Effects Of β-Carotene On Lipid Synthesis Of Beef Cattle

Intramuscular fat and backfat thickness are very important economic characters of bovine that dealt with fat deposition. The process of fat deposition, is the result of proliferation, differentiation and apotosis of preadipocytes at cell level.also the result of selective expression of adipogenic genes in different time and space at molecular. And β-carotene is known to be an adipogenic factor influencing both in vitro and in vivo cell development. This study aimed to determine its effect on heifers adipose tissue development of beef steers during the early phase of postnatal development until90d of age and preadipocytes, respectively.To investigate the induction of preadipocyte differentiation, cells from subcutaneous and intramuscular adipose tissues of Simon tal hybrid cattle were isolated and cultured. After treatment of cells with0,10,20,30,50and80μM β-carotene, there were three repetition each processing. Then collcet cells and culture medium at0,5,10,15,20,25h after changing the culture. Cellular lipid content was assessed by Oil Red O staining and a triglyceride (TG) assay. And the relative expression of β-carotene-15,15’-momoxygenase1(BCMO1), β-carotene-9’,10’-momoxygenase2(BCO2), peroxisome proliferator-activated receptor-y (PPARy), retinoic acid X receptor a (RXRa), were also investigated. Moreover, Simmental catalo bullock (n=120) of healthy without disease and having similar body condition and weight were randomly divided into four groups. After15d of adaptation, it is90d of β-carotene supplementation. In the supplementation phase, the four groups of steers were fed the same ration but at different β-carotene levels (0,600,1200or1800mg/d). Then percentage of intramuscular fat and backfat thickness was measured. And the expression level of BCMOl,BCO2,PPARγ and RXRa was also analysed.The results of cell experiment in vitro showed that BSP and BIP differentiation level was suppressed obviously after P-carotene were added. BCO2expression increased obviously as β-carotene added(P<0.05). PPARy and RXRa expression were decreased obviously after β-carotene was added(P<0.05). The result of feeding experiment was that percentage of intramuscular fat and backfat thickness all decreased obviously after dealt with β-carotene(P<0.05). We also investigated the expression level of BCMO1, BCO2, PPARy and RXRa of intramuscular adipose tissues, and the expression level of BCMO1increased,PPARy and RXRa decrease obviously(P<0.05).Besides, we found that BCMO1did not nearly express in adipocytes of bovine, but BCO2had a good expression, while BCO2did not nearly express in adipocytes of bovine, but BCMO1expressed in intramuscular adipose tissues. We reckon initially that there are two different regulatory mechanism which BCMO1and BCO2operate respectively in intramuscular adipose tissues and adipocytes of bovine,but this conclusion also needs a large number of repeated experiments to test and verify. Therefore, in order to get high quality beef with good marbling, under the condition of not affecting normal growth and development of cattle, we can minimize the P-carotene or carotenoid content of feed. Moreover,we also further validated the advisability of using cell test in vitro to research animal production.