Patterns of plasma LH, FSH, oestradiol and corticosteroids from birth to the first oestrous cycle in Meishan gilts.

Abstract

Hormonal changes associated with pubertal development in a breed of pig exhibiting early puberty were determined. In Expt 1, blood from prepubertal Meishan gilts was collected at about 1 (n = 5), 10 (n = 5), 20 (n = 4), 30 (n = 5), 50 (n = 5), 70 (n = 10), 80 (n = 10) and 90 (n = 7) days of age. In Expt 2, females were sampled between 99 and 116 days of age before (n = 16) or during (n = 9) the first oestrous cycle. Serial blood samples were collected through a jugular catheter at 20 min intervals. In Expt 2, age at puberty was determined by daily examination for oestrus and weekly evaluation of plasma progesterone and found to occur at 111 days of age. Hormone profiles determined at least 19 days before the first oestrus were grouped to constitute a prepubertal stage. In Expt 1, mean concentration of LH was high at 1 day of age, significantly lower at 10 days and showed nonsignificant variations until 90 days. Frequency of LH pulses increased between 10 and 50 days (0.42 versus 0.85 pulse h-1, P < 0.05), decreased between 50 and 70 days (0.49 pulse h-1, P < 0.05) and remained low thereafter. Amplitude of LH pulses was high between 1 and 30 days and declined progressively until 80 days. Mean concentration of FSH was high between 1 and 20 days and decreased progressively until 80 days (7.2 and 2.3 ng ml-1, respectively, at 20 and 80 days, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)