INICIO DEL CELO, TASA DE GESTACIÓN Y RELACIÓN DEL TIEMPO DE INSEMINACIÓN CON LOS NIVELES DE PROGESTERONA EN VACAS BRAHMAN

Objetive. To establish oestrus frecuency, fertility rate and progesterone levels in cows brahman. Materials and methods. Materials and methods. Onset of Materials and methods. oestrus, pregnancy rate and the P4 levels were analyzed to the moment of AI in Brahman cows (n=160) in a farm of Cundinamarca department (Colombia). Results. esults. The biggest frequency of oestrus was observed in the morning (68.75%) regarding the afternoon (31.25%). Average values of P4 were of 0.22 ng/ml, with values maxima and minima of 3.035 ng/ ml. and 0.000 ng/ml, respectively. The efficiency in the oestrus detection for levels of P4 was high (96.25%). The average of time lapsed among the moment of the oestrus detection and the insemination was of (12.6 hours). An statistical association did not found among the levels from P4 to the moment of the insemination with the fertility rate of (45%). Conclusions. Conclusions. The Conclusions. climatic conditions or the season can affect the onset of oestrus, that the levels of P4 by itself do not explain the rates of fertility, that the P4 is useful in the handling of reproductive control and that the AI different to the scheme AM - PM could improve the fertility rates of the programs of AI in the Colombian humid tropic.