Milk from Irish grass-fed cows. Irish grass-fed cows. In Ireland, cows graze on the green pastures of small family farms. Their milk is churned to make Kerrygold Pure Irish Butter. Made with milk from grass-fed cows not treated with rBST or other growth hormones (No significant difference has been shown between milk from rBST-treated and non rBST-treated cows).