Effects of Dietary Supplementation of β-carotene on Body Fat Color and Vitamin A Content in Tissue of Yak

The purpose of the experiment was to investigate the effect of different levels of β-carotene (β-C) on body fat color and vitamin A content in yaks.In the study,12 yaks aged 2-3 years were randomly divided into 4 groups with 3 replicates.0,720,1 440,1 620 mg/d β-C were added to the basal diet in each group.After 90 days of feeding,the fat,muscle chromaticity,backfat thickness,the contents of β-C and metabolite vitamin A in different tissues of yak were determined.The results showed that,adding different level of β-C in diets,the yellowing (b^*) of back,chest fat and hindquarter of yak were significantly higher than that of control group (P<0.05),while brightness (L^*) and redness (a^*) had no significant change(P>0.05).The backfat thickness of yak reached the maximum value in the middle dose group,and the serum contents of β-C and vitamin A of the control group was significantly lower than each β-C group (P<0.05),and vitamin A content showed an increasing trend with the increase of β-C addition level (P<0.05).The content of β-C in body fat,abdominal fat,heart,liver,spleen,lung,kidney jejunum and other organs of yak reached the maximum value in the middle dose group.Except for the high content of vitamin A in the liver,there was no significant difference of vitamin A content in other tissues among the other treatment groups (P<0.05).In conclusion,dietary supplementation of β-C could affect the color of yak body fat.In the middle dose group,the content of β-C in body fat,heart,liver,spleen,jejunum and other tissues and organs of yak reached the maximum,and the optimum intake was 1 440 mg/d.The addition of β-C in diet had no effect on vitamin A content in yak tissues and organs except liver and serum.