Abstract: An experiment was conducted to study the effect of microbial phytase supplementation and citric acid on thyroid activity, relative weight of lymphoid organs and pH values of some GI-tract segments in broiler chickens fed corn-soybean meal based diets. The data was analyzed using a Randomized Complete Block Design (RCBD) with factorial arrangement of 3x3 with three levels of citric acids (0, 3 and 6%) and three levels of phytase (0, 500 and 1000 IU kg-1). There were three replicates (with ten chicks in each replicate) for each treatment. A total of 270 Ross 308 broilers chicks were used. The results indicated that addition of citric acid to diets caused significant decrease in pH values of crop, gizzard, duodenum, jejunum and ileum (p<0.05) and caused significant increase (p<0.01) in plasma Triiodothyronine (T3) concentration, T3:T4 ratio and relative weight of bursa and thymus but had no significant effect on Thyroxin (T4) concentrations. Microbial phytase significantly increased relative weight of thymus (p<0.01) but had no significant effects on thyroid gland activity, relative weight of bursa and values of pH in different parts of the GI-tract.
Rouhollah Nourmohammadi, Seyed Mohammad Hosseini, Hamed Saraee, Alireza Arab and Hamed Arefinia, 2011. Plasma Thyroid Hormone Concentrations and pH Values of Some GI-Tract Segments of Broilers Fed on Different Dietary Citric Acid and Microbial Phytase Levels. Journal of Animal and Veterinary Advances, 10: 1450-1454.