The physiological stage of pigs may influence total tract digestibility of nutrients because the digestibility of energy and some nutrients increases as body weight increases, but the impact of physiological stage may be greater for high-fiber diets than for diets with less concentration of fiber. Full fat rice bran (FFRB) and defatted rice bran (DFRB) are produced in the rice milling process and is available for animal feeding. However, because of the high concentration of dietary fiber, FFRB and DFRB may be better suited for diets fed to sows than for diets for weanling or growing pigs, but there is a lack of data on the digestibility of energy and nutrients in FFRB and DFRB fed to sows. Therefore, the objective of this experiment was to test the null-hypothesis that the apparent total tract digestibility (ATTD) of gross energy (GE), dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and P in a corn-soybean meal diet and in diets containing FFRB or DFRB is not different between lactating sows and gestating sows if both groups are allowed to consume their diet on an ad libitum basis.

Animals, Housing, Experimental design, and diets

Twenty-four gestating sows that were 35 ± 0.8 days into gestation (parity 2 to 6) and 24 lactating sows parity 2 to 6 were randomly allotted to 2 blocks of 12 sows, 3 diets, and 4 sows per treatment in each block for total of 8 replicate sows per treatment. Gestating sows were housed for 12 d in individual stalls, but on day 13, sows were moved to metabolism crates where they stayed for 12 d. Lactating sows were moved to farrowing crates 4 d before farrowing and remained there until weaning on day 20 post-farrowing. A basal diet based on corn and soybean meal and 2 diets based on corn, soybean meal, and 40% FFRB or DFRB were used. All diets contained 500 units per kg of microbial phytase, 0.50% titanium dioxide as an indigestible marker, and vitamins and minerals in concentrations that met or exceeded the requirement for gestating and lactating sows. Gestating sows were fed at 3.5 times the maintenance metabolizable energy requirement (i.e., 100 kcal/kg body weight^0.75), which was considered close to voluntary feed intake. Lactating sows were fed 2 kg of experimental diet from d 110 of gestation until farrowing, but on the day of parturition, sows were offered only 1 kg of feed.  However, from d 2 after farrowing sows were allowed free access to feed. Both groups of sows had free access to water at all times throughout the experiment. Gestating and lactating sows were fed experimental diets for 24 d. The initial 17 d were considered an adaptation period to the diet. Fecal samples were collected via rectal palpation on d 18 to 23 after initiation of feeding experimental diets. In gestating sows, that period corresponded to d 6 to 11 after sows were moved to metabolism crates, and in lactating sows, the collection period was from d 13 to 18 of lactation. Data were analyzed using the MIXED procedure of SAS as a randomized complete block design with a 2 × 3 factorial arrangement for diets and a 2 × 2 factorial arrangement for ingredients. The fixed effects were the physiological stage of sows, the diet or ingredient, and the interaction between physiological stage and diet or ingredient.

Results

The daily feed intake of sows was not affected by dietary treatment, but lactating sows had a greater (P < 0.05) daily feed intake than gestating sows (Table 1). Lactating sows had also a greater (P < 0.01) ATTD of DM, OM, GE, NDF, and digestible energy than gestating sows, regardless the source of diet used. In addition, the ATTD of DM, OM, GE, and NDF was greater (P < 0.01) for the basal diet than for diets containing FFRB or DFRB regardless of physiological stage of sows, but the concentration of digestible energy was greater (P < 0.01) in diets containing FFRB than in diet containing DFRB or basal diet. Full fat rice bran had a greater (P < 0.01) ATTD of GE, DM, and NDF and digestible energy than sows fed DFRB. Lactating sows had also greater (P < 0.01) ATTD of P than gestating sows, regardless the source of diet used. However, the ATTD of P was increased (P < 0.05) in basal diet, than if rice bran was included to the diets. In addition, this increasing was greater (P < 0.05) if basal diet was fed by lactating sows, but this was not the case for gestating sows (interaction, P < 0.05).

Key points

• Lactating sows have greater digestibility of GE, DM, NDF, and P than gestating sows.
• The hypothesis that ATTD of GE and nutrients is not different between gestating and lactating sows was rejected.
• Full fat rice bran has greater concentration of digestible energy compared with DFRB, regardless of physiological stage of sows.

Table 1. Effects of reproductive stage of sows on apparent total tract digestibility (ATTD) of gross energy (GE), dry matter (DM), neutral detergent fiber (NDF), and P, and concentration of digestible energy (DE) in a corn-soybean meal basal diet and in diets containing full fat rice bran (FFRB) and defatted rice bran (DFRB)¹

• ^{a - e}Values within a row lacking a common superscript letter are different (P < 0.05).
• ¹Data are means of 8 observations per treatment.