Livestock Feed Calculator

How the Livestock Feed Calculator works

The formula. As-fed weight = bodyweight × intake percentage ÷ forage dry matter. For example, a 600 kg suckling cow at 2.5% needs 15 kg DM, which is 15 ÷ 0.85 = 17.6 kg of hay a day. A second example: the same cow on grass silage at 30% DM needs 15 ÷ 0.30 = 50 kg. Multiply by head and days to see how many bales the winter takes.

Ruminants and horses eat a fairly predictable amount of forage relative to their bodyweight, which makes winter feed budgeting a matter of multiplication once you know three things: how much dry matter an animal eats, how much water the forage contains, and how many animal-days you need to cover. This calculator handles all three and converts the answer into bales.

Dry matter intake. Animals eat to a dry matter (DM) requirement, not a fresh weight. A dry beef cow eats around 2 percent of her bodyweight in DM each day, a suckling cow 2.5 percent, a high-yielding dairy cow 3 to 4 percent. Sheep and goats eat proportionally more, 2 percent when dry and up to 3.5 to 4 percent in late pregnancy and lactation. Horses at maintenance eat about 2 percent, and ponies and native breeds should be held to that or less. The calculator uses these typical percentages and weights when you leave the fields blank; enter your own if you have weighed stock or a nutritionist's figure.

Dry matter of forages. Hay is about 85 percent dry matter, so a 600 kg cow needing 15 kg DM eats about 17.6 kg of hay. Haylage at 60 percent DM needs 25 kg, and grass silage at 30 percent DM needs 50 kg of fresh weight for the same nutrition. This is why silage bales are so heavy and why comparing forages by fresh weight is misleading. Analyse silage if you can; clamp DM ranges from 25 to 40 percent and it changes the figures a lot.

Bales. Small hay bales weigh around 20 kg, round bales 200 to 300 kg, large squares 400 to 500 kg; haylage and silage bales are heavier because of the water, typically 500 to 700 kg. The bale counts use these mid-range weights and round up; weigh a few of your own bales if you can, as they vary with the baler and how dry the crop was. Clamp silage is shown per cubic metre at around 700 kg.

Waste. Feeding on the ground wastes 20 percent or more; ring feeders and racks cut it to 5 to 10 percent. The final line adds 10 percent to the total for waste and spoilage, and it is sensible to add a further margin for a long winter. A 150-day winter for a spring-calving herd is typical; housed dairy cows are fed year-round.

Beyond forage. These figures cover the bulk forage requirement. Animals in late pregnancy, lactation or growth usually need concentrates or a better forage as well, and quality matters as much as quantity: poor hay may not meet maintenance even when eaten to appetite. Mineral and water needs are separate; a cow drinks 40 to 80 litres a day.

Livestock feed calculator: daily feed by animal

Typical body weight and intake for each animal, per head per day.

Dry matter and as-fed intake per head per day

Sources: Fodder.

Checked against: 50 head at 10 kg a day for 30 days = 15 tonnes

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