The authors arguement is essentially “I can’t see future humans in space slaughtering cows”. Thanks to a lack of imagination the only conceivable conclusion is everyone must be vegan. Brilliant!
I can imagine humanity genetically engineering cows to be more space efficient, be unable to move, and to efficiently consume artificial diets made of algae.
Hopefully we'll stick to chicken and eggs.
At that point, why not just directly grow the meat itself and skip the animal? It's already possible with today's technology and is getting cheaper every year: https://en.wikipedia.org/wiki/Cultured_meat
If you can replace an animal's metabolism, immune system, and various regulatory systems with synthetic substitutes, people wouldn't be eating cultured meat. They would be cyborgs.