日粮中添加β-胡萝卜素对牦牛皮下脂肪颜色及组织中维生素A含量的影响

试验旨在探究日粮中添加不同水平β-胡萝卜素（β-C）对牦牛皮下脂肪颜色及组织维生素A含量的影响。试验选取12头2~3岁牦牛为研究对象，随机分为4个组，每组3个重复。各处理组日粮分别在基础日粮中添加0（对照）、720（低剂量）、1 440（中剂量）、1 620 mg/d（高剂量）β-C，饲养90 d后，分别测定牦牛脂肪、肌肉色度、背膘厚度及不同组织中β-C和代谢产物维生素A的含量，结果表明：日粮中添加不同水平β-C，牦牛背部、胸部脂肪及半腱肌的黄度值（b^*）显著高于对照组（P<0.05），亮度值（L^*）和红度值（a^*）没有显著变化（P>0.05）；牦牛背膘厚度在中剂量组达到最大值；对照组牦牛血清中β-C及维生素A含量显著低于各试验组（P<0.05），且维生素A含量随β-C添加量的上升呈上升趋势（P<0.05）；牦牛皮下脂肪、腹腔脂肪、心脏、肝脏、脾脏、肺脏、肾脏及空肠等组织器官中β-C含量在中剂量组均达到最大值，除肝脏中维生素A含量较高外，其他组织中维生素A含量在各处理组间差异不显著（P<0.05）。综上所述，日粮添加β-C影响牦牛皮下脂肪颜色，且在中剂量组牦牛皮下脂肪、心脏、肝脏、脾脏及空肠等组织器官中β-C含量达到最大值，故推荐其最佳摄入量为1 440 mg/d；在日粮中添加β-C影响牦牛肝脏和血清中维生素A含量，对其余组织器官中维生素A含量没有影响。

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.