Chickens from Lines Selected for High or Low Body Weight Differ in Adipocyte Cellularity in Several Adipose Tissue Depots (814.3)

The Virginia lines of chickens are a model of obesity and hypophagia that resulted from long‐term selection for high (HWS) or low (LWS) juvenile (56 days of age) body weight, respectively. We hypothesized that there are differences in adipocyte cellularity between HWS and LWS chickens. At day 65, abdominal and clavicular fat were collected from HWS and LWS males (n = 9) for histological analysis. The mean area and diameter, density and size distribution of adipocytes were analyzed using NIS‐Elements Advanced Research Software (Nikon). The statistical model included main effects of fat depot (abdominal or clavicular fat), genetic line (HWS or LWS), and the interaction between them. Means were separated using Tukey’s Test. Adipocyte areas and diameters were greater in HWS than LWS in abdominal (P < 0.0001) and clavicular fat (P < 0.0001). Adipocytes were larger in clavicular fat than abdominal fat (P < 0.01). Overall cellular density was less (P < 0.0001) in HWS than LWS in both abdominal fat and clavicular fat. Most of the adipocytes in HWS were between 1,000 and 4,000 µm2, with some as large as 9,500 µm2. The LWS contained greater numbers of small cells, with most adipocytes between 500 and 2,000 µm2, and no adipocytes larger than 5,200 µm2. The results show that adipocytes in HWS chickens were larger and sparser as compared to the LWS. There were “oversized” adipocytes in HWS, indicative of obesity.