Efecto de la época del año y del ciclo lunar sobre variables reproductivas en bovinos

In this study, the effect of season and lunar cycle on calf sex, gestation length, and calving and pregnancy frequency was evaluated. Were analyzed 125,499 reproductive records between 1992 and 2014, from 36 farms located in the Maracaibo Lake basin, Venezuela. According to the proportion of moonlight the lunar cycle was divided into 30 periods of 0.984 days each, and into four periods (2 days around new moon; 2 days around full moon; 13 days in the waxing phase; and 13 days in the waning phase). Three seasons were established: dry (December-March), intermediate (April-August) and rainy (September-December). Data were analyzed by logistic regression of the SAS statistical program (sex of the calf), and analysis of variance using the general linear model (duration of gestation and frequency of births and pregnancies). There was no effect of season or lunar cycle on sex ratio. On the proportion of pregnancies and parturitions there was no effect of season, but there was of the lunar cycle. The highest proportion of pregnancies and parturitions occurred around the new moon and full moon. The time of year and the lunar cycle affected the length of gestation.