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 Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nieuwhof, G. J. Articles by Norman, H. D. Search for Related Content PubMed Articles by Nieuwhof, G. J. Articles by Norman, H. D.

Ages at Calving and Calving Intervals for Dairy Cattle in the United States

Department of Animal Sciences, University of Maryland, College Park 20742

R. L. Powell and H. D. Norman

Animal Improvement Programs Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705

ABSTRACT

Calving ages and intervals for cows first calving in 1966 to 1986 were examined for five dairy cattle breeds. For parities one through seven, mean age at each parity was lowest for Jerseys and highest for Ayrshires and Brown Swiss. Registered cows usually were older than grades for a specific parity. Notable exceptions were that registered Guernseys, Holsteins, and Jerseys were younger than grades at first parity. Trends in calving ages over time generally were positive for given parities; if parity was not considered, trends were negative except for Jerseys and significant except for Ayrshires and Holsteins. In later years, trend for Guernseys was no longer significant. Calving intervals were shortest for Jerseys and longest for Brown Swiss and Guernseys. Mean calving intervals decreased from first to second interval and then increased through sixth for all breeds. Calving intervals for Holsteins ranged from 393 d following second parity to 405 d following sixth. Registered cows had longer calving intervals than did grades. Trends for calving intervals generally were positive for given parities; trends for more recent data were less positive and significant only for Guernseys. No evidence of generally deteriorating reproductive performance across time was found.

¹ Present address: Department of Animal Breeding, Agricultural University, Wageningen, Netherlands.

This article has been cited by other articles:

				R. L. Powell and H. D. Norman Major advances in genetic evaluation techniques. J Dairy Sci, April 1, 2006; 89(4): 1337 - 1348. [Abstract] [Full Text] [PDF]

				E. Hare, H. D. Norman, and J. R. Wright Trends in Calving Ages and Calving Intervals for Dairy Cattle Breeds in the United States J Dairy Sci, January 1, 2006; 89(1): 365 - 370. [Abstract] [Full Text] [PDF]