Changes of β-carotene and retinol levels and BCO1 gene and protein expressions in yak tissues at different nutritional seasons

In order to explore relationship between the yellow fat and β-carotene metabolism in yaks, contents of β-carotene and retinol in tissues, serum and digestive tract contents were analysed at periods of rich and deficient nutrition. Expressions of β-carotene 15, 15’-monooxygenase 1 (BCO1) gene and protein were also studied using real-time PCR and western blot. It was shown that contents of β-carotene in serum, liver, pancreas, duodenum, jejunum and contents of rumen and ileum were higher in the period of rich nutrition than in the period of deficient nutrition (P < 0.05). Content of retinol in liver was much higher in the period of rich nutrition than in the period of deficient nutrition (P < 0.05). Expression levels of BCO1 mRNA in kidney, jejunum, ileum, duodenum, muscle and rumen in the period of rich nutrition were significantly lower than in the period of deficient nutrition (P < 0.05), besides pancreas. Expressions of BCO1 protein in duodenum, jejunum, kidney, muscle, and rumen were lower in the period of rich nutrition than in the period of deficient nutrition (P < 0.05)