Progesterone levels during the normal and silent cycle in cattle in the Colombian tropics

Objective. Determine the sequence of changes in the levels of progesterone (NP) during the normal cycle (NC) and Quiet Cycle (CS). Materials and methods. 94 Females of the breed Holstein x Cebu (HC), Simmental x Cebu (SC), Romosinuano (R) and Cebu (C) were studied from puberty and during the first three estrous cycles. Blood samples were taken to determine concentrations of progesterone by radioimmunoassay, 184 progesterone profiles were determined for CN and 153 for CS. For the analysis of the information the statistical program SAS was used. Results. The R group presented a pattern of variations of the NP through the phases of the CN that has significant differences with the behavior of NP in the phases of CN groups SC, HC and C. Progesterone levels in each phase of the CS are consistent with a low luteal phase progesterone levels. Only significant differences were found in the late luteal phase when comparing CN with CS, however, numerical differences arise at all stages between these two types of cycles.. Conclusions. Progesterone concentrations have a marked effect on the presentation of CS, however, is difficult to define a concentration of progesterone that characterize each event (CN or CS), however, it is clear that progesterone affects the chances to be a favorable or unfavorable reproductive response.