How much hay does a cow need for winter?

Short answer

About 30 lb a day · 3,600 lb per 120 days before waste, about 4,100 with it · 4 round bales a cow

A 1,200-lb cow eats about 30 lb of hay a day — 2.5% of her body weight — which is 3,600 lb over a 120-day winter before waste and about 4,100 lb from a ring feeder: four 1,000-lb round bales. For a 200-day winter it is 6,000 lb, 3 tons, before waste, and about seven rounds with it. Cold is the variable nobody's table includes: below a 32°F wind chill her energy need rises about 1% per degree, and a wet coat doubles that.

The arithmetic

Dry matter per day = body weight × 2–2.5%. WVU uses 2–2.5%; Cornell uses 2.5 lb per 100 lb of cow, 3.0 lb once waste is in. 1,200 lb × 2.5% = 30 lb.
Hay as fed = dry matter ÷ 0.92. Grass hay runs 90–93% dry matter (WVU), so 24 lb of dry matter at 2% is about 26 lb of hay; at 2.5%, about 33 lb.
Season = per-day × days. Cornell plans on at least 200 days: 30 × 200 = 6,000 lb, 3 tons per cow. A Gulf Coast winter is closer to 120 days: 3,600 lb.
Add waste. WVU says 5–20% depending on storage and feeder; our calculator uses 15% for a ring feeder and 30% on the ground. 3,600 × 1.15 = 4,140 lb, about 4.1 round bales at 1,000 lb.

If everyone agrees a cow eats 25–33 lb a day, why do hay orders differ by 2×?

The intake rate is the one thing the sources agree on. Days and bale weight are where the real spread is.

West Virginia University: 2–2.5% of body weight; its worked examples use 2%, 2.25% and 2.5% in different places and skip the waste line it says to include
Cornell Small Farms: 2.5% base, 3.0% with waste, 200-day minimum plan
Oregon State University: Beef cattle 1–3%, dairy 3–4.5%; 10–50% waste
Our hay calculator: 2.5% as fed, 25–30 lb for a 1,200-lb cow, waste by feeding method

Everyone lands on 25–33 lb a day for a mature cow. The 2× spread in what people actually buy comes from days (120 vs 200) and from what "a round bale" weighs — 400 lb for a light 4×4, 1,700 lb for a dense 5×6 — not from the intake rate.

Use 30 lb a day, count your real days from the end of grazing to green-up, and weigh a bale before you order fifty of them.

What changes your number

Days. The biggest lever. Count from the day pasture stops growing to the day it carries them again, and add two weeks.
What a bale weighs. 4×4: 400–600 lb. 4×5: 700–1,000. 5×6: 1,200–1,700 (WVU). "Fifty round bales" means nothing until you know which.
Calving date. Intake rises to 2.6–2.8% after calving (WVU). Spring calvers hit that in the last weeks of the hay season, when the pile is lowest.
Feeder. A ring feeder with a skirt versus hay unrolled on the ground is the difference between 15% and 30% waste on the whole pile.
Hay quality. Cold-weather increases are energy, not pounds: a cow physically cannot eat 40% more poor hay. That is when a protein cube or better hay earns its price.
Wind break and bedding. A dry coat out of the wind has a lower critical temperature of 32°F; a wet one, 59°F. Shelter moves the cow from the steep column of the cold table back to the gentle one.

A number we won't give you

A bale count for a wet cold snap. Oklahoma State's wet-coat rule — 2% more energy for every °F below 59°F — adds up to more than double at 4°F, and the same source calls meeting that with hay "virtually impossible": a cow on a roughage diet cannot be switched that fast without digestive trouble. The published advice is a smaller increase through the storm, carried a day or two after. So the cold table below gives you the requirement, not a feeding plan, and we don't pretend otherwise.

