Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2001
Publication Date: 7/1/2001
Citation: Ford, J.J., Zimmerman, D.R., Wise, T.H., Leymaster, K.A., Christenson, R.K. 2001. Increased plasma follicle-stimulating hormone concentrations in prepubertal gilts from lines selected for increased number of corpora lutea. Journal of Animal Science. 79(7):1877-1882. Interpretive Summary: Ovulation rate is one of the limiting steps for litter size in swine. Direct selection for increased number of corpora lutea was practiced for greater than 10 generations in two lines. Ovulation rate increased, relative to an appropriate control line for each selected line, by greater than three. Following the development of these lines, blood samples were obtained from gilts during prepubertal development and assayed for concentrations of plasma follicle-stimulating hormone (FSH). Plasma concentrations of FSH were greater in both lines of gilts selected for greater number of corpora lutea than in their appropriate control line. These observations add strong support to an earlier finding that concluded plasma FSH should be considered as a trait to select indirectly to improve ovulation rate in pigs. These findings will be useful to scientists to aid in the design of additional studies. Additionally, pig-breeding companies will have interest in these findings as a selection method that is cheaper than surgical observation that is required for direct selection of ovulation rate.
Technical Abstract: Secretion of follicle-stimulating hormone (FSH) was evaluated in gilts from two studies in which ovulation rate increased through direct selection for number of corpora lutea (CL). Plasma FSH concentrations were greater (P<0.05) at 53 (13.5%), and 75 (21.3%) d of age in selected than in control gilts of the University of Nebraska gene pool lines. Likewise, plasma FSH was greater (P<0.05), relative to controls, on d 34 (>24%), 55 (>13%), and 85 (>10%) in White Composite gilts selected for either increased ovulation rate or for greater uterine capacity. Ovarian and uterine wt were less (P<0.01) in the control than in the ovulation rate line. Controls had fewer (P<0.01) CL (14.6) than gilts of the ovulation rate line (17.7) but similar (P>0.10) numbers to gilts of the uterine capacity line (14.7). Plasma FSH on d 85 correlated positively with subsequent ovulation rate within each line (P<0.03, 0.001, and 0.08; r=0.17, 0.30, and 0.15 for control, ovulation rate and uterine capacity lines, respectively). Ovarian wt at 160 d of age also correlated with subsequent ovulation rate (P<0.03 and 0.001; r=0.23 and 0.38) in control and ovulation rate gilts but not in uterine capacity gilts (P>0.10; r=0.11). Gilts selected for increased number of CL, in two independent studies, had greater concentrations of FSH during prepubertal development than respective controls.