RESUMO
The aim of this study was to investigate the influence of dietary supplementation of bovine lactoferrin (bLF) on growth performance, carcass traits, histomorphology of jejunum, immune function and hepatic and splenic gene expression of interferon-gamma (IFN-γ) and interleukine-2 (IL-2) in broiler chickens. A total of 240 one-day-old Ross 308 male broiler chickens were randomly allotted into six dietary treatments with four replicate pens (10 chicks per pen) and fed experimental diet in 3 feeding phases (starter: d 0-10, grower: d 11-24 and finisher: d 25-42). The experimental treatments were (1) corn-soya bean meal-based basal diet (control), (2-5) basal diet supplemented with 200, 400, 600, 800 mg/kg bLF, respectively, and (6) basal diet supplemented with 200 mg/kg oxytetracycline (OTC). The average body weight gain (ABWG) of broilers fed 800 mg/kg bLF was 8.48% higher than those fed a corn-soybean meal-based diet during the starter period (d 0-10) (linear effect, p = 0.002; quadratic effect, p = 0.24). Average daily feed intake (ADFI) and the feed conversion ratio (FCR) were not affected (p>0.05) by bLF supplementation. At 42 days of age, the breast meat percentage and carcass yield of broilers fed 800 mg/kg bLF compared with the control group significantly increased by 9.51% and 6.03% respectively (p < 0.05). Compared with the chicks fed the control diet, the chicks fed diets supplemented with bLF had higher villus height, muscle thickness and villus surface area (p > 0.05). Dietary bLF inclusion increased the total immunoglobulin (IgT) titre against sheep red blood cells (SRBCs) antigen (linear effect, p = 0.031; quadratic effect, p = 0.035) and improved the phytohaemagglutinin-P (PHA-P)-skin test of broilers. Compared with the control, bLF enhanced the gene expression of IFN-γ in spleen (p = 0.048, linear effect, p = 0.009; quadratic effect, p = 0.093) and liver (p = 0.012, linear effect, p = 0.008; quadratic effect, p = 0.01) and IL-2 expression in spleen (p = 0.021, linear effect, p = 0.026; quadratic effect, p = 0.103). The bLF supplementation had no effect on IL-2 gene expression in liver (p > 0.05, linear effect, p = 0.213; quadratic effect, p = 0.159). In conclusion, we found that supplementation of broiler diets with 800 mg/kg bLF can improve the growth performance, carcass yield, cell-mediated and antibody-mediated immune responses and enhance the IL-2 and IFN-γ gene expression of broilers.