Effects of selenium supplementation on growth performance, thyroid hormone levels, antioxidant enzyme and disaccharidase activities in broiler chick

Abstract

The objectives of this investigation were to study the effect of selenium supplementation and fasting on growth performance and flock uniformity, thyroid hormone (T3) levels, antioxidant enzyme and disaccharidase activities of broiler chicks. One thousand nine hundred and twenty, day old, male chicks (Cobb 500) from parent stock without selenium supplementation in diet were allocated into 6 treatments. The treatment were T1: chicks were fed immediately after arrival and received basal diet, T2 and T3 chicks were fed immediately after arrival and received basal diet plus 0.2 ppm as organic selenium and 0.2 ppm as inorganic selenium, respectively. T4, T5 and T6 chicks were fasted for 48 h after arrival and received diets as same as T1, T2 and T3, respectively. At days 14, 28 and 42 of age, body weight and feed intake were recorded. Individual body weight was measured from 50% of chicks in each treatment at days 14 and 28 of age and 100% of chicks in each treatment at days 42 for uniformity calculation. On the first day, ten extra chicks were collected for blood samples from heart for background thyroid hormone (T3) levels. Chicks were killed using carbon dioxide inhalation chamber, liver samples were collected for background antioxidant enzyme activities. On days 7, 14, 21 and 42, one chicks from each replicate pen was selected and blood and liver sample were collected for determine thyroid hormone levels and antioxidant enzyme activities. At days 21, jejunum from each chick was excised and mucosa was scraped for determination of disaccharidase activities. At the overall period (days 1-42 of age), fed chicks had significantly (p<0.05) higher body weight gain, ADG, feed intake and DFI than fasted chicks. On the contrary, fasted chicks had significantly (p<0.05) better FCR than fed chicks. Chicks that received diet supplemented with OS had the highest final body weight and body weight uniformity. In addition, selenium supplemented chicks had significantly (p<0.05) higher GSH-Px (days 7 and 42 of age) and SOD (days 14 and 42 of age) activity than control. It was found that fed chicks and selenium supplemented chicks had significantly (p<0.05) higher T3 levels than fasted chicks and control. There were no significant difference on CAT (days 1-42) and disaccharidase activity (days 21) from treatment diet. In conclusion, fasting chicks for 48 h reduced body weight, feed intake and flock uniformity, but these chicks had better FCR and mortality rate compared to fed chicks. Selenium supplementation in both fed and fasted chicks helped to increase GSH-Px (days 7 and 42 of age) and SOD 14 and 42 of age, enhance T3 levels in the second week, trended to increase disaccharidased at days 21 of age and improve growth performance. Organic selenium supplemented chicks had better growth performance (ADG, FCR at days 15-28 of age and flock uniformity at days 1-42 of age ) and uniformity than inorganic selenium supplemented chicks.