Effects of in ovo feeding of xylobiose and xylotriose on growth performance, carcass traits, ileal histomorphometry, and immune-related gene expression in broiler chickens

Abstract

Xylooligosaccharides (XOS) are known as prebiotics which promote beneficial gut microbes, improve gut health and the performance of broilers. Xylobiose (XOS2) and xylotriose (XOS3) are two compounds in the XOS group. In ovo feeding could deliver these prebiotics to the embryo, and this is considered as an effective method for studying the effects of the prebiotics during embryonic development and the post-hatch period. This study investigated the effects of in ovo feeding of XOS2 and XOS3 on growth performance, carcass traits, ileal histomorphometry, and immune-related gene expression in broilers. A total of 144 fertilized eggs of Cobb 500 broilers were divided into three groups: (a) non-injected control (CON), (b) XOS2, and (c) XOS3. The eggs from XOS2 and XOS3 groups were injected with 0.5 ml of 0.85% normal saline solution containing 3 mg of XOS2 and 3 mg of XOS3, respectively, into their amniotic sac on the 17th embryonic day. A total of 131 hatched chicks were raised in 18 replicate pens (5 or more chicks per pen) following standard management practices and fed a corn-soybean meal-based diet for 21 days. The feed intake and body weight (BW) data were recorded weekly. The chickens were euthanized on day 7, day 14, and day 21 to collect ileum sections, and the carcass traits were recorded on only day 21. Total RNA was extracted from ileum tissues, and qPCR was performed to measure the gene expression. All the statistical analyses considered the significance level at a P value <0.05. The result showed that in ovo treatments did not affect the hatchability of the eggs. The XOS2 group showed a trend to increase the BW on day 0, compared to CON (P=0.052), and the XOS3 group showed better FCR improvement than the XOS2 group in the first week. There was no difference (P>0.05) among the groups for the weight of the breast muscle, drumsticks, gizzard, proventriculus, and carcass weight at the age of 21 days. The histomorphometry of the ileum on day 7 revealed a significant reduction (P<0.05) of villi height (VH), villi width (VW), and crypt depth (CD) in XOS2, compared to the CON group. On day 7, a lower CD and a higher VH to CD ratio were recorded in XOS3, compared to CON. On day 14, XOS3 showed an increase in VW and villi surface area (VSA) compared to XOS2 birds. On day 7, the expression of IL10 in XOS2 was higher compared to CON and XOS3, and CD56 was significantly higher (P<0.05) in the XOS2 compared to CON group. On day 21, the XOS2 and XOS3 significantly lower the expression of IFNγ. Overall, XOS2 and XOS3 significantly increased immunity until day 21. In conclusion, in ovo XOS feeding demonstrated the potential to modulate gut morphology and immunity of the chickens during the post-hatch days.