Question for Cow Owners

How much do you feed a cow? on a daily basis? My parents bought cows recently, and I dont live with them, but I have some ducks on their land, so I go out there a lot. They have had them maybe a month, and I feel like they have gotten thinner by a bit. now I've only seen how they feed the cows, maybe once, but it doesn't look like a lot. And do you guys like Scoop Manuer(sorry if that is spelled wrong) like on a daily basis?

This is more for my own curiosity because even if I did my own research, they didn't listen to me about the goats. :/