You are likely to get all kinds of advice with a question like this one. I prefer to workout 7 days a week, but Sundays are my "choice" day when I can work out hard or easy (like a walk or Yoga) whereas weekdays are for the weight lifting, running, or other cardio workouts.
In your situation, you can think of you Saturday as giving some muscles a rest or break, but yet working other muscles with the hard work of lifting bags of feed and other strenuous activity. So, before taking another day off, think about which muscle groups you use on other days. If you have light workouts like walking, Pilates, or Yoga on regular days, then Saturdays becomes your strength day. If you lift weights 3-5 days a week, plus do your heavy "farm" work on Saturdays, then yes, you would want another "light" workout day or a day to totally rest your muscles.
It all depends on your strength, fitness level, energy, age, and activities the other six days of the week. Your body will tell you, and you will figure it out!
Best wishes and keep up the great work!