higher marbling grade and oleic acid,monounsaturated/saturated fatty acids ratio in the longissimus dorsi muscle compared to Angus cattle(P＜0.05).As serum VA levels in-creased,DHA was significantly higher and n-6/n-3 fatty acid ratio significantly lower in the longis-simus dorsi muscle of Woking black cattle(P＜0.05).Whereas VA was elevated in Angus cattle,a significant decrease in DHA and a significant increase in n-6/n-3 fatty acids(P＜0.05)were found.Furthermore,a notable up-or down-regulation(P＜0.05)of LPL,FABP4,PPARγ,C APZA2 and Villin 2 was observed in Woking black or Angus cattle,respectively,as VA levels increased.Based on these results,it was suggested that Woking black cattle require an appropriate increase in dieta-ry VA during the late fattening stage,which was found to produce a higher marbling grade and a higher percentage of beneficial fatty acids for human health when serum VA reached 80.7 IU/dL.Whereas Angus cattle still need to be restricted in ration VA content in the late fattening stage,when serum VA is elevated to 73.6 IU/dL,they produce beef that not only has a lower marbling grade but also has a corresponding reduction in fatty acids beneficial to human health.