Experiments were conducted to assess effects of nursery feeding programs (using complex or simple diets, including or excluding antibiotics) on growth performance of barrows and gilts up to market weight (approximately 115 kg body weight), plasma levels of growth-related hormones, chemical body composition and carcass traits at market weight. Reducing nursery diet complexity decreased (P < 0.05) growth performance and plasma levels of triiodothyronine during the nursery period, but had no negative carry-over effects on growth performance or hormone plasma levels thereafter. Excluding antibiotics from nursery diets reduced nursery growth performance and plasma levels of insulin-like growth factor-1 and triiodothyronine but appeared to induce subsequent compensatory growth. In general, nursery feeding programs had no effect on body composition and carcass traits at market weight and no effect on wean-to-finish growth performance or carcass value at market weight. This represents an opportunity to improve profitability in commercial pork production. / Ontario Pork; The Ontario Ministry of Agriculture, Food and Rural Affairs; Canadian Agriculture and Agri-Food Swine Research Cluster