HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Guilbault, L. A. Articles by Wilcox, C. J. Search for Related Content PubMed PubMed Citation Articles by Guilbault, L. A. Articles by Wilcox, C. J.

Periparturient Endocrine Changes of Conceptus and Maternal Units in Holstein Heifers Bearing Genetically Different Conceptuses¹

University of Florida, Gainesville 32611

Abstract

Holstein heifers (n = 21) were balanced across sires and assigned to three service-sire-breed groups in which heifers were inseminated artificially to either purebred Angus (n = 7), Holstein (n = 7) or Brahman (n = 7) bulls. Semen from four bulls was used for each service sire-breed group. Blood samples were collected from a jugular vein thrice weekly from d 160 to 265 of pregnancy, daily thereafter until 15 d postpartum, and then thrice weekly until d 60 postpartura. Concentrations of progesterone, estrone, estradiol and estrone sulfate from 23 d prepartum to parturition, and of 15-keto-13,14-dihydro-prostaglandin F₂ (PGFM) from 2 d prepartum to d 15 postpartum were measured by radioimmunoassay. Heifers within the Brahman-service-sire group had longer gestations (P<.05) than those of Holstein- or Angus-service-sire groups (285.0 vs 278.7, 279.0 d). Calf birth weight was lower (P<.05) in Angus- than Holstein- and Brahman-service-sire groups (30.6 vs 36.1, 43.4 kg). Daily trends of prepartum maternal progesterone concentrations were approximately 1 ng/ml lower (P<.01) in Angus- than Holstein- or Brahman-service-sire groups until luteolysis occurred. Heifers bearing crossbred Angus conceptuses had lower daily trends of prepartum estrogens concentrations (P<.01), whereas heifers of the Holstein- and, even more dramatically, of the Brahman-service-sire groups had a higher magnitude and greater rise of plasma estrogens concentrations between d –10 and –1 prepartum (P<.01). Postpartum mean concentrations (P<.05) and response curves of PGFM were lower (P<.01) in the Angus- than in the Holstein- or Brahman-service-sire groups. Calf birth weights were correlated with least-squares means for maternal concentrations of prepartum estrone (r = .57), estradiol (r = .59) and estrone sulfate (r = .64) and postpartum maternal concentrations of PGFM (r = .56). Functional responses of the conceptus (e.g., estrogens) and maternal units (e.g., progesterone and PGFM) were influenced by conceptus genotype during the periparturient period.

¹ Florida Agr. Exp. Sta. Journal Series 6075. This research was supported in part by the Upjohn Company, Kalamazoo, MI.

² Dairy Sci. Dept., Institute of Food and Agr. Sci.

³ On student leave from Agriculture Canada, Research Station, Lennoxville, Quebec, Canada. Research completed as partial requirements for Ph.D. at the Univ. of Florida.

⁴ Address reprint requests to: Dairy Sci. Dept. IFAS, Univ. of Florida, Gainesville, FL 32611.