What is an Animal Unit (AU)?

One AU is a 1,000 lb animal eating about 26 lb of dry matter per day. We convert other stock with AU equivalents: cow-calf 1.0, horse 1.25, sheep 0.2, goat 0.17.

What does take-half-leave-half mean?

Only about half of the year’s forage production is counted as usable (utilization 0.5). Leaving residual protects roots and regrowth — grazing everything green is how pastures crash.

How many sheep on 5 average acres?

With a 6-month season in our worked example: usable forage 5,000 lb DM, each sheep needs about 952 lb per season, so floor(5000/952) = 5 sheep.

How do I spot overgrazing?

Bare soil expanding, favorite plants disappearing, animals lingering at the gate for hay, and recovery that never catches the next rotation. Cut stock or add rest — do not add animals to a tired paddock.

How Many Animals Can Your Pasture Support?

Pasture is a solar panel with hooves on it. Stock it like a buffet you intend to refill, not a warehouse to empty. Our calculator uses Animal Units (AU): one AU is a 1,000 lb animal eating about 26 lb of dry matter per day. Sheep count as 0.2 AU, goats 0.17, a cow-calf pair 1.0, a horse 1.25. Usable forage applies take-half-leave-half (50% utilization) to annual production. Work your acres in the pasture stocking rate calculator.

Forage production classes

Pasture quality	lb DM / acre / year
Good	3,000
Average	2,000
Poor	1,000

Usable forage per acre = production × 0.5. Average land thus offers 1,000 lb DM/acre/year to animals after the leave-half rule.

Be honest about quality. Wishful “good” ratings on thin fescue with bare patches will overstock you by spring.

Season length

Default grazing season in our data is 6 months. Season days = round(months × 30.5). Six months → 183 days. Dry-lot winters do not count as pasture days — that is when the goat hay calculator (and stored forage) takes over.

Demand per animal

Dry matter per animal per season = AU × 26 lb/day × season days.

Animal	AU	DM in 183-day season (approx)
Cow with calf	1.0	4,758 lb
Horse	1.25	5,948 lb
Sheep	0.2	952 lb
Goat	0.17	809 lb

Locked worked example: 5 acres, average, sheep, 6 months

Usable DM = 5 × 2,000 × 0.5 = 5,000 lb
Season days = 183
Sheep need ≈ 0.2 × 26 × 183 ≈ 951.6 lb each
Max head = floor(5,000 / 951.6) = 5 sheep

That is capacity on paper for continuous planning assumptions. Rotation that improves harvest efficiency can help in practice — still start from honest production and utilization, not from Instagram paddocks.

Quick capacity sketches

Acres	Quality	Animal	~Max head (6-mo, 0.5 util.)
5	Average	Sheep	5
10	Good	Goat	floor(10×3000×0.5 / 809) ≈ 18
10	Poor	Sheep	floor(10×1000×0.5 / 952) ≈ 5
20	Average	Cow-calf	floor(20×2000×0.5 / 4758) ≈ 4

Horses at 1.25 AU burn pasture fast — many “horse pastures” are really exercise lots plus hay. Run the numbers before the boarding agreement.

Take-half-leave-half in the field

Leaving residual is not waste; it is the plant’s solar panel for regrowth. Graze to a target height for your species, then move. If animals can take every leaf every week, you no longer have a pasture — you have a dirt lot with occasional weeds.

Rotation multiplies management, not magic. It can raise how much of the grown forage you safely harvest, but it cannot invent rainfall. Pair rotation with rest periods long enough for recovery.

Overgrazing warning signs

Bare soil patches growing month to month
Preferred forage vanishing while weeds increase
Animals loud at the gate long before the calendar says hay season
Manure and flies concentrated because stock never leave a sacrifice area
Recovery paddocks that look the same two weeks after a “rest”

Response: reduce numbers, shorten grazings, lengthen rest, or feed more hay. Adding animals to a failing paddock accelerates the crash.

Water and winter sit beside AU math

Daily water scales with stock — use the rainwater & water needs calculator so troughs match headcount. Winter feed is a separate budget: a dairy doe’s hay at 4% body weight does not disappear because she saw grass in June.

Mixed species can share a farm if you account for total AU, not “a few goats won’t matter.” Five sheep at 0.2 each are 1.0 AU — the same forage budget as one cow-calf pair for the season math.

Improving carrying capacity the hard way

You can raise production class over years with fertility, pH, species selection, and rest — that moves land from poor (1,000) toward average (2,000) or good (3,000) lb DM/acre. You cannot legislate rain. Irrigation and adaptive multi-paddock grazing are tools; they still need measured residual and fewer animals when drought hits.

Clip-and-weigh a square yard occasionally, or walk with an extension agent. Eyeballing “looks green” after a wet May is how October gets ugly.

When hay fields and pasture share a farm, do not double-count the same acres as full grazing AU and full hay tonnage without a plan for which months they serve.

Drought and contingency

Write a drought trigger: when paddocks hit residual targets early, start hay or sell stock. Waiting until ribs show is late. Our utilization already banks on leaving half — drought means even less new growth to share.

Small acreage owners often succeed with sheep or goats at 0.2 / 0.17 AU rather than forcing a cow-calf pair onto five thin acres. Ego stocking — buying the species you admire rather than the AU you can feed — is the most expensive pasture mistake. Run the calculator twice: once for the dream herd, once for the herd that matches usable DM.

Fences, water points, and shade drive real paddock layouts as much as AU math. A perfect stocking rate on paper fails if animals tramp a single gate area into dust. Move water with the rotation when you can.

Bottom line

1 AU ≈ 1,000 lb animal at 26 lb DM/day. Apply 0.5 utilization to 1,000 / 2,000 / 3,000 lb DM/acre production classes. Sheep 0.2 AU, goats 0.17, horses 1.25. On 5 average acres for 6 months, expect about 5 sheep in our locked example. Watch for overgrazing, and confirm every scenario in the pasture stocking rate calculator before the trailer unloads.