The effects of feeding rice in substitution of corn and the degree of starch gelatinization of rice on the digestibility of dietary components and productive performance of young pigs

A 28-d trial was conducted to evaluate the effect of the main cereal of the diet (corn or rice), heat processing (HP) of rice, and the degree of starch gelatinization (SG) of rice on apparent total tract digestibility (ATTD) of dietary components and productive performance of pigs weaned at 25 d of age. The experimental design was a completely randomized, with 4 treatments and 8 replicates per treatment (5 pigs penned together). Control pigs were fed a complex diet without growth promoters and based on milk products, fish meal, and 50% cooked and flaked corn, with a degree of SG of 84%. Experimental groups received the same complex diet as the control group, but the corn was substituted by rice with 3 different degrees of SG; 11% that corresponded to raw rice and 52 or 76% that corresponded to cooked rice processed under 2 different conditions. Pig growth was measured at 25, 39, and 53 d of age, and ATTD was determined at 29, 39, and 53 d of age. The ATTD of all dietary components except for N increased with age (P < 0.01) and were greater for the rice than for the corn diet. Heat processing of rice improved ATTD of all dietary components at 29 d of age, but no beneficial effects were observed at 39 or 53 d of age. Modifying the conditions of HP to increase the degree of SG of rice from 52 to 76% and to reduce mean particle size from 480 to 405 mu m did not result in further improvement of nutrient digestibility. From 25 to 53 d of age, pigs fed rice consumed more feed (678 vs. 618 g/d; P < 0.05), grew faster (466 vs. 407 g/d; P < 0.01), and tended to have greater G:F (0.685 vs. 0.662; P < 0.10) than pigs fed corn. In fact, from 25 to 39 d of age, pigs fed rice consumed 23% more feed (P < 0.01), grew 29% faster (P < 0.01), and had 5% greater G:F (P < 0.05) than pigs fed corn. Feeding rice improved performance of weanling pigs, and HP of rice under mild conditions enhanced diet digestibility and productive performance of pigs. Severe processing of rice increased the degree of SG but did not further improve diet digestibility or growth performance.