Starch digestion rate as a key predictor of feed efficiency in broilers fed diets with varying ratios of sorghum and broken rice.

This study evaluated whether starch digestion rate (SDR) acts as an independent predictor of feed conversion ratio (FCR), comparable to conventional nutritional indices of apparent metabolizable energy (AME) and metabolizable crude protein (MCP). A total of 216 twenty-two-day-old Arbor Acres male broilers were allotted to 6 dietary treatments with sorghum-to-broken rice ratios of 0:100 (BR100), 20:80 (S20BR80), 40:60 (S40BR60), 60:40 (S60BR40), 80:20 (S80BR20), and 100:0 (S100) and fed the corresponding diets from d 22 to 30. All diets were formulated to be isocaloric and isonitrogenous. Increasing dietary inclusion of sorghum prolonged total small intestinal mean retention time (P < 0.001). Starch digestibility in the duodenum, jejunum, and ileum decreased with increasing dietary sorghum proportion (P < 0.001), whereas starch disappearance rate in broilers fed the S100 diet was lower than that in the other dietary treatments in the jejunum and ileum (P < 0.05). Starch digestion kinetic analysis revealed significant differences in SDR across dietary treatments (Kruskal‑Wallis test, P = 0.011). The SDR values of the six diet treatments ranged from 0.179 to 0.568 min-1, whereas potential starch digestibility declined with increasing dietary sorghum inclusion (P < 0.001). Average daily feed intake (ADFI) and FCR were not affected by dietary treatment; however, average daily gain (ADG) was greater in broilers fed the BR100 and S20BR80 diets than in those fed the S60BR40 and S100 diets (P < 0.05). AME did not differ among treatments, whereas CP retention was greater in broilers fed the BR100 diet than in those fed the S80BR20 and S100 diets (P < 0.05). Feed efficiency indices were strongly correlated with SDR, and multiple regression analysis identified SDR as the primary predictor of FCR, accounting for the largest proportion of explained variance. In conclusion, dietary sorghum-to-broken rice ratio modulated starch digestion kinetics and feed efficiency in broilers, with SDR identified as a key determinant of feed efficiency. These findings emphasize the importance of considering starch digestion dynamics, rather than nutrient concentrations alone, in broiler diet formulation.