Well if the baby is gaining weight and passing urine >5 times/day on breast milk, it means breast milk is adequate. However, for whatever reason, if you want to substitute your milk with top feeds, I would suggest that you continue with breast milk as much as possible and add 1-2 feeds of top milk like lactogen 1 (I don't know what is Auvin milk). Preferably avoid cow milk. If the stools are not hurting the baby then its ok. Start weaning foods by 5-6 months.