RESUMO
This study was conducted to determine the effects of dietary inclusion levels of iodine supplementation and duration of feeding on performance, carcass characteristics, meat iodine, thyroid hormones and some indices including red blood cell, haematocrit, haemoglobin, aspartate transaminase, alanine transaminase and alkaline phosphatase in broilers. A total of 450 one-day-old male broiler chicks were used during a 42 days experiment in 9 treatments with five replicates pen for each treatment. The experimental design was a 3 × 3 factorial arrangement of treatments including three levels of iodine (0, 2.5 and 5 mg/kg as a source of potassium iodide) during the T (total, 1-42 days), GF (grower and finisher, 11-42 days) and F (finisher, 25-42 days) periods (p < .05). The results demonstrated that none of the performance data (feed intake, body weight gain and feed conversion ratio) were influenced by level and duration of iodine consumption (p > .05). The diet supplemented with 5 mg/kg iodine had no effects on relative weights during total (T) and grower and finisher (GF) periods, but there was an effect on the finisher (F) period. Moreover, increasing the iodine level from 0 to 5 mg/kg linearly decreased the relative weights of the both small intestine and jejunum (p < .05). Increasing the iodine level from 0 to 5 mg/kg linearly increased the breast iodine content. Also, the highest breast meat enrichment was observed during the T period (p < .05). Blood triiodothyronine concentration was not changed by any of the iodine level and duration of consumption, but tetraiodothyronine concentration was higher for T period than GF and F ones (p < .05) and even linearly increased by increasing the level of dietary iodine for 0 to 5 mg/kg (p < .05). It was concluded that 5 mg/kg iodine from day 1 to day 42 of age is needed in the diet to enrich the broiler meat.
