Evaluation of olive leaf extract as a growth promoter on the performance, blood biochemical parameters, and caecal microflora of broiler chickens

ABSTRACT The objective of the study was to examine the effects of an alcoholic liquid olive leaf extract (OLE) obtained from fresh leaves on the growth performance, carcass weight, caecal microflora, and some plasma variables, such as triglycerides, total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) cholesterol in broiler chickens. A total of 375 one-day-old male broilers (Ross 308) were randomly divided into five treatments with five replicate pens (15 birds each) per treatment. The birds were fed either a basal diet with no supplement (control), with 75 (OLE75), 150 (OLE150), 300 (OLE300), and 600 (OLE600) mg kg−1 oleuropein, provided by 0.66, 1.33, 2.65, and 5.32 g kg−1 of the OLE. The dietary supplementation of OLE linearly increased daily body weight gain (BWG), feed intake (FI), and carcass weight and improved feed conversion ratio (FCR). Although the OLE600 broilers had the highest daily FI among the treatments, there were significant increases in their BWG and improvements in FCR compared with the control, OLE75, and OLE150 birds. The carcass weights of OLE150, OLE300, and OLE600 birds were higher than those of the control group. The OLE600 diet increased the dressing percentage compared with the OLE75, OLE150, and OLE300 diets. The abdominal fat weight and the plasma HDL concentration of the control broilers were lower than those of all OLE birds. All doses of OLE supplementation decreased the caecal E. coli content. A growth-promoting effect is obtained from the dietary supplementation of 600 mg kg−1 oleuropein due to its beneficial effect on growth performance and caecal microflora populations of broilers.摘要 本研究旨在探讨以新鲜橄榄叶为原料制备的酒精性液体橄榄叶提取物（Olive Leaf Extract, OLE）对肉鸡生长性能、屠体重、盲肠微生物区系以及甘油三酯（Triglycerides）、总胆固醇（Total Cholesterol）、高密度脂蛋白（High-Density Lipoprotein, HDL）、低密度脂蛋白（Low-Density Lipoprotein, LDL）胆固醇等血浆指标的影响。试验共计选取375只1日龄雄性罗斯308（Ross 308）肉鸡，随机分为5个处理组，每组设置5个重复栏，每栏饲养15只肉鸡。试验肉鸡分别饲喂基础日粮（对照组，无额外添加物），以及添加75、150、300、600 mg·kg⁻¹橄榄苦苷的日粮，对应添加量分别为0.66、1.33、2.65、5.32 g·kg⁻¹的OLE，各组依次记为OLE75、OLE150、OLE300、OLE600组。日粮添加OLE可线性提升肉鸡的日增重（Body Weight Gain, BWG）、采食量（Feed Intake, FI）与屠体重，并改善饲料转化率（Feed Conversion Ratio, FCR）。尽管OLE600组肉鸡的日采食量在所有处理组中最高，但与对照组、OLE75组及OLE150组相比，其日增重仍显著提升，饲料转化率得到明显改善。OLE150、OLE300及OLE600组肉鸡的屠体重均显著高于对照组。与OLE75、OLE150及OLE300组日粮相比，OLE600组日粮可提高肉鸡屠宰率。对照组肉鸡的腹脂重量与血浆高密度脂蛋白浓度均低于所有OLE处理组。各添加剂量的OLE均能降低肉鸡盲肠大肠杆菌含量。日粮添加600 mg·kg⁻¹橄榄苦苷可发挥促生长作用，因其对肉鸡生长性能及盲肠微生物区系种群具有积极有益的调控效果。