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Follicular Fluid Concentrations of Estradiol-17ß and Progesterone and Secretory Patterns of LH and FSH in Prepubertal Gilts Reared in Confinement or Outdoor Lots^1,2,

Purdue University^,5, West Lafayette, IN 47907

Abstract

One-hundred-twenty crossbred gilts from two experiments were assigned randomly to a 2 x 5 factorial experiment. Gilts were reared in two environments (confinement or outside) and assigned to be slaughtered at 4, 5, 6, 7 or 8 mo of age. Beginning at 6 mo of age, blood samples were taken at weekly intervals from each gilt via venipuncture. Serum concentrations of progesterone were analyzed to determine when gilts attained puberty. On the day prior to slaughter, six pigs within a treatment group were cannulated and blood samples were taken at 20-min intervals for 4 h. At slaughter, follicular fluid (FF) was aspirated and the volume determined from those follicles having a diameter of at least 4 mm. No effect of environment was found on the proportion of gilts that attained puberty by 8 mo of age. For the 12 gilts that reached puberty during the study, the age at puberty for gilts reared in outdoor lots (202 ± 5 d) was less (P<.05) than those reared in confinement (224 ± 8 d). Mean concentrations of serum luteinizing hormone (LH; P=.98) and number of secretory spikes of LH (P=.76) were similar between gilts reared in confinement and those reared in outdoor lots. No differences in average serum concentrations of follicle stimulating hormone (FSH) or number of secretory spikes of FSH were found between gilts subjected to these environments (P=.95). Concentrations of estradiol-17ß in FF were not affected by environment or age (P>.25). Progesterone concentrations in FF from small and medium follicles of pigs reared outdoors decreased steadily with advancing age (4.8 mo), while progesterone concentrations in FF from small and medium follicles of pigs reared in confinement were not related to age.

¹ Journal Paper No. 10,297, Purdue Univ. Agr. Exp. Sta.

² The authors gratefully acknowledge Dr. G. D. Niswender, Colorado State Univ., Ft. Collins, for supplying antiserum to LH and progesterone; Dr. R. J. Ryan, Mayo Clinic, Rochester, MN, for supplying radioiodination grade porcine FSH; and Dr. N. R. Mason, Eli Lilly and Co., Indianapolis, IN, for providing antiserum to estradiol-17ß. The technical assistance of D. Blair, C. Thomas and R. Lummer is greatly appreciated.

³ Present address; Dept of Anim. Sci., Washington State Univ., Pullman, WA 91164.

⁴ To whom reprints should be addressed.

⁵ Dept. of Anim. Sci.