The effect of in ovo injection with organic zinc on the hatchability of broiler breeder hen eggs and evaluation of productivity in offspring broiler chickens

The present study investigates the effect of in ovo injection with organic zinc on the hatchability of egg breeder hens and evaluation of performance, carcass characteristics, blood parameters, liver enzymes, immune response, cecal microflora and breast fatty acid profile in production broiler chickens. In total, 320 fertile eggs from Ross308 breeder hens at the age of 55 weeks with the same average weight (65±1g) were selected for injection. Experimental treatments for in ovo injection include, treatment 1: negative control group (no injection), treatment 2: positive control (injection of 0.272 ml of normal saline solution), treatment 3: injection of 0.272 ml of saline solution containing 150 μg of organic zinc (40.8 μg for each egg) and treatment 4: injection of 0.272 ml of solution containing 300 μg of organic zinc (81.6 μg for each egg). 160 chickens were used in a completely randomized design including 4 treatments and 4 repetitions and ten birds during three raising periods, respectively, the starter (1-14 days old), growth (15-28 days old) and finisher (29-42 days old). The chickens were raised with diets based on corn-soybean meal. The results showed that the hatchability decreased in positive control and injected treatments (P <0.05). In the starter period, the feed conversion ratio (FCR) improved in the first and fourth treatments (P ≤0.05). In addition, after in ovo injection, no negative effect on production performance (feed consumption, body weight and FCR) was observed in the whole period (P >0.05). The fourth treatment (high zinc) showed the highest levels of cholesterol, triglyceride, VLDL, AST and ALT, as well as alkaline phosphatase and creatine kinase in the groups injected with zinc than the group without was zinc (P <0.05). The leukocytes and antibody titer at 28 days were significantly increased in treatments containing zinc (P <0.05). In addition, the reduction of gram-negative coliform and Escherichia coli bacteria and the parallel increase of gram-positive Bifidobacterium and lactobacillus bacteria in the groups injected with zinc were quite noticeable and significant (P <0.05). In conclusion, the results showed that the in ovo injection with organic zinc can maintain and even improve the hatchability and the performance of the bird, without any negative effect on the carcass characteristics of broiler chickens and with the potential to have a significant effect on health-giving traits including blood parameters, liver enzymes, immune system and intestinal microflora. So, Zn had a positive effect on some outcomes of interest, with no negative outcomes.本研究探讨了鸡胚内注射（in ovo injection）有机锌对种蛋孵化率的影响，并评估了商品肉鸡的生产性能、屠宰特性、血液指标、肝脏酶活、免疫应答、盲肠微生物群以及胸肌脂肪酸组成。共选取55周龄Ross308种母鸡的320枚可育蛋，平均蛋重为65±1g，用于注射实验。鸡胚内注射实验分组如下：处理1为阴性对照组（不注射）；处理2为阳性对照组（注射0.272ml生理盐水）；处理3为注射0.272ml含150μg有机锌的生理盐水（每枚蛋含锌40.8μg）；处理4为注射0.272ml含300μg有机锌的溶液（每枚蛋含锌81.6μg）。本实验采用完全随机设计，将160只肉鸡分为4个处理组、4个重复组，每个重复组10只鸡，分别在育雏期（1~14日龄）、生长期（15~28日龄）和育肥期（29~42日龄）三个饲养阶段开展饲养。肉鸡饲喂以玉米-豆粕为基础的日粮。结果显示，阳性对照组及各注射处理组的孵化率均有所下降（P<0.05）。在育雏期，处理1与处理4的饲料转化率（FCR）得到显著改善（P≤0.05）。此外，鸡胚内注射后，全饲养周期内肉鸡的生产性能（采食量、体重及饲料转化率）未出现负面影响（P>0.05）。与未注射锌的对照组相比，处理4（高锌组）的血清胆固醇、甘油三酯、极低密度脂蛋白（VLDL）、天冬氨酸转氨酶（AST）、丙氨酸转氨酶（ALT）、碱性磷酸酶及肌酸激酶水平均为各组最高（P<0.05）。28日龄时，含锌处理组的白细胞计数与抗体滴度均显著升高（P<0.05）。此外，锌注射组的革兰氏阴性大肠菌群与大肠埃希氏菌（Escherichia coli）数量减少，而革兰氏阳性菌双歧杆菌属（Bifidobacterium）与乳杆菌属（lactobacillus）数量平行增加，该变化显著且极具统计学意义（P<0.05）。综上，本研究结果表明，鸡胚内注射有机锌可维持甚至提高肉鸡的孵化率与生产性能，且对肉鸡屠宰特性无负面影响，同时对血液指标、肝脏酶活、免疫系统及肠道微生物群等健康相关性状具有显著改善潜力。因此，锌对部分目标指标具有积极作用，且未产生负面效应。