Resumen

WILLIAMS, S.I.; FERNANDEZ, V.C.  y  DE LA SOTA, R.L.. Follicular dynamics and time of ovulation in gilts and postweaning sows. InVet [online]. 2010, vol.12, n.1, pp.33-42. ISSN 1668-3498.

Follicular development in sows, includes the process of recruitment and selection; however, follicle waves were described only in prepubertal period. Recent technical advances have made possible to study ovarian activity in pig using real time ultrasonography. The objective of this study was to determine the number and follicles size at estrus and the follicular development pattern till the ovulation time in gilts and weaning sows. From the onset of estrus onward, ovaries were scanned every 8 h and number, size, location of ovarian follicles and ovulation time were recorded Ovaries were visualized by transabdominal (gilts) and transrectal (sows) scanning. For transrectal scanning, a sector transducer was attached to a polyvinyl chloride fixed-angle transrectal stabilizing cord. Ovulation time was defined as the time of the first scanning when no presumptive ovulatory follicles were found minus 4 h, and ovulation was confirmed by a further scanning 8 h later. The number of follicles 3-5 mm decreased from the onset of oestrus onward, perhaps, because some of them became atretic and because others moved to the pool of follicles 6-7 mm. The number of follicles medium size (6-7 mm) increased slowly at the onset of estrus, then plateaued, and finally decreased, because they moved to a the pool of follicles 8-9mm, and remained till time of ovulation. Despite differences between gilts and sows in ovulation time (36.5±1.8 vs 29.1±2.6 h, respectively) and preovulatory follicles size (5.6±0.5 vs 7.0±1.0 mm, respectively), it was concluded that ultrasonography is very useful to study follicular dynamics from the onset of estrus to ovulation and thus to use this information to implement fixed-time artificial insemination protocols.

Palabras clave : Folicular dynamics; Ovulation time; Ultrasound; Gilts; Sows.

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