When they are stronger and last longer
I hope these links help with your project :)
https://www.hunker.com/12383329/what-are-examples-of-inorganic-fertilizers
http://www.gardenguides.com/129239-examples-inorganic-fertilizers.html
Try to convince mother to switch for breastfeeding if at all possible
Breastfeeding is the best for infants....but the word "to switch" doesn't match.
If the infant has taken feeding bottles yet, it's time to change the very first days.
Hope I helped !
-a urine test
-a blood test
-a rectal prostate exam