Sources and Method

HerdMath's calculators use average figures from university extension services. This page lists the sources and says where they differ from each other.

How the numbers are used

The calculators add or multiply published averages: for example, a due date is the breeding date plus the average gestation length. Real animals vary, so every result is a planning estimate with a normal range, not a promise. Where sources disagree, we use a typical middle value and show the range.

Gestation lengths

• University of Nebraska–Lincoln Extension, G2175: gestation lengths for the main livestock species (cattle about 9 months, sheep and goats about 5 months, pigs 3 months 3 weeks 3 days, horses about 11 months).
• eXtension: How long does a cow's pregnancy last? Cattle: 283 days is common, with a range of 279 to 287 days.
• Penn State Extension: Goat reproduction and genetics. Goats: about 148 to 152 days.
• University of Missouri Extension, G2611: sheep and goat breeding season. Sheep: about 144 to 152 days.

Egg incubation

• Penn State 4-H: incubation period of other species.
• Oklahoma State Extension: Artificial incubation.
• University of Missouri Extension, G8353: Small flock series, incubation of poultry.
• University of Maine Extension, Bulletin 2072: Hatching your own chicks.

Chicken eggs take 21 days and most duck eggs 28 days in these sources. Muscovy ducks are listed anywhere from 33 to 37 days (we use 35), and Coturnix quail from 16 to 18 days (we use 17 to 18), so the calculator treats those as typical rather than exact.

Beef yield from hanging weight

• Oklahoma State Extension: Buying beef for home freezers.
• Oklahoma State Extension: Custom beef processing, expected yields.
• Iowa State Extension, PM 2076: Beef and pork whole animal buying guide.

These sources put take-home beef at roughly two-thirds of hanging weight, and they say the exact share depends on bone-in or boneless cuts, trim and aging. Our hanging weight calculator uses 62 percent for beef (and a 60 percent dressing percentage) as its default planning figure, and you can change both.

Corrections

If you find a number that disagrees with a source, email hello@herdmath.com and we will check it and fix it.