So cows and pigs - like many fruiting plants - co-evolved with the creatures that fed on them. In both cases, those creatures became necessary for their long-term survival.
Angiosperm co-evolution goes back hundreds of millions of years. Animal husbandry goes back what, 10,000? That’s an evolutionary blip. Yes, long enough to select for traits we prefer, but not long enough to develop the kind of symbiosis we see with fruits. Domestic pigs and cows do get some benefits from being kept, but we certainly aren’t necessary, except maybe some sheep.
Why does the length of time matter? Domesticated varieties of cows and pigs would go extinct if humans stopped raising them for meat. The only niche where they can survive is a farm. They are in symbiosis now even if they weren’t 10,000 years ago.
Time matters because that’s how evolution cements biological distinction. Domesticated cow and pig varieties can certainly survive off of farms. There’s the famous example of the cow that escaped to live with a herd of bison, and feral pigs are a well known phenomenon. Yes they are in symbiosis, but it’s not biologically obligatory symbiosis.
