| Cysteine is one of the important sulfur-containing amino acids, which is vital to thegrowth of Rex Rabbit and its fur. It is a complex physiological procedure of the absorption ofcysteine in animals. And there are many kinds of amino acid transporters related to cysteine,including ASCT1, ASCT2and SNAT2which are encoded by SLC1A4, SLC1A5and SLC38A2,respectively. ASCT1and ASCT2form the Na+-dependent and neutral amino acid transporterfamily ASC and SNAT2is the member of the Na+-dependent and neutral amino acidtransporter family A. Their expressions are all found in many organizations of Rex Rabbit.The Objective of this experiment was to investigate the effect of dietary cysteinesupplement levels on growth performance, fur quality and the expressions of SLC1A4,SLC1A5and SLC38A2of Rex Rabbit, determining the most appropriate cysteine level of dietfor Rex Rabbit and the best time of using. One hundred and forty-four healthy83-day-old RexRabbits were divided randomly into four groups with thirty-six replicates in each group. Andeach replicate contained one rabbit. The control group was fed with basal diet of0.25%cysteine and the three experimental groups were fed with the diets of0.60%,0.70%and0.80%cysteine (the diets adding0.35%,0.45%and0.55%cysteine to basal diet), respectively.The experiment included a pretral period of7days and an experimental period of40days.During every10days, four rabbits were slaughtered randomly in each group to sample for thedeterminations of fur quality and the expressions of SLC1A4, SLC1A5and SLC38A2. Theresults showed that:1. The final weight and average daily gain increased significantly in the group with thediet of0.70%cysteine (P<0.05). Feed conversion ratio in this group was the minimum.Average daily feed intake had no significant difference in all groups (P>0.05).2. At the age of130-day-old, the skin area of rabbits in the groups with the diets of0.60%and0.70%cysteine were significantly larger than other groups (P<0.05). Cysteine increased the hair density of100-day-old rabbits in three experimental groups significantly(P<0.05). And the hair density of Rex Rabbits with diets of0.70%cysteine at130-day-oldwas much greater than other groups except the one with diet of0.60%cysteine (P<0.05),being the maximum. There were no significant differences in the skin thickness between fourgroups (P>0.05).3. The contents of cysteine in diets resulted in the significant changes of the expressionsof SLC1A4, SLC1A5and SLC38A2in the skin, liver and duodenum tissues (P<0.05). Theexpression of SLC1A4in skin tissue from the group with diet of0.70%cysteine was themaximum at the age of110days. To others, the expressions all increased to the highest valuesin the groups with diet of0.70%cysteine initially and decreased afterwards. This status ofSLC1A5in the skin and duodenum tissues appeared in110-day-old rabbits and becamesignificant at the age of100days in the liver and duodenum tissues for SLC1A4and in theliver tissue for SLC1A5of Rex Rabbit. Be different from them, the status of SLC38A2wasfound at the age of100days in the skin and duodenum tissues and120days in the liver tissue.The expressions of SLC1A5in the skin and liver tissues recovered at the age of130days, thesame as SLC38A2in the skin and duodenum tissues.In conclusion, cysteine levels of diet affect the growth performance and fur quality ofRex Rabbit, and regulate amino acid transporter genes. Synthesizing the above indices, themost appropriate cysteine level of diet for Rex Rabbit is0.70%, and feeding with diet addingcysteine gets the optimum efficiency before110-day-old. |
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