title: Low doses of bovine somatotropin enhance conceptus development and fertility in lactating dairy cows.
abstract: Objectives were to evaluate the effects of administering either one or two low doses of slow-release recombinant bovine somatotropin (bST) on hormone concentrations, conceptus development, and fertility in dairy cows. Cows from two farms were detected in estrus on or after 50 days postpartum (n = 1483), inseminated, and enrolled in the study (Day 0). Within farm, cows were blocked by parity and assigned randomly to receive a single placebo injection at insemination (control), a single injection with 325 mg of bST at insemination (S-bST), or two injections with 325 mg of bST administered on Days 0 and 14 (T-bST). From a subset of cows, blood was collected twice weekly from Day 0 to 42 for determination of hormone concentrations and on Day 19 for isolation of leucocytes and analysis of transcript abundance of selected interferon-stimulated genes. Pregnancy was diagnosed on Days 31 and 66, and ultrasonographic morphometry of the conceptus was performed on Days 34 and 48 in a subset of cows. Cows that received T-bST had increased plasma concentrations of GH and IGF1 for 4 wk, increased mRNA expression of ISG15 and RTP4 in leukocytes, earlier rise in the pregnancy-specific protein B in plasma of pregnant cows, increased conceptus size, and enhanced fertility. Cows that received S-bST had increased concentrations of GH and IGF1 for only 2 wk and it was insufficient to alter conceptus development and fertility. In conclusion, supplementation with low doses of bST during the pre- and peri-implantation periods enhanced conceptus development, reduced embryonic losses, and improved fertility in dairy cows.
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville, Florida.
authors.forename: Eduardo S
authors.initials: ES
authors.lastname: Ribeiro
authors.forename: Ralph G S
authors.initials: RG
authors.lastname: Bruno
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Farias
authors.forename: Juan A
authors.initials: JA
authors.lastname: Hernández-Rivera
authors.forename: Gabriel C
authors.initials: GC
authors.lastname: Gomes
authors.forename: Ricardo
authors.initials: R
authors.lastname: Surjus
authors.forename: Luis F V
authors.initials: LF
authors.lastname: Becker
authors.forename: Alyssa
authors.initials: A
authors.lastname: Birt
authors.forename: Troy L
authors.initials: TL
authors.lastname: Ott
authors.forename: Josh R
authors.initials: JR
authors.lastname: Branen
authors.forename: R Garth
authors.initials: RG
authors.lastname: Sasser
authors.forename: Duane H
authors.initials: DH
authors.lastname: Keisler
authors.forename: William W
authors.initials: WW
authors.lastname: Thatcher
authors.forename: Todd R
authors.initials: TR
authors.lastname: Bilby
authors.forename: José E P
authors.initials: JE
authors.lastname: Santos
mesh_terms: D000818:Animals; D002417:Cattle / Q000196:embryology / Q000502:physiology; D003612:Dairying; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000187:drug effects*; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000187:drug effects*; D013006:Growth Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D011247:Pregnancy; D018873:Pregnancy Rate
chemical_list: D013006:Growth Hormone
keywords: bST; conceptus; dairy cow; fertility