<Table> <Tr> <Th> Mammal </Th> <Th_colspan="3"> Gestation period (days) </Th> <Th> Reference </Th> </Tr> <Tr> <Th> </Th> <Th> Min </Th> <Th> Max </Th> <Th> Average </Th> <Th> </Th> </Tr> <Tr> <Td> Alpaca </Td> <Td> </Td> <Td> </Td> <Td> 345 </Td> <Td> </Td> </Tr> <Tr> <Td> Baboon </Td> <Td> </Td> <Td> </Td> <Td> 187 </Td> <Td> </Td> </Tr> <Tr> <Td> Bear (black) </Td> <Td> </Td> <Td> </Td> <Td> 220 </Td> <Td> </Td> </Tr> <Tr> <Td> Bear (grizzly) </Td> <Td> </Td> <Td> </Td> <Td> 215 </Td> <Td> </Td> </Tr> <Tr> <Td> Bear (polar) </Td> <Td> </Td> <Td> </Td> <Td> 241 </Td> <Td> </Td> </Tr> <Tr> <Td> Beaver </Td> <Td> </Td> <Td> </Td> <Td> 122 </Td> <Td> </Td> </Tr> <Tr> <Td> American bison </Td> <Td> </Td> <Td> </Td> <Td> 217 </Td> <Td> </Td> </Tr> <Tr> <Td> Camel (Bactrian) </Td> <Td> 360 </Td> <Td> 420 </Td> <Td> 390 </Td> <Td> </Td> </Tr> <Tr> <Td> Cat (domestic) </Td> <Td> 58 </Td> <Td> 67 </Td> <Td> 64 </Td> <Td> </Td> </Tr> <Tr> <Td> Chimpanzee </Td> <Td> 230 </Td> <Td> 250 </Td> <Td> 240 </Td> <Td> </Td> </Tr> <Tr> <Td> Chinchilla </Td> <Td> 105 </Td> <Td> 115 </Td> <Td> 110 </Td> <Td> </Td> </Tr> <Tr> <Td> Chipmunk </Td> <Td> </Td> <Td> </Td> <Td> 31 </Td> <Td> </Td> </Tr> <Tr> <Td> Cow </Td> <Td> 279 </Td> <Td> 292 </Td> <Td> 286 </Td> <Td> </Td> </Tr> <Tr> <Td> Deer (white - tailed) </Td> <Td> </Td> <Td> </Td> <Td> 201 </Td> <Td> </Td> </Tr> <Tr> <Td> Dog (domestic) </Td> <Td> 58 </Td> <Td> 65 </Td> <Td> 61 </Td> <Td> </Td> </Tr> <Tr> <Td> Donkey </Td> <Td> </Td> <Td> </Td> <Td> 365 </Td> <Td> </Td> </Tr> <Tr> <Td> Walrus </Td> <Td> </Td> <Td> </Td> <Td> 456 </Td> <Td> </Td> </Tr> <Tr> <Td> Elephant (Asian) </Td> <Td> </Td> <Td> </Td> <Td> 617 </Td> <Td> </Td> </Tr> <Tr> <Td> Elephant (African) </Td> <Td> </Td> <Td> </Td> <Td> 645 </Td> <Td> </Td> </Tr> <Tr> <Td> Elk (wapiti) </Td> <Td> 240 </Td> <Td> 250 </Td> <Td> 245 </Td> <Td> </Td> </Tr> <Tr> <Td> European mink </Td> <Td> 38 </Td> <Td> 76 </Td> <Td> 57 </Td> <Td> </Td> </Tr> <Tr> <Td> Ferret (domestic) </Td> <Td> 41 </Td> <Td> 42 </Td> <Td> 41 </Td> <Td> </Td> </Tr> <Tr> <Td> Fox (red) </Td> <Td> </Td> <Td> </Td> <Td> 52 </Td> <Td> </Td> </Tr> <Tr> <Td> Gerbil </Td> <Td> 22 </Td> <Td> 26 </Td> <Td> 24 </Td> <Td> </Td> </Tr> <Tr> <Td> Giraffe </Td> <Td> 420 </Td> <Td> 450 </Td> <Td> 430 </Td> <Td> </Td> </Tr> <Tr> <Td> Goat (domestic) </Td> <Td> 145 </Td> <Td> 155 </Td> <Td> 150 </Td> <Td> </Td> </Tr> <Tr> <Td> Gorilla </Td> <Td> 255 </Td> <Td> 260 </Td> <Td> 257 </Td> <Td> </Td> </Tr> <Tr> <Td> Guinea pig </Td> <Td> 56 </Td> <Td> 74 </Td> <Td> 65 </Td> <Td> </Td> </Tr> <Tr> <Td> Hamster </Td> <Td> 16 </Td> <Td> 23 </Td> <Td> 20 </Td> <Td> </Td> </Tr> <Tr> <Td> Hippopotamus </Td> <Td> 225 </Td> <Td> 250 </Td> <Td> 237 </Td> <Td> </Td> </Tr> <Tr> <Td> Horse </Td> <Td> 330 </Td> <Td> 342 </Td> <Td> 336 </Td> <Td> </Td> </Tr> <Tr> <Td> Human </Td> <Td> 259 </Td> <Td> 280 </Td> <Td> 270 </Td> <Td> </Td> </Tr> <Tr> <Td> Kangaroo </Td> <Td> </Td> <Td> </Td> <Td> 42 </Td> <Td> </Td> </Tr> <Tr> <Td> Leopard </Td> <Td> 92 </Td> <Td> 95 </Td> <Td> 93 </Td> <Td> </Td> </Tr> <Tr> <Td> Lion </Td> <Td> </Td> <Td> </Td> <Td> 108 </Td> <Td> </Td> </Tr> <Tr> <Td> Llama </Td> <Td> </Td> <Td> </Td> <Td> 330 </Td> <Td> </Td> </Tr> <Tr> <Td> Mink </Td> <Td> 40 </Td> <Td> 75 </Td> <Td> 57 </Td> <Td> </Td> </Tr> <Tr> <Td> Monkey (rhesus) </Td> <Td> </Td> <Td> </Td> <Td> 164 </Td> <Td> </Td> </Tr> <Tr> <Td> Moose </Td> <Td> 240 </Td> <Td> 250 </Td> <Td> 245 </Td> <Td> </Td> </Tr> <Tr> <Td> Mouse (domestic white) </Td> <Td> </Td> <Td> </Td> <Td> 19 </Td> <Td> </Td> </Tr> <Tr> <Td> Mouse (meadow) </Td> <Td> </Td> <Td> </Td> <Td> 21 </Td> <Td> </Td> </Tr> <Tr> <Td> Muskrat </Td> <Td> 28 </Td> <Td> 30 </Td> <Td> 29 </Td> <Td> </Td> </Tr> <Tr> <Td> Opossum (Virginia) </Td> <Td> 12 </Td> <Td> 13 </Td> <Td> 12 </Td> <Td> </Td> </Tr> <Tr> <Td> Otter </Td> <Td> 60 </Td> <Td> 86 </Td> <Td> 73 </Td> <Td> </Td> </Tr> <Tr> <Td> Pig (domestic) </Td> <Td> 112 </Td> <Td> 115 </Td> <Td> 113 </Td> <Td> </Td> </Tr> <Tr> <Td> Porcupine </Td> <Td> </Td> <Td> </Td> <Td> 210 </Td> <Td> </Td> </Tr> <Tr> <Td> Puma </Td> <Td> </Td> <Td> </Td> <Td> 90 </Td> <Td> </Td> </Tr> <Tr> <Td> Rabbit (domestic) </Td> <Td> 28 </Td> <Td> 35 </Td> <Td> 31 </Td> <Td> </Td> </Tr> <Tr> <Td> Raccoon </Td> <Td> </Td> <Td> </Td> <Td> 63 </Td> <Td> </Td> </Tr> <Tr> <Td> Rat </Td> <Td> 21 </Td> <Td> 23 </Td> <Td> 22 </Td> <Td> </Td> </Tr> <Tr> <Td> Rhinoceros (black) </Td> <Td> </Td> <Td> </Td> <Td> 450 </Td> <Td> </Td> </Tr> <Tr> <Td> Seal </Td> <Td> </Td> <Td> </Td> <Td> 330 </Td> <Td> </Td> </Tr> <Tr> <Td> Sea lion (California) </Td> <Td> </Td> <Td> </Td> <Td> 350 </Td> <Td> </Td> </Tr> <Tr> <Td> Squirrel (gray) </Td> <Td> 30 </Td> <Td> 40 </Td> <Td> 35 </Td> <Td> </Td> </Tr> <Tr> <Td> Tiger </Td> <Td> 105 </Td> <Td> 113 </Td> <Td> 109 </Td> <Td> </Td> </Tr> <Tr> <Td> Whale (sperm) </Td> <Td> 480 </Td> <Td> 590 </Td> <Td> 535 </Td> <Td> </Td> </Tr> <Tr> <Td> Wolf </Td> <Td> 60 </Td> <Td> 68 </Td> <Td> 64 </Td> <Td> </Td> </Tr> <Tr> <Td> Wombat </Td> <Td> 26 </Td> <Td> 28 </Td> <Td> 27 </Td> <Td> </Td> </Tr> <Tr> <Td> Zebra (Grant's) </Td> <Td> 361 </Td> <Td> 390 </Td> <Td> 375 </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> Mammal </Th> <Th_colspan="3"> Gestation period (days) </Th> <Th> Reference </Th> </Tr>

What is the length of a cows pregnancy
find me the text answering this question