Values for digestible energy (DE) and metabolizable energy (ME) in feed ingredients are usually determined in growing pigs and subsequently applied to all groups of pigs. Results of recent research, however, indicate that the energy content of soybean meal (SBM) is greater than previously thought when fed to growing pigs. This increase in energy may be due to changes in the pigs themselves or differences in methodology, but there are no recent experiments assessing DE and ME in SBM when fed to sows. Therefore, it remains unclear if sows also have greater DE and ME in SBM compared with current book values. Likewise, there are no recent data for the DE and ME in soybean hulls although soybean hulls are often added to diets for gestating sows. Therefore, an experiment was conducted to test the hypothesis that gestating and lactating sows have greater DE and ME in SBM and soybean hulls than growing pigs and that DE and ME in SBM fed to both growing pigs and sows are greater than current book values. The second hypothesis was that there is no difference in apparent total tract digestibility (ATTD) of gross energy (GE) and DE between gestating and lactating sows.

Experimental Design

There were three dietary treatments, and all diets were formulated to contain Ca, P, and all micronutrients at or above the requirements for growing pigs, which is also above the requirement for gestating and lactating sows. A basal diet contained corn as the sole source of energy, and two additional diets contained corn and 30% SBM or corn and 20% soybean hulls as the energy sources. Titanium dioxide was included in all diets to allow for the calculation of digestibility in lactation sows.

Animals, housing, feeding and sample collection

Twenty-four growing pigs (initial body weight (BW): 40.51 ± 2.83 kg) were allotted to a completely randomized design with three diets and eight replicate pigs per diet and had free access to water throughout the experiment. Pigs were housed individually in metabolism crates (0.81 m × 1.52 m). A screen and a urine pan were placed under the slatted floor to allow for the total, but separate, collection of urine and fecal materials.

Twenty-four gestating sows that were approximately 65 days into gestation (parity two to six) were allotted to two blocks of 12 sows using a randomized complete block design with three diets and four sows per diet in each block for a total of eight replicate sows for each diet. Breeding group was the blocking factor. Experimental diets were identical to those used for growing pigs.

Twenty-four multiparous lactating sows were used in a randomized complete block design with two blocks of 12 sows, three diets, and four sows per diet in each block for a total of eight replicate sows per treatment. Breeding group was the blocking factor. Sows had seven days of adaptation to the diets and fecal samples were collected via rectal palpation for five days starting on day 12 of lactation. Lactating sows had ad libitum access to diets and water throughout the experiment.

At the conclusion of the experiment, samples were analyzed for dry matter and GE using standard procedures, and ATTD of dry matter and GE as well as DE and ME were calculated.

Results

Lactating sows had greater (P < 0.05) DE for soybean hulls than gestating sows, whereas gestating sows had greater (P < 0.05) DE for corn than lactating sows (Table 1). Gestating sows also had greater (P < 0.05) ME of corn than growing pigs, whereas growing pigs had greater (P < 0.05) ME of SBM than gestating sows.

Conclusion

Soybean hulls contain less DE and ME than corn and SBM, but there are no consistent differences in DE and ME among growing pigs, gestating, and lactating sows.

Appreciation

Funding for this research form the United Soybean Board (St. Louis, MO) is greatly appreciated

Table 1. Apparent total tract digestibility (ATTD) of dry matter (DM) and gross energy (GE) and concentrations of digestible energy (DE) and metabolizable energy (ME) in corn, soybean meal, and soybean hulls fed to growing pigs, gestating sows, and lactating sows¹, as-fed basis

^a-cWithin a row, means without a common superscript differ (P < 0.05).

¹Each least square mean represents 8 observations per diet or ingredient.