No abstract

Effects of dietary copper-loaded chitosan nanoparticle (CNP-Cu) supplementation on growth performance, hematological and immunological characteristics, and the cecal microbiota in broilers were investigated. Three hundred healthy Avian × Avian (1-d-old) broilers were randomly assigned into 5 dietary groups (20 birds per replicate with 3 replicates per group). Birds were fed with 0 (the control group), 50, 100, 150 mg/kg of CNP-Cu and 50 mg/kg chlorotetracycline (CTC, a positive control group) for 42 d. Results indicated that supplemental CNP-Cu could improve growth performance, affect the immune system, enhance protein synthesis, and be beneficial to cecal microbiota of Avian broilers, especially the dietary supplementation with 100 mg/kg of CNP-Cu. Supplementation with 100 mg/kg of CNP-Cu increased the average daily gain(P < 0.05) and the contents of IgA (P < 0.01), IgG (P < 0.01), IgM (P < 0.01), complement C3 (P < 0.05), and complement C4 (P < 0.05). Thymus, spleen, and bursa of Fabricus indexes and the populations of Lactobacillus and Bifidobacterium in cecal digesta were increased (P < 0.05) by 100 mg/kg of CNP-Cu supplementation, and the population of coliforms was decreased (P < 0.05). Dietary supplementation with 100 mg/kg of CNP-Cu increased (P < 0.05) concentrations of serum total protein and albumin, and decreased (P < 0.05) the content of urea nitrogen in serum. Effects of dietary supplementation with 100 mg/kg of CNP-Cu were similar to 50 mg/kg of CTC supplementation. These results may indicate that CNP-Cu could be a new substitute for CTC in dietary supplementation.

Many countries and cities around the world are located in humid subtropical areas, such as the south of China. Summers in these areas are very hot and humid, with daily temperature averages above 30°C and 75% RH. It has been reported that high temperatures reduce feed intake, egg production, egg weight, and egg quality [1][2][3]. The detrimental effects of high temper- SUMMARYBabcock Brown layers (n = 960), 40 wk of age, were allocated to 1 of 5 dietary treatments groups, each of which included 6 replicates of 32 hens. Each group received the same basal diet formulated with corn, peanut meal, and crystalline amino acids for 8 wk. l-Threonine was added to the basal diet at 0 (control), 0.1, 0.2, 0.3, and 0.4%, to achieve 0.47 (NRC, 1994), 0.57, 0.67, 0.77, and 0.87% threonine, respectively. Although supplementing the diet with lthreonine did not affect ADFI, FCR, egg weight, or egg quality (P > 0.05), the egg production response to supplemental l-threonine was quadratic, and it was maximized at 0.2% supplemental l-threonine. No differences were observed for uric acid, lactate dehydrogenase, alkaline phosphatase, Ca, and P concentrations among the treatments. Serum total protein concentration increased quadratically to supplemental threonine, and the response was maximized at 0.2 and 0.3% supplemental l-threonine. Serum free threonine increased quadratically as supplemental threonine increased, and the response was maximized between 0.2 and 0.3% supplemental lthreonine. The addition of l-threonine at 0.3% of the diet resulted in linearly increasing levels of IgG and total Ig (P < 0.05) as compared with those of the control group. In conclusion, current NRC (1994) recommendations for dietary threonine are insufficient for modern commercial laying hens strains reared under subtropical summer climates. We suggest that 0.2% threonine resulted in optimal egg production, whereas 0.3% l-threonine may have had a positive effect on the humoral immune response of laying hens under conditions of high temperature and humidity.