Dietary fat and triiodothyronine (T-3) interactions in the broiler chicken

Male, Indian River, broiler chickens growing from 7 to 28 d were fed on die ts containing 180 g elude protein, 300, 600 of 1200 kcal fat calories and 0 or 1 mg T-3/kg diet, Birds were bled and sacrificed at d 28, 29 and 30. Me asurements taken at these intervals included in vitro lipogenesis (IVL), gr owth and feed consumption and hepatic enzyme activities. Plasma metabolites as well as thyroid hormones were also determined. Dietary fat levels did n ot influence growth or feed intake. In contrast, T-3 decreased growth and f eed intake by 25% without altering the efficiency of feed utilization. Diet ary T-3 and additional fat decreased IVL and lipogenic enzyme activities, D ietary T-3 increased plasma T-3 and decreased plasma T-4. Dietary fat energ y levels had no effect upon plasma thyroid hormone levels. Although both ad ditional dietary fat and T-3 modify broiler lipid metabolism, there was no additional treatment effect when high-fat diets were supplemented with T-3. In contrast to previous reports, T-3 did not increase any parameter associ ated with lipid metabolism.