Exploring the effects of dietary starch digestion kinetics on net energy utilization in peak laying hens

Feed energy constitutes a major cost factor in laying hen production, yet current net energy (NE) evaluation ignores the impact of starch digestion kinetics. This study evaluated the effects of different starch digestion kinetics on productive performance and energy utilization in peak laying hens. A total of 360 Hy-Line Brown hens (35 weeks of age) were randomly assigned to four diets: rapid (RAP), medium (MED), slow (SLO) and resistant starch diet (RES). Productive performance was measured for 35 d in 280 hens, and respiratory calorimetry was conducted for 5 d in 48 hens selected from an additional group of 80 hens. The results indicated that the RAP diet showed the highest in vitro starch digestion rate constant k (P < 0.05), with more pronounced postprandial glucose and insulin fluctuations. In terms of laying performance, hens fed the MED diet had higher hen-day egg production (HDEP) than in the RAP diet (P < 0.05). Compared with the RAP diet, the MED, SLO and RES diets increased total retained nitrogen (TRN), and the SLO and RES diets further increased total retained nitrogen rate (TRNR) (P < 0.05). No differences were observed in the heat increment (HI) to dietary gross energy (GE) ratio or the NE:GE ratio among the MED, SLO, and RES diets (P > 0.05), whereas the RAP diet showed the highest HI:GE ratio and the lowest NE:GE ratio (P < 0.05). Quadratic regression revealed a significant relationship between the starch digestion rate constant k and the HI:GE ratio (P = 0.030). Overall, an optimal range of glucose release rates may improve NE utilization in peak laying hens, supporting the potential value of incorporating starch digestion kinetics in NE evaluation.