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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Peters, R. R. Articles by Tucker, H. A. Search for Related Content PubMed PubMed Citation Articles by Peters, R. R. Articles by Tucker, H. A.

Growth and Hormonal Response of Heifers to Various Photoperiods¹

Michigan State University, East Lansing 48824

Abstract

Body growth and dry matter intake were measured in three groups of 16 Holstein heifers exposed to (1) natural, (2) 16 hr light: 8 hr dark (16L:8D) or (3) 24L:0D photoperiods from November 11 to March 10. Average daily gain (ADG) of heifers subjected to 16L:8D was 11 (P<.05) and 17% (P<.02) greater than ADG of animals receiving 24L:0D or natural photoperiod, respectively. Heifers subjected to 16L:8D consumed 6.9 and 8.3% more (P<.01) dry matter per day than did animals exposed to 24L:0D or natural photoperiod, respectively. Yet feed to gain ratio of heifers exposed to 16L:8D was lower than that of heifers exposed to 24L:0D or natural photoperiod. Serum prolactin (PRL) and growth hormone (GH) were measured in six heifers in each treatment group at 30-min intervals, and serum total glucocorticoids were measured at 2-hr intervals over a 6-hr period on December 26, February 6 and March 7. Concentrations of serum PR1 remained low (<3 ng/ml) regardless of photoperiod treatment; this would be expected, however, because mean ambient temperatures were below 0 C on all sampling days. Serum GH and total glucocorticoids were likewise unaffected by photoperiod treatment. This study demonstrates that an 8-hr period of darkness is necessary to achieve increases in weight gain when Holstein heifers are supplemented with light during the autumn-winter season in Michigan, but the mechanisms whereby photoperiod affects body growth remain unknown.

¹ Michigan Agr. Exp. Sta. Journal Article No. 9355. This research was supported in part by USPHS Grant HD09883 and USDA grant 901-15-2.

² The authors acknowledge the National Institutes of Health for generous supplies of NIH-P-B3 prolactin and NIH-GH-B12 growth hormone. We thank Drs. John Gill and Clyde Anderson for statistical and computer programming assistance.

³ Anim. Reprod. Lab., Dept. of Dairy Sci.

This article has been cited by other articles:

				V. R. Osborne, N. E. Odongo, A. M. Edwards, and B. W. McBride Effects of Photoperiod and Glucose-Supplemented Drinking Water on the Performance of Dairy Calves J Dairy Sci, November 1, 2007; 90(11): 5199 - 5207. [Abstract] [Full Text] [PDF]

				H. Tucker and R. Ringer Controlled photoperiodic environments for food animals Science, June 25, 1982; 216(4553): 1381 - 1386. [PDF]