Effects of replacing extruded soybean meal with Periplaneta americana residue on laying performance, egg quality, and ovarian transcriptomic profiles in Guangxi Yao chickens.

The present study evaluated the effects of graded replacement of extruded soybean meal with Periplaneta americana residue (PAR) on laying performance, egg quality, ovarian function, and ovarian transcriptomic profiles in Guangxi Yao chickens. A total of 210 female chickens at 30 d of age were randomly assigned to 6 dietary treatments, with 5 replicate cages of 7 birds each. PAR replaced 0%, 10%, 20%, 30%, 40%, or 50% of the extruded soybean meal, corresponding to dietary inclusion levels of approximately 0%, 1.82%, 3.61%, 5.42%, 7.19%, and 8.95%. The feeding trial lasted 24 wk. Laying performance and egg quality were assessed at the replicate-cage level, whereas ovarian follicle characteristics, reproductive hormones, immunoglobulins, histomorphology, and transcriptomic profiles were evaluated thereafter. Dietary treatment affected average egg weight (AEW; P = 0.004), with birds in the 10% replacement group producing heavier eggs than those in the control and 20% replacement groups. Average daily feed intake (ADFI), laying rate (LR), and feed-to-egg ratio (F:E) were not significantly affected, although ADFI exhibited significant linear and quadratic responses to increasing PAR replacement. Egg shape index (ESI) differed among treatments (P = 0.002), whereas yolk weight (YW), yolk color score (YCS), yolk proportion (YP), albumen height (AH), Haugh unit (HU), and eggshell thickness (EST) remained unchanged. Ovarian estradiol (E2) concentration differed among treatments, whereas ovarian follicle numbers did not. RNA sequencing (RNA-seq) revealed treatment-associated changes in genes and pathways related to lipid metabolism, ovarian function, cellular signaling, and immune regulation, although principal component analysis (PCA) indicated substantial overlap among treatment groups. Weighted gene co-expression network analysis (WGCNA) identified an exploratory module associated with EST, and reverse transcription quantitative polymerase chain reaction (RT-qPCR) showed moderate agreement with the RNA-seq results. Overall, replacing up to 50% of extruded soybean meal with PAR did not adversely affect most production, egg-quality, or ovarian-follicle traits, whereas the clearest production response was an increase in AEW at the 10% replacement level.