Rotational Grazing Paddock Planner

Introduction to paddock planning for a rotational grazing system

A prescribed grazing plan turns three separate questions into one arithmetic problem: how much dry matter the herd removes each day, how fast the sward replaces it, and how long each subdivision must be left alone before it is fit to graze again. This planner answers all three at once. It sizes the whole grazed land base from the forage-animal balance, divides that land base into the number of paddocks your chosen recovery period demands, and then reports the area of a single paddock, the pre-graze forage mass that paddock has to be carrying on the day the gate opens, and the stocking density the herd will exert while it is standing there.

The distinction that makes rotational grazing worth the fencing bill is the difference between stocking rate and stocking density. The USDA NRCS National Range and Pasture Handbook defines stocking rate as the number and class of animals using a unit of land for a specified period of time, and stocking density as the relationship between animal numbers and land area at any instant of time. Continuous stocking welds the two together: if the herd can reach every acre every day, density equals rate. Subdividing deliberately pulls them apart. A herd running on fifteen paddocks carries the same seasonal stocking rate but exerts fifteen times the instantaneous density, and it is that density — combined with a real recovery period — that lifts harvest efficiency and keeps the plants ahead of the animals.

That efficiency gain is not a rounding error. NRCS reports that under continuous grazing, harvest efficiency usually averages 25 percent on rangeland, 30 percent on pastureland and 35 percent on grazed cropland, while extension guidance for short grazing periods on managed pasture puts realistic utilisation between roughly 65 and 80 percent. For a fixed herd and a fixed growth rate, moving from a 25 percent to a 65 percent harvest efficiency cuts the land area required by more than half. The planner shows exactly that comparison for your own numbers rather than asking you to take it on faith.

• Total grazeable area the herd needs at the growth rate and harvest efficiency you enter.
• Paddock count derived from the recovery period and the grazing period.
• Area of one paddock, plus the harvestable forage mass it must carry at turn-in.
• Stocking rate and stocking density side by side, in animal units and in live weight.
• A harvest-efficiency scenario table that prices the cost of a loose rotation in hectares or acres.

How to use the paddock planner with your own forage figures

Choose your unit system first. The metric and imperial buttons above the form convert every entered value in place, so a plan drafted in kilograms of dry matter per hectare per day can be handed to a contractor in pounds per acre without retyping anything. Then work down the form from the herd side to the pasture side, and finish with the two timing inputs that define the rotation.

Number of animals and average live weight establish the live-weight base of one grazing group. Plan one group at a time. If the mob contains 550 kg cows and 250 kg yearlings, either split them into two runs of the calculator or enter a weighted average, but do not enter the heaviest animal and hope for the best — a 10 percent error in average weight is a 10 percent error in every area figure that follows.

Daily dry matter intake is entered as a percentage of live weight. NRCS calculates intake and stocking rates for beef cattle at 2.6 percent of body weight and for lactating dairy cows at 3.0 percent; the same handbook adopts 26 lb of oven-dry forage per day as the standard demand of a 1,000 lb animal unit, which is precisely 2.6 percent. West Virginia University Extension uses about 2.5 percent for most classes of livestock on pasture. Anything from 2.0 percent (dry cows on mature forage) to 3.5 percent (rapidly growing stock or high-quality leafy regrowth) is defensible; the field is left open so that sheep, goats and dairy enterprises can plan honestly.

Pasture growth rate is the average daily accumulation of dry matter over the planning window, not fresh weight. A rising-plate meter, a grazing stick or a set of clipped quadrats will get you there. Temperate grass-clover pasture in active growth commonly runs 40 to 80 kg DM/ha/day; midsummer slump can drop below 20, and dormancy approaches zero. Use the rate you expect during the period you are planning for, not the annual average, because the paddock layout has to work in the tight month rather than the easy one.

Harvest efficiency is the share of the forage grown that actually ends up inside an animal. NRCS defines it as the total percent of vegetation ingested by the grazing animal compared with the total amount grown in the area in a given year, and it is deliberately lower than 100 percent because of trampling, fouling, selective refusal, senescence and the residual you leave to power regrowth. It is the single input that rewards better rotation management, and it is where the payoff of subdividing shows up in the arithmetic.

