I am witness to many instances of mothers offering their milk to other mothers who need or want supplemental milk. (feedthebabyllc.com)
I needed to start supplementing at about 2 1/2 months this time, and we are currently giving her 4 bottles of supplemental milk per day. (doulasanantonio.wordpress.com)
If you have a nursing pet, and it needs supplemental milk, find a commercial product designed specifically for your species. (lowchensaustralia.com)