Ovarian Follicular Dynamics and Hormonal Changes in Goats during Early Pregnancy

Abstract

Abstract. The present study was conducted to characterize follicular development and its hormonal control during early pregnancy in goats. The ovaries of goats (n=8) were scanned daily for follicles (> or = 2 mm in diameter) and corpora lutea by transrectal ultrasound with blood sampling from the jugular vein for monitoring the hormonal changes during the first thirty-five days after mating. During early pregnancy, three (37.5%), four (50%) and one (12.5%) goat showed nine, eight and seven waves of follicular development, respectively. The corpora lutea were detected as early as Day 3.61 ± 0.45 (7.47 ± 0.43 mm) of pregnancy (Day 0=day of mating) and attained their maximal cross-sectional diameter (10.64 ± 0.37 mm) on Day 25.7 ± 0.8 of pregnancy, respectively. A transient rise in FSH levels was temporally associated with the day of follicular wave emergence (up to three days prior to wave emergence). The plasma LH and estradiol levels were negatively correlated with the progesterone concentration. The rise in plasma immunoreactive (ir) inhibin levels was negatively correlated with the FSH concentration and positively correlated with the number of large-sized follicles. Alternatively, the mean plasma ir-inhibin levels showed a noticeable decline with the progression of pregnancy. The present results demonstrated that follicular development during early pregnancy shows a wave-like pattern, with seven to nine waves developing until Day 35 after breeding, and that the number of follicular waves can be predicted by the number of FSH peaks. The current study also demonstrated that the role of inhibin as an FSH regulator is maintained throughout early pregnancy. Key words: Follicle development, Goat, Inhibin, Ovary, Pregnancy (J. Reprod. Dev. 56: [520][521][522][523][524][525][526] 2010) ollicular development during the estrous cycle in goats is characterized by wave-like patterns [1,2]. Each wave of follicular growth consists of a cohort of small follicles that continue to grow into one or more large preovulatory follicles through three main events, recruitment, selection and dominance, while the others undergo atresia [3]. The number of follicular waves per cycle varies from two to five, with a four-wave pattern being the most predominant [1,2]. Follicular growth throughout pregnancy has been described in ruminants [4,5], with less attention being given to goats [6].Repeated ultrasound scanning of pregnant cow (monotocous species) and ewe (polytocous species) ovaries revealed that the regularity of the emergence of follicular waves did not change during early pregnancy [4,5,7,8] and that waves of follicular growth continued regularly under conditions of basal LH and FSH [8], but decreased progressively as pregnancy progressed [9,10]. It was noticeable that the location and diameter of the largest follicles and the total number of follicles were drastically affected with the presence of the corpus luteum (CL) of pregnancy and the conceptus [5,7,8].In goats, limited studies have been conducted to characterize follicu...

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