Feed preference in pigs: relationship between cereal preference and nutrient composition and digestibility

The present work aimed to identify the nutritional characteristics that best explain cereal feed preference in pigs. A total of 25 cereals of known preference (at 60% of inclusion in complete feed) from a previous study were evaluated. The cereals were analyzed for DM, OM, crude fiber, ether extract, CP, GE, digestible starch, and glycemic index. Additionally, for 12 of the cereals, complete feeds (the same composition as those previously used to measure preference) were prepared, analyzed for DM, OM, CP, and starch, and fed to pigs (33 ± 5.1 kg BW) fitted with ileal T-cannulae to assess the apparent ileal (AID) and total tract digestibility (ATTD) of these nutrients using titanium dioxide as an indigestible marker. The relationships among the different energy and nutrient contents were studied by principal component (PC) analysis, and the correlations between the generated PC scores and cereal preference were analyzed. A correlation between preference and the second PC obtained with data of the 25 cereals was observed (P < 0.01), which indicated that crude fiber (negatively) and digestible starch, OM, and glycemic index (positively) were correlated with feed preference. Statistically significant linear relationships with preference were confirmed for crude fiber, digestible starch, and glycemic index (R(2) = 0.38, 0.36, and 0.23, respectively; P < 0.02). Similarly, the first PC obtained with data of the 12 feeds also correlated with preference (P < 0.01), indicating that the digestible nutrients (positively) and the nondigestible nutrients (negatively) were correlated with preference. Statistically significant relationships with preference were observed for the contents of starch (total, digestible AID, and digestible ATTD: R(2) = 0.62, 0.66, and 0.63, respectively; P < 0.01), AID DM (digestible and nondigestible: R(2) = 0.41 and 0.44, respectively; P < 0.05), ATTD DM (digestible and nondigestible: R(2) = 0.67 and 0.70, respectively; P < 0.01), AID OM (digestible and nondigestible: R(2) = 0.45 and 0.43, respectively; P < 0.05), and ATTD OM (digestible and nondigestible: R(2) = 0.64 and 0.66, respectively; P < 0.01). It is concluded that cereal preference in pigs is positively related with their content in digestible nutrients, such as starch, and negatively related with their nondigestible nutrients, such as crude fiber.