Effect of energy levels in isoproteinic diets on performance, metabolism and thyroid hormones in broilers

Abstract

A study was conducted on the effects of three dietary energy levels (2 600, 2 900, and 3 200 Kcal EM/kg) in isoproteinic diets for broiler chicks, on the productive erformance, plasma thyroid hormone (T4 and T3) levels and metabolic rate, determined at 28 and 49 days of age and at environmental temperatures of 15ºC, 25ºC, and 35ºC. Birds fed the highest energy level showed the most rapid weight gain and greater feed intake. Metabolic rate was dependent on ambient temperature and age of the birds, but not on the dietary energy level. No correlation was observed between plasma thyroid hormone concentration and energy intake.