This experiment was conducted at the Purdue University swine research and education center. The objective of this study was to determine if the inclusion of fiber (8.48% vs 14.85% NDF) in the diet influenced boar bodyweight, backfat depth, loin depth, Knauer sow caliper measurement, flank to flank distance, and visual body condition score (BCS). Twenty-seven boars from two age groups (7 months and 18 months) and two genetic lines (maternal and terminal) were utilized over a twelve-week period with one week prior to the study data serving as baseline for statistical analysis. Fecal samples were also taken and scored using the Bristol stool scoring system. Timepoints for sample collection were on weeks -1,3,7, and 11. Boars were blocked by age and breed and randomly allotted to receive 2.72 kg/d of corn-soybean meal diet (CON, n=13) formulated to meet NRC (2012) requirements or an isocaloric (estimated ME=3285 Kcal/kg) corn-soybean meal diet with 14.3% soyhulls and supplemental choice white grease (4.65%) inclusions (FIBER, n=14). Data were analyzed using PROC GLM in SAS 9.4 (Cary, North Carolina) with boar serving as the experimental unit. Weeks were analyzed individually and changes in bodyweight, backfat depth, loin depth, caliper measurements, flank to flank distance, and BCS were evaluated from week -1 to week 12. Significance was determined at P< 0.05 and a trend was observed at 0.05< P≤0.10. FIBER boars gained 8.4 kg more than CON boars during the 12-week study (P=0.0221). On weeks 3 and 11, FIBER boars tended to have increased backfat depth compared to CON boars (P< 0.0950), resulting in FIBER boars gaining 2.9 mm more backfat compared to CON (P=0.0053) over the 12-week study. No difference in loin muscle depth was observed between treatments. On weeks 7 (3.7 vs 3.4, P=0.0923) and 11(3.9 vs 3.5, P=0.0615) FIBER boars tended to have higher BCS score compared to Con boars. FIBER boars on week 11 tended to have larger tape measurements (105.9 cm vs 103.9 cm, P=0.0945) and larger caliper score (19.4 vs 17.6, P=0.0029) than CON boars, but no difference in overall 12 week change for both measurements. FIBER boars tended to have softer stools during week 3 of the trial compared to CON boars (P=0.0535), but the fecal scores were not different at any other week.
Overall, boars fed a high fiber diet had increased body weight, backfat depth and BCS indicating an underestimation of the net energy value of soyhulls in limit fed boars. Future research is needed with varying levels and types of fiber inclusion in the diet to understand how to correctly implement fiber into the boar diet and to refine the net energy values of fibrous feedstuffs like soyhulls for boars.