Grazing period is how many days the herd occupies one paddock, and recovery period is how long that paddock is then left alone. Keep the grazing period shorter than the time it takes a grazed tiller to push a new leaf — roughly three days on actively growing temperate pasture — or the animals will bite the regrowth before they leave, which is the classic cause of a paddock that never seems to recover. The recovery period should reflect the season: grass-clover swards need about 21 days of regrowth in spring and up to 42 days in midsummer, and the paddock count must be built for the longest recovery you expect, not the shortest.

• Animals: head count in one grazing group that moves together.
• Average live weight: mean weight per head, in kilograms or pounds.
• Daily dry matter intake: intake as a percentage of live weight.
• Pasture growth rate: dry matter accumulated per unit area per day.
• Harvest efficiency: percentage of grown dry matter actually ingested.
• Grazing period: days the herd occupies one paddock before moving.
• Recovery period: minimum days of rest before that paddock is re-grazed.

Press Calculate plan and the results panel reports the whole balance sheet at once: area, paddock count, paddock size, forage mass required at turn-in, animal-unit demand, stocking rate and stocking density. Download plan saves the same figures as a plain-text file you can staple to a grazing chart, and Reset restores the reference scenario used in the worked example below.

Formula set: demand, harvest efficiency, paddock area and paddock count

Every quantity below is on a dry matter basis. Fresh forage is 75 to 85 percent water, so a plan built on green weight overstates the feed on offer by a factor of four or more. Write $n$ for head count, $W$ for average live weight, $I$ for daily intake as a percent of live weight, $g$ for daily dry matter growth per unit area, $H$ for harvest efficiency in percent, $G$ for the grazing period in days and $R$ for the target recovery period in days.

Step 1 — daily herd demand. Live weight times the intake fraction gives the dry matter the group removes every day. This is the demand side of the forage-animal balance and it does not depend on how the land is subdivided.

Formula: D_day = n ⁢ W ⁢ I / 100

$$D_{\text{day}}=nW\frac{I}{100}$$

Step 2 — animal units. NRCS expresses forage demand in animal units, where one AU is a 1,000 lb (453.6 kg) cow with a calf up to six months old, consuming 26 lb (11.79 kg) of oven-dry forage per day. Converting the herd to animal units lets you check the plan against published carrying-capacity tables and against AUM-based lease arithmetic.

Formula: AU = (n ⁢ W) / (453.6 ⁢ kg)

$$\mathrm{AU}=\frac{nW}{453.6\text{kg}}$$

Step 3 — paddock count. The number of subdivisions is set purely by the timing you want: divide the days of rest a paddock needs by the days it will be grazed, then add one paddock for the herd to stand on while the others recover. West Virginia University Extension states the rule exactly this way, and Penn State Extension writes it as maximum days rest divided by days grazing, plus one. The ceiling function is used here so that the delivered rest is never shorter than the rest you asked for.

Formula: P = ⌈ R / G ⌉ + 1

$$P=\lceil \frac{R}{G}\rceil +1$$

Rounding up means the rotation usually delivers slightly more rest than requested. The recovery period the layout actually provides, and the length of one full rotation cycle, follow directly.

Formula: R_actual = (P − 1) ⁢ G, C = P ⁢ G

$$R_{\text{actual}}=(P-1)G,C=PG$$

Step 4 — total grazeable area. At equilibrium the herd removes exactly as much dry matter each day as the whole land base delivers to it. Only the harvested share $gH/100$ of the growth reaches an animal, so the area required is daily demand divided by harvested growth per unit area. Note that the grazing period cancels out of this expression: subdividing the land does not change how much land the herd needs, only how that land is used.

Formula: A = D_day / (g ⁢ H / 100)

$$A=\frac{D_{\text{day}}}{g\frac{H}{100}}$$

Step 5 — area of one paddock. Divide the land base by the number of subdivisions. This is the number that gets stepped out with a fence reel, and it is where the original version of this page went wrong: the total land base and a single paddock differ by a factor of $P$, which for a fifteen-paddock rotation is a fifteen-fold error.

Formula: a = A / P

$$a=\frac{A}{P}$$

Step 6 — the forage mass check. WVU Extension sizes paddocks the other way round, from measured forage: paddock area equals intake per head per day, times head, times days on the paddock, divided by the grazable dry matter available per unit area. Rearranging that identity gives the pre-graze harvestable forage mass your paddock must be carrying on the day you open the gate, which is exactly what a rising-plate meter reading (above residual) should show. If the field measurement is far below this figure, the paddock is too small, the recovery period is too short, or the growth rate you entered is optimistic.

