Effect of 25-Hydroxycholecalciferol supplementation on broiler chicken skeletal muscle growth and development
Hutton, Kelly C.
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To determine the effect of 25-hydroxycholecalciferol (25OHD3) on broiler chicken skeletal muscle growth and development, day-old male Ross 708 broiler chickens (Aviagen Group, Huntsville, AL; n = 150) were randomly assigned to one of two corn and soybean meal-based diets. The control diet (CTL) was formulated to contain 5,000 IU D3/kg of diet, while the experimental diet (25OHD3) contained 2,240 IU vitamin D3/kg diet + 69 µg 25OHD3/kg diet. Chickens were housed in Start Grow cage units (Alternative Design Manufacturing and Supply, Siloam Springs, AR) and allowed ad libitum access to feed and water. At the end of each seven-day period, ten birds from each treatment were harvested. Two hours prior to harvest, birds were injected intraperitoneally with 5’-bromo-2’deoxyuridine (BrdU) to facilitate labeling of mitotically active cells. Prior to harvest, blood was collected from each bird. The left Pectoralis major (PM) and Biceps femoris (BF) muscles were removed and weighed to determine muscle yields, while the right PM and BF were processed for cyrohistological determination of skeletal muscle fiber cross-sectional area and enumeration of Myf-5+ satellite cells, and mitotically active cells. Average daily gain (ADG), average daily feed intake (ADFI) and feed efficiency (G:F) were determined weekly. Circulating 25OHD3 concentrations were greater in 25OHD3-fed birds on d 7, 14, 21, 28, 35, 42, and 49 when compared to CTL (P < 0.001). No differences among treatment groups were observed in ADG, ADFI, G:F, PM and BF muscle mass, or the number of mitotic active cells. However, broiler chickens fed 25OHD3 tended to have greater Myf-5+ satellite cell density (P = 0.09) on d 14, greater total nuclear density (P = 0.05) on d 28, and greater PM muscle fiber cross-sectional area (P = 0.09) on d 49 compared to their CTL counterparts. These results suggest that feeding 25OHD3 in place of vitamin D3 may impact broiler chicken skeletal muscle growth in a satellite cell-mediated manner.