Effects of dietary metabolizable energy and crude protein levels on production performance, serum biochemical indices and cecal microbiota of Taihe Silky Fowl during the brooding period

This experiment investigated the effects of dietary metabolizable energy (ME) and crude protein (CP) levels and as well as interactions on the production performance, serum biochemical indexes, and cecum microbiota of Taihe Silky Fowl during the brooding period. In the experiment, 2160 3-week-old (21-day-old) Taihe Silky Fowl, with similar body weights and good health conditions, were randomly divided into 9 groups according to a 3 × 3 two-factor random experimental design. Each group had 6 replicates, with 40 chickens per replicate. The diets with 3 different levels of ME (11.7 MJ/kg, 12.1 MJ/kg, 12.6 MJ/kg) and 3 different levels of CP (19.0 %, 20.0 %, 21.0 %) were provided. The results were as follows: as the dietary ME level increased, the feed conversion ratio (FCR) of Taihe Silky Fowl during the brooding period significantly decreased (P < 0.05), and the eviscerated yield rate increased and then decreased significantly (P < 0.05), reaching the highest value in the 12.1 MJ/kg group. Serum triglyceride (TG) content significantly increased (P < 0.05). Different dietary ME levels significantly affected the cecal microbiota structure. The abundance of the Bacteroidetes phylum was highest in the 12.1 MJ/kg group, particularly the Bacteroides genus, which promotes the growth and development of Taihe Silky Fowl during the brooding period by exerting probiotic effects. However, the different levels of CP in the diets, as well as the interaction between ME and CP levels did not have significant effects on the growth performance, slaughter performance, organ indices, or serum biochemical indices of Taihe Silky Fowl during the brooding period. In conclusion, it is recommended to maintain the dietary ME level for Taihe Silky Fowl during the brooding period at 12.1 MJ/kg and the CP level at 19.0 %.