This is similar to the pregnancy period of a woman, which is closer to around 9 months or ~260 days. However, actual gestation period of a cow can range from 270 days to 295 days, depending primarily on breed[s], age, body condition and nutritional health.Gestation period is also controlled by genetics, but not rate of maturity.his is similar to the pregnancy period of a woman,  which is closer to around 9 months o â¦ r ~260 days.    However, actual gestation period of a cow can range from 270 days  to 295 days, depending primarily on breed[s], age, body condition  and nutritional health.
Whereas fertilized chicken eggs usually take exactly 21 days to hatch, most duck eggs take 28 days, apart from Muscovy ducks. As a general rule of thumb, the eggs of Muscovy ducks take 35 days, but once again, it can vary slightly depending on conditions.
General Hatching rules for chicken eggs. 1  Don't set fewer than six eggs. 2  Chicken eggs take twenty-one days to hatch when incubated at optimal temperature. 3  Still-air incubator temperature should be 101.5, measured at the top of the egg, while forced-air (or turbofan) incubators should keep a temperature of 99.5. Still-air incubator temperature must be higher because the non-moving air inside the incubator rests in layers, cooler at the bottom of the incubator and warmer at the top.