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This study was carried out to investigate the length of the estrous cycle and duration of estrus in Korean native goats. The effects of the type of last estrus : induced or natural, and the length of preceeding estrous cycle on the subsequent cycle and duration of estrus in goats were also examined. From 481 observations, the mean length of estrous cycles was 18.1{pm}0.5days. The cycle length was significantly(P<0.05) shorter following induced estrus (15.2{pm}0.8 d) than natural estrus(19.0{pm}0.6 d). Significantly higher(P<0.05) incidence of short estrous cycle was observed following induced estrus(40%) than natural estrus(27%). The frequency distribution in the estrous cycle was 30%, 3%, 56% and 11% for short(3-11 d), medium(12-16 d), normal(17-24 d) and long({geqq}25 d), respectively. The most frequent type of short estrous cycle was 6 days in length. Mean duration of estrus was 34.0{pm}0.5 h with a range of 18 to 84 h. Duration of estrus was not significantly different the preceeding natural (33.8{pm}0.6 h) and induced estrus (34.4{pm}1.1 h), and was not significantly affected by the last cycle length. These results suggest that the short estrus cycles are more frequent following induced estrus than natural one, and the duration of estrus are affected greatly by the various intrinsic and extrinsic factors.
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