This experiment was conducted to determine the effect of active yeast (AY) and inactive-stabilized yeast (Thepax) supplementation to the rations in different levels on broiler performance. In the experiment carried out according to the randomized plot design, there were 5 different treatment groups as control group (Group 1), 0.1% Thepax (Group 2), 0.2% Thepax (Group 3), 0.1% AY (Group 4) and 0.2% AY (Group 5). In the experiment, the effects of active and inactive yeasts on body weight gain (BWG), feed consumption, feed conversion rate, carcass weight (CW), carcass yield (CY), abdominal fat amount and mortality were investigated. In the present experiment, the final live weight, the cumulative feed consumption and feed conversion were insignificant. The statistical difference between the groups in the experiment was significant in carcass weight, but insignificant in the amount of abdominal fat and mortality rate. Inactive-stabilized yeast (Thepax 0.1%) was more effective than 0.2% AY on BWG. Only 0.1% Thepax increased the CW besides CY was high in 0.1%, 0.2% Thepax and 0.1% AY groups. It has been observed that active and inactive yeasts are used in broiler chickens without any problem.

The aim of this study was to determine the effects of in ovo injection of Saccharomyces cerevisiae (SC) to fertile Ross 308 broiler eggs or dietary supplementation on growth performance, internal organ development, gut histomorphology and cecum microbiota during 14 d of growing period. This study was designed as 2×2 factorial experimental design. Fertile 92 Ross 308 eggs were injected with SC solution 0.2ml at 18d of hatch and 90 eggs non-injected as control, afterward dietary SC supplementation was applied during the 14 d to broiler diet. In this study, 160 broiler chicks were used in four treatment groups at 10 replicate for each treatment group and 4 chicks for each replicates. Treatment groups were A) in ovo SC injection + dietary SC supplementation, B) in ovo SC injection + basal diet, C) no injection + dietary SC supplementation, D) no injection + basal diet as control. Live weight, feed consumption, feed conversion ratio and gut histomorphology, caecum microbiota, internal organ weight were recorded at 14 days of age. Live weight gain increased in C group than in the D group. Feed consumption, feed conversion ratio and internal organ weights were not affected by the treatments. Villi length and villi width increased in A group among the other treatment groups in jejunum, villi length increased in A and C groups among the other groups in ileum. Villi length/villi width ratio increased in A group than in the D group in ileum, was not different in jejunum. LAB counts in caecum were higher in A group than those of C and D groups, but was not different from B group. Enterobactericaea count was lower in A and B group than in the D group, was not different from C group. To conclude, results showed that dietary Saccharomyces cerevisiae supplementation increased broiler growth at 14 day by increasing villi development and improving gut health.