Pig diets formulated with different sources of starch based in vitro kinetics of starch digestion

The effects of different feed ingredients with their different in vitro kinetics of starch digestion were evaluated in weaned pig diets based on the growth performance and postprandial response of serum glucose (Glu), insulin (Ins), and urea (Ur). Three studies were conducted: In vitro study – in vitro determination of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) fractions in corn grain, broken rice, wheat grain, and green banana flour; Experiment 1 (Exp. 1) – growth performance of 96 weaned pigs from 21 to 59 d of age; and Experiment 2 (Exp. 2) – In vivo determination of serum Glu, Ins, and Ur responses to diets in 32 pigs with 42 d of age (eight replicates per treatment in both experiments with three and one pig per pen in Exp. 1 and 2, respectively). In Exp. 1 and Exp. 2, the experimental diets were as follows: C, a diet based on corn grain as the main starch source; C25, a diet with 25% replacement of corn grain by broken rice; C50, a diet with 50% replacement of corn grain by broken rice (25%) and wheat grain (25%); and C55, a diet with 55% replacement of corn grain by broken rice (20%), wheat grain (20%), and green banana flour (15%). The RDS fraction was greater in corn grain (31.1%) than in broken rice (28.5%), wheat grain (26.1%), and green banana flour (14.8%). The greatest SDS content was found in broken rice (39.5%), followed by green banana flour (20.0%), corn grain (17.3%), and wheat grain (8.4%). The RS fraction was greater in green banana flour (44.7%), followed by corn grain (21.5%), wheat grain (15.0%), and broken rice (11.4%). In the first 15d of the Exp. 1, pigs fed diet C25 had greater (P<0.05) average daily gain (ADG) than pigs submitted to diets C and C50, and better gain to feed (G:F) compared with animals that received C diet. However, in Exp. 2, Glu, Ins, and Ur serum levels were similar for pigs fed experimental diets. In conclusion, the growth performance in the first 15d of nursery phase was influenced by diets with greater SDS levels, although the starch profile in feed ingredients couldn´t be able to change serum levels of Glu, Ins and Ur.