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.
Candling fertile chicken eggs during incubation. Once fertilized chicken eggs have been under a brooding hen or in an incubator for a period of about three or four days, you can candle the eggs to see if they've started developing.o, how long does it take for fertilized chicken eggs to hatch? The answer to that is 21 days exactly, although you need to bear in mind that this can vary, depending on a number of circumstances.