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

This Article Full Text Full Text (PDF) Interpretive Summary 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 Google Scholar Articles by Gulay, M. S. Articles by Bachman, K. C. PubMed PubMed Citation Articles by Gulay, M. S. Articles by Bachman, K. C.

Short communication: Effect of estrogen supplemented at dry-off on temporal changes in concentrations of lactose in blood plasma of Holstein cows

M. S. Gulay^*, M. J. Hayen, H. H. Head^,1 and K. C. Bachman

^* Mehmet Akif Ersoy University, Faculty of Veterinary Medicine, Department of Physiology, 15100, Burdur, Turkey
University of Florida, Department of Animal Sciences, Gainesville 32611-0910

¹ Corresponding author: hhhead{at}ufl.edu

The objective was to determine the effect of supplemental estrogen (estradiol cypionate, ECP) at dry-off on temporal changes in concentrations of lactose in blood plasma of Holstein cows as an indicator of rate of mammary involution. Thirty-two Holstein cows (8/group) were assigned randomly to 4 treatment groups: 30-d dry, 30-d dry + ECP, 60-d dry, and 60-d dry + ECP. A single injection (7.5 mL) of cottonseed oil (30- and 60-d dry) or ECP (15 mg) in oil (30- and 60-d dry + ECP) was administered intramuscularly at dry-off. Blood samples were collected from the coccygeal vein of all cows 24 h before dry-off and at dry-off, and then 8 samples were collected throughout the subsequent 48 h to monitor concentrations of lactose in blood plasma. No significant effects of ECP on the overall mean concentrations of lactose were detected. Concentrations of lactose increased and were greatest in blood collected 20 h (520.4 ± 54.1, 268.1 ± 48.2, 345.0 ± 52.3, 418.4 ± 49.8 µM, for the 4 treatment groups respective to the order listed above) after supplemental ECP and final milk removal. At 40 h, concentrations approached those observed 24 h before dry-off (140.5 ± 52.1, 57.6 ± 47.1, 90.1 ± 51.4, 61.2 ± 48.4 µM, respectively). Concentrations of lactose at 20 h were positively correlated with milk yield of cows at dry-off. Similar temporal profiles of lactose in blood plasma of cows supplemented or not with ECP indicated that ECP at dry-off did not markedly alter the course of tight junction leakage that typically occurs in mammary epithelial tissue during progressive early involution when milk removal is discontinued.

Key Words: dry period • estrogen • plasma lactose