Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 2003
Publication Date: February 1, 2004
Citation: FORD, J.J., WISE, T.H., CHRISTENSON, R.K. 2004. LACK OF AN ASSOCIATION BETWEEN PLASMA FOLLICLE-STIMULATING HORMONE CONCENTRATIONS AND OVARIAN WEIGHT IN PREPUBERTAL GILTS. JOURNAL OF ANIMAL SCIENCE. v. 82(2). p. 472-478. Interpretive Summary: In previous studies, we determined that improvement in ovulation rate in pigs through direct selection for number of corpora lutea produced a significant increase in plasma concentrations of follicle-stimulating hormone (FSH) during early prepubertal development in gilts. The current study investigated if the difference in FSH was the consequence of altered age at puberty and if greater FSH hastened ovarian development. We observed that age at puberty was similar in the line selected for greater number of corpora as in the control line, and at 85 days of age, ovarian weight was similar in both of these lines. Therefore, we conclude that the increase in plasma FSH concentrations during prepubertal development results from greater synthesis and secretion and not from an alteration in rate of pubertal development. Furthermore, ovaries of prepubertal gilts in the line selected from greater number of ovulations are unresponsive to the greater concentrations of FSH than these gilts possess. These findings will be of use to investigators as they design subsequent studies to improve litter size in pigs.
Technical Abstract: Selection for increased number of corpora lutea in gilts is associated with increased plasma follicle-stimulating hormone (FSH) concentrations during pubertal development. The current study evaluated ovarian weight at 85 d of age in 270 gilts from control (CO) and ovulation rate (OR) lines and correlated this ovarian weight to FSH concentrations at 65, 75, and 85 d of age. Gilts were produced during two farrowing seasons, spring and fall, and age at first estrus was monitored from 160 to 240 d. Plasma FSH was greater in OR than in CO gilts at 65 (P < 0.01) and 75 d (difference in spring greater than in fall, P < 0.01), but FSH at these ages was not correlated with ovarian weight at 85 d. At 85 d, FSH did not differ in gilts of these lines; however FSH was negatively correlated (r = -0.27, P < 0.01) with ovarian weight. Proportion of gilts detected in estrus was less for spring-born CO gilts than for spring-born OR or fall-born CO and OR gilts (78 vs 92%, season x line, P < 0.02). Age at first estrus was similar in the two lines but was earlier (P < 0.01) for spring-born than for fall-born gilts (194 vs 204 d). Concentrations of FSH at each of the ages examined were not correlated with age at first estrus. These observations support the conclusion that selection for greater number of corpora lutea produces a correlated increase in plasma FSH during early pubertal development. This increase in FSH most likely reflects differences in FSH synthesis and release and not differences in stage of pubertal development.