Per animal, 120 days, ring feeder

Animal	Hay per day	Season (120 days)	With 15% waste	Small squares (50 lb)	Rounds (1,000 lb)
Weaned calf, 500 lb	13 lb	1,560 lb	1,794 lb	36	1.8
Bred cow, 1,200 lb, dry	30 lb	3,600 lb	4,140 lb	83	4.1
Cow, 1,200 lb, after calving (+15%)	34 lb	4,080 lb	4,692 lb	94	4.7
Cow, 1,400 lb, dry	35 lb	4,200 lb	4,830 lb	97	4.8
Bull, 1,800 lb	45 lb	5,400 lb	6,210 lb	125	6.2

Per-day figures are hay as fed at roughly 2.5% of body weight. The after-calving step follows WVU: intake rises to 2.6–2.8% post-calving. The round-bale column assumes 1,000 lb; a 4×5 round weighs 700–1,000 lb and a 5×6 1,200–1,700 (WVU), so weigh one.

The whole herd — 1,200-lb cows, ring feeder

Cows	Hay per day	120 days + 15%	Rounds (1,000 lb)	200 days + 15%	Rounds (1,000 lb)
1	30 lb	4,140 lb	5	6,900 lb	7
2	60 lb	8,280 lb	9	13,800 lb	14
5	150 lb	20,700 lb	21	34,500 lb	35
10	300 lb	41,400 lb	42	69,000 lb	69
20	600 lb	82,800 lb	83	138,000 lb	138

Cornell plans on at least 200 days in New York; a Gulf Coast herd is closer to 120. Add the 10–15% cushion either way.

Cold weather — the line the tables leave out

Wind chill	Dry coat: energy needed	16 lb/day of good hay becomes	Wet coat: energy needed
32°F	+0%	16 lb	+54%
20°F	+12%	17.9 lb	+78%
10°F	+22%	19.5 lb	+98%
0°F	+32%	21.1 lb	+118%
-10°F	+42%	22.7 lb	+138%

Oklahoma State's rule, published by Nebraska Extension: with a dry winter coat the lower critical temperature is 32°F and each degree of wind chill below it raises the energy requirement about 1%; with a wet coat the threshold is 59°F and the slope is 2% per degree. The wet column is a requirement, not a feeding plan — see the note above the table.

Run your own numbers

This is our winter hay calculator with five cows filled in. Change the head count, weight, days, feeder or bale size and the count follows.

Your animals

Species	Head	Avg weight (lb)
Goat
Sheep
Cattle
Horse
Alpaca / Llama
Donkey

Days of winter feedingNov–Feb is ~120. Gulf Coast might be 60–90; the north, 150+.How you feedBale typePrice per bale ($, optional)

You’ll need about

21 bales

Total hay (with waste): 20,700 lb
That’s: 10.3 tons
Per day, all animals: 173 lb

5 cattle: 150 lb/day → 18,000 lb+ 15% waste

Hard winter, late kids, or a doe in milk? Most folks buy a 10% cushion (23 bales) — hay is scarcest and priciest in February.

The same tool lives at /tools/hay-calculator with every species and the arithmetic explained.

What the winter costs

Cornell's worked example: 20 cows × 200 days × 30 lb = 60 tons; at $40 a 4×4 round, about three to the ton, that is $7,200, and they budget $8,000 to carry insurance hay. For one 1,200-lb cow from a ring feeder that is about 2.1 tons for a 120-day winter or 3.5 tons for 200 — roughly $250–520 a head at $120–150 a ton, depending on your winter. Small squares at $180–265 a ton cost half again as much per pound; what you are paying for is handling it without a tractor.

What to do with the surplus

Rounds that made it to spring are worth keeping if they were under roof or on pallets under a tarp; the outside foot of a round left on bare ground is usually gone by then anyway. Feed the oldest first next fall, and if you are truly long, spring is when a neighbor who ran short will pay full price for it.

Then stop planning from averages

The table above is somebody else's cattle. In Homestead Paradise you log the bales you actually buy and the animals you actually have: each pen shows feed cost per head per day, each item of feed shows the day it runs out, and the budget page shows whether winter is running over what you planned. 14-day free trial, no card.

Start your 14-day trial — no card

Keep planning

How much hay do goats need for winter?How much hay do sheep need for winter?How many bales of hay do I need for winter?What does it cost to feed livestock through winter, per head?How much water do livestock drink in winter?What does a stock tank heater cost to run?

Sources

Every figure on this page comes from a land-grant university extension service, a government agriculture or energy agency, or a breed registry — never from another blog.