Formula: F_entry = (D_day ⁢ G) / a = g ⁢ C ⁢ H / 100

$$F_{\text{entry}}=\frac{D_{\text{day}}G}{a}=gC\frac{H}{100}$$

Step 7 — rate versus density. Stocking rate spreads the herd over the whole land base for the season; stocking density places it on one paddock at one instant. Their ratio is the paddock count, which is the clearest possible statement of what subdivision buys you.

Formula: S_rate = AU / A, S_density = AU / a = P ⁢ S_rate

$$S_{\text{rate}}=\frac{\mathrm{AU}}{A},S_{\text{density}}=\frac{\mathrm{AU}}{a}=P{S}_{\text{rate}}$$

Unit conversions used throughout are exact: 1 hectare = 2.4710538 acres, 1 kilogram = 2.2046226 pounds, and therefore 1 kg DM/ha = 0.8921791 lb DM/acre. Animal-unit-months are reported as animal units multiplied by days divided by 30.4, consistent with the 790 lb per AUM figure tabulated by NRCS for a cow with calf.

Worked example: 50 cows on a 28-day recovery interval

These are the values the calculator loads by default, so you can follow every line on screen. A single grazing group of 50 beef cows averages 550 kg live weight. Intake is planned at the NRCS beef figure of 2.6 percent of body weight. The grass-clover sward is growing 55 kg DM/ha/day, harvest efficiency is set at a realistic 55 percent for a two-day move, and the plan calls for 28 days of recovery before any paddock is grazed again.

• Daily herd demand = 50 × 550 kg × 0.026 = 715 kg DM/day
• Animal units = (50 × 550) ÷ 453.6 = 60.6 AU (cross-check: 60.6 AU × 11.79 kg = 715 kg DM/day)
• Paddocks = ⌈28 ÷ 2⌉ + 1 = 14 + 1 = 15 paddocks
• Delivered recovery = (15 − 1) × 2 = 28 days; full cycle = 15 × 2 = 30 days
• Harvested growth = 55 × 0.55 = 30.25 kg DM/ha/day
• Total grazeable area = 715 ÷ 30.25 = 23.64 ha (58.41 ac)
• Area of one paddock = 23.64 ÷ 15 = 1.58 ha (3.89 ac)
• Demand per grazing stay = 715 × 2 = 1,430 kg DM
• Harvestable forage needed at turn-in = 1,430 ÷ 1.576 = 907.5 kg DM/ha (809.7 lb DM/ac) above residual
• Stocking rate = 60.6 AU ÷ 23.64 ha = 2.56 AU/ha (1.04 AU/ac)
• Stocking density = 60.6 AU ÷ 1.576 ha = 38.5 AU/ha, i.e. 17,452 kg live weight per hectare

Two independent checks confirm the plan hangs together. First, the forage-mass route used by WVU Extension: demand per stay divided by paddock area gives 1,430 ÷ 1.5758 = 907.5 kg DM/ha of harvestable feed required at turn-in. Second, the gross accumulation route: over a 30-day cycle the sward grows 55 × 30 = 1,650 kg DM/ha, of which 55 percent — 907.5 kg DM/ha — is harvested, leaving 742.5 kg DM/ha as residual, trampling and senescence. The two paths agree exactly, which is the signature of a consistent forage-animal balance.

It is worth reading that 907.5 kg DM/ha against the field. WVU Extension reports that average grass-clover stands commonly offer 1,000 to 2,000 lb DM/acre (1,121 to 2,242 kg DM/ha) of grazable forage in each grazing period, so this plan sits just below the bottom of that band — a comparatively light pre-graze cover, which is exactly what a fast 30-day cycle produces even on a strong growth rate. That is not an error, but it does say the system carries little buffer. Stretching recovery to 40 days would raise the cycle to 42 days, lift turn-in cover to about 1,270 kg DM/ha, and put the plan in the middle of the published range at the cost of 21 paddocks instead of 15.

Now note what the stocking density tells you. The same 50 cows on the same 23.64 ha under continuous stocking would exert 2.56 AU/ha at every instant. Split into 15 paddocks they exert 38.5 AU/ha for two days at a time and nothing at all for the other 28. That fifteen-fold density is what forces even defoliation, drives dung and urine distribution across the whole farm rather than around the water point, and makes a 55 percent harvest efficiency achievable instead of the 30 percent NRCS reports for continuously stocked pastureland.

