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The Effects of Triamcinolone Acetonide on Plasma Glucocorticoid Levels and Occurrence of Estrus in Gilts^{1 ,2,}

University of Missouri⁴, Columbia 65211

Abstract

Three experiments were conducted to examine the effect of adrenal corticoids on occurrence of estrus in gilts. In the first experiment, 10 mg of triamcinolone acetonide (TA), a synthetic glucocorticoid, were given to four ovariectomized and five diestrous gilts. Plasma glucocorticoid concentration declined to non-detectable levels within 5 hr of TA administration and remained at this level for 4 days in diestrous gilts and for 6 days in ovariectomized gilts. The second experiment examined the relationship between glucocorticoids and the expression of estrus in thirty-eight ovariectomized gilts. Seven of nine control gilts given .4 mg estradiol benzoate (EB) and three of four gilts given 10 mg TA 2 days before administration of .4 mg EB exhibited estrus. However, only one of four gilts displayed estrus when 10 mg TA were given simultaneously with EB, and none of seven gilts showed estrus after receiving 10 mg TA on days –7, –4, 0 and 4 (day 0 = the day of EB administration). The third experiment was conducted to determine the effect of TA on the expression of first estrus following relocation and exposure to a boar of gilts reared in confinement. Forty-three gilts were randomly assigned to a treatment or control group. Gilts in the treatment group were given 10 mg TA, and gilts in the control group received saline on days –3, 0, 4 and 8 (day 0 = the day of relocation and initial exposure to a boar). Gilts not exhibiting behavioral estrus by day 10 were given 80 IU ACTH. On day 20, all gilts failing to exhibit estrus were subjected to a laparoscopic examination of the reproductive tract and ovaries. Within 20 days after relocation and exposure to a boar, 15 of 21 control gilts and six of 22 treated gilts displayed first estrus (P<.01). However, ovarian stimulation had occurred in 10 treated gilts prior to laparoscopic examination. Seven of these gilts had corpora lutea present on the ovaries, two had cystic follicles and one had mature follicles. Therefore, treatment with TA did not alter the proportion of gilts demonstrating ovarian stimulation following relocation and exposure to a boar but significantly reduced the proportion of gilts exhibiting behavioral estrus.

¹ Contribution from the Missouri Agr. Exp. Sta. Journal Ser. No. 8427. Approved by the Director.

² This investigation was supported in part by Grant Number CSRS 701-15-44 from the USDA. The authors express appreciation to Lei Yen and Tom Cantley for technical assistance in the development of the corticoid assay and to Betty Nichols for secretarial assistance.

³ Present address: Dept. of Biol. Sci., IU-PU at Fort Wayne, 2101 Coliseum Blvd, East, Fort Wayne, In 46805.

⁴ Dept. of Anim. Husb.