Table 1.

Factors related to boar management affecting boar semen quality

Factor	Details	Effect of semen quality	Reference
Boar selection
Breed	Pietrain and Duroc vs. GL, LW, YS	Reduced sperm counts	[5]
Back fat	Back fat thickness in highly selected Piétrain	Positive association with motility	[8]
Housing
Group housing	Groups of prepupebertal boars vs individual	Higher sperm counts	[45]
Photoperiod	24 h of complete light or darkness for 3 months	Reduced volume and concentration	[11]
Heat stress	34.5 °C (8 h) or 31 °C (16 h) for 90 days vs. 23 °C	Reduced motility, reduced morphology	[48]
Nutrition
Feed restriction	1.4 times below maintenance	Reduced sperm counts	[51]
Protein restriction	12.0% crude protein (CP) in growers	Reduced sperm counts	[51]
Selenium	0.06 ppm vs 0.5 ppm continuously	Reduced motility, reduced morphology	[56]
	Organic vs inorganic	Increase concentration, increase oxidative stress, increase PGHX	[57, 60]
L carnitine	625 mg/boar/day supplementation	Improved morphology in Piétrain	[61]
Collection
Collection frequency	Twice a day during 4 days compared to once every 2 days	Reduced motility and morphology	[9]
Collection pen	Pen allowing sexual stimulus	higher sperm counts	[63]

GL German Landrace, LW Large white, YS Yorkshire