The primary function of the reproductive system is to perpetuate the species. This system also provides the mechanism for the recombination of genetic material that allows for evolutionary change and adaptation. Manipulation of the reproductive system in breeding management programs facilitates rapid and dramatic changes in the conformation and productivity of domestic animals. Theriogenology is the veterinary specialty that deals with reproduction. (Also see chapters on the management of reproduction in cattle, goats, horses, pigs, sheep, and dogs and cats.)
Approximate Gestation Periods
Species | Days, Except Where Noted |
|---|---|
Domestic Animals | |
Cat | 65 |
Cattle | 9 months |
Dog | 62–64a |
Donkey | 365 |
Goat | 150 |
Horse | 11 months |
Llama, alpaca | 11.5 months |
Pig | 114 |
Rabbit | 31 |
Sheep | 150 |
Wild Animals | |
Bear (black) | 210 |
Bison | 280 |
Camel | 365–400 |
Chimpanzee | 236 |
Coyote | 63 |
Deer (mule and white-tailed) | 200 |
Elephant | 660 |
Elk, wapiti | 255 |
Giraffe | 425 |
Gorilla | 270 |
Hare | 36 |
Hippopotamus | 240 |
Leopard | 95 |
Lion | 108 |
Marmoset | 150 |
Monkey (macaque) | 180 |
Moose | 235 |
Muskox | 255 |
Muskrat | 29 |
Nutria, coypu | 130 |
Opossum | 12 |
Otter (river) | 9.5–12.5 monthsb |
Panther | 90 |
Porcupine | 210 |
Pronghorn | 250 |
Raccoon | 63 |
Reindeer | 225 |
Rhinoceros (African) | 480 |
Seal | 330 |
Shrew | 20 |
Skunk | 63 |
Squirrel (gray) | 40 |
Tapir | 390 |
Tiger | 103 |
Walrus | 450 |
Whale | 450 |
Woodchuck | 31 |
Wolf | 63 |
Farmed Fur Animals | |
Chinchilla | 111 |
Ferret | 42 |
Fox | 52 |
Mink | |
– European | 41 |
– American | 40–75 |
See also the table "Select Physiological Data of Laboratory Animals" in the topic Colony Monitoring of Laboratory Animals. | |
a Gestation period is 58–72 d from breeding at unknown stage of estrus; from day of ovulation (which can be determined by progesterone or luteinizing hormone monitoring), gestation period is 62–64 d. | |
bIncludes a delayed implantation period of 7.5–10.5 mo. | |
Approximate Incubation Periods
Species | Days |
|---|---|
Domestic Birds | |
Chicken | 21 |
Duck | 28 |
– Muscovy duck | 35 |
Goose | 28 |
Guinea fowl | 28 |
Turkey | 28 |
Caged and Game Birds | |
Budgerigar | 18 |
Finch | 14 |
Parrot | 26 |
Pheasant | 24 |
Pigeon | 18 |
Quail | 16 |
Swan | 35 |
Features of the Reproductive Cycle
Species | Age at Puberty | Cycle Type and Length (Range) | Duration of Estrus (Range) | Best Time to Breed | First Estrus After Parturition (Range) | Comments |
|---|---|---|---|---|---|---|
Cattle | 10–12 mo, usually first bred at approx. 14–15 mo | Polyestrous all year; 21 d (18–24) | 18 h (6–24) | Insemination from midestrus until 6 h after end of estrus | 20–60 d | Ovulation occurs 10–12 h after end of estrus. |
Sheep | 6–9 mo | Seasonally polyestrous, early autumn to winter; 17 d (14–20) | 24–36 h | 18–20 h after onset of estrus | Next autumn | Ovulation occurs near end of estrus. |
Goat | 5–7 mo | Seasonally polyestrous, early autumn to late winter; 21 d | 24–48 h | Daily during estrus | Next autumn | Many intersexes are born in hornless strains. |
Pig | 6–7 mo | Polyestrous all year; 21 d (19–23) | 40–60 h | Daily during estrus | 4–10 d after weaning | Ovulation usually occurs approx. 40 h after onset of estrus. |
Horse | 10–24 mo | Seasonally polyestrous, early spring through summer; approx. 21 d (19–23) | 5–7 d | Last few days of estrus, just before ovulation; should be bred at 2-day intervals | 9 d (4–14) | Ovulation usually occurs 1–2 d before end of estrus. Double ovulation occurs in approx. 20% of estrous periods, but twins rarely progress to term. |
Alpaca | 12–18 mo | Polyestrous all year in North America; not applicable | Up to 36 d | When a large, viable follicle is present | Fertile within 15–20 d | Alpacas are induced ovulators. |
Dog | 6–24 mo; earlier in smaller breeds, later in larger breeds | Monestrous all year; 6–7 mo | 9 d (3–21) | Day 2 after ovulation | 4–5 mo | Proestrus bleeding lasts 7–10 d. Ovulation usually occurs 1–3 d after onset of estrus. Ova shed before first polar body has been extruded (primary oocyte). |
Cat | 4–12 mo | Seasonally polyestrous, spring through early autumn; 14–21 d | 6–7 d | Daily from day 2 of estrus | 4–6 wk | Induced ovulation occurs 24–48 h after breeding. Pseudopregnancy lasts 40 d. Infertile breedings delay onset of next cycle by approx. 45 d. |
The reproductive system is incredibly complex in both its anatomy and physiology, and all aspects must be considered when resolving reproductive problems. The differences in the reproductive system between the sexes and among species are extensive. Both sexes have primary sex organs and primary regulatory centers. Gonads and function-adapted, tubular genital organs constitute primary sex organs in both sexes. The pituitary gland and the hypothalamus are the primary regulatory centers; thus, the regulatory function is, in part, neuroendocrine. In pregnant females, the fetoplacental unit plays a substantial role in maintaining and terminating pregnancy.
For the temporal and physiological features of the reproductive cycles of selected species, see the tables Approximate Gestation Periods, Approximate Incubation Periods, and Features of the Reproductive Cycle.
