This study investigated the effect of the serine protease on metabolizable energy and amino acids’ digestibility of different soybean meal for broilers. A total of 684 broilers chickens form 14 to 23 d age were distributed with nineteen treatments, six replicates, and six birds per replicate. Nine samples of soybean meal from different regions in Brazil were used, with some samples supplemented with the protease enzyme and others without addition. Apparent and corrected-for-nitrogen-balance metabolizable energy were evaluated, as well as the coefficients of amino acid digestibility. All collected data were submitted to ANOVA at a significance level of 5% and Tukey’s test was applied. The results showed that the addition of the protease enzyme significantly increased the values of AME and AMEn in all soybean meal samples. The soybean meal of different origins has significant variations in AME and AMEn. The addition of the protease improved the digestibility of essential amino acids compared to soybean meal without enzyme addition. These results indicate that supplementation with serine protease can improve the metabolizable energy and amino acid digestibility of soybean meal from different regions in the diet of broilers, potentially being an effective strategy to enhance nutrient utilization and animal performance.

Three experiments were carried out to verify the effects of the enzyme phytase, alone or combined with an enzyme complex, in diets deficient in available phosphorus (AP), calcium (Ca), and metabolizable energy (ME) on broiler performance, ME, and dietary amino acid digestibility. A total of 1,538 male Cobb 500 broilers were allocated to the three experiments, each of which consisted of five treatments: positive control (PC; basal ration); negative control 1 (NC1; PC minus 0.15% of AP, 0.16% of Ca, and 68 kcal kg-1 ME); negative control 2 (NC2; PC minus 0.15% of AP, 0.16% of Ca, and 101 kcal kg-1 of ME); NC1 plus phytase; and NC2 plus phytase plus enzymatic complex. Body weight gain (WG) and feed intake were measured from 1-21 days and from 1-42 days, and the corrected feed conversion rate (FCR) for mortality was calculated. In the second and third experiments, the apparent ME corrected for nitrogen balance (AMEn) and standardized digestibility of amino acids, respectively, were determined, for the diets supplemented with phytase and the enzymatic complex. In the first experiment, enzyme supplementation increased (p < 0.05) WG at 21 days and 42 days relative to the negative controls. Phytase inclusion improved (p < 0.05) FCR at the initial phase compared to the NC1 diet. In the second experiment, enzyme supplementation did not affect (p > 0.05) AMEn. In the third experiment, both enzyme treatments improved (p < 0.05) the digestibility of amino acids in the supplemented diets compared to the deficient diets. Supplementation with phytase and carbohydrases preserves the performance of broilers fed diets deficient in AP, Ca, and ME and improves amino acid digestibility.

The objective of this study was to evaluate the effect of adding different xylanase and beta-glucanase enzyme blends to maize- and soybean meal-based diets on performance and energy metabolizability in broilers. Two experiments were carried out with broilers of the COBB 500 strain. In the first experiment, 1960 chicks were assigned to a completely randomized design with a 2 x 3 + 1 factorial arrangement, totaling seven treatments, namely, T1- Positive control (PC); T2 - Negative control 1 (NC1; PC minus 200 kcal kg(-1) ME); T3 - NC1 + Blend A; T4 - NC1 + Blend B; T5 - Negative control 2 (NC2; PC minus 167 kcal kg(-1) ME and 5% amino acids); T6 - NC2 + Blend A; and T7 - NC2 + Blend B. Fourteen replicates were used per treatment and 20 birds per experimental unit. The parameters evaluated at 21 and 42 days of age were weight gain (WG), feed intake (F1) and feed conversion (FC). At 42 days, production efficiency index (PEI), viability and the yields of cuts were also calculated. Birds that received diets with a reduced nutritional value showed a reduction in WG and PEI and worsened FC as compared those of PC treatment (p < 0.05). However, the birds that consumed the NC2 diet with Blend B exhibited a similar WG to those in PC group (p > 0.05) from 1 to 21 days of life. For the yield of thigh + drumstick, the factors were statistically similar (p > 0.05) to those observed in the PC birds. In the second experiment, 432 fourteen-day-old chicks were distributed in a completely randomized design with seven treatments, with eight replicates per treatment and six birds per experimental unit. The apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) values were determined. Overall, the NC2 diet with Blend B provided the highest AME and AMEn values; however, NC1 with the same enzyme blend was the treatment which provided the lowest values. The addition of xylanase and beta-glucanase enzyme blends to maize- and soybean meal-based diets improves WG at 21 days as well as PEI in broilers; however, it does not influence the yield of cuts. Enzymes (Blend B) improve the energy metabolization of broiler diets with reduced energy and amino acid levels.

This experiment evaluated the influence of chromium (Cr) and vitamin E (VitE) supplementation on the performance, glucose levels, thyroid hormone levels, immune and oxidative response, and 70 kilodalton heat shock protein (HSP70) mRNA expression of broilers under heat stress (HS). Male chickens (n = 768, 22 days old) were randomly assigned to a 4x3 factorial with 4 Cr levels (0, 500, 1000, and 1500 ppb) and 3 VitE levels (0, 150, and 300 mg/kg), totaling 12 treatments with 8 replicates and 8 birds per experimental unit. Performance, glucose levels, thyroid hormone levels, heterophil-to-lymphocyte (H:L) ratio, malondialdehyde (MDA) in muscle, relative weight of lymphoid organs, and HSP70 mRNA expression were measured. VitE at 150 mg/kg improved FI and BWG (p ≤ 0.05). The combination of Cr 1500 ppb and VitE 150 mg/kg reduced FCR (p ≤ 0.05). Cr and VitE had single effects on glucose levels (p ≤ 0.05) and their interaction influenced thyroid hormone levels (p ≤ 0.05). Cr 1500 ppb with VitE 300 mg/kg lowered the H:L ratio and HSP70 mRNA expression (p ≤ 0.05). VitE at 300 mg/kg increased spleen relative weight (p ≤ 0.05). Cr supplementation reduced MDA concentrations (p ≤ 0.05). In conclusion, Cr and VitE, individually or combined, benefitted performance, glucose and thyroid hormone levels, immune and oxidative response, and heat stress tolerance.