PSVIII-5 Determination of true digestibility and the endogenous outputs of magnesium in corn for growing pigs by using the regression analysis technique

Abstract

Abstract Dietary magnesium (Mg) is essential to bone mineralization. Supplemental Mg is typically not considered in commercial swine diets by assuming high bioavailability of Mg from bulky feed ingredients such as corn grain. The objectives of this study were to determine true ileal and fecal digestibility and the endogenous losses of Mg associated with corn in growing pigs by the regression analysis technique. A total of 48 barrows, with an average initial body weight (BW) 32 kg, were randomly assigned to 6 grower pig diets and were fed close to ad libitum for 10 d, with 8-d adaptation and 2-d collection fecal and the terminal ileal digesta samples, according to a randomized complete block design. Six cornstarch-based diets, containing 6 levels of Mg at 0.22, 0.32, 0.38, 0.51, 0.71 and 0.79 g/kg dry matter intake (DMI) of diets, were formulated from corn. There were linear relationships (P < 0.05), expressed as g/kg DMI, between the ileal and fecal outputs of Mg and the total intake of dietary Mg, suggesting that true ileal and fecal Mg indigestibility values (94.8±12.5 vs. 89.2±17.7%); and the ileal and fecal endogenous Mg outputs (0.16±0.02 vs. 0.21±0.11, g/kg DMI of diets) associated with corn could be estimated by the regression analysis. Our results have shown that Mg associated with conventional corn grain was very poorly digested and the gastrointestinal endogenous fecal loss of Mg was significant in the grower pig. Thus, Mg bioavailability in feeds for pigs should be assessed and supplemental of Mg may be warranted in swine diet formulation.