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 Palmer, J. E. Articles by Barrantes, R. E. Search for Related Content PubMed PubMed Citation Articles by Palmer, J. E. Articles by Barrantes, R. E.

Genetic Trends in Milk Production in an Experiment Station Jersey Herd

Departments of Dairy Science and Statistics, University of Florida, Gainesville 32601

ABSTRACT

First-calf heifers (625 lactation records, 50 paternal half-sister groups) at the Florida Agricultural Experiment Station averaged 2,773 kg milk, 5.22% milk fat, and 144 kg milk fat for 1931 to 1968. Weighted regression analyses of least-squares year constants, with sires included or omitted from the model, estimated annual trends. Genetic trends for milk and fat yields and fat percentage were 37.5 ± 6.4 kg, 1.45 ± .31 kg, and —.016 ± .004% ; environmental trends were —14.0 kg, —.29 kg, and +.017%. If negative environmental trends in yields were accepted at face value, possible explanations include gradual increase in herd size, other management practices which might have led to increased competition between heifers and older cows, and the addition of animals of the four other major dairy breeds.