Study of the sexual cycle and seasonal reproductive pattern in creole goats
1990
Santa Maria, Alejandro | Cox, Jose | Munoz | Elias (Concepcion Univ., Chillan (Chile). Fac. de Ciencias Agropecuarias y Forestales)
Between April 1987 and March 1988 the sexual activity of 12 mature creole goats was measured. Blood samples were obtained every two days during two consecutive cycles, to measure the progesterone levels. Oestrus detection was done at 6 hours interval during one hour each. The results were submitted to Stepwise regression to estimate the relationship between sexual activity, temperature, humidity and photoperiod. The length of cycles and oestrus was 20.33 +- 4.03 days, range 5-35 days (n=121) and 29.37 +- 11.18 hours, range 6 to 84 hours (n=121), respectively. Sexual activity was detected from February to October, with 100% in June and July. No activity was observed in November to January. The Stepwise regression showed a 68% of association between monthly sexual activity and photoperiod. The serum progesterone levels remained low from the day of heat (2,15 nmol/l), increasing to day 10 (22.48 nmol/l), reaching to highest values the 14th day (25.71 nmol/l). Four days prior the next oestrus was still high (21.21 nmol/l), falling two days before the oestrus (6.41 nmol/l), when the minimun level was recorded again (1.67 nmol/l)
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