Size a dairy herd by choosing the milk you want per person per day, multiplying by the community and 365, and dividing by each animal’s annual yield. For 100 people at 0.5 liter each, that is 18,250 liters or about 4,822 gallons a year, which needs 2-4 Holstein cows (1,500-2,500 gallons each) or 16-32 dairy goats (150-300 gallons each), plus replacement stock and a source of breeding males.
Part of Dairy Production at Scale
Herd sizing is the calculation that converts a target milk supply per person into a number of milking animals, using the yield per animal and the length of its lactation.
The Parent Table Hides Its Own Target
The parent article gives, for 100 people, 3-5 Holstein cows, 4-6 Jersey cows and 15-25 goats, with sheep as supplementary only. It never states the milk per person those counts are meant to deliver, and they do not deliver the same amount. Reconstruct it from the table’s own yields.
| Animal | Count | Annual yield per animal | Herd total | Per person per day |
|---|---|---|---|---|
| Holstein | 3 at the low yield | 1,500 gal | 4,500 gal = 17,033 L | 0.47 L |
| Holstein | 5 at the high yield | 2,500 gal | 12,500 gal = 47,313 L | 1.30 L |
| Jersey | 4 at the low yield | 1,000 gal | 4,000 gal = 15,140 L | 0.41 L |
| Jersey | 6 at the high yield | 1,600 gal | 9,600 gal = 36,336 L | 1.00 L |
| Goat | 15 at the low yield | 150 gal | 2,250 gal = 8,516 L | 0.23 L |
| Goat | 25 at the high yield | 300 gal | 7,500 gal = 28,388 L | 0.78 L |
Working for the first row: 3 × 1,500 = 4,500 gallons; × 3.785 = 17,033 liters; ÷ (100 people × 365 days) = 0.467. The other rows follow the same steps. The table’s counts therefore span about 0.2 to 1.3 liters per person per day. They are a rough guide at different implied targets, not a single design.
What You Need
- A decision on the target: milk per person per day, and what share goes to butter and cheese (see Dairy and Egg Calorie Efficiency for dairy’s real contribution)
- The animals’ own expected yield, which depends on feed; the parent table’s yields are marked “no-grain”
- A breeding plan; see Seasonal milk production cycles
Method: The Sizing Calculation
Step 1: Annual need. Target × population × 365. For 0.5 L × 100 × 365 = 18,250 L. In gallons, 18,250 ÷ 3.785 = 4,822.
Step 2: Annual yield per animal, per calendar year. The parent’s yields check out as a 305-day lactation: 5-8 gallons a day × 305 = 1,525-2,440 gallons, matching 1,500-2,500, and a goat’s 0.5-1 gallon × 300 days gives 150-300. The 305-day figure is a standard dairy convention from general knowledge, not a wiki figure. With a dry period of about 60 days, a lactation plus dry period is a year, so the annual yield is already the yield per cow per calendar year, dry cows included.
Step 3: Divide. Cows = need ÷ yield: 4,822 ÷ 2,500 = 1.9 and 4,822 ÷ 1,500 = 3.2, so 2-4 Holstein cows. For Jerseys, 4,822 ÷ 1,600 = 3.0 and 4,822 ÷ 1,000 = 4.8, so 3-5. For goats, 4,822 ÷ 300 = 16 and 4,822 ÷ 150 = 32, so 16-32 goats. Round up, because losses and illness make a herd smaller in the field than on paper.
Step 4: Add the non-milking stock. Replacement heifers or doe-kids, a bull or a plan for breeding without one, and calves and kids still on milk. These are not in the parent’s counts.
Step 5: Check feed. Hay Making says roughly 2 tons of hay gets a mature cow through a 150-day winter. At 2-4 cows that is 4-8 tons for the winter, before pasture; see Pasture Management.
Which Animal
The parent article notes goats are easier to manage and feed on marginal land, and cows give more volume per animal. Cattle Management and Goat Raising cover each. A mix gives resilience: a disease or a failed breeding season does not remove the whole supply.
Common Mistakes
- Taking the parent’s “3-5 cows” as a promise. It is a range of 0.4-1.3 liters per person depending on yield.
- Counting only milking animals. The herd also carries heifers, calves and bulls.
- Planning on the high yield. The yields are no-grain figures at their best; use the low end.
- Forgetting that every animal must calve. Milk starts with birth; see Birthing Assistance for calving trouble.
Safety
Bulls and calving cows are the dangerous animals
A bull can kill a handler; keep one in a strong pen with a double gate, never handle it alone, and consider breeding without keeping one. A cow with a new calf will defend it. Hand-milking exposes the milker to kicks; restrain the animal. Milk from the herd is raw milk until it is pasteurized, and raw milk can carry tuberculosis, brucellosis and listeria.
What’s Next
- Learn next: Seasonal milk production cycles — keeping milk flowing across the year
- Combine with: Livestock Feed Conversion — what the animals cost in feed