Aixia Zhu, Wenjing Pan, Jiaqi Zhang, Shiqin Zhang, Chunwei Wang, Di Kong, Kai Peng, Fan Chen, Xin Yang
A total of 288 male Cobb broilers were randomly assigned to four dietary treatments: crumbled-pellet feed (CPF), hard-pellet feed (HPF), standard-nutrient soft-pellet feed (SPF), and low-nutrient SPF, each with eight replicates of nine birds. The 42-day trial was divided into stage 1 (days 1-21) and stage 2 (days 22-42). In stage 1, the broilers fed standard-nutrient SPF showed higher final body weight (FBW) and lower dry matter feed conversion ratio (DMFCR) than those fed CPF (p < 0.05), along with enhanced liver antioxidant capacity, reduced serum uric acid (UA) and creatinine (CREA), and improved intestinal morphology and disaccharidase activities compared with the CPF group. In stage 2, continued SPF feeding increased abdominal fat, serum total cholesterol (TC), and liver malondialdehyde (MDA) and reduced intestinal microbiota diversity (p < 0.05). In contrast, the broilers switched to HPF in stage 2 achieved growth performance comparable to that of the broilers fed SPF throughout both stages (TG3) but without health impairment. Low-nutrient SPF maintained growth despite reduced protein levels but increased dysbiosis risk. Under the conditions tested in this study, feeding standard-nutrient SPF in stage 1 followed by HPF in stage 2 appeared to be the most effective strategy among those tested, maximizing performance while preserving health. However, because the dietary formulations were intentionally adjusted to achieve the desired nutrient levels for each feed type, the observed effects reflect the combined influence of feed form and nutrient composition; further studies with iso-nutrient controls are needed to confirm the specific role of feed form.