With regard to the age of the

parents, the litter is the best when they are in their prime; but with
regard to the seasons of the year, the litter is the best that comes
at the beginning of winter; and the summer litter the poorest,
consisting as it usually does of animals small and thin and flaccid.
The boar, if it be well fed, is sexually capable at all hours, night
and day; but otherwise is peculiarly salacious early in the morning.
As it grows old the sexual passion dies away, as we have already
remarked. Very often a boar, when more or less impotent from age or
debility, finding itself unable to accomplish the sexual commerce with
due speed, and growing fatigued with the standing posture, will roll
the sow over on the ground, and the pair will conclude the operation
side by side of one another. The sow is sure of conception if it drops
its lugs in rutting time; if the ears do not thus drop, it may have to
rut a second time before impregnation takes place.