Cattle hay calculator

How much hay a cow eats

A 1,200 lb lactating cow on average hay eats about 2.5% of body weight as dry matter — roughly 30 lb DM a day, or about 34 lb as-fed of 88% DM hay, before storage and feeder waste. That is the OSU intake table, not a guess. The calculator up top sizes a whole winter.

Storage: MSU hay calculator ranges. Feeder waste: OSU Beef Cattle Manual. Your stack and your ring will differ.

Worked example: 30 cows, 120 days

Illustrative calculator example, not a count of the herd on this place. The form above already opens on these inputs: 30 cows, 1,200 lb, dry cow / average hay (2.2%), 120 days, a 1,000 lb bale, 88% dry matter (12% in the moisture box is the same hay), barn storage at 2%, and a plain bale ring at 10%. Hit Calculate and the winter number should match this walk-through.

The 30 lb dry-matter line in the table above is one 1,200 lb lactating cow. This example is thirty dry cows. Herd dry matter is 30 × 1,200 × 2.2% = 792 lb DM/day. The tool then divides by the hay’s dry-matter fraction, then by what is left after feeder waste and storage loss: 792 ÷ 0.88 ÷ 0.90 ÷ 0.98 ≈ 1,020 lb of as-fed hay to purchase per day. The screen rounds that daily figure to 1,020 lb.

Over 120 days that is about 122,449 lb. The calculator shows it as 61.2 tons, or 122.4 of those 1,000 lb bales, before hay already on hand comes off. With on-hand tons and bales at zero, hay to buy and herd need match. Example only — enter your herd, days, bale weight, dry matter, and losses above. Round the buying decision up in practice, and let the calculator carry the exact inputs.

The four numbers people mix up

Dry matter per day is what the animals need from the feed. In the example, 792 lb.

As-fed per day is that dry matter divided by the hay’s dry-matter fraction. Wetter hay weighs more for the same feed. 792 ÷ 0.88 = 900 lb as-fed, before any waste.

Purchased per day is as-fed after storage loss and feeder waste. The tool divides by (1 − feeder loss) and by (1 − storage loss): 900 ÷ 0.90 ÷ 0.98 ≈ 1,020 lb. That is the “As-fed / day” line on the result. Both losses are in that number; changing either preset changes the buy.

Bales and tons are those purchased pounds across the days on hay, divided by the bale weight you typed. Tons or bales on hand are subtracted when you enter them. 122,449 lb is 61.2 tons, or 122.4 bales at 1,000 lb. “1,000 lb” is an input, not a fact about every bale. Weigh one, or estimate it with the round bale weight calculator, before you trust the count.

Winter planning checklist

The intake and loss tables above stay the source. Fill the form in this order.

Count each group. Cows, bulls, heifers, stockers, horses or donkeys, sheep or goats. Open the extra groups and pick the intake class that fits the animals actually on hay.

Use the days actually on hay. If a group changes class, or comes off pasture partway through the winter, split the season and run those days on their own.

Weigh a representative bale when you buy by the bale. The 1,000 lb box is a starting input. A light bale makes the stack shorter than the count suggests.

Enter hay already on hand before you decide what to buy. Tons or bales in the barn come off the winter need. Keep a margin for weather and a change in quality; the page leaves that margin to you. Mark the stack on the hay inventory sheet, then punch the same numbers here.

After the hay number

Tons and bales are a quantity, not a feed bill and not a ration. Compare what that hay costs per pound of energy on the TDN cost calculator. If the question is whether to cut it or buy it, run make vs buy. When the pasture days run out, stocking rate is the grazing side of the same winter. Dry matter, as-fed, and waste are in the glossary.