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 Young, A. W. Articles by Bradley, N. W. Search for Related Content PubMed PubMed Citation Articles by Young, A. W. Articles by Bradley, N. W.

Effects of an Oral Progestogen on Feedlot Heifers¹

University of Kentucky, Lexington³

Abstract

Eighty good-to-choice Angus feeder heifers averaging 283 kg. were used to study the effects of feeding 0, 0.20, 0.40 and 0.60 mg. per head daily of an oral progestogen, melengestrol acetate (MGA). Soybean meal was fed at the rate of 0.68 kg. per head daily and served as the MGA carrier.

Results of twice-a-day observations for estrus showed that 0.40 mg. was the minimal effective daily dosage for successful suppression of estrus. A few of the heifers fed the 0.20 mg. level were observed in estrus during the trial. Ovaries from 21.4% of these heifers had corpora lutea at slaughter, indicating incomplete inhibition of ovulation.

Average daily gain and feed efficiency were not significantly affected over the 154-day feeding period.

Analysis of carcass data indicated that heifers fed MGA yielded carcasses which were not significantly different from those of the controls.

Significantly (P<.05) heavier reproductive tracts were observed from heifers fed the 0.6C mg. level when compared with control heifers or heifers receiving the 0.20 and 0.40 mg, levels of treatment. Ovarian weights were significantly (P<.05) greater for the 0.20 mg. level compared with other levels. Follicular fluid expressed as a percentage of total ovarian weight was significantly increased (P<.01) for all levels compared with controls.

Results from this experiment show that MGA can effectively prevent estrus in feedlot heifers when fed at the rate of 0.40 mg. per head daily. However, MGA did not significantly affect over-all merit of heifers in terms of rate of gain, feed efficiency or carcass quality.

¹ The investigation reported in this paper (No. 67-5-26) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.

² Present address: U.S.D.A. Animal Husbandry Research Division, University of Nebraska, Lincoln.

³ Department of Animal Sciences.

⁴ 17-acetoxy-6-methyl-16-methlyenepregna-4,6-dinene-3,20-dione.

⁵ Furnished by the Upjohn Company, Kalamazoo, Michigan.