PSI-11 - Comparative digestibility of energy and concentrations of energy in corn, soybean meal, and soybean hulls fed to growing pigs and gestating and lactating sows

Abstract: The objective was to test the hypothesis that the apparent total tract digestibility (ATTD) of gross energy (GE) and concentrations of digestible energy (DE) and metabolizable energy (ME) in corn, soybean meal (SBM), and soybean hulls are not different among growing pigs, gestating sows, and lactating sows. A basal diet contained corn as the sole source of energy. Two additional diets were formulated to contain corn and 30% SBM or corn and 20% soybean hulls. All diets contained 0.40% TiO₂ as an index. Twenty-four growing pigs (initial weight = 40.51 ± 2.83 kg), 24 multiparous gestating sows, and 24 multiparous lactating sows were allotted to the three diets. Growing pigs and gestating sows were housed in metabolism crates and limit fed at 3.0 and 1.5 times the energy requirement for maintenance, respectively. Fecal and urine samples were quantitatively collected for growing pigs and gestating sows. Lactating sows were allowed ad libitum access to diets and feces were collected via rectal palpation. The ATTD of GE and concentrations of DE and ME in SBM and soybean hulls were calculated by difference. Data were analyzed using Proc MIXED of SAS. Within each feed ingredient, the statistical model included physiological status as fixed variable. Results indicated the ATTD of GE in corn was greater (P < 0.05) in gestating sows than in growing pigs or lactating sows (Table 1). Concentration of DE in corn was greater (P < 0.05) in gestating sows than in lactating sows, but there were no differences between growing pigs and gestating or lactating sows. Concentration of ME in corn was greater (P < 0.05) in gestating sows than in growing pigs. The ATTD of GE in SBM was not different among the three ingredients, but DE in SBM fed to lactating sows was less (P < 0.05) compared with growing pigs or gestating sows. The ME and ME to DE were greater (P < 0.05) in SBM fed to growing pigs than in SBM fed to gestating sows. The ATTD of GE and DE in soybean hulls fed to lactating sows were greater (P < 0.05) compared with growing pigs or gestating sows. The ATTD of GE, DE, and ME to DE in soybean hulls were not different between growing pigs and gestating sows, but ME tended to be greater (P < 0.10) in growing pigs than in gestating sows. In conclusion, differences in digestibility of energy and concentrations of energy among growing pigs and sows depended on the feed ingredients used in diets. However, sows had greater utilization of energy in soybean hulls than current book values and as a consequence, the value of feeding soybean hulls to gestating and lactating sows is greater than currently thought.