The objective of this study was to investigate the effects of four dietary levels of L-threonine (0, 2.5, 5 and 7.5 g/kg) with or without Saccharomyces cerevisiae (SC) on performance, carcass characteristics, intestinal morphology and immune system of broiler chickens. A total of 360 1-d-old male broiler chicks were randomly allocated to eight treatments with three replicates of 15 birds. The experiment was done at 0 to 3 weeks (as starter phase) and 3 to 6 weeks (as grower phase). Growth performance traits including weight gain, feed intake and feed conversion ratio were recorded at the end of each week. At the end of the experiment eight birds per treatment were killed and carcass analysis was done. Sampling for blood evaluation was done on 7, 28 and 42 days of age. Results of this study indicated that use of SC did not affect feed intake, weight gain and feed conversion ratio in chicks in contrast with the L-threonine. Use of L-threonine improved feed conversion ratio and gain of birds. Carcass traits were not influenced by dietary L-threonine and SC supplements. Use of L-threonine increased the intestinal morphology parameters such as crypt depth and villi height and width in both jejunum and ileum segments. On the other hand, villi height and width and crypt depth increased in both jejunum and ileum segments when dietary L-threonine increased. Effect of SC supplement on intestinal morphology was not significant. Results of CBC (cell blood counts) parameters, such as white blood cells, red blood cells, haematocrit and haemoglobin showed that these parameters were not affected by dietary treatments. Furthermore, the immune response (antibody titre) against Newcastle disease was not affected by SC on both 26 and 42 days of age. However, use of L-threonine influenced the chicks' immune response at 42 days of age. Our results have shown that the supplementation of L-threonine as a source of dietary-threonine in combination with SC improved growth performance and intestinal morphology traits in broilers.

The effect of cinnamon powder (CNP) feeding on some blood metabolites in broiler chicks was studied in a 49-day experiment. The feeding program consisted of a starter diet until day 21, a grower diet until day 42 and a finisher diet until day 49. There were five treatments: a negative control diet, without the additive (control: T1); 250 mg/kg (T2); 500 mg/kg (T3); 1000 mg/kg (T4); and 2000 mg/kg (T5) of CNP in the diet. A total of 320 one-day-old mixed-sex broilers (Ross 308) were distributed into 16 pens with 20 chickens each, comprising 3 replicates per treatment (except for T1, which had 4 replicates). Serum glucose was measured weekly and reported periodically. At the end of the experiment serum cholesterol, triglycerides, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were determined. There were no significant differences among treatments regarding broiler performance and carcass characteristics, except for the finisher phase, when T2 resulted in a significant decrease in feed conversion ratio and weight gain (p<0.05). In the lowest level of cinnamon supplementation (T2), a significant increase in glucose level in starter, finisher and overall rearing period was observed, as well as an increase in triglyceride levels at the finisher phase as compared to T4 and T5 (p<0/05). However, cholesterol, AST and ALT levels were not statistically different among treatments. Therefore, it was concluded that the use of cinnamon powder can affect on some blood metabolites and broiler performance.