Features of the Reproductive Cycle
|Species||Age at puberty||Cycle Type||Cycle Length||Duration of Estrus||Breast Feeding Time||First Estrus After Parturition||Remarks|
|Cattle||4-18 (12) mo, usually first bred ~15 mo||Polyestrous, all year||21 days (18-24)||18 hr (10-24)||Insemination from mid-estrus until 6 hr after end||Varies,* best to breed at 60-90 days||Ovulation 10-12 hr after end of estrus. Uterine bleeding ~24 hr after ovulation in most but may require vaginal exam for detection.|
|Horse||10-24 (18) mo||Seasonally polyestrous early spring on.||Very variable, ~21 days||6 days (2-10)||Last few days; should be bred at (19-26)||4-14 days (9) 2-day intervals||Double ovulation occurs in ~20% of estrous periods, but twins rarely progress to term.|
|Sheep||7-12 (9) mo||Seasonally polyestrous, early fall to winter. Prolonged seasons in Dorsets & Merinos.||16½ days (14-20)||24-48 hr||18-20 hr after onset of estrus||Next fall||Ovulation near end of estrus.|
|Pig||4-9 (7) mo||Polyestrous, all year.||21 days (16-24)||2-3 days||~24 hr after onset of estrus||4-10 days after weaning||Ovulation usually ~40 hr after beginning of estrus.|
|Goat||4-8 (5) mo||Seasonally polyestrous, early fall to late winter.||18-21 days (19)||2-3 days||Daily during estrus||Next fall||Many intersexes born in hornless strains.|
|Dog||5-24 mo; earlier in smaller breeds later in larger breeds||Unseasonally monestrous.||3½ - 13 mo||2-21 days (6-12 av)||From day 2 of estrus, and on alternate days thereafter until end of estrus||Few months (2- to 3½-mo period of metestrus, followed by a highly variable period of anestrus)||Proestrous bleeding 7-10 days. Ovulation usually 1-3 days after first acceptance. Ova shed before 1st polar body has been extruded.Pseudopregnancy usually ends between 60 and 70 days.|
|Cat||4-12 (10) mo; 12-18 mo in Persians||Provoked ovulation seasonally polyestrous spring and early fall.||14-21 days||6-7 days||Daily from day 2 of estrus||4-6 wk||Ovulation 24-48 hr after coitus. Pseudopregnancy lasts 36 days.Infertile matings prolong onset of next cycle ~45 days.|
|Rhesus monkey (Macaca mulatta)||3 yr||Polyestrous all year, tendency to anovulatory cycles in summer in USA.||27-28 days (23-33)||~3 days||Near ovulation, day 10-13 of cycle||After weaning of previous young||Menstruation lasts 4-6 days. Ovulation usually ~13 days after onset.|
* Many normal cows ovulate as early as 8-12 days after parturition, with or without detectable signs of estrus.
Philippine Veterinary Drug Directory (PVET) 16th Edition. (2018). Medicomm Pacific, Inc.