-This experiment was conducted with the objective of evaluating cysteamine (CS) supplementation in broiler chick diets with different energy density patterns. A total of 980 chicks of the Cobb 500 strain at one day of age were allocated into 28 plots. A completely randomized design in a 2 × 2 factorial arrangement, with 7 replications, was adopted. The factors under study were the supplementation (or absence) of cysteamine (60 mg/kg and 80 mg/kg of feed in the starter and growth/finishing phases, respectively) and two patterns of apparent metabolizable energy corrected by nitrogen balance (AMEn) in the diets. The energy levels (Mcal/kg of feed) practiced in pattern 1 were 3.00; 3.10; and 3.20, and for pattern 2, they were 3.05; 3.20; and 3.30 in the starter, growth and finishing phases, respectively. The diets were on the basis of corn and soybean meal with a feeding program with three diets. Feed intake, weight gain, feed conversion, feasibility and carcass yield were evaluated. There was no interaction between the CS supplementation and AME patterns in the diet upon the performance and/or carcass characteristic evaluated. Broilers fed the diet supplemented with CS presented improved feed conversion along the rearing cycle, but feed intake and weight gain were not affected by the supplementation of CS. The highest pattern of energy density (2) provided increased weigh gain in the starter phase of rearing and better feed conversion of the birds over the whole rearing period. The carcass yield was not influenced by the cysteamine supplementation and/or energy levels studied.

An experiment was conducted with the purpose of evaluating enzyme blends on the performance, carcass traits, and bone mineralization of broilers. In total, 928 one-day-old Cobb 500 male chicks of were used. A completely randomized design with four treatments with eight replicates of 29 birds each was adopted. The evaluated treatments were: 1-Positive Control (PC), feed containing the nutritional recommendations of the genetic company's manual; 2-Negative Control (NC), feed with reductions of 75 kcal/kg AME and 0.10 and 0.12 percent points of phosphorus and calcium, respectively; 3 -NC + enzyme blend (amylase + β-glucanase, xylanase, and phytase; 250 g/t of feed) and 4 -NC + enzyme complex (phytase, amylase, xylanase, glucanase, pectinase, cellulase, and protease; 200 g/t of feed). Birds fed the diet with reduced nutrient levels (NC) presented the worst performance (p<0.05). The supplementation of the enzyme blend promoted similar (p<0.05) weight gain and feed conversion ratio as those obtained with the PC diet during the period of 1-21 days of age. During the phase of 22-42 days and the entire experimental period, weight gain and feed conversion ratio improved with the use of the enzyme combinations compared with the NC group, but remained lower than the PC group. Enzymes combinations did not affect (p>0.05) carcass or parts yields. The broilers fed the reduced-nutrient and energy diet presented lower (p<0.05) tibial ash, calcium, and phosphorus contents that the other treatments. The use of enzyme combinations improved the performance of broilers fed diets with reduced nutrient and energy levels.

-The objective of this experiment was to evaluate the use of probiotic based upon Bacillus subtilis C-3102 (BS) in broiler diets containing or not conventional additive growth-promoter (AGP). A total of 1,824 one-day-old chicks of the Cobb-500 strain were used and distributed into 48 plots (1.50 × 2.00 m). A completely randomized design with four treatments and 12 repetitions was adopted. The treatments evaluated were: 1-Negative Control -AGP-free diet (NC); 2 -Positive Control, with AGP halquinol 30 mg/kg diet (PC); 3 -NC + BS (3x10 5 cfu/g diet); and 4 -PC + BS (3x10 5 cfu/g diet). The diets were on corn, soybean meal and meat and bone meal basis, formulated according to the nutrient allowances of the Strain Cobb Guide, following a feed program with three diets (starter, grower and finisher). At 21 and 42 days of age, feed intake, weight gain and feed conversion were evaluated, and carcass yield characteristics were determined at 42 days of age. Throughout the trial period (starter and total phases), better feed conversion was found for broilers fed diet with both additives (AGP and BS) combined. At the end of the experiment (1 to 42 days), the highest weight gain also occurred in broilers fed diets with a combination of the two additives. In present study, the use of BS or AGP alone in diets did not affect the performance of broilers. The carcass yield was not influenced by the use of the additives and beneficial effects of supplementation of BS and AGP combined in the diet on broiler performance were observed.