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) All Versions of this Article: jas.2006-447v1 85/2/388    most recent 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Theilgaard, P. Articles by Løvendahl, P. Search for Related Content PubMed PubMed Citation Articles by Theilgaard, P. Articles by Løvendahl, P.

Variation in plasma growth hormone during first parity in lactating cows¹

Danish Institute of Agricultural Sciences, PO Box 50, DK-8830 Tjele, Denmark

² Corresponding author: peth{at}dca.upv.es

This study analyzed genetic and phenotypic variation in plasma GH during lactation in first parity dairy cows. The heritability and repeatability were examined using an algorithm for separation of basal and peak concentrations and different power transformations. Blood samples were obtained 17 times during first parity in 85 Holstein, 67 Red Dane, and 62 Jersey cows and assayed for GH. Each breed comprised 2 genetic groups; thus, a total of 6 genetic groups were defined. Across genetic groups, cows were assigned to 1 of 2 total mixed rations with a low or a normal energy concentration. The separation algorithm identified only 4.0% of the plasma GH concentrations as peaks. After excluding peak concentrations, the repeatability of GH during lactation was improved. A log-transformation was found appropriate for GH. The log-transformed GH concentrations for lactating dairy cows had a heritability ranging between 0.14 in early lactation to 0.08 in mid and late lactation. The repeatability was 0.24 in early lactation and increased to between 0.58 and 0.61 in mid and late lactation. We conclude that for GH concentrations in lactating cows that are sampled infrequently, the exclusion of peak values to obtain a basal GH concentration was not effective in clarifying phenotypic or genetic effects.

Key Words: breed • dairy cow • heritability • lactation • somatotropin

This article has been cited by other articles:

				C. Hayhurst, M. K. Sorensen, M. D. Royal, and P. Lovendahl Metabolic Regulation in Danish Bull Calves and the Relationship to the Fertility of Their Female Offspring J Dairy Sci, August 1, 2007; 90(8): 3909 - 3916. [Abstract] [Full Text] [PDF]