This experiment was conducted at 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 of boars influenced semen characteristics, concentration, motility, and morphology. Twenty-seven boars from two age groups (7 months and 18 months) and two genetic lines (maternal and terminal) were utilized in this study over a twelve-week period with one week prior to the study data serving as a baseline for statistical analysis. 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). Semen was collected once per week per boar using the gloved hand method. While at the farm 3 mL of semen was mixed with 27 mL of extender (Androhep Plus, Minitube) to make a 1:10 dilution. The semen was then driven approximately 19 kilometers to Purdue University where concentration (Nucleocounter SP-100), motility (Computer Assisted Sperm Analysis, CASA, CEROS II), and sperm cell morphology were analyzed. Statistical analysis were conducted using PROC MIXED in SAS 9.4 (Cary, NC), with the main effects of diet, age, and breed with week as a repeated measure. Significance was determined at P< 0.05 and a trend was observed at 0.05< P≤0.10. Fiber in the diet did not affect any semen characteristics throughout the study. However, the percent morphologically normal sperm was higher in young boars compared to the older boars (80.6% vs 74.1%, P=0.0143) resulting from fewer head/tail abnormalities (1.8% vs 2.4%, P=0.0249) and distal droplets (7.2% vs 9.6%, P=0.0508). Maternal boars had fewer proximal droplets (6.9% vs 9.9%, P= 0.0325) and tended to have fewer head/tail abnormalities (1.8% vs 2.3%, P=0.0800). Terminal boars tended to have fewer distal midpiece reflex abnormalities than maternal boars (3.3% vs 4.8%, P=0.0948).