I try to keep them on younger grass before it gets woody. I have not tried keeping them on different types of grasses to see how they do and taste.
I have tried old apples and pitted peaches, onions and garlic, and oranges and grapefruits as daily snacks. These things did change there flavors and I will never try the onions and garlic again. The citrus I will do again if I can find a large amount of old citrus and will have room in my freezers.
The citrus gave it a very light grain type flavor with a tang like taste. We love it but it cost too much unless I can get a good size truck load that are somewhat bad and sort out the bad and store the good ones cold. The bad ones make good compost.
The say with milk cows that it should be feed right after milking so it dose not flavor the milk to much.
We could not tell a difference with the apples but they were only getting two 5 gallon buckets between 3 heifers for 120 days. We did quarter them before feeding because I didn’t want to find a cow that choked; but who knows how often that will happen.