Gestating sows have been found to have greater digestibility of energy than growing pigs. One possible explanation is that sows' larger intestinal tracts and more efficient fermentation of fiber allow them to extract more energy from their feed.

Gestating sows are usually restricted in their feed allowance while growing pigs are fed ad libitum. This confounds comparisons between sows and growing pigs because feeding level affects the rate at which feed passes through the intestinal tract and may affect the efficiency of digestion.

Therefore, an experiment was conducted to separate the effects of physiological stage from the effects of the level of feed intake on digestibility of gross energy (GE) and neutral detergent fiber (NDF) in full fat rice bran (FFRB) and defatted rice bran (DFRB).

A total of 48 sows and 24 growing gilts were used in the experiment. The sows were parity 2 to 6, at an average of 35 days gestation, and the gilts had an average body weight of 51.53 kg. All pigs were randomly allotted to three diets. The basal diet was based on corn and soybean meal and for the other two diets, 40% of either FFRB or DFRB was included. The gilts were fed 3.5 × the maintenance ME requirement.  The sows were fed at two levels of intake (1.5 or 3.5 × maintenance ME requirement). Urine and feces were collected, and the difference procedure was used to determine the DE and ME in FFRB and DFRB.

There was no difference in apparent total tract digestibility (ATTD) of GE, DE, ME, or ATTD of NDF between sows fed 3.5 × ME or 1.5 × ME (Table 1). ATTD of GE, DE, and ME were greater (P < 0.05) in sows fed FFRB than in sows fed DFRB.

Sows had greater (P < 0.05) ATTD of GE, DE, and ME than growing gilts fed the same diets (Table 2). ATTD of GE, DE, and ME in diets containing FFRB was greater (P < 0.05) than in diets containing DFRB, regardless of physiological stage. There was no effect of physiological stage or ingredient on ATTD of NDF.

• The concentrations of DE and ME for gestating sows fed FFRB and DFRB are greater than values obtained in growing pigs.
• Level of feed intake does not affect the digestibility of energy, dry matter, organic matter, or NDF in diets fed to gestating sows.
• The increased digestibility of energy and concentrations of DE and ME in sows fed FFRB or DFRB is not due to limited feed intake or improved digestibility of NDF relative to growing gilts.

Table 1. Effect of intake level on apparent total tract digestibility (ATTD) of GE, DM, OM, and NDF and concentration of DE and ME in full fat rice bran (FFRB) or defatted rice bran (DFRB) fed to gestating sows

Table 2.  Effects of the physiological stage on the apparent total tract digestibility (ATTD) of GE and NDF and concentration of DE and ME of full fat rice bran (FFRB) or defatted rice bran (DFRB) in gestating sows and growing gilts¹

¹Both growing gilts and gestating sows were provided feed in the amount of 3.5 × the maintenance requirement for ME (NRC, 2012).

This report is based on unpublished research by Gloria Casas and Hans H. Stein.