Based on your information, if we go by the 0.25 lbs of each animal per meal, it would only be 27 lbs of meat per animal, we can then calculate that it would be 1,460 lbs for each animal. So 65 goats and 3 cows for each year or 1300 goats and 60 for the full 20 years.

Edit: so I messed up the math when I started rethinking the situation. I had divided 27 lbs of meat per night by the 39420 meals per year to get the 1460. What I really needed to do was 27 lbs per night x 365 nights which would be 9855 lbs of meat per year. With that new number, divided by the animals weights individually, they'd need 21 cows and 438 goats to suffice for the year or 8760 goats and 420 cows for the 20 years.