Interpreting the output: stocking rate versus stocking density

Total grazeable area is a carrying-capacity statement. It answers whether the land base can carry this group at this growth rate at all, and it is completely independent of how you subdivide. If the figure exceeds the ground you actually own, no amount of fencing will fix it — the options are fewer animals, a higher harvest efficiency, purchased or stockpiled feed, or a shorter grazing season on that land.

Paddock count is a scheduling statement. It answers how many subdivisions the calendar requires, and it changes nothing about total area. Fifteen paddocks and three paddocks on the same 23.64 ha carry the same stocking rate; what differs is the recovery each paddock receives and therefore the harvest efficiency you can realistically sustain. If you already have fewer paddocks than the result calls for, temporary polywire is far cheaper than permanent fence and gets you most of the benefit.

Paddock area is the fence line. Step it out, then verify it against the harvestable forage at turn-in figure with a plate meter or grazing stick before you commit. If the sward is carrying less than the model demands, either the growth rate was optimistic or the paddock has not had its full recovery, and the herd will run short before the move is due.

Stocking density is the management lever. Density equals stocking rate multiplied by paddock count, so every additional subdivision raises instantaneous density without touching the seasonal stocking rate. NRCS conservation practice standard 528, Prescribed Grazing, and its management-intensive rotational grazing enhancement both frame the objective in exactly these terms: increase stock density, shorten grazing periods, enhance plant recovery, and thereby increase harvest efficiency and manure distribution. The table below prices that objective in land.

Read that table as a ceiling rather than a promise. The NRCS continuous-grazing figures are annual averages used for initial carrying-capacity estimates and are deliberately conservative; the Penn State figures assume competent short-duration management with adequate water in every paddock. Most farms transitioning from set stocking land somewhere in the middle for the first two or three seasons, which is why the worked example uses 55 percent rather than the headline 80 percent. The scenario table in the results panel recomputes this same comparison for whatever herd, growth rate and unit system you enter.

Pair the arithmetic with a fast field routine: pre-graze cover, post-graze residual, and the actual number of days it takes a paddock to come back. If residual is consistently below target, drop the harvest efficiency you plan with or shorten the grazing period. If animals leave stemmy, rejected material behind, either the paddock is oversized for the move or the recovery period has run past optimum and quality has gone. If regrowth is faster than planned, shorten recovery and take the surplus paddocks out as hay or silage rather than letting the wedge run away from you.

Limitations and assumptions behind this grazing model

This is a steady-state forage-animal balance and every one of its assumptions can be broken by a real paddock. Being explicit about them is what separates a planning tool from a guess.

• Constant growth. The model assumes the growth rate you enter holds across the rotation cycle. Real growth curves are strongly seasonal; a spring flush can triple midsummer growth and dormancy can drive it to zero. Re-run the plan whenever a pasture walk says growth has moved.
• Equilibrium rotation. The land-base equation assumes the system is already cycling, with every paddock at a different stage of recovery. It does not model the transition weeks when you first subdivide, and it does not model a standing stockpile that was accumulated before the plan started.
• Uniform pasture. One growth rate is applied to every paddock. Soil type, aspect, drainage, sward composition and fertility vary across most farms, and NRCS practice standard 528 expects the plan to reflect that variation paddock by paddock.
• Harvest efficiency is an input, not a prediction. The calculator cannot know whether your water layout, fence discipline and move timing will actually deliver the efficiency you type in. Published figures are averages over many sites and seasons.
• No supplement, hay or browse. All demand is met from pasture. If the group receives silage, concentrate or significant browse, subtract that dry matter from herd demand before planning.
• Live weight is treated as static. Growing stock gain weight through the season, so a plan built on turn-out weight will progressively understate demand. Re-run it mid-season with current weights.
• Animal-unit equivalents are approximate. The 1,000 lb, 26 lb/day animal unit is a planning convention. NRCS itself notes that forage consumption varies with forage quality, standing crop, animal age, supplementation, topography, breed, species and physiological state.
• Nothing here sizes water or infrastructure. High stocking density needs water within reasonable walking distance of every paddock, and lane, gate and shade provision all constrain a layout that looks fine on paper.

The planner also assumes strictly positive inputs. Zero or negative head counts, weights, intakes, growth rates, grazing periods or harvest efficiencies are rejected with an explicit message rather than returning zero, infinity or a stale figure, because a silently wrong grazing plan is more expensive than an error message.

Grazier questions about paddock size, rest and recovery

Sources for the grazing figures used here