Dinámica folicular de vaquillas criollas al pastoreo en el altiplano ecuatoriano

The aim was to characterize the behavior pattern of follicular dynamics in creoles heifer (CR) to grazing in the high mountains of Ecuador. It was carried out in the Irquis experimental farm at the University of Cuenca, in 2016. The average weight was 243.3±45.0kg. Body condition (CC) 2.5±0.4, scale 1-5 points. Age 19.9±4.8 months. Daily scans were performed during an estrous cycle. Every 48h the levels of Progesterone (P4) were determined. A pattern of two and three follicular waves was established (44.4 and 55.6% respectively). The average duration of the estrous cycle was 20.3±0.03 days (two waves) and 23.6±0.02 days (three waves). The size of the preovulatory follicle (FPO) was 15.3±0.04mm for two-wave animals and for those with three waves, 13.8±1.48mm. The subordinate follicle (FS) reached its maximum size on day 4.0±0.04, with 8.0±0.04mm (two waves) and 4.8±0.03 days with 7.4±0.03mm (three waves). The development of the corpus luteum (CL) presented three phases: growth (until day 6), static (6-18 days) and regression (>18 days). On day 12, the CL reached its largest size 21.7±1.45mm and 23.5±0.61mm for animals of two and three waves respectively. P4 reached levels above 1ng / ml from day 4 (5.8±3.35ng/ml two waves and 5.1±1.15ng / ml three waves). The levels of P4 during the estrous cycle were higher than those reported in other breed. In conclusion, Creole genotype heifers have their own characteristics, which are influenced by the pattern of follicular behavior (two or three waves).