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To characterize the secretory patterns of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) during prepubertal development of the gilt, blood samples were collected at 20-min intervals for 4 h once a week from four littermate gilts 10 to 18 wk of age and from another group of four littermate gilts 19 to 25 wk of age. Puberty occurred in the latter group during wk 25. Serum concentrations of LH, FSH and PRL were averaged for each 4-h sampling period within each gilt, and any single value greater than one standard deviation above the mean for that period was identified as a secretory spike. Mean LH was greater at 16 wk of age than during wk 11, 12 and 13, and serum LH levels were higher at 25 than 22 wk of age. Frequency and magnitude of LH spikes were greatest at 16 wk in the group of gilts 10 to 18 wk of age, but magnitude of LH spikes did not change from 19 to 25 wk. The frequency of FSH secretory spikes did not change in gilts from 10 to 25 wk of age. No changes in mean serum concentrations of PRL, frequency of PRL spikes and magnitude of PRL spikes were observed during prepubertal development. Spikes of FSH and PRL occurred with more than random synchrony throughout the study. Spikes of LH and FSH or LH and PRL were highly synchronized during early prepubertal development (10 to 18 wk), but less synchronized in gilts 19 to 25 wk of age.

Forty-eight prepubertal gilts (178.7 +/- 4.1 d; 94.2 +/- 4.1 kg), 16 in each of three trials, were assigned randomly to receive 0 (C) or 10 ppm zearalenone (Z) daily in 2.5 kg of a 14% protein finishing ration for 2 wk. Blood samples were collected at 20-min intervals for 4 h 1 wk after the start of the experiment and 1 wk after Z was withdrawn. Two weeks after Z was withdrawn, gilts were exposed to mature boars 15 min per day for 3 wk. Gilts in estrus were mated to two different boars 12 h apart. Twice each week, blood was sampled and analyzed for progesterone to establish age of puberty. Age at puberty differed (P = .008) among replicates but was similar (P = .13) between Z and C gilts within each replicate. Mean serum concentrations of LH were suppressed (P = .025) during consumption of Z (.25 vs .42 ng/ml) but were similar (P = .16) to concentrations in C gilts 1 wk after Z was withdrawn (.35 vs .45 ng/ml). Frequency and amplitude of LH secretory spikes did not differ (P greater than .50) between Z and C gilts during either sampling period. Mean serum concentrations of FSH were similar (P = .25) between Z and C gilts. Number of corpora lutea and live fetuses were similar (P = .29 and P = .94, respectively) between Z and C gilts. Fetal weights were greater (P = .025) and crown to rump length tended to be greater (P = .10) in fetuses from Z gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Mature ewes were injected intravenously with the opioid antagonist naloxone (1.1 mg/kg) during the breeding season. Ewes with luteal phase concentrations of plasma progesterone responded with a significant (P less than 0.05) increase in plasma LH 14-23 min after naloxone injection. In contrast, non-luteal ewes with low plasma progesterone did not respond to injection of naloxone with an LH increase. Similar treatment of castrated males (wethers) with this dosage of naloxone failed to increase plasma LH. Electroacupuncture (EA) treatment of luteal phase ewes prevented the ability of exogenous naloxone to increase plasma LH. Treatment of wethers by EA decreased significantly (P less than 0.01) their high basal concentrations of plasma LH, but similar EA treatment of intact ewes did not change their low basal concentrations of LH.