Document Type

Thesis - University Access Only

Award Date

2004

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Jeffrey A. Clapper

Abstract

Boars naturally have greater serum concentrations of estradiol-17β (E2) and IGF-I than barrows and gilts. Administration of E2 has been found to affect components of the circulating and anterior pituitary gland (AP) IGF-I system in pigs. Anastrozole (A), an aromatase inhibitor, may be useful in decreasing serum concentrations of E2 to further study the effects of E2 on the IGF-I system in the pig. Two experiments were conducted to determine whether 1) administration of 1 or 10 mg/d of A to mature boars would decrease serum concentrations of E2 and affect the IGF-I system and 2) administration of 10 mg/d of A to pre-pubertal growing boars would decrease serum concentrations of E2 and affect components of the serum and AP IGF-I system versus untreated boars and barrows. In Exp. 1, 12 crossbred boars (292 d, 158 kg) were administered either 0, 1, or 10 mg/d of A (n = 4/group) beginning on d 1. Blood samples were collected on d 0, 8, 15, 29, and 36 via jugular venipuncture. Boars were slaughtered on d 37 when AP were collected. Serum concentrations of E2 , IGF-I, and AP concentrations of IGF-I, LH, and growth hormone (GH) were determined by RIA. Relative amounts of serum and AP IGF-binding proteins (IGFBP) were determined by Western ligand blot analysis. Orthogonal contrasts identified that mean serum concentrations of E2 were greater (P < 0.01) in the O mg group than in the 1 and 10 mg groups. Mean serum concentrations of E2 were suppressed (P < 0.05) in the 10 mg group compared to the O and 1 mg groups through d 36; however, no difference (P > 0.05) existed between O and 1 mg groups. V Mean AP concentrations of LH tended to be decreased (P < 0.09) in the 10 mg group compared to the 1 mg and O mg groups. Mean relative amounts of serum IGFBP-3 (41- kDa) were greater (P < 0.05) in the 10 mg group compared to the 1 mg group. No differences (P > 0.05) were detected in mean serum or AP concentrations of IGF-1, mean AP concentrations of GH, or relative amounts of any other serum or AP IGFBP among treatment groups. In Exp. 2, 24 crossbred boars and 12 barrows (101 d, 44 kg) were stratified by litter to one of three treatment groups (n = 12): boars administered O mg/d of A (B), boars administered IO mg/d of A (AB), and barrows administered O mg/d of A (BAR). Pigs were bled and weighed on d O and every 14 d thereafter, then slaughtered on d 84 when a blood sample and AP were collected. Pigs in the AB group were fed the A amended diet beginning on d 1. Serum concentrations ofE2, IGF-1, AP concentrations of IGF-1, LH, and GH, and relative amounts of serum and AP IGFBP were determined as in Exp. I. Mean serum concentrations of E2 did not differ (P > 0.05) between Band AB pigs on d O; however, on d 15 through 84 mean serum concentrations of E2 were greater (P < 0.05) in B than in AB pigs. On d 29, mean serum concentrations of IGF-1 were greater (P < 0.05) in B vs BAR pigs. On d 43 through 84, mean serum concentrations of IGF-1 did not differ (P > 0.05) in Band AB pigs; and each was greater (P < 0.05) than in BAR pigs. Mean relative amounts of the 24-kDa form of IGFBP-4 in serum were greater (P < 0.01) in AB than in Band BAR pigs. Mean relative amounts of serum IGFBP-3 did not differ (P > 0.05) in Band AB pigs, but each was greater (P < 0.01) than in BAR pigs. Mean AP concentrations of IGF-I, LH, and GH did not differ (P > 0.05) in Band AB pigs, but each was greater (P < 0.01) than in BAR pigs. Mean relative amounts of AP IGFBP-2 and -5 were less (P < 0.01) in AB than in B pigs, but each was greater (P < 0.01) than in BAR pigs. These results indicate anastrozole administered at a dosage of 10 mg/d suppresses serum concentrations of E2 in pigs. Chronic administration of A to boars increased relative amounts of the 24 -kDa form of IGFBP -4 and decreased relative amounts of AP IGFBP-2 and -5. These data further support a role for E2 in regulating components of the IGF system in pigs.

Library of Congress Subject Headings

Estradiol.
Somatomedin.
Insulin-like growth factor-binding proteins.
Swine -- Growth.

Publisher

South Dakota State University

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Rights Statement

In Copyright