Mars: More about Farms
Greenhouses and hydroponics are well established and understood and I'm sure that the production rate information is out there. Remember... you can't just order another tanker load of hydroponic nutrient mix.
I looked around and found this... "1 square foot will yield roughly .112 lbs of winter wheat or .107 lbs of spring wheat. For 4 cups of flour you would need to plant roughly 9 square feet."
For sake of argument, assume that using hydroponics the per foot yield is doubled. So 9 square feet will get 8 cups of flour... in about three months. Or somewhere between 4 cups and 8 cups. A loaf of bread takes a couple of cups of flour each loaf. For that 3x3 foot spot in the greenhouse occupied for 3 months by wheat plants... you get four loaves of bread, maybe. Three months is 90 days, one loaf a bread a day is... 4 into 90, 22.5... call it 23. You need 23 3x3 foot sections of greenhouse to have one loaf of bread per day per person. 207 square feet. 20x10 ish... each person... if your greenhouse growing space (not counting pathways) is 20 feet by 50 feet... you can grow enough wheat to feed five people bread, 20 x 100 feet, 10 people. (More or less assuming bread is the only thing eaten, which it wouldn't be, but if other crops take similar space it's still ball park. A person could, unhappily, live on a loaf of bread a day.) Figure walkways and for each 10 people in your colony you need a 30 x 100 foot greenhouse. At least. And no crop failures. Ball park. Okay? Those greenhouses all need artificial lights and heat and air.
How big is your Mars colony? How many people? How much of a cushion for crop failure is necessary for comfort and security?
Your Mars Colony needs farms. Vast stretches of farms. Huge expanses of farms.
The argument that there is so obviously not room for livestock is unsupportable. If a 30 x 100 foot greenhouse can be constructed for every 10 colonists, a group of 100 colonists can certainly spring for two "barns" for milk goats, quail, chicken, and rabbit pens. Ducks, geese, and juvenile bunnies can occupy floor space in greenhouses, if it's set up that way. What would be a real luxury is anything that grows on trees or bushes or woody vines.
This all, of course, assumes the ability to construct greenhouses, light them, make the air to pressurize them, and the energy to heat them, as well as import or construct all the hardware and internals.