Effect of In Ovo Ascorbic Acid Injection and Thermal Manipulation During Incubation on Intestine Morphology of Broilers Reared under Cold and Heat Stress

ABSTRACT It was investigated if pre-incubation ascorbic acid (AA) injection in fertile eggs incubated at high temperature impacts the performance, the yield of carcass and parts, and the intestine morphology of broilers reared under heat stress. Three thousand Cobb® fertile broiler eggs were randomly distributed according to weight into three incubations treatments (eggs not injected with AA and incubated at 37.5°C; eggs not injected with AA and incubated at 39°C; and eggs injected with 6 µg AA/100 µL water prior to incubation and incubated at 39ºC). The hatched birds were reared at thermoneutral, cold, and hot house temperatures. Broilers reared under hot temperature presented lower feed intake and weight gain than the broilers of the different rearing temperatures. Egg incubation at 39.0 ºC and 39.0 ºC + AA reduced broiler viability. Carcass and cut yields were not influenced by incubation and rearing procedures. Duodenal goblet cell count was lower in broilers from eggs of the treatment 39ºC + AA than in broilers from the other incubation treatments and in broiler rearing in hot temperature. In the jejunum, the goblet cell counts were higher in broilers that were reared under hot than thermoneutral temperatures. The incubation treatment of 39 ºC+AA increased the goblet cell counts in the ileum of broilers reared under cold temperatures. Rearing temperature influenced the duodenal villi counts, which were lower under cold rearing conditions than in the two other rearing temperatures. The results showed that egg incubation at 39°C, independently of ascorbic acid injection, did not produce an effective epigenetic heat adaptation in broilers.摘要 本研究探讨了高温孵化条件下，对受精蛋预注射抗坏血酸（ascorbic acid, AA）是否会对热应激饲养条件下肉仔鸡的生产性能、胴体及各分割部位产率与肠道形态学特征产生影响。试验将3000枚科宝（Cobb®）肉仔鸡受精蛋按体重随机分为3个孵化处理组：①未注射AA且于37.5℃下孵化的蛋；②未注射AA且于39℃下孵化的蛋；③孵化前注射6 μg AA/100 μL水溶液并于39℃下孵化的蛋。将出雏后的肉仔鸡分别置于热中性、低温与高温舍温环境中饲养。结果显示，高温饲养的肉仔鸡采食量与增重均低于其他饲养温度组的肉仔鸡。39.0℃孵化以及39.0℃+AA孵化处理均会降低肉仔鸡存活率。孵化与饲养处理对胴体及各分割部位产率无显著影响。相较于其他孵化处理组以及高温饲养的肉仔鸡，39℃+AA处理组孵化出的肉仔鸡十二指肠杯状细胞数量更低。在空肠中，高温饲养组肉仔鸡的杯状细胞数量高于热中性饲养组。39℃+AA孵化处理可提升低温饲养条件下肉仔鸡回肠的杯状细胞数量。饲养温度对十二指肠绒毛数量存在显著影响，低温饲养条件下的绒毛数量低于另外两种饲养温度组。研究结果表明，无论是否注射抗坏血酸，39℃的蛋孵化条件均无法使肉仔鸡获得有效的表观遗传热适应性。