Livestock Gestation Chart: Days by Species and Breed

Gestation at a glance
Species	Average	Normal range	About	Source
Cattle (beef average)	283 days	274–292 days (±9)	9.3 months	MS State Extension
Goat	150 days	145–155 days	4.9 months	Merck Veterinary Manual
Sheep	147 days	144–152 days	4.8 months	NMSU Extension
Horse	340 days	320–370 days	11.2 months	Nebraska Extension
Pig	114 days	111–117 days	3.7 months	UNH Extension

Cattle windows are our average ±9-day method. Months are approximate conversions, not the calculation method. The horse range includes dates before the prematurity cutoff; it is not a safety guarantee.

Cattle by breed

Cattle gestation by breed
Breed	Average	Window	Source
Angus	279 days	270–288 days	K-State
Red Angus	282 days	273–291 days	USMARC via Virginia Tech
Hereford	284 days	275–293 days	USMARC via Virginia Tech
Gelbvieh	284 days	275–293 days	USMARC via Virginia Tech
Charolais	283 days	274–292 days	USMARC via Virginia Tech
Simmental	285 days	276–294 days	USMARC via Virginia Tech
Limousin	286 days	277–295 days	USMARC via Virginia Tech
Brangus	286 days	277–295 days	Texas A&M
Brahman	293 days	284–302 days	Texas A&M
Holstein (dairy)	279 days	270–288 days	CDCB
Jersey (dairy)	280 days	271–289 days	CDCB
Milking Shorthorn (dairy)	281 days	272–290 days	CDCB
Ayrshire (dairy)	282 days	273–291 days	CDCB
Guernsey (dairy)	285 days	276–294 days	CDCB
Brown Swiss (dairy)	287 days	278–296 days	CDCB

USMARC values are means for calves by sires of each breed (Cundiff et al., 2001). The K-State Angus value is the mean of 101,787 Angus AI pregnancies, 2000–2020, rounded for this calculator. CDCB dairy values are means for cows, rounded to whole days. Windows are average ±9 days (our method, about ±2 standard deviations of the 4.69-day standard deviation).

Sheep by breed

Sheep gestation by breed
Breed	Average	Window	Source
Most breeds	147 days	144–152 days	NMSU Extension
Finnsheep & early-maturing prolific breeds	145 days	142–150 days	Montana State
Rambouillet & fine-wool breeds	150 days	147–155 days	Montana State

Breed windows are the species range shifted by the breed difference (our method).

Heat-cycle reference

Livestock heat cycles
Species	Average cycle	Typical range	Source
Cattle	21 days	18–24 days	MS State Extension
Goat	21 days	17–24 days	UC ANR
Sheep	17 days	14–19 days	NMSU Extension
Horse	21 days	Not given	MSD Veterinary Manual
Pig	21 days	18–24 days	UC ANR (Merck text)

What the averages and windows mean

An average gives you a central planning date. A window keeps the variation in view. The tables use the same values as the calculator, and each row names the source so you can check the reference rather than treating the number as universal. The approximate month conversions are only a familiar way to describe the length; the calculator always adds elapsed days.

Cattle windows are our average-plus-or-minus-9-day method, based on about twice the Angus study’s 4.69-day standard deviation. Applying that width to other cattle breeds is a planning convention, not evidence that every breed has the same measured distribution. Sheep breed windows similarly shift the 144–152-day species range according to the selected average. Goat, horse, and pig windows use their cited species ranges directly.

Keep a breeding exposure period separate from a gestation range. If the animal stayed with the male, the first and last exposure dates widen the calendar window even when the species reference stays unchanged. Reverse mode works backward from a birth date using the same averages and boundaries. Neither direction confirms conception or evaluates an animal’s health.

Use the cow, goat, sheep, or horse calculator for a dated result. Pigs are available in the homepage calculator. The breeding guides explain the source context, while the herd planner keeps separate animals and exposure groups organized. Always preserve actual observations and birth records separately from the estimates.