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.本研究探讨了卵内注射（in ovo injection）有机锌对罗斯308（Ross308）种母鸡孵化率的影响，以及对商品肉鸡生产性能、屠宰性能、血液指标、肝脏酶活、免疫应答、盲肠微生物区系与胸肌脂肪酸组成的评价。本试验总计选取55周龄、平均体重一致（65±1g）的罗斯308种母鸡受精蛋320枚用于卵内注射。试验设置4个处理组：处理1为阴性对照组（不进行注射），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有机锌的生理盐水溶液（每枚蛋对应40.8μg有机锌），处理4为注射0.272ml含300μg有机锌的溶液（每枚蛋对应81.6μg有机锌）。本试验采用完全随机设计，设置4个处理组与4个重复组，每个重复纳入10只试验鸡，总计使用160只肉鸡，试验分为三个饲养阶段：育雏期（1~14日龄）、生长期（15~28日龄）、育肥期（29~42日龄）。所有试验肉鸡均饲喂玉米-豆粕型基础日粮。试验结果显示，阳性对照组与各卵内注射组的孵化率均显著降低（P<0.05）。育雏期，处理1与处理4的料重比（FCR）显著改善（P≤0.05）。此外，全饲养周期内，卵内注射未对生产性能（采食量、体增重与料重比）产生负面影响（P>0.05）。相较于未注射锌的对照组，第4组（高锌组）的胆固醇、甘油三酯、极低密度脂蛋白（VLDL）、天冬氨酸氨基转移酶（AST）、丙氨酸氨基转移酶（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，各锌注射组的白细胞计数与抗体滴度均显著升高（P<0.05）。此外，锌注射组中革兰氏阴性大肠菌群与大肠杆菌（Escherichia coli）数量显著降低，同时革兰氏阳性双歧杆菌（Bifidobacterium）与乳杆菌（lactobacillus）数量显著升高，差异均具有统计学意义（P<0.05）。综上，试验结果表明，卵内注射有机锌可维持甚至提升肉鸡的孵化率与生产性能，且不会对肉鸡屠宰性能产生负面影响，同时对血液指标、肝脏酶活、免疫系统及肠道微生物区系等健康相关性状具有显著改善潜力。因此，锌对部分目标观测指标具有积极作用，未产生任何负面影响。