Hepatic Gene Expression Profiles of Growing versus Finished Beef Steers

Growing and finishing phases are two important animal production stages, which differ fundamentally in compositional growth. However, the physiological mechanisms altered concomitantly with the shift in whole-body compositional gain as cattle fatten (growing vs. finished steers), are poorly understood. Microarray analysis using the Bovine Gene 1.0 ST Array was conducted to determine shifts in hepatic genomic expression profiles of growing vs. finishing beef steers. The specific overall hypothesis tested was that genes involved in amino acid, carbohydrate and lipid metabolism, antioxidant capacity and immune responses were differentially expressed in growing vs. finishing steers. Sixteen weaned Angus steers (BW = 209 ± 29.4 kg) were randomly assigned (n = 8) to develop through growing (final BW = 301 kg) or finished (final BW = 576 kg) growth phases and individually fed enough of a cotton seed hull-based diet to achieve a constant ADG (1.5 kg/d). Steers had ad libitum access to fresh water and an industry standard vitamin-mineral supplement. Liver samples were collected for RNA extraction and microarray analysis.