My pigs won't breed help!

[Shoggoth]

AGE of the male and female matter, to young no breeding, to old no breeding... and just having one of each, drops the chance of a successful pregnancy to one 5% chance per day. And the sow may be getting pregnant, but you will not know, until the second trimester, and the sow may be aborting the pregnancy, due to cold, heat, injury or malnutrition, which you also will not be notified about during the first trimester.

I thought this was the case as well, but I had a 13 year old chinchilla (4 years past life expectancy) that became pregnant well before the first year was over, and became pregnant once more after that.