Effects of supplementation with vitamin D3 on growth performance, lipid metabolism and cecal microbiota in broiler chickens

Lower intramuscular fat (IMF) and excessive abdominal fat reduce carcass quality in broilers. The study aimed to investigate the effects of dietary VD₃ on growth performance, lipid metabolism and cecal microbiota in broilers over an 84-d feeding experiment. One-day-old male <i>Luhua</i> broilers (210) were randomly assigned to control (basal diet) and VD group (basal diet supplemented with 3,750 IU/kg VD₃). Samples were collected after a 12-h fasted feeding on days 28, 56, and 84. Supplementary VD₃ significantly enhanced average daily gain (ADG) in broilers aged 57-84 d and 1-84 d, and increased leg muscle rate and fat content in breast and leg muscles and reduced abdominal fat rate of broilers at 84 d. VD₃ increased TG and glycogen content in the liver of 28- and 84-d-old broilers, serum TG and VLDL-C content at 56 and 84 d, and TC, HDL-C and LDL-C at 84 d. VD₃ increased mRNA expressions of genes related to <i>de novo</i> lipogenesis (DNL) (<i>mTOR</i>, <i>SREBP-1c</i>, <i>FAS</i> and <i>ACC</i>), lipid oxidation (<i>AMPK</i>, <i>PPARα</i>, <i>CPT-1α</i> and <i>ACO</i>) and lipid transport (<i>ApoB</i> and <i>MTTP</i>), and FAS, ACC and CPT1 enzyme activities in the liver. However, mRNA levels of genes involved in DNL and cellular lipid uptake (<i>LPL</i> and <i>FATP1</i>) and LPL activity were decreased in abdominal adipose tissue, and that of genes involved in lipid oxidation and lipolysis (<i>HSL</i> and <i>ATGL</i>) was increased by VD₃. <i>LPL</i> and <i>FATP1</i> expression in breast and leg muscles was increased by VD₃. Moreover, VD₃ increased the abundance of cecum <i>Bacteroides</i> at 28 and 84 d, <i>Rikenellaceae_RC9_gut_group</i> and <i>Faecalibacterium</i> at 56 and 84 d, and <i>Lachnoclostridium</i> at 84 d. These bacteria were correlated with increased DNL, lipid oxidation and lipid transport in liver, and cellular lipid uptake in muscle, as well as decreased DNL and cellular lipid uptake, and increased lipid oxidation and lipolysis in abdominal adipose tissue. Altogether, supplementary VD₃ in basal diet improved growth performance, increased IMF, and reduced abdominal fat rate, which is significant for enhancing feed utilization and improving the carcass quality of broilers. The regulation of VD₃ on lipid metabolism could was associated with variation in cecal microbiota